T4lJKurl GPA Standard - Guide Lines on Reapplying a Used Plant & Equipments

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Guidelines for Reapplying

Used Plants and Equipment

Prepared for:

GPA Technical Section A: Facilities Design

by

Michael W. Conder, P.E.

yright Gas Processors Associationded by IHS under license with GPA

Not for Resaleeproduction or networking permitted without license from I HS

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GPA Disclaimer

GPA publications necessarily address problems of a general nature and may be used by

anyone desiring to do so. Every effort has been made by GPA to assure accuracy andreliability of the information contained in its publications. With respect to particular

circumstances, local, state, and federal laws and regulations should be reviewed. It is not the

intent of GPA to assume the duties of employers, manufacturers, or suppliers to warn and

properly train employees, or others exposed, concerning health and safety risks or

precautions.

GPA makes no representation, warranty, or guarantee in connection with this publication

and hereby expressly disclaims any liability or responsibility for loss or damage resulting

from its use or for the violation of any federal, state, or municipal regulation with which this

publication may conflict, or any infringement of letters of patent regarding apparatus,

equipment, or method so covered.

“Copyrignt 2002 by Gas Processors Association. All rights reserved. No part of this Report

may be reproduced without written consent of the Gas Processors Association.”



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Introduction

Reapplying used equipment and/or plant systems has been done successfully in the natural gas processingindustry for many years. It has been proven for all types and sizes of plants. However, until now there

has been little published information on how to complete a project of this sort successfully.

This monograph has been written to help those who may be interested in reapplying used equipment

and/or plants in the gas processing industry. It is the result of many years of experiences of members of

the Gas Processors Association Technical Section A: Facilities Design, and of their fellow workers.

Much of this knowledge has come the hard way: by making mistakes. So I have included many anecdotes

to help illustrate the points made in the text: these are called “Cases in Point”. All of these cases have

actually occurred to one or more members of the Section A committee, or to their fellow workers but, to

paraphrase the saying, the names have been deleted to protect the innocent.

The title of this monograph is “Guidelines for Reapplying Used Equipment”. The word “Guidelines” has

been specifically chosen because that is what they are: guidelines. They are not rules, regulations, best

practices, or standards. They are merely recommendations and advice, thing to consider when one is

developing or implementing a project that includes used equipment. They are not all inclusive. Indeed,

one thing the cases prove is that every project will have some new and unexpected problem to handle.

And as with all advice, the one receiving it must evaluate the advice and decide whether it is worthwhile

to follow or mere bunk.

This monograph only deals with the unique aspects of used equipment. The plant designer will also need

to follow the same installation requirements and good engineering practices that new equipment requires.

The monograph is organized in sections, dealing with an overview of some of the characteristics of a

project that includes used equipment, through the acquisition of the equipment to the refurbishment and

installation of the equipment.

I would like to thank the Gas Processors Association for giving me the opportunity to write this

monograph. I would also like to thank my coworkers and fellow committee members who have passed on

their fascinating, and occasionally embarrassing, anecdotes of past projects. This monograph would not

have been possible without access to their experiences.

Michael W. Conder, P.E.

March, 2002



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IndexI. Introduction

A. Reasons for Reuse

B. Limitations

C. Project RisksD. Typical Project Procedure

II. Selecting a Plant

A. Finding and Acquiring the Plant

B. Prepurchase Plant Inspection

1. On-site Visual

2. Functional

3. Non-destructive Testing

C. Plant Information and PSM

D. Purchase Agreements

E. Original vs. Modern Codes

III. Reapplying a Plant

A. Process redesign

B. Plant Modifications/Combinations

1. Process Modifications

2. Equipment Modifications

3. Assembling New Plants from Old

Equipment

IV. Moving a Plant

A. Skid MountedB. Block Mounted

V. Refurbishing the Plant

A. General

B. On-site vs. Shop

C. Replace vs. Repair

D. Cleaning

E. Component Guidelines

1. Piping

2. Valves

3. Pressure Vessels and Filters

4. Towers

5. Heat Exchangers

a. Shell & Tube Exchangers

b. Air Cooled Exchangers

c. Plate-fin Exchangers

d. Other Exchangers

6. Fired Heaters

a. Fire Tube Heaters

b. Multi-tube Heaters

7. Pumpsa. Centrifugal Pumps

b. Reciprocating Pumps

8. Compressors

a. Reciprocating Compressors

b. Centrifugal Compressors

c. Expanders

9. Equipment Drivers

a. Gas Engine Drivers

b. Electric Motors

10. Instruments

a. Control scheme b. Controllers/transmitters

c. Control Valves

d. Relief Valves

e. Gauges

f. Tubing

11. Electrical

a. Equipment

b Wiring

12. Structural Steel

13. Insulation

14. Paint

V. Dismantling/Installing the Plant

A. Differences in Construction Techniques

1. Dismantling

2. Installation

3. Safety/Environmental

a. Dismantling b. Refurbishing

c. Construction

B. Training

VI. Summary



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Page 1 September 2002

On Reapplying Used Gas Processing Plants

I. Introduction

The dynamic world of gas processing often demands changes. Although installing new plants andequipment is the traditional method of meeting these needs, time and schedule limitations often

require using existing equipment for the project, in part or in whole. This monograph is intended to

help the plant designer in the reapplication of used equipment as part or all of gas processing plants.

Each project that includes used plants or equipment will have its own unique requirements and

problems. The only absolute statement concerning this type of project is that there are no absolutes.

This monograph is not intended to present the reader with specifications and standards for reapplying

used plants and equipment. Rather, it is intended to provide ideas to be considered, some pitfalls to

avoid and some specific experiences of companies who have installed used plants and equipment.

A. Reasons for Reuse

Why should one consider employing used equipment in a project? The reasons vary according to each

project, but two frequent reasons are to lower overall capital costs and/or to shorten the project

schedule.

Many managers and engineers in the gas processing industry believe that used equipment is “junk”;

many others believe that used equipment will cut the cost of a project by 50% or more. Although

there is a kernel of truth in both of these opinions, the reality is usually somewhere in between.

While cost reductions can be significant, they may not be as great as one would first believe. As an

example, consider the installation of a “typical” block-mounted plant. Experience has shown that the

installed cost of such a plant is normally 2.5 to 3 times the cost of major equipment; i.e., the

equipment cost is only 35-40% of the project cost. If the cost of the refurbished used equipment is 50-

75% of the cost of new equipment, then total project costs will be reduced by only 10-20%. Since

skid-mounted plants include most of the piping and instrumentation with the equipment, total project

cost savings can be 15-25% of an equivalent new plant.

These project savings are at risk if the used equipment requires extensive refurbishing, or if the need

for refurbishing is not discovered until the end of the project. Proper preparation and inspection at the beginning of the project can protect the savings in capital cost and project duration.

Projects that are based on used plants or equipment fall into three categories:

• complete used process systems, such as skidded plants, with or without process modifications

• plants which employ only a few used pieces in a mostly new unit





GPA Technical Section A Monograph: Guidelines for Reapplying Used Plants and Equipment Final Draft

September 20022

• plants assembled from many used pieces into a new arrangement, often coming from several

different sources

Each has its advantages and disadvantages. There often is a trade-off between total cost of the plant

and process flexibility. In other words, employing used items in a plant extensively can reduce the

overall project cost but may require some compromises in the overall plant design which could lead todecreased plant performance (higher operating costs, lower recoveries, etc.). The optimum balance

between these trade-offs will be a function of many factors, including project life, plant complexity,

processing economics, performance specifications, plant location, etc.

Rapplying used plants and equipment is not always the best path to a successful project. Early in the

project, the project designer must be realistic in evaluating the extra effort of reengineering,

inspecting, purchasing, dismantling, refurbishing and moving the used items over the effort required

to install new items. Many times there will be no savings in project time or capital cost; in fact, the

used plant may have higher project costs than the costs of a new plant. The plant designer should be

prepared to change direction if a new plant is warranted.

In many cases, project cost savings are not the major consideration in a decision to reapply a used

plant. Schedule reduction can often be the overriding factor. Refurbishing a plant rarely takes more

than 6-8 weeks unless extensive modifications or equipment replacements are required, while new

plants are rarely available in less than 12-16 weeks. If the plant is the limiting factor in the project

timeline, the resulting improvement in project economics from having the plant available earlier can

be many times more than the project cost savings.

Case in Point: A company purchased a cryogenic plant that had been built from used equipment.

The plant had been difficult to operate, due to the lack of proper engineering during design and

installation. Soon after the purchase, the plant was shut down and the gas diverted to a nearby

plant that had excess capacity.

A surge in drilling and gas production soon filled the nearby plant, and new capacity was needed

to meet a contractual deadline with the gas producers. The company compared the time and cost

to build a new plant with higher product recovery against rebuilding the old plant, and decided to

rebuild the old plant to handle the new gas. The plant was inspected, redesigned, costs were

estimated and the project was approved.

Once the refurbishing began, it was discovered than the plant was in far worse shape thanoriginally expected. Project costs skyrocketed, but the plant was eventually started on time.

A review of the project showed that a new plant would have been about the same cost as the final

project cost but taken about a month longer to complete. The value of the extra product recovery

would have easily offset the revenue received from starting the plant a month earlier. The project

was deemed as success, though, since it did meet the required deadline.



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September 20023

B. Limitations

Compared to building a new plant for a project, reapplying an existing plant can often be difficult and

occasionally impossible. It is rare to find the exact size plant with the best process design for an

acceptable price. Many projects based on used plants or equipment are built with compromises in

plant performance and/or capacity. Making the right fit can often require flexibility and creativity.

Case in Point: A company needed to install a large straight refrigeration processing plant as

quickly as possible to eliminate a hydrocarbon dew point problem in its transmission line. After a

detailed review of the available plants, and after a couple of inspection trips, no plant was found

which had the required capacity. In fact, the closest possibility to meet their needs was to build a

plant using two separate trains, although the cost of two 50% units exceeded the company’s

budget.

During the search for the plant, the company found a used gas/gas exchanger, electric compressor and gas chiller from a refrigerated lean oil plant. A search of the market turned up a vessel that

could be modified as a cold separator and two air coolers that would be suitable for propane

refrigerant condensing. The company was able to blend these major items with a used

compressor, new piping and instruments and new equipment and was able to complete the plant in

less time than a new plant would have taken.

Case in Point : A company wished to build a fractionator for its produced Y-grade but lacked the

budget to build a new plant. However, it had an old refrigerated lean oil plant that was no longer

needed. The company was able to use two old towers, one new tower, various reboilers, cross

exchangers, pumps, vessels, hot oil heater and air coolers to build a three-tower fractionating system that met their requirements on a significantly lower budget.

Some plants and equipment are more suitable for reuse than other plants. For process plants, the

easiest to reuse (and perhaps the most common) are medium-sized skid-mounted liquids recovery

units. Block-mounted liquids recovery plants are also good candidates for reuse. Plants in corrosive

service, such as amine treaters and sulfur recovery units, are more difficult to reuse and usually cost

more to refurbish. Small plants may cost more to purchase and refurbish than new plants, especially if

the new plants are “on-the-shelf” plants like field glycol regenerators.

Original plant locations and operating conditions are also important parameters. A plant that is stilloperating will probably need less refurbishing than a plant that has been shut down for a period of

time. A plant located near the Gulf Coast will probably need more refurbishing than an identical plant

in West Texas. Moving a Gulf Coast plant to Wyoming will incur extra cost for winterizing, while

moving a plant from Wyoming to Louisiana may require extra costs for high performance painting.



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September 20024

C. Project Risks

Most new equipment and plants come with some sort of mechanical and/or process guarantee. Used

equipment comes with no guarantees whatsoever; they are normally purchased on an “as-is, where-is”

basis. Therefore, used plants can be riskier than new plants. They can also need a lot more

engineering and check-out work than new plants, due to the need to identify the plant’s condition anddesign capabilities and to reengineer it into the new process. The added risk has to be managed by:

• being realistic about cost savings

• being aware of used plant market conditions

• verifying the condition of the used plant

• confirming the design and condition of the plant

• taking no shortcuts in cleaning or refurbishing the plant, regardless of its history

• confirming that the plant’s documentation meets today’s requirements

D. Typical Project Procedure No two projects are developed in the same exact manner. However, projects that employ used plants

or equipment often follow a well-proven path. A generalized description of a typical project

development is as follows:

• Identify the process and economic needs for the project.

• Review the available internal assets that may fit the project needs.

• Locate and review the available items on the open market. This is often done through one or

more used equipment brokers.

• Select one or more candidates for the project for detailed review. This can include a process

redesign, identifying modifications that may make the used items more suitable for the new

use, or even selecting the items with the lowest price.• Inspect the selected item(s) thoroughly, including visual and non-destructive inspections.

• Verify everything; don’t take someone’s word about the plant’s condition or capabilities.

• Negotiate a purchase agreement.

• Acquire the item.

• Move the item to a location for refurbishing and/or modifying as needed.

• Move the item to the new project site.

• Install the item.

II. Selecting a Plant

A. Finding and Acquiring the Plant

Used plants and equipment usually come from one of three sources: internal ownership, direct

from the current owner and through a used equipment broker. Of these, the internal ownership is

usually the preferred source, while getting a plant through the brokers is probably the most

common source.



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September 20025

Using assets already owned by the company building a new project will usually be the best way to

reapply the used plant. No cash transaction is required, although an internal charge between

internal corporate groups may be required. However, one should account for the market value of

the used plant by including an opportunity cost in project economics. Also, coordination of the

plant “acquisition” and locating critical plant documents and operating histories are usually easier

when using existing assets.

There can be a few drawbacks to using a plant that a company already owns. One problem may be

dealing with the book value of the asset. If it has not been sufficiently depreciated, using an

existing asset may require an uncomfortable write-down of the asset’s value. This can also drive a

company to set the asking price of a used plant much higher than the prevailing market for similar

equipment.

Another drawback is the limited inventory normally available with internal assets. Although there

are exceptions, the modern economics of gas processing have lead to the disposal of unused assets.Therefore, most companies do not have an extensive selection of unused plants and equipment and

it is relatively rare to find the exact fit plant in one’s inventory.

Larger companies often have a number of plants that are inactive and available for reuse on a new

project. However, many of these companies are so large that an engineer in one area has no idea

what is available from other areas of the company: a case of the “left hand” not knowing what the

“right hand” is doing. Even companies with asset disposal programs may not know all the items

that may be available in the company that would fit the new project.

The second source is direct from the current owner, normally an owner who is also a plant

operator. This eliminates the “middle man” and can provide an easier, lower cost plant

acquisition.

This route does have its drawbacks. Since most owners do not stay in touch with the used

equipment market, they often have an inflated idea of the value of their plant. In addition, they

may not be experienced in the sale of used equipment, and may not have an effective internal

procedure to ensure the efficient completion of a purchase. They also may not be serious about

selling the plant.

Case in Point: A company needed a propane refrigeration plant and found one which was

owned by an operating company. The first company sent out inspectors and performed

enough design work to determine the suitability of the plant for their project. After several

weeks and considerable expense, the company made an offer to the operating company. The

operating company reviewed the offer for a few more weeks, then decided not to sell the plant.






September 20026

Plant brokers are the third source of used plants. Successful brokers are experienced in the buying

and selling of used plants and equipment, and can often make the process easier on all parties.

Good brokers know what equipment is currently available on the market, and the better brokers

know which equipment or plants could be made available at the right price.

Although most brokers can represent the plant and equipment sellers, some brokers can offer

several other services. Some brokers own all or part of the equipment outright. Some brokers can

dismantle, refurbish and reinstall plants and equipment. Other brokers can also offer engineering

services.

A few common sense guidelines in dealing with a broker:

• Do not use too many brokers to find your equipment. The market for a particular type and

size of a plant is often small and relatively efficient, so when too many people are looking

for a particular plant, the implicit demand can often drive up the price of the plant.

Case in Point: A company needed dozens of 30,000 gallon propane bullets for a large

storage project. Due to the large number required, the company contacted several

equipment brokers. After some of the owners heard from several of these brokers, they

increased their asking prices. The company was able to find all the tanks they needed,

but paid about 10% more per tank than the previous market indicated.

• Do not go around the selected broker. Many brokers will ask for non-circumvention

agreements before they reveal too many details about a plant. Remember, the broker’s

product is his knowledge of the available plants and his experience in completing the plant

purchases.

• Deal with reputable brokers. Check with industry peers about their experiences with the

broker. While a successful prior experience is no guarantee of future success, heeding the

lessons learned from someone else’s negative experience with a broker can prevent future

problems.

• Be wary of brokers who require large deposits on equipment. These deposits are usually

nonrefundable and usually represent earnest money. They provide the purchaser with the

sole right to purchase the plant or equipment, and can represent the lost opportunity cost

for the seller if the purchase falls through. Typical deposits range about 5-10% of the

overall purchase price. Higher deposit requirements can be a warning flag to the purchaser.

Case in Point: A company wanted to purchase several pressure vessels through abroker. After inspecting the vessels, the broker required a 50% deposit to hold them.

After receiving the deposit, the broker no longer answered the phone and apparently

left town. The company was unable to purchase the vessels from owner, and lost the

cost of the inspection as well as the deposit.

B. Pre-purchase Plant Inspection

A proper plant inspection is usually a necessary task before completing the purchase of the plant.

Even a visual inspection can reveal situations that are not clear in plant drawings or photos. More






September 20027

detailed inspections are strongly advisable and can help prove the integrity of the plant and

equipment.

Inspections need not be made by company personnel. Most cities around the gas patch have

companies offer many types of inspection services. These companies usually have the equipment

and experienced personnel to provide any level of plant or equipment testing.

1. On-site Visual

There is no a substitute for a good on-site visual inspection. It will give a buyer a good feel

for the condition of the plant, how it has been maintained, how long the plant has been

inoperative, which equipment and/or instrumentation items have been replaced from the

original design (or are missing from the unit). A visual inspection is often required to locate

the plant documentation, especially for a plant that has been shut down. Although visual

inspections aren’t foolproof, they can be used to gather valuable information.

Case in Point: A company was looking at purchasing a refrigeration plant which was

being stored in a yard. A representative traveled to the yard and inspected the plant visually. All pieces were in the yard except for a hot oil skid that was still located at the

original plant site. Since the site was a day’s drive away, the representative relied on

photos to inspect the hot oil skid. The plant was purchased based on this information.

However, when the hot oil skid was delivered, the hot oil pumps had been removed.

Although the seller was able to locate substitute pumps, a visual inspection could have

revealed the problem before the plant purchase.

2. Functional

A plant’s prior operating history can often provide good information about the plant’s value

and suitability, especially if one can talk to the plant’s operators. The operators usually can

answer questions that the plant owners can’t, such as:• Was the plant easy to start and operate?

• Was the plant easy to maintain?

• Was this plant safe to operate?

• Were there any equipment replacements, modifications or repairs that may not be

common knowledge?

• Were there any special procedures that made the plant easier to maintain and/or

operate?

• Did any particular piece of equipment cause an undue proportion of operating

problems?

• Has maintenance been kept up to date, or has it slacked off recently?• Are any plant records “stashed” in the plant that aren’t available elsewhere?

• Has the plant been in full or partial compliance with OSHA’s Process Safety

Management (PSM) requirements?

This doesn’t mean that the plant owners are trying to hide any plant defects. Due to personnel

changes or lost records, they are often not completely aware of the plant’s operating and

maintenance history or its current condition.



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September 20028

Case in Point: A company purchased a used horizontal tank to use as a demethanizer

surge tank. The company sent a third-party inspector to inspect the vessel, and spent the

extra money to have the vessel steam-cleaned. The vessel passed all the inspections and

was installed at the new site.

During plant start-up, though, the operators could never get a level in the tank. They tried

checking all the instrumentation: calibrated the level transmitter, hooked up a bypass

around the gauge glass, and so on. Since the level controller was tied into the pumps, it

was difficult to operate without a good level indication.

They eventually got back with the inspector, who vaguely recalled some sort of standpipe

inside the vessel. The company isolated and drained the vessel, opened it up and looked

inside. It turned out that the bridle was tied into the flange with the standpipe. They had

to put a man into a contained breathing suit, send him into the vessel and cold-cut the

standpipe. This fixed the problem.

3. Non-destructive Testing

Used plant piping and equipment can be inspected before or after purchase through non-

destructive testing. This includes visual inspection, ultrasonic thickness (UT) testing, dye

penetrant testing, radiographic examination, borescope examination and pressure testing. In

most cases, a site visit will support an external visual examination and UT testing with a

portable thickness tester.

Case in Point: A company was considering the purchase of a high pressure vessel as an

inlet scrubber. A vessel was located and a representative traveled to inspect the vessel.

The vessel exterior looked good but the vessel interior was not accessible. The

representative made a number of UT checks at appropriate locations on the vessel. All checks showed nominal wall thickness until he checked the side of the vessel. This point

showed a thickness of less than 50% of the vessel’s original wall thickness. The vessel

was rejected.

C. Plant Information and PSM

One of the more difficult tasks in reapplying a used plant is gathering technical information about

the equipment and its operation. This includes job books, process flow diagrams, piping &

instrumentation diagrams, equipment data sheets, ASME U-1A Manufacturers’ Data Reports for

Pressure Vessels (and any repair reports), outline drawings, installation drawings, equipment

manuals, etc. The problems are compounded when the plant has changed ownership several

times, or when the original equipment manufacturer and/or engineering/constructor have gone outof business.

Until recently, enough documentation could usually be generated through visual inspections and

record searches to proceed with the plant project. However, for plants being built or operated in

the United States, the requirements of OSHA’s Process Safety Management (PSM) program have

increased the required level of documentation. Although this monograph discusses specific PSM



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September 20029

requirements for projects in the United States, the same informational concepts can still be useful

for projects located in other parts of the world.

Case in Point: A cryogenic plant was recently purchased from a company which had

purchased several identical plants at one time for different locations. The job books appeared

to match the purchased plant. However, when the ASME data sheets were compared with theactual nameplates on the pressure vessels, the serial numbers did not match, but were one or

two numbers off. The error apparently happened when the engineering contractor mixed up

the data sheets between the different plants while assembling the job books.

Proper and complete documentation of equipment, especially ASME-Coded pressure vessels and

heat exchangers, is required by PSM as part of the new project’s Mechanical Integrity program.

Unfortunately, the required documentation for used equipment is frequently unavailable from the

seller. When the documentation isn’t available, the purchasing company will need to decide if it

can develop enough information to meet the company’s PSM program requirements or if it needs

to look for different equipment with better documentation.

On the other hand, used plants that have been covered by a proper PSM program will normally

have most of the equipment and piping information that a plant designer needs for a successful

project. This can be especially helpful for the plant designer who may be moving a plant from the

United States to another country.

Control valves, relief valves, pumps, compressors and other equipment often have serial numbers

that can be used to get original design conditions and operating manuals from the original

manufacturer. The manufacturers often have records of equipment modifications. Equipment

items rebuilt by a third party often have their own serial numbers issued by the remanufacturer.

Missing documentation for pressure vessels and heat exchangers can often be located through theoriginal manufacturer, through the engineering contractor or through the National Board of

Pressure Vessel inspectors, if the items were registered at the time of original manufacture.

Problems arise if these venues are unsuccessful; these problems sometimes limit or eliminate the

equipment’s usability. Some possible methods to handle missing pressure vessel documentation

are detailed in a section below.

D. Purchase Agreements

Most purchases of used plants and equipment are made on an “as-is, where is” basis, with no

guarantees or representations as to the fitness of the equipment. Purchases are often negotiated,

and there are a few points that can often be made part of the purchase agreement that will prevent

problems in reapplying the used plant and equipment. A few of these points are as follows:

• Environmental concerns are often a major consideration and significant risk in purchasing

used plants and equipment. Therefore, consider including requirements that the plant be

free and clear of all fluids, gases and chemicals that may be inside the equipment and

piping. The plant should also be made free and clear of all asbestos insulation. Include

any details as may be appropriate for the disposal of all wastes.

• Most sellers will not warrant the condition of the equipment. A method of minimizing the

risk of purchasing ASME-Coded equipment, especially in larger pressure vessels such as



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September 200210

storage tanks, is to make the sale contingent on the equipment passing certain inspections

and/or tests. This can often include a successful hydrostatic pressure test of the vessel as

well as various NDT examinations. Costs of these tests are often born by the purchaser or

added to the sale price of the equipment.

• Some equipment brokers are involved in plant dismantling and can offer their equipment

on an “as-is, F.O.B. truck” basis. This can reduce the complexity and risk for the purchaser.

• As mentioned above, documentation for used plants and equipment is often hard to get.

Consider including a requirement in the purchase agreement that requires the seller to

provide ASME Form U-1A data sheets for all pressure vessels. If the equipment is still

owned by the plant operator, consider requiring that the purchaser supply all files, PSM

Mechanical Integrity data and job books associated with the equipment, including any that

may be in the seller’s home office, engineering office and/or safety office. Job books that

are incomplete at one site may be supplemented by information from job books at a

different site.

Case in Point : A company purchased a plant for use in a new project. The job booksat the site were incomplete, and were missing much of the maintenance procedures for

the equipment and instrumentation. One book was missing completely. However, the

selling company had another incomplete set of job books in their home office. A

complete set of jobs books was built out of the two incomplete sets.

E. Original Codes vs. Modern Codes

Most plants and equipment were built according to the various codes of their day. Although most

of these codes are still used today, they have evolved and generally become more demanding over

the years. Therefore, a plant or piece of equipment that may have been built twenty or thirty years

ago according to the prevailing codes of the day may not meet all the requirements of current

codes. In a few special cases, though, the earlier codes may be more demanding than current

codes.

Case in Point : A company located propane storage tanks needed for a project. These tanks

were code-stamped for 200 psi and were originally thought to be unsuitable for their 250 psi

requirement. Further review revealed that these tanks were built in the late 1940’s under the

then-current ASME Code that had used a 5:1 stress safety factor. Since later versions of the

Code use a 4:1 safety factor, the storage tanks were allowed to be rerated and Code stamped

for 250 psi by performing a hydrostatic pressure test under the supervision of a qualified

Code inspector.

III. Reapplying a Plant

A. Process Redesign

Used equipment and plants are frequently placed in services that differ from their initial design.

For example, amine plants treating natural gas may be reused to treat natural gas liquids. Propane

storage tanks may be reused as inlet scrubbers. Gas compressors may be used as refrigeration

compressors. Cryogenic plants designed for lean gas may be modified for rich gas.



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September 200211

In these cases, the plant designer needs to gather as much information as possible about the

existing equipment, including (but not limited to): maximum and minimum design temperatures

and pressures; metallurgy; performance data sheets; ranges of instrumentation; capacities;

pressure drops; etc. The plant designer needs to take all these into account when developing a

new process design.

For most plants, especially those with heat exchangers, a detailed design or re-rating will probably

be necessary to make sure the equipment is suitable for the new service. Inadequate design could

lead to equipment operating beyond its design limits.

Case in Point: A company modified a cryogenic plant that had been designed for lean gas for

use on a rich gas stream by adding a propane chiller in the process. A cursory process design

was performed by the used equipment vendor. The plant was a conventional cryogenic unit

using a split flow design, with one portion of the inlet gas being cooled by the residue gas and

the remaining gas being cooled by the reboiler, chiller and side reboiler.

Unfortunately, the process design was not done well and although the plant’s liquid product

met specifications, the residue gas from the plant was very cold, occasionally below –20°F.

Since this was the minimum design temperature of the residue piping, the safety switches shut

the plant down. The owner ran the plant in this mode until it was sold.

The new owner performed a detailed process design and determined that the reboiler required

most of the inlet gas flow to provide enough heat for the demethanizer. With little inlet gas

flowing through the gas-gas exchanger, the residue gas was short-changed and left the plant

very cold. The new owner installed a new trim reboiler using an external heat source,

reducing the amount of inlet gas needed by the reboiler. This allowed more inlet gas to flow

through the gas-gas exchanger, heating the residue gas to its proper temperature. The newinstallation was a success.

Case in Point: A company moved a glycol regenerator from a plant to a compressor station

as part of a new triethylene glycol (TEG) dehydration service. The plant capacity, design

pressures and temperatures were all checked and found adequate for the new service. The

plant was refurbished and installed at the new site.

After start-up, though, the new unit was not meeting the required dew point and the pumps

were requiring an excessive amount of maintenance. A quick review showed that the lean

glycol going to the contactor was over 200°F instead of the expected 120°F.

A process check of the exchanger showed that the exchanger was too small for the service,

although it was meeting its design capacity. The exchanger had been designed for

regenerating ethylene glycol, cooling the lean glycol from 240°F to 120°F. The conversion to

TEG service doubled the required capacity, as the new design required cooling the lean glycol

from 380°F to 120°F. A new, larger exchanger was purchased and installed and the

problems were eliminated.



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September 200212

B. Plant Modifications/Combinations

1. Process Modifications

The process conditions of a new project rarely match the original design conditions of an

existing plant. This usually requires that the existing plant be re-rated for the new conditions.This work can include a combination of process simulations, exchanger ratings, vessel sizing

checks, etc. This is an area in which design creativity may be able to provide a significant

improvement to the project.

It is common for the process designer to try to make the process fit the equipment, rather than

making the equipment fit the process (as in new plant design). Although this has resulted in

successful reapplications of used plants, it may not result in the best process for the particular

project. In general, it is usually better to make the equipment fit the process.

A few points to consider when checking the process design of a used plant:

• Remember that few things in a used plant are totally fixed. Don’t get locked intoviewing the existing process design as the best for the new project. Often replacing an

exchanger or vessel with a new item or “rearranging” the equipment will change a used

plant from a poor fit to an excellent fit.

Case in Point: A company wished to convert an existing refrigerated J-T plant to

a full cryogenic expander plant. Although the exchangers were rated for 1000

psig, the cold separator downstream of the J-T valve was rated for a lower

pressure. Replacing this vessel with one designed for 1000 psig made the plant

upgrade feasible. In addition, adding an exchanger and changing the service of

other exchangers increased the plant’s recovery significantly.

• There are no guarantees that used equipment will be able to perform as well as the

original design. This is especially true when it comes to both shell & tube and plate-

fin heat exchangers, which could be fouled beyond the original fouling factor.

Consider using a safety factor when doing a detailed design on the exchangers, such as

using only 90% of the fully fouled exchanger in the design calculations.

In addition, tubular exchangers (air coolers and shell & tube exchangers) which have

been in service for several years may have developed tube leaks. Normal procedure is

to plug the leaking tubes. Therefore, some exchangers may only have 80-90% of the

original tubes available for the service.

• Be sure that the equipment is appropriate for the service. Prior usage does not

guarantee correct application.

Case in Point: A company acquired a cryogenic processing plant which had been

built from used equipment. The original design of the cryogenic unit had been for

lean gas, and the unit had been modified for rich gas by adding a refrigeration

loop, a new demethanizer and several used shell & tube exchangers.



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September 200213

Unfortunately, the new owner did not receive equipment data for these used

exchangers.

The plant was operated for a year before the new owner decided to modify the

plant to correct certain process problems. Several of the exchangers were

inspected to get the equipment information necessary for a process redesign and todevelop the exchanger’s mechanical integrity information. Once the insulation was

removed from the side reboiler’s nameplate, it was discovered that the exchanger

was a carbon steel unit only rated for –20°F, even though the exchanger was

connected with stainless steel piping and had been operating well below –50°F.

Apparently, the company that had revamped the cryogenic unit ignored the

temperature rating and relied on the fact that the exchanger was originally built by

a now-defunct company that had the word “Cryogenic” in its name. The

exchanger was replaced.

• Don’t depend on original nameplate data when resizing control valves or pumps.

Control valves can easily have revised trims, either increasing or decreasing their capacity. Pumps can have new impellers (centrifugal pumps) or plungers

(reciprocating pumps) which change their capacities. Belt-driven equipment can have

different sheaves to change the operating speed (and capacity) of the equipment. Of

course, these ideas can also be used to help the equipment fit the new process better.

2. Equipment Modifications

In many cases, used equipment will be close to the correct design but will require some

modifications to fit correctly. These modifications may be obvious, like the size of a nozzle,

or subtle, like the minor change in design conditions that can adversely affect the equipment’s

performance. The plant designer needs to review all the potential design conditions for the

new application and make sure the equipment fits the needs.

Case in Point: A company moved a propane refrigeration plant from a Gulf Coast

location to a Rocky Mountain location. The plant was started successfully in the spring,

but had problems condensing the propane refrigerant during the summer. The project

engineer assumed that the condenser would have enough surface area to condense the

same amount of propane as the original plant, especially since the ambient temperatures

were lower at the new site. What he had forgotten was that the air density also changed,

and the cooler fans could not move enough air to meet the require duty.

Case in Point: A company moved a cryogenic plant from a Gulf Coast location to a

Rocky Mountain location. The plant was started successfully in the summer and ran well

through the fall. When winter came, though, the plant began to have a number of

shutdowns, especially during the night shift. The plant designer investigated and found

that the regeneration gas cooler was prone to freezing during cold weather. In adition,

several of the water dump lines had a tendency to freeze. The cooler had been mounted on

top of the skid, which provided good cooling in the Gulf Coast but promoted freezing in

the colder climate. Eventually the dump lines were heat traced and insulated, and the



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September 200214

cooler was modified with over-the-end recirculation louvers. These modifications

eliminated the freezing problems.

3. Assembling New Plants from Old Equipment

One of the more intriguing ideas with used equipment is the thought of building an entirely

new plant with used equipment for the major components. While this can be donesuccessfully, the final project may not have saved much time or capital cost. With this

approach, the plant designer has to provide the complete piping, structural, electrical.

instrumentation, infrastructure and utilities design and construction. The used equipment has

to be located, evaluated, purchased, refurbished, possibly modified and fit into the new design.

In many cases, the effort is not worth the savings.

Case in Point: A company needed to build a dew point control plant using propane

refrigeration. Although several used plants were located, it would have taken two of the

identified plants in parallel trains to meet the new plant’s flow requirements. However,

the plant designer located several major pieces needed by the process design: a gas-gas

exchanger, chiller, propane condenser and electric refrigeration condenser. These itemswere purchased and a new plant was developed around them.

The plant had some initial operating problems with the used equipment, especially the

compressor, but not an unusually large number of problems. After the plant was

completed, a post project review showed that a new plant could have been built for about

the same amount of capital in about the same time length, but with many fewer design and

construction problems for the plant designer.

IV. Moving a Plant

A. Skid Mounted Plant

A skid mounted plant is normally designed to be moved easily. This does not mean that the skid

can be picked up with little or no preparation, though. Skids are often designed with equipment

that needs to be removed and shipped separately, such as towers, heat exchangers, air coolers,

even pressure relief valves. Plant personnel may have modified the original design by adding

equipment or piping that complicates the relocation of the skid. This can include piping or

equipment that sticks out beyond the original transportation envelope, or items that change the

weight and/or center of gravity of the skid.

Case in Point: A company purchased a used skid-mounted amine plant, and set about moving

the regeneration skid. They reviewed the original design information and determined that a

100 ton crane would just be able to move the skid. When they began the lift on the skid, the

crane’s indicator showed that the skid was more than 15 tons heavier than their highest

estimate. After looking closer, they discovered that the plant operators had filled one of the

skid bays between the skid runners with concrete to catch drips from the pumping equipment.

The company was able to move the skid, but had to get a larger crane to do the job.



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September 200215

Skids that are “full-box” skids are the easiest to lift and move. They often still have lifting eyes

built into the upper part of the steel structure. Many skids have been designed to be lifted using a

custom spreader bar; this information is often available only from the original skid fabricator, and

only sometimes mentioned in the plant’s job books.

Some skids are designed with removable bolt-on cross braces to minimize twisting duringtransportation; these need to be replaced before moving the skid. These skids can often be

identified by empty bolt holes in the diagonally opposite corners of the skid side bays.

Regardless of design, the skid’s structural design and current installation should be reviewed

before moving to make sure that the skid can be moved safely and without damage to the skid’s

equipment and piping.

Case in Point: A company located a used process skid that fit their needs. The skid was

located in a well-tended plant that had gravel placed up to the top of the skid runners. The

company purchased the skids, and went to remove it from the site. When they scraped the

gravel back to expose the runners, they found that the lower half of the skid steel wasembedded into concrete. They were able to move the skid, but only after considerable extra

effort, expense and time to chip out the concrete.

B. Block Mounted Plant

By its very nature, a block mounted plant is harder to move than a skid mounted plant, but it can

be done successfully and economically. Because of this extra effort, block mounted plants are

often quite a bit less expensive to purchase than skid mounted plants of an equivalent size and

vintage.

The first thought a plant designer may have in moving a block mounted plant is to reuse the

existing piping interconnecting to save time and capital cost. This can be done, but it requiresextra care and effort in both the dismantling and construction efforts. In many cases, though,

reusing standard carbon steel piping may not be worth the effort required for a successful move.

Normally, reusing the piping can only be done when the plant’s original layout is duplicated

exactly at the new site. When doing this, the plant designer should consider the original layout

drawings are a general guideline and not and exact dimensional representation of the completed

original plant. After all, few plants are constructed with tight dimensional tolerances: most plants

are built with the “close enough, we’ll make it fit” philosophy.

Therefore, the plant designer should take care and use a survey team to get exact dimensions and

equipment spacing of the original plant, then take extra care that the foundations at the new site

are installed using these same dimensions. The tighter the tolerances, the better the fit.

Piping should be piece-marked before or during its removal. The numbering of each piece should

be identified on a master piping drawing. On tight runs with little “spring”, the plant designer

should consider making one or two piping cuts in different planes to make it easier to install the

piping if the fit is not perfect.



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September 200216

V. Refurbishing the Plant

A. General

One of the most important tasks for a successful project that includes used plants or equipment is

the refurbishing. Few used plants or equipment items, if any, are in such pristine condition that

they can be moved from one place to another and started without some sort of rework. Even new,unused plants that have been in storage for a period of time will need some level of refurbishing.

The first step in any refurbishing work is a detailed inspection of the plant or equipment. The

inspector should keep written records of his findings for future reference. The inspection should

not rely on drawings or data sheets to determine the design of the item being inspected; the

inspector should confirm equipment dimensions, metal thickness, tower internals, etc.

B. On-Site vs. Shop

The great temptation of reapplying a used plant is to do a minimal amount of refurbishing and to

move the plant only once. Although minimizing refurbishing may save capital in the short run, it

frequently results a plant that has high downtime and operating costs. However, additional liftand travel charges can be eliminated if the refurbishing is done on site.

Successful refurbishing requires a good inspection and detailed knowledge of the plant and its

equipment. If the plant is essentially unused, if it doesn’t require extensive modifications, if its

control scheme fits well at the new site, and if there is an experienced work force available at the

site, then on-site refurbishing may be the cost-effective choice. Normally, though, refurbishing

will be more cost effective in a shop environment, where labor costs are lower and refurbishing

experts are more available.

The plant designer needs to define the level of refurbishment in detail. Refurbishment means

different things to different companies. To one, it may mean a general cleaning, repair andrepainting. To another, it may mean a complete rebuilding of the unit from the ground up.

Case in Point: A company needed to move a glycol regeneration skid from a shut-down plant

to a new site as part of a large project. The skid had been inoperative for several years, and

the company decided to have it refurbished in the shop. They specified many refurbishing

details for the process equipment and reboiler, and these items were cleaned and rebuilt. But

they did not specify the level of refurbishment for the piping and painting.

When the skid was received, the company discovered that the shop had only done the bare

minimum: repainting over the existing paint with little cleaning. The smaller process lines

had not been cleaned internally. In the absence of detailed instructions, the shop had done

the minimum required by other of its clients.

Case in Point: A company bid out the refurbishment of a cryogenic skid to several shops.

The bid package was detailed and specific, and the company awarded the job to the low

bidder. About halfway through the job, the client’s representative made a shop inspection.

He was surprised to find that one of the skids had been completely disassembled and was in

the paint shop for sand blasting and painting. All the piping and equipment had been



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September 200217

removed and was being repainted separately. Although this was beyond the requirements of

the bid specification, when asked the shop manager said that the work was being done to their

normal level of refurbishment.

C. Replace vs. Repair

Since the point of reapplying a used plant or equipment is to save time and money, the tendency isto repair and refurbish as many items as possible. On occasion, though, the equipment is not

worth the cost and effort required to repair it; it’s just throwing good money after bad. Sometimes

this equipment is obvious; sometimes it becomes apparent only after money has been spent

inspecting the equipment in detail. A few of the identifying characteristics of items that should be

replaced include:

• equipment that is out of production with a limited availability of spare parts

• equipment that does not meet current safety or emission standards

• equipment that does not have sufficient documentation to meet PSM standards

Case in Point: A company installed a used skid-mounted cryogenic plant that was purchased

from a third party. During the punch list inspection, an engineer was asked by some of thenon-technical company people about the difference between carbon steel piping and the

cryogenic stainless steel piping. After explaining the cold temperature characteristics of

carbon steel versus stainless steel, he also tried to show how the carbon steel was magnetic

while the stainless steel wasn’t magnetic. Much to his surprised, when he put the magnet on

the painted stainless steel pipe from the cold separator, the magnet stuck!

After a brief face-saving explanation, the engineer investigated the piping specifications of the

plant. Although the engineer learned that carbon steel pipe can be used at temperatures well

below –50°F (under the correct circumstances, of course), there were no records to show that

this piping was the right material or had been installed with the correct procedures. There

were also no records to show that it had been installed in the proper manner to be able to

meet those temperatures. Since they could not confirm the piping, the company decided to

replace the piping with stainless steel piping.

D. Cleaning

Cleaning a used plant properly is a critical and difficult task. Many projects have had significant

cost over-runs and the resulting plants have had low reliability due to inadequate cleaning of the

equipment and/or piping. All equipment and piping should be cleaned thoroughly. This often

requires taking the equipment and piping apart to clean it manually. It may be more cost effective

to replace small bore piping than to spend the time and effort on cleaning.

This point cannot be emphasized too greatly. Most of the problems that occur in reapplied plants

and equipment can be traced back to inadequate redesign or inadequate cleaning. The plant

designer should also recognize that circulating a cleaning fluid through a used piece of equipment

does not mean that the equipment has been completely cleaned, especially in multi-tube heat

transfer equipment.

Case in Point: A company moved an amine plant to a new location. As part of the project,

they solution-washed the entire system, including the direct-fired multi-tube heater that heated



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September 200218

the amine reboiler’s heat transfer fluid. After the plant was in operation, an operator who

was monitoring the heater’s flames noticed that several tubes were red hot and sagging. The

plant was shut down immediately. On inspection, these tubes were found to be coked up,

allowing very little flow through the tubes. The washing solution could not penetrate and

clean the blocked tubes, and the low flow let the tubes overheat. A catastrophic failure was

avoided only by the diligence of the operator.

Case in Point: A company purchased a propane refrigeration plant from a major company

and moved it to a new location. They did a thorough cleaning of the process piping and

equipment, the propane side of the chiller and the propane system’s vessels. After the plant

was started up, the chiller could not cool the gas to the proper temperature. The propane side

of the chiller was examined and found to be “gunked up”. An analysis determined that the

“gunk” was actually a radiator “stop-leak” solution. This “gunk” had built up in the

propane piping and was washed into the chiller by the new, clean liquid propane.

Case in Point: A company built a new cryogenic plant which had supplemental propane

refrigeration. The gas chiller was part of the plate-fin exchanger of the plant. To reduce project cost, the company used a propane bullet that it owned to store propane for the

refrigeration system’s make-up.

The plant was started up normally but the chiller quickly stopped working. The company’s

engineers assumed that the propane side of the chiller had plugged up with hydrates, and

tried pumping methanol into the chiller’s inlet nozzle. When this didn’t work, they pulled the

screen on the inlet nozzle.

The screen was an 80 mesh screen with a conical perforated plate backer. The entire screen

was plugged with fine silt. Apparently, the silt had been in the bottom of the propane make-up

tank that had not been properly cleaned. The company replaced the screens with 40 mesh screens and successfully restarted the plant.

Case in Point: A company installed a new, unused amine treater that had been sitting around

for 2-3 years. This was a fast-paced project with a high profile, and every day’s delay had to

be explained to management in great detail. The company cut the project schedule by

installing the plant without a lot of equipment testing. Unfortunately, when the amine system

was started, a heat exchanger tube bundle started leaking. The plant was shut down, the

bundle had to be sent offsite for tube re-rolling, delaying start-up by about a week. The

justification for not testing the equipment was that it had never been used and should have

been in great shape

E. Component Guidelines

The following section provides refurbishing recommendations for specific items that are normally

part of a natural gas processing plant. One common task throughout the recommendations is to

perform a detailed inspection of each and every item in the plant. This can take a significant

amount of time and money, but the benefits of finding a problem early in the project will usually

be worth the effort spent in the inspections.



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September 200219

1. Piping

Piping in used plants can be divided into two types: on-skid and off-skid. In general, on-skid

piping is usually reused, while off-skid piping is evaluated on a case-by-case basis. Reusing

off-skid piping requires matching the equipment layout at the new plant with the original

layout to a relatively high degree of accuracy. This usually requires a detailed survey of the

original layout, since its dimensions may differ slightly from the original design drawings.Many companies have considered that smaller carbon steel piping is not worth the effort to

mark, ship and reinstall.

Most process plant piping is designed, fabricated and inspected in accordance with

ANSI/ASME B31.3 “Chemical and Petroleum Refinery Piping.” Unfortunately, inspection

records and X-ray films are rarely available. This may increase the work required to develop

proper documentation to meet PSM standards.

Although it is not specifically required to meet PSM, many companies perform piping

inspections under API-570 guidelines. A qualified API-570 inspector’s training and

experience can often be invaluable to a project.

In gas processing plants connected to gathering systems, some piping may be constructed to

ANSI/ASME B31.8. Normally this is limited to yard piping, especially around a pig receiver

and/or slug catcher. This may or may not be appropriate for the new plant.

Case in Point : A company acquired a process plant which had a buried slug catcher

and a significant amount of field piping in the plant yard. No construction or PSM

information was available at the time of the plant acquisition, although it was known

that the slug catcher had been built under field piping codes.

The company was unable to determine where the field piping started and where the ANSI B31.3 piping began. In fact, it was impossible to determine if any of the piping

had been built, inspected or tested to meet the requirements of the B31.3 standards. A

visual inspection showed several welds to be of very questionable quality, with poor

weld caps and poorly aligned butt welds. The company elected to replace the piping

with correctly installed new piping before they restarted the plant.

Piping should be checked for internal and external corrosion, especially carbon steel piping in

sour service or in amine treating/sulfur recovery units.

• Consider replacing off-skid carbon steel piping 4-6” and smaller. Larger piping and

alloy piping can be cut and modified to fit at the new site.

• Pay particular attention to piping in pulsating service, especially screwed piping

around reciprocating compressors and pumps. Consider replacing small screwed

nipples either with welded pipe or with heavy wall (such as Sch. 160) screwed nipples.

• Consider inspecting existing piping in accordance with the latest version of

ANSI/ASME B31.3. This may require determining the minimum thickness of the

piping segment, calculating the allowable pressure, X-raying at leat 5% of the welds

and/or hydrotesting or pneumatic testing the piping.



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2. Valves

Many larger valves can be rebuilt successfully. The rebuilding can be done on site or the

valves can be sent to a shop. Many companies offer rebuilt valves on an exchange basis. A

few valve manufacturers have their own valve remanufacturing programs.

Certain valves should probably be replaced rather than rebuilt. Smaller valves, especiallyscrewed valves, are often not worth the expense of rebuilding. Older valves, unusual valves

and obsolete valves are often impossible to rebuild economically due to the unavailability of

replacement parts. Some valves such as welded bonnet weld-in valves, are not designed to be

rebuilt.

• Inspect all valves visually for damage to the sealing surfaces.

• Consider replacing all 2” and smaller screwed valves with new valves.

• Consider pressure testing all valves for leaks. Since some valve designs may leak in

one direction but not the other, test each valve from both sides. Replace or rebuild

leaking valves.

• Make sure that the valve rebuilder has a proven ability to provide quality rebuilds.

• Consider whether or not a new valve should be used in critical services; there are timeswhen the rebuilt valve just may not be good enough.

Case in Point : A new plant was built from a combination of new and used

equipment, including rebuilt ball valves with new actuators as automatic plant

block-in valves. These valves had limit switches that would not allow process

equipment to be started until the valves were wide open. Although the valves met

all performance standards, the stems had enough side-to-side play in them that it

was impossible to activate the limit switches reliably. Eventually the valves were

replaced with new valves that actuated the limit switches correctly.

3. Pressure Vessels and Filters

Pressure vessels, especially high pressure or large vessels, are probably the most common item

in any gas processing plant, and one of the easiest to reapply. Without a proper engineering

review, though, they are also one of the easiest to misapply.

As mentioned above, proper and complete documentation of ASME-Coded pressure vessels

and heat exchangers is required by the PSM regulation as part of the new project’s Mechanical

Integrity program. It is also good, safe and proper engineering practice. Unfortunately, this

level of documentation is frequently unavailable for used equipment, which can render it

unusable. There are a number of ways that may be able to provide sufficient information to

satisfy the PSM and company safety requirements.

Although it is not specifically required to meet PSM, many companies perform pressure vessel

inspections under API-510 guidelines. A qualified API-510 inspector’s training and

experience can often be invaluable to a project.

The main problem with missing U-1A forms is that the vessel’s material is unknown, and it’s

allowable stress value and/or level of radiographic examination cannot be easily determined.

Sometimes, though, the U-1A’s can be located but have problems.



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Case in Point: A company purchased and installed a cryogenic plant at a new location.

The stainless steel demethanizer had a pressure vessel nameplate but no paper

documentation was available. Although the original manufacturer was no longer in

business, the company was not concerned since the vessel had a National Board Number.

The company contacted the National Board and ordered a new U-1A Manufacturers’ Data Report. The company was surprised when the U-1A that matched the National

Board Number was for a carbon steel fuel gas scrubber instead of the demethanizer.

OSHA has recently issued a ruling that allows an owner to re-rate a vessel that has an ASME

nameplate but no material information. It requires that the owner (1) assume the minimum

stress and radiographic values, (2) determine the minimum existing wall thickness, (3)

recalculate the MAWP of the vessel using these values, and (4) performing a new hydrotest.

This will usually reduce the vessel’s MAWP, sometimes to 60% of the original stamped

MAWP.

Case in Point: A company acquired a horizontal pressure vessel that was originallyrated for 500 psig. No code papers were available with the vessel. The ASME Board

could not locate code papers, and the manufacturer had gone out of business.

The company’s API-510 inspector determined the vessel’s minimum wall thickness,

added a 1/16” corrosion allowance and determined a new MAWP of 280 psig. Since

the vessel only required 250 psig in its new application, this was acceptable.

Pressure vessel manufacturers often stamp material information directly on the vessel’s heads

and shell segments. This can be either the allowable stress level (e.g., “X70000”, or 70,000

psi stress level) or the material designation itself (e.g., “SA-515”). This information can be

used to recalculate the vessel’s MAWP.

In addition, some larger vessels, especially pressure storage vessels, may have duplicate

nameplate information stamped directly on a manway nozzle.

In some cases, an inspection company can use special analyzers to determine the chemical

composition of the base metal. Although this equipment cannot always positively identify the

grade of steel (and its corresponding stress rating), it may be able to determine a higher

allowable stress level than the minimum assumption.

An undocumented pressure vessel sometimes can be completely re-rated by an ASME-

qualified shop, even if the procedures above are unsuccessful. This can involve determining

the remaining wall thickness, cutting out coupons from the vessel’s shell head for

metallurgical analysis and material verification, recalculating the vessel stress design, and

performing a new pressure test. If all these are unsuccessful, the plant designer should use

company standards, government pressure vessel regulations, good engineering practice and

PSM requirements in determining the suitability of the item for pressure service. In most

cases, a pressure vessel that cannot be re-rated should not be used in pressure service.



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September 200222

There are a number of other points and concerns with pressure vessels and filters which need

to be kept in mind when working with used plants and equipment. These include:

• One important point for selecting a used vessel is the existence of a manway or other

access into the vessel. This will allow visual inspection of the vessel interior. It will also

facilitate any internal modifications of the vessel, such as adding an inlet baffle, vortex

breaker or repairing/replacing a mist eliminator.• Pay particular attention to inspecting vessels at areas of high wear and/or corrosion. These

areas include near and opposite the inlet and outlet nozzles, along the bottom of the vessel,

around the vessel’s normal liquid level, the inside of the bottom head, and any other area

where fluid velocities could be high.

• Confirm that the inlet and outlet nozzles are the proper size. In most circumstances, these

can be modified in a shop for a reasonable cost. In some circumstances, especially in

larger and/or thick walled vessels, changing nozzles may make the modified unit more

expensive than a new unit. However, the schedule time reduction may be a more

important factor than the relative cost.

• Don’t get caught up with reapplying small, low pressure carbon steel vessels or filters.

When a company is assembling a plant out of used equipment, it is usually quicker andmore cost effective to replace these smaller items with new items.

• Reused vessels are normally placed in the same process service as originally designed.

Creative plant designers are able to see beyond the original design and are able to change

the vessel’s configuration. For example, vertical vessels may be placed in horizontal

service, while horizontal vessels may be modified with the addition of a skirt for vertical

service.

Case in Point: A company had an immediate need for a 48” diameter, 1200 psi

scrubber to eliminate some operating problems. New equipment had a twelve week

delivery which was deemed too long. No used scrubbers could be found.

One broker, though, had a 48” diameter molecular sieve tower. This tower was

modified by adding connections for a level bridle and an internal mesh pad, and was

delivered in less than three weeks. Total cost was about 80% of a new unit.

Case in Point: A company needed a high pressure horizontal vessel to handle liquid

slugs from a pipeline. No such vessel was available. However, they located a large

diameter surplus absorber tower that was the right size. They acquired the vessel and

moved it to a shop that modified some nozzles, cut off the vessel skirt and added saddle

supports. The vessel was installed at a fraction of the time and cost of a new vessel.

• Make sure that the metallurgy of the vessel is appropriate for the new service. For

example, some vessels use high strength steels to minimize wall thickness; these steels

may not be suitable for use in a hydrogen sulfide environment or in an amine system. As

another example, a vessel in low temperature service, -20°F design temperature, may or

may not be able to be re-rated for use in a propane refrigeration system. Some of these

questions will need to be answered by experts on pressure vessel design and the ASME

Code.



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September 200223

• Be aware that some separators may have proprietary internals designed to improve the

efficiency of the separation. These internals may or may not be suitable for the new

application, and may no longer be available.

Case in Point: A company relocated an older 48” diameter vertical scrubber from

one plant to another. Although the calculated required diameter of the scrubber wasless than 42”, the scrubber suffered from excessive carry-over. The vessel was taken

out of service and opened for inspection. It was found that the scrubber had various

plates annulus rings and downcomer pipes as internals. The arrangement of these

internals was such that the scrubber had an effective area less than that of a 36”

diameter scrubber.

• Filters should be fitted with new elements or media and, where used, o-rings for the

closures. The closures should be inspected for cracks, especially the closure style with

“hammer tabs”.

Case in Point: A company installed two horizontal liquids filters as part of a new stabilizer system. The filters were installed on a new skid with other equipment to

reduce field installation time. After the skid was installed, the start-up crew tried to

open the screw-on filter closures to install new elements. One enclosure opened

readily, but the other would not open. The “hammer tabs” on the filter head were

bent, cracked and broken, hampering the efforts to open the closure. Eventually, the

closure had to be replaced in the field by a certified ASME shop. This required cutting

the closure off, acquiring and rewelding the new closure, and radiograph and pressure

testing. A complete inspection would have discovered this problem before the skid was

shipped, and the work could have been done in the shop.

4. Towers

Although it may be obvious to most engineers, towers are a marriage of a pressure vessel and

internals usually designed to provide contact between two dissimilar fluids. The comments

above apply to the pressure vessel portion of the tower. The tower internals are a different

matter altogether.

Towers are either packed or trayed. Packing can be random or structured; since structured

packing is relatively new, there are many more random packed towers on the used equipment

market than towers with structured packing.

The plant designer should consider the following when reapplying a tower:

• The easiest, and probably most common, modification to make a tower perform well

with the new process conditions is to replace its packing or trays. Packed towers may

also need a change in their liquid distributors and/or redistributors if the liquid flows or

properties vary much from the original design. Tray replacements should try to match

the existing tray and downcomer supports to eliminate extensive (and expensive)

rewelding.



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September 200224

• Trayed towers can often be modified to increase capacity. A common conversion is to

replace the trays with random or structured packing. This may require removing most

of the existing tray and downcomer supports.

• Remove the random packing from packed towers and replace if necessary. Clean the

towers after the packing is removed. Packing can be replaced at a shop or at the job

site.• Trayed towers should be completely inspected. This usually means going through the

tower and inspecting each tray. Common problems include missing valves,

downcomer blockages, tray and downcomer leaks, non-level trays and damaged tray

decks.

• Small trayed towers, 12”-16” diameter, with welded trays and no manways may not be

suitable for reuse. The internals of these towers cannot be inspected without cutting

the tower apart, which will require a repair by an ASME Code shop. Like small thin-

walled pressure vessels, it may more cost effective to replace these instead of trying to

reuse them.

• Towers with sieve trays require special engineering attention when reapplying them. It

may be more cost effective to replace all sieve trays with modern valve trays.

5. Heat Exchangers

Virtually all gas processing plants have at least one heat exchanger. Most exchangers are shell

& tube exchangers or air cooled exchangers. Many newer skid-mounted amine units have

plate and frame exchangers. Cryogenic plants often have plate-fin exchangers. Since these

units are also pressure vessels, the comments above on pressure vessels also apply to heat

exchangers.

a. Shell & Tube Exchangers

Shell & tube exchangers are the most widely available exchangers on the used equipment

market. These can be reapplied in new services if a few precautions are taken. The plant

designer should consider the following comments and suggestions:

• Shell & tube exchangers can be readily re-rated if the internal geometries are

known. These include tube diameter, wall thickness and pitch as well as internal

baffle type, spacing and per cent cut. If these are not available, some reasonable

assumptions may provide a “close enough” exchanger re-rating.

• Consider using an experienced consulting service for re-rating the exchangers.

While several computer programs are available for this work, experience is often

needed to interpret the results properly, especially concerning tube side vibration.

• In certain circumstances, the tube velocities in exchangers are critical to good plant

performance. Some typical examples of these are gas exchangers with glycolinjection, amine exchangers in rich amine service and water coolers. Any

reapplication of shell & tube exchangers should pay particular attention to the tube

velocities.

• If pressure and temperature design conditions are similar for both sides of the

exchanger, a re-rating should consider switching the hot side fluid to the cold side

and visa versa. In some circumstances, this may improve the performance of the

exchanger.



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September 200225

• Fixed tube bundles can complicate exchanger refurbishing. The shell side of such

exchangers can often be cleaned chemically such as with a hot caustic wash. The

tube side of the exchangers should be cleaned (hydrolanced or hydroblasted) where

possible.

• Pressure testing of the exchanger should be done one side at a time after the

exchanger is cleaned. If the channel side of the exchanger can be removed, theexchanger can be easily checked for tube leaks during a hydrotest. The pressured

water on the shell side will flow out of any leaking tubes and can be seen on the

tubesheet.

Case in Point: A company relocated a BEM-type shell & tube exchanger from

one plant to another. The exchanger had only been shut down for 18 months

before it was relocated, and it had full Mechanical Integrity information from

the PSM program. The engineer at the new site decided to pressure test the

exchanger to check for tube leaks, even though there had been no evidence of

leaks while the plant was operating. As soon as pressure was applied, water

gushed from the exchanger’s head connection. Both head gaskets had failed.The gaskets were replaced and the exchanger passed the next test successfully.

b. Air cooled Exchangers

Air cooled exchangers are usually also Code-rated pressure vessels, and the comments

above on pressure vessels also apply to them. The plant designer should consider the

following comments and suggestions:

• Air coolers should always be checked to make sure they are suitable for the

intended service. This requires either an accurate data sheet or detailed verification

of the cooler’s mechanical design. The fact that a cooler has enough tubes for the

service does not mean it is suitable for that service.

Case in Point: A company needed to replace a discharge gas cooler on a

small gas compressor. They found a spare cooler that was about the same size

as the cooler they were replacing, and prepared to install it. The plant

designer used the serial number, contacted the original manufacturer,

purchased the cooler’s original design data sheet and re-rated the cooler. It

turned out that the cooler had originally been in liquid hydrocarbon service

and had seven tube passes instead of the assumed single pass. The calculated

pressure drop exceeded 50 psig. The company found a different cooler.

• Tube plugs on the header boxes should be pulled and the tubes should be visuallyinspected. The tubes should be cleaned (hydrolanced or hydroblasted) and pressure

tested for leaks. Leaking tubes should be plugged.

Case in Point: A company rebuilt a high speed compressor package and

moved it to a new site as part of a major plant expansion. The plant was

started in the winter, and the compressor ran fine for several months. When

the weather warmed up, though, the air coolers on the compressor’s jacket

water and discharge gas began to overheat, reducing the capacity of the



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September 200226

compressor. The plant operator shut the compressor down, pulled several tube

plugs and visually inspected the tubes. The tubes had a significant dirt and

scale build-up. The coolers were then hydrolanced and returned to service

with no further problems.

• Tube fins should be cleaned and combed straight. “Flood” backwashing is oftenmore effective in cleaning the fins than high pressure washing.

• Fans should be checked and balanced. Fan gearboxes should be inspected and

rebuilt if necessary; as a minimum, the gearbox oil should be replaced. Fan

bearings and belts should be replaced. Fan motors should be inspected and

refurbishing according to the suggestions in the following sections.

c. Plate-fin Exchangers

Plate-fin exchangers are specialized exchangers normally found in cryogenic plants.

These exchangers have a reputation for plugging, especially in older plants with limited

inlet filtration.

The plant designer should consider the following points when reapplying plate-fin

exchangers:

• Most plate-fin exchangers are designed for full test pressure on one side with

ambient pressure on the other side(s). Consider pressure testing each side of the

plate-fin exchanger to its test pressure in this manner.

• Plate-fin exchangers should be pressure tested pneumatically and should not be

hydrotested, since it is difficult or impossible to get all the water out of the

exchanger. The remaining water could freeze when the plant is started and damage

or destroy the exchanger.

Case in Point: A company installed a cryogenic unit on a fast track, high

profile project. Everything seemed to go fine until the company did the final

pre-start leak test. The high pressure cryogenic section of the plant wouldn’t

hold pressure. A check on the plate-fin exchanger confirmed that it was

leaking from the high pressure inlet side to the lower pressure passes. Since

everything else was ready to go, the company had to scramble and get a new

exchanger, causing a major project delay.

• Be aware of the prior service location of plate-fin exchangers. The aluminum in

older exchangers can be damaged by mercury in the inlet gas, even if the exchanger

was operating on a gas stream that had no prior history of mercury contamination.Inspect the exchangers for such damages, and install mercury removal systems if

the exchangers are going into service in an area in which mercury has been

reported.

Case in Point: A company was having a cryogenic unit refurbished for service

in a new location. When the refurbishing company removed the exchanger, a

small amount of mercury fell onto the ground, requiring remediation of the



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September 200227

ground. The company hired a metallurgist to inspect the exchanger, and no

damage was found.

In spite of this, the company was still concerned about the potential for

cracking. The plant designer decided to hydrotest the exchanger at 150% of its

design pressure (instead of a pneumatic test at 110% of its design pressure) tomake sure the exchanger had no hidden cracks. Since water is very difficult to

remove from a plate-fin exchanger after a field hydrotest, methanol was used

as the test fluid.

Overall, the presence of mercury delayed the completion of the refurbishing by

several weeks. This also increased project costs due to the remediation

charge, retesting cost, and disposal of the hazardous methanol that may have

been contaminated by mercury. However, these costs and delays were less

than the cost and delay that would have been experienced if the exchanger had

been replaced with a new unit.

• Plate-fin exchangers are very specialized devices that have historically been

difficult to re-rate. They usually had to be re-rated by engineers who are familiar

with them or by the exchanger manufacturers themselves. Recently, some process

simulation packages have plate-fin rating subroutines.

• Plate-fin exchangers can be cleaned to improve performance if they are not

completely plugged. If the piping to and from the exchanger has break-out spools,

cleaning solutions can be circulated to remove deposits. If the exchangers do not

have such spools, they should be added. Cleaning may not be able to restore the

original design performance, though, as some passages may be completely blocked

and protected from the cleaning solution.

If the contamination is dry and dusty, such as molecular sieve fines, the exchangers

may be able to be “blown” clean. This involves sealing the exchanger with a

manufactured or home-made rupture disk, pressuring the exchanger with gas or air

to about 5-10% of its design pressure and letting the rupture disk “blow”. The

resulting surge of gas will blow most of the free solids out of the exchanger.

Case in Point: A company installed a cryogenic plant that used plate-fin

exchangers. The plant was initially unable to meet design conditions. A

review of the plant indicated that the main plate-fin exchanger had a major

loss of thermal performance. The exchanger was taken out of service, and

deposits were scraped from the exchanger’s internal surfaces. These scrapings

were used to select an appropriate cleaning solution. The cleaning solution

was circulated for several hours. After the exchanger was placed back into

service, it exceeded its expected thermal performance.



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September 200228

d. Other Exchangers

The most common type of exchangers in this category are plate & frame exchangers and

pipe-pipe or hair-pin exchangers. These are usually relatively small, low cost exchangers.

Plate & frame exchangers are normally found in amine plants, while hair-pin exchangers

are found in many services.

Plate & frame exchangers are either welded or bolted exchangers, and are characterized by

having many narrow flow passages for the process fluids. The cleaning techniques and

limitations of welded plate & frame exchangers are similar to those of plate-fin

exchangers. Bolted plate & frame exchangers can be removed and cleaned easily; in fact,

they were originally designed to facilitate cleaning. In process plants, though, the work is

exacting and takes special skills, especially if plate gaskets need to be changed. It is

usually better either to contract with companies that specialize in this work, remove the

exchanger for off-site disassembly and cleaning, or to replace the plate and frame

exchanger with a new unit.

Hair pin and pipe-pipe exchangers should be refurbished in the same manner as other shell

& tube exchangers. These types of exchangers are normally relatively small exchangers

and as such are difficult to clean if the tube bundle is not removable. Hair pin exchangers

often have longitudinally finned tubes that are prone to plugging. If they cannot be

removed, it may be more cost effective to replace these with new units.

6. Fired Heaters

For purposes of this monograph, fired heaters fall into two classes: fire-tube heaters (such as

glycol of amine reboilers) and multi-tube heaters (such as lean oil still heaters or regeneration

gas heaters). Each has its own points that the plant designer should consider.

A common characteristic of fired heaters is the burner management system and fuel gas train.

Any hazards analysis undertaken on the heater as part of OSHA’s PSM regulations will

probably flag outdated burner controls as a fire/explosion hazard, recommending a system

upgrade. Even in areas not covered by PSM regulations, the plant designer should consider

improving the heater’s safety by updating them with pilot burners, remote ignition systems,

PLC controls and double block and vent systems on the pilot and min burner gas piping. The

associated cost of updated controls can increase costs significantly and may make the used

heater less cost effective than a new heater.

a. Fire tube heaters

• Pay particular attention to the condition of the fire tube. This is often much easier and

safer to replace or repair during refurbishing than it is after the heater is filled with the

fluid to be heated.

Case in Point : A company installed a used amine plant with a large 3-burner fire

tube reboiler. Although the shell was pressure tested successfully, amine solution

began to leak into one of the fire tubes after only a few months of service. The tube

was removed and inspected. The failure occurred under two tack-welded saddles



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September 200229

that were installed at the tubes’ midpoints to maintain the clearance distance

between the firetubes. The failure was apparently caused by crevice corrosion.

The saddles were redesigned and seal welded to eliminate the problem.

• Burners and/or stacks may need to be replaced if the heater is reinstalled at an altitude

significantly higher or lower than its initial design, due to increased or reduced draftavailable.

b. Multi-tube heaters

• Burners in used multi-tube heaters may be obsolete, low efficiency or of a high-NOx

design. The plant designer should consider replacing or modifying the burners.

• Burners and/or stacks may need to be replaced if the heater is reinstalled at an altitude

significantly higher or lower than its initial design, due to increased or reduced draft

available, similar to fire tube heaters.

• Multi-tube heaters can be placed in new services with a careful engineering and re-

rating. Some heaters may not be suitable for changing to the new service due to

metallurgical or thermal constraints.• Changing services can often change the thermal duty of the heater. For example, a

lean oil still reboiler with a flux rate of 10,000-12,000 BTU/hr-°F, operating at 400-

450°F, will have a higher flux rate than can be safely used if the heater is converted for

use as an amine reboiler. Since amine reboilers operate at 240-250°F and should not

exceed flux rates of about 5,000–6,000 BTU/hr-°F, the heater would need to be derated

about 50% for amine service.

• Consider using a bore scope to inspect the tubes’ internal condition. If the tubes

require cleaning, use a high rate chemical wash and re-inspect the tubes after the

cleaning is completed. A tube or tube pass that cannot be inspected cannot be assumed

to be “clean” just because the heater has been chemically washed.

• Consider conducting a metallurgical survey on the heater tubes to determine their creep

and remaining tube life.

7. Pumps

a. Centrifugal Pumps

Centrifugal pumps are normally easy to reapply in a process plant. They are designed to

be repairable, and are common enough that repair shops and parts frequently are readily

available.

Because of this, pumps are often changed in an operating plant to meet new operating

conditions. Therefore, the original specification sheets may not reflect the current pumpdesign. Pump impellers can easily be replaced or trimmed, providing different head and

flow characteristics than the original design. Pump motors may have been changed; in

cases where the original motor has special design elements (such as bearing capacities or

alignment requirements), a new standard motor may not be the correct installation.

Centrifugal pump horsepower depends on the specific gravity of the fluid pumped. For

example, a pump in light hydrocarbon service with a 20 HP motor will probably need a 40



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September 200230

HP motor if it is moved to amine service. The plant designer needs to check the

horsepower requirements along the entire pump curve, from shutoff to full runout.

Although a properly functioning PSM Management of Change (MOC) program would

update rating sheets for any significant change from the original design (as part of the

Process Safety Information, PSI), records are not always updated or available. Thechanges may have predated the PSM regulation; the file may not have been updated; the

update may have remained with the MOC and not been noted in the PSI; or the plant may

have come from a reseller’s inventory without the original PSM documentation. Of

course, if the plant originated outside the United States, PSM information will probably

not have been generated in the first place.

The plant designer should consider the following items when refurbishing centrifugal

pumps:

• Pumps should be completely disassembled and inspected.

• Wear rings should be inspected and replaced if necessary.

• Seals should be replaced and updated if necessary.• Bearings should also be replaced, and any part that does not meet specifications

should be modified or replaced.

• Couplings should be checked for wear and alignment tolerances.

• Oiled pumps should have their oil reservoirs cleaned and the oiling equipment

should be inspected.

Case in Point A company had two demethanizer bottoms pumps that fed a

reciprocating pipeline pump. These pumps were high head, single stage horizontal

pumps fitted with single seals. The pump seals were a frequent source of VOC

emissions, and were tagged as a high VOC point during almost every VOC inspection.

The company looked into replacing the seals with tandem seals and seal pots. Since

these were older pumps, the cost to upgrade them was higher than the replacement

cost of the pumps. The company decided to replace the pumps with new inline vertical

pumps with cartridge-type tandem seals and seal pots.

Vertical turbine pumps, also called can pumps, are multistage pumps that require special

design review for the new application. These pumps rely on a balanced pressure force to

prevent excessive bearing loads. They also frequently require very tight alignment

tolerance.

Case in Point: A company installed two vertical turbine can pumps for pumping a

cryogenic plant’s product into a pipeline. Although the normal pipeline was about

800 psig, the MAWP of the pipeline was over 1200 psig. Per standard design

specifications, the pumps were designed to be able to meet the higher MAWP.

When the first pump was started with an 800 psig discharge, it ran for only a few

minutes before the motor’s bearings failed. The second pump lasted longer, but less

than an hour.



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September 200231

The engineers contacted the factory and discovered that operating the pumps at the

lower pressure upset the thrust balance of the pumps and overloaded the motors’

thrust bearings. The two solutions were to destage the pumps (remove several of the

pump bowls) or place a back pressure valve on the pumps so they would see a constant

1400 psig discharge pressure. Since the latter solution would cost a significant increase in electrical usage, and since the pipeline had never seen the higher

pressures, the pumps were destaged.

b. Reciprocating Pumps

Reciprocating pumps used in natural gas processing plants are usually plunger type pumps.

They are commonly used in amine plants, glycol dehydration units and as NGL liquids

pipeline pumps. As with centrifugal pumps, these should be completely rebuilt by a

competent shop.

The plant designer should consider the following items when refurbishing reciprocating

pumps:• Packing, bearings and all gaskets should be replaced.

• Plungers, crankshafts, valves, valve seats and rods should be inspected and

replaced as required.

• Bearings should also be replaced, and any part that does not meet specifications

should be modified or replaced.

• Rod bores should be inspected and checked for ovality.

• Pump performance can be adjusted by changing the pump speed and/or the plunger

diameter. Most reciprocating pumps have a wide range of plungers available.

Some older pumps, though, may have a limited range of the most common plunger

diameters still available. Remember that the maximum discharge pressure

capability of the pump will usually be reduced as the plunger size is increased and

visa versa. In hydrocarbon service, most plant designers try to limit the pump

speed to about 80% of the maximum allowable speed.

• Oiled pumps should have their oil reservoirs cleaned and the oiling equipment

should be inspected.

Although reciprocating pumps have been used for decades, many advances have recently

been made in their design. This is especially true concerning sealing systems. These

improvements may not be available in older pumps.

Case in Point A company modified a processing plant and needed new pipeline pumps to handle the increased liquids production. They selected three older

surplus plunger pumps for this service and had them completely rebuilt. Once they

were installed and started up, one of the pumps had a leak around the screwed

valve cap. No amount of tightening gaskets would seal the leak. Replacing the

gaskets with various elastomeric and crushable metallic gaskets was also

unsuccessful. Eventually the pump rebuilder was called back in to examine the

problem. He determined that the sealing surface was no longer perpendicular to



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September 200232

the axis of the screw threads. The pump head was removed, resurfaced, and

reinstalled. The leak was eliminated.

It was later noted that the latest model of the same pump used a bolt-on valve cap,

which reduces the chances of a leak. Replacing the old style pump head with the

new style would have both prevented the start-up problems and eliminated future problems.

8. Compressors

a. Reciprocating Compressors

Reciprocating compressors are probably reused in new services more often than any other

equipment type in the gas processing industry. Many new plants have been built which

have remanufactured compressors and/or gas engine drivers as the only used equipment.

The plant designer should consider the following points when reapplying reciprocating

compressors:

• Old out-moded integral compressors are often hard to reapply in a new service.Parts for these compressors are often hard or impossible to find. Emissions from

integral compressors may be more than allowed for the plant. Fuel efficiencies of

older gas engine drivers are significantly lower than modern units.

• Compressor cylinders can usually be replaced to fit process requirements.

• Some lean-burn engine drivers will require extensive modifications to meet

modern emission requirements.

• Suction scrubbers on packaged compressors should be checked carefully for proper

sizing in the new service.

Case in Point: A propane refrigeration plant was built with a high-speed

reciprocating compressor to provide the refrigerant compression. The 4-throw

compressor had originally been in field service, and had been modified into a

two stage unit with three low pressure cylinders and one high pressure

cylinder. The original skid had two inlet scrubbers on the compressor skid

(one for each bank of cylinders), and the compressor rebuilder kept that

arrangement. The plant and compressor was said to have operated without

significant or unusual problems for over 10 years.

During the plant move, the compressor was rebuilt. The scrubbers were

inspected internally, and the scrubber that fed two cylinders had a damaged

mist pad. Since the scrubber did not have a manway to access the pad , thecompany decided to replace it instead. The engineer decided to see if they

could use a smaller scrubber to save cost, but was surprised to discover that

the diameter of the existing scrubber was almost 12” too small for the service.

A check with the maintenance records showed that the two cylinders had been

losing compressor valves several times more often than the other low pressure

cylinder, confirming the size error. The scrubber was replaced with a larger,

off-skid vessel. Valve maintenance costs for the compressor were nearly

eliminated.



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September 200233

• New compressor pulsation bottles are usually designed and stamped as ASME

Code vessels. Older compressors often do not have the pulsation bottles Code

stamped. This may or may not be a problem, depending on the companies

standards, PSM program, insurance requirements, etc.

b. Centrifugal Compressors

Centrifugal compressors are high speed machinery that is normally refurbished by shops

specializing in their refurbishing. These shops have the experienced personnel and

machine tools required to refurbish centrifugal compressors correctly, especially if

compressor modifications are required.

Some centrifugal compressors are packaged with their lubrication systems, while others

have stand-alone lubrication systems. It is often more cost effective to have the compressor

refurbisher do the work on systems packaged with the compressors. Stand-alone

lubrication systems may be refurbished separately following the same guidelines used for

similar equipment and piping. However, special care should be taken to make sure all theold lubricating oil and deposits have been removed from the old piping and equipment.

Consider chemical cleaning and pickling of the piping as part of the refurbishment.

Depending on the system, it may be more cost effective to replace the piping with new

carbon steel or stainless steel piping.

Some considerations when refurbishing centrifugal compressors:

• Centrifugal compressors are usually custom designed for a particular application.

Unlike reciprocating compressors, they are heavily affected by the operating

conditions, including inlet and outlet temperatures and pressures and molecular

weight of the gas. It is rare that a centrifugal compressor can be moved from one

application to another without having major rework on the compressor wheel

design.

• Good rotor dynamics are an absolute necessity for a successful installation.

Consider having the refurbishing company prepare a complete review of the rotor

dynamics and perform a spin test on the rotor assembly to prevent future problems.

Case in Point: A company wanted to move a centrifugal compressor from one

plant to a similar application in another plant. They contacted the original

manufacturer, who re-rated the compressor’s performance. The manufacturer

said that the existing rotor assembly’s performance was marginal, so they

recommended installing a new rotor assembly designed for the new conditions.They would not warrantee the original rotor assembly but would warranty a

new assembly.

The company decided to use the original rotor assembly, reducing delivery by

about a month and eliminating a significant cost. The manufacturer was

directed to replace the bearings and perform a visual check of the rotor

assembly only.



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September 200234

The compressor performed well when it was first started up. As time went on,

though, the compressor began to see an increase in vibration. An investigation

showed that the old assembly was hitting a critical speed during start-up and

shut down, which was progressively damaging the compressor. Eventually, the

company was forced to shut the unit down, remove it, send it to the

manufacturer and have a new rotor assembly installed. Total downtime wasabout 2 months, and total costs were almost three times the original savings,

not including the lost production.

If the company had performed a spin test of the original rotor assembly, they

may have discovered the critical speed problem. If they had purchased a new

rotor assembly, they also would have had a unit with better performance and a

warranty.

• In any reapplication, ensure the driver, gear train and coupling have sufficient

horsepower and capacities for the new application.

• Check compressor nozzle sizing. Changes in operating conditions may requirenozzle changes as well as rotor assembly changes.

• Ensure that the compressor’s scrubbers and gas coolers will be able to handle any

increase in temperature or flow rate for the new process application.

• If the compressor has a spare rotor assembly, the time required for refurbishing

may be shortened by sending the spare assembly to the shop for

rework/replacement before the whole compressor can be removed.

• Consider upgrading a centrifugal compressor’s surge control system as part of

refurbishing, especially if the system is more than 10 years old. This system is

critical to the best operation of the compressor, and modern systems are

significantly more advanced than older systems.

• Refurbishing should include replacing the compressor bearings and visually

inspecting the rotor assembly as a minimum.

Gas turbines should also be refurbished by a specialty shop. In many cases, the individual

units may be exchanged for newer units. This can be beneficial, in that newer units may

have better metallurgy and/or have better emission factors. Several turbine shops offer

temporary leases of turbine drivers for use while the original driver is being rebuilt.

A few points to consider when refurbishing gas turbines:

• Certain states require companies to get new or updated permits whenever they

change to a driver with a different serial number from that on the permit. Thiscould limit the flexibility of engine exchanges.

• Consider upgrading control systems when refurbishing a turbine. Older control

systems may no longer have spare parts available.

c. Expanders

Expanders and expander compressors are high speed centrifugal machinery and should

also be refurbished by a specialty shop. Most of the suggestions for centrifugal



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September 200235

compressors also apply to expanders and expander compressors. These units are even

more sensitive to changes in process conditions, and will need new expander and

compressor wheels for almost every new application. The units may also require new inlet

valves as well.

The plant designer should also consider the following:• Consider upgrading a relay-based shut down panel to a PLC-based shutdown

system.

• Consider upgrading the thrust control system to a more current system.

• Expander compressors are subject to surge problems and require some sort of surge

control, normally a minimum flow control system. This design should be reviewed

for the new application to make sure it will provide the necessary performance to

protect the machine.

• Lubrication systems on early expander units were simplistic and did not always

provide good protection for the machine. These systems have evolved significantly

over the years, in the system and equipment design. Consider modernizing the

lubrication system to more recent standards.

9. Equipment Drivers

a. Gas Engine Drivers

Gas engine drivers, like centrifugal pumps and high speed reciprocating compressors, are

easy to reapply in a process plant. They are designed to be repairable, and are common

enough that repair shops and parts frequently are readily available. There is an

experienced, active industry in rebuilding and reapplying gas engine drivers, and experts in

that area should be consulted for rebuilding requirements.

The main difficulty in reapplying a gas engine is meeting emission requirements for the

new project. This can dictate whether or not a lean burn engine can be reused in a plant, or

whether a rich burn engine with a retrofitted catalytic reactor will be allowed by emission

regulations.

Like much used equipment, gas engine drivers available for reapplications may not meet

the company’s standards. Control panels may need to be upgraded. Starters may need to

be changed from vane type to turbine type. Cylinder heads may need to be upgraded to a

more reliable and/or lower emission design. Again, the experts should be consulted in

making these decisions.

Even with all the experts available, rebuilding a gas engine driver may have unexpecteddifficulties. The prior operating history has a large effect on the cost and success of an

engine rebuild.

Case in Point: A company purchased a cryogenic plant with several identical

compressors driven by gas engine drivers. The plant had been running at low rates

for several years, and had been losing money during this time. The engines and

compressors were sent to a shop for refurbishing.



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September 200236

When the engines’ cylinder heads were removed, the rebuilders discovered that the

cooling passages in heads were almost completely closed with rust and scale. The

scale was difficult to remove, and all cleaning methods failed on about half the heads.

These heads were replaced, but the engines were older models that required custom

adapters for associated parts. This caused an unexpected increase in the cost and

time required for the engine rebuilding.

It was later determined that the engines were cooled with a central cooling system. In

order to reduce operating costs, this system was not charged with a standard coolant

fluid, but used industrial water for the cooling system. This water had a high minerals

content, which contributed to the severe scaling in the cylinder heads.

b. Electric Motors

Electric motors are easy to reapply and refurbish due to their standardization. Exceptions

are specialty motors and motors with special mating faces that can be difficult to replace.

The plant designer should consider the following suggestions and comments:• Minimum motor refurbishing should include inspection/replacement of the motor

bearings and “meggering’ of the motor windings to test the integrity of the

insulation. Motor windings can also be reinsulated at a relatively low cost.

• On TEFC motors, inspect the motor fan.

• When possible, run-test the motors.

• Motors that were originally installed at or near sea level may need to be derated for

higher altitudes. This is because the lower air density at higher altitudes reduces

the amount of heat that can be removed from the motor. A heavily loaded motor at

sea level could burn out when operated in the same service at 6000’ elevation.

• When possible, replace “U” frame motors and odd voltage motors with modern

motors. The electrical efficiency costs can often pay for the replacement in a short

period of time.

• Smaller electric motors (50 HP and lower) can often be replaced for about the same

cost as refurbishing.

10. Instruments

a. Control scheme

The overall control scheme of a process plant should be reviewed to make sure it fits the

new condition. The new installation may require a revision in the overall control scheme

or in the controls required for a single piece of equipment.

This is especially true for the pressure and flow control systems of cryogenic plants.

Differences in compression design, pipeline requirements, flow requirements, etc., will all

have an effect on the control system. For example, a plant may have been designed to

control demethanizer pressure by adjusting the expander, while the new installation may

need to use the expander for inlet flow control.



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September 200237

b. Controllers/transmitters

Controllers and transmitters in used gas plants may be readily reused or may need to be

replaced. Many older gas plants that are candidates for reuse have pneumatic

instrumentation, either local pneumatic controllers or pneumatic transmitters with board-

mounted pneumatic controllers. Recent gas plants have been designed almost exclusivelywith electronic instrumentation and computer control systems.

A plant with pneumatic controls can easily be upgraded to electronic controls by adding

electronic transmitters and I/P relays for the control valves. Level controllers may be more

problematic since a differential pressure transmitter is normally used in this service, and

may not be suited for the vessel’s process fluid.

Electronic controllers and transmitters need to be reviewed to make sure they are

compatible with the selected control system, especially if a computer-based control system

with smart-type transmitters or network-type control wiring is being planned for the new

installation.

All controllers and transmitters should be inspected and refurbished, preferably in a shop

environment. The controllers should be calibrated and checked for proper operation and

application before being placed in operation.

Case in Point: A company moved a scrubber and its controls from an inlet service to

a hydrocarbon separation service in the middle of the new process. After start-up, the

level controller did not react to the increasing level, even though it had been properly

checked and calibrated. After much investigation, the float was removed and checked.

Although the float was in good condition, it was designed for a liquid with a specific

gravity of 1.0 and did not work properly on the 0.5 specific gravity hydrocarbonliquid.

c. Control Valves

Control valves in a used plant are usually able to handle the new process conditions as

long as the process does not vary greatly form the original design. Many larger control

valves have changeable trims that can change their flow capacities to meet new process

conditions.

The plant designer should consider the following suggestions and comments concerning

control valves:

• Nameplates on control valves that have changeable trim are not reliable in defining

the current trim in the valve. The nameplates are often not updated when a trim is

changed. Notes on trim changes may also have not been updated as part of the

plant’s PSM program.

• Minimum refurbishing of control valves should include a complete disassembly

and inspection of the valve, preferably in a shop environment. All gaskets and

elastomers should be replaced, and the valve seat should be reworked or replaced.

Unless it is in exceptional condition, the valve trim should also be replaced.



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September 200238

• Control valves should be manually stroked to prove their operability. Don’t rely on

the movement of the valve stem; if possible, observe the plug movement itself (this

requires removing the valve from the piping).

Case in Point: After a company started a used amine plant, they were unable

to get the design flow. After spending several days trouble shooting thecentrifugal charge pumps, they investigated the control valve. This valve

appeared to be fine, since it stroked properly and was correctly sized for the

service. After several more days, they took the control valve apart. This valve

was a dual plug valve, and the bottom plug had broken off the valve stem and

frozen to the seat. Replacing the valve stem and plugs fixed the problem.

The rebuilt valve should be stroked “on the bench” for proper operation; where

possible, the valve should also be stroked with normal process pressures.

Case in Point: A company built a processing plant using a combination of

new and refurbished equipment. During the plant start-up, one of the inlet ESD valves would not open. Since it was a winter start-up in a cold climate,

the operators assumed that ice had frozen the valve shut. When the valve still

failed to open after repeated injections of methanol, the instrument technician

climbed up into the pipe rack where the valve was located. He checked the

valve actuator, which was filled with rust and had a punctured diaphragm.

The actuator had not be refurbished. A simple bench test of the valve would

have saved a 12 hour delay in starting the plant.

Case in Point: A company built a plant using refurbished automatic switching

valves. The plant’s shut down & control system was designed in such a

manner that it required limit switches on these automatic block valves. During start-up, the proximity limit switches operated sporadically, causing several

unanticipated shutdowns. Technicians adjusted the limit switches, but the

problems continued. A technician finally measured the play in the stem under

pressure, and discovered that the valve stem play under pressure exceeded that

allowed by the proximity switch. The switch was changed to a lever-type

switch and the problem was eliminated.

It may be appropriate to disconnect or remove skid mounted valves on skid-

mounted equipment or piping that is to be pressure tested.

Case in Point: A company moved an amine unit from one location to another.

The regeneration skid was thoroughly cleaned and hydrostatically tested.

Upon start-up, the charcoal filter level control valve opened and closed, but

was unable to control the vessel level properly. Upon removal of the ball-style

valve, the shaft connecting the body to the actuator/indicator was found

snapped in two. It was theorized that the installed valve attempted to actuate

under the residual test pressure, exceeding the design torque on the shaft.






September 200239

• Several companies provide exchange services for control valves. These companies

can also provide rebuilt or remanufactured control valves to replace the existing

valves.

• Control valves in older plants may be obsolete and replacement parts may no

longer be available.

• Consider the service of the control valve itself. In some severe services, the valve body may be eroded and/or corroded enough to reduce its pressure rating. Also, a

given body may be ill-suited for the proposed new service.

Case in Point: A company started a new amine plant that was deigned using

industry standard procedures. After less than a year operation, the amine level

control valves from the amine contactor eroded through the valve body and

caused an amine leak. The valve was replaced with a stainless steel valve that

eliminated the failures.

Although the case above was not in a used plant, it illustrates a need to inspect the

control valve body when inspecting the control trim.

d. Relief Valves

New process conditions for the used plant will require recalculating the required relief

valve capacities. This has always been good engineering practice and is now required by

PSM. Do not assume that existing relief valves will be adequate even when the new

conditions are the same as or close to the original conditions. The original installation

may not have been correctly designed.

Case in Point: A company was redesigning a standard cryogenic unit that had been

designed and built in the late ‘70’s. The demethanizer was protected by a carbon steel

relief valve located downstream of the residue gas/gas exchanger. The valve was

correctly sized to protect the demethanizer from the maximum relieving requirements;

in fact, it was about 15% oversize (a common occurrence with relief valves using

standard orifice sizes).

But when the designer checked the pressure drop on the inlet of the relief valve, he

found that the pressure drop through the exchanger exceeded 10% of the valve’s set

pressure. This exceeded the allowable pressure drop as per API RP-520 (3% of set

pressure). The valve had to be moved to a point between the demethanizer and the

exchanger, which then required a stainless steel relief valve to meet the new operating

temperature.

The plant designer should consider the following suggestions and comments concerning

relief valves:

• All used relief valves should be tested for proper operation prior to placing them in

service. Plants subject to OSHA’s PSM regulations should review their

documentation requirements and make sure the testing documentation meets these

requirements. Information on the new relief valve design and design basis



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September 200240

(specification sheets) will be needed for the Process Safety Information portion of

PSM.

• Several companies provide exchange services for relief valves. These companies

can also provide rebuilt or remanufactured relief valves to replace the existing

valves.

• Some gas processing plants, especially those that were originally “low budget” plants, often have relief valves that cannot be rebuilt economically. The cost of the

rebuild and testing often exceeds the cost of a new valve. These valves should be

replaced or upgraded.

• Some valves may be so outdated that replacement parts are no longer available.

These valves should be replaced.

• In some cases, a revised process or more thorough review of relieving scenarios

will require a relief valve that is larger than the existing equipment connection. In

this case, a supplemental or replacement relief valve can be added to the equipment

inlet or outlet piping. All new relief valves should be installed in accordance with

API RP-520 and RP-521, “Recommended Practice for the Design and Installation

of Pressure-Relieving Systems in Refineries: Part 1 – Design” and “Part 2 – Installation”.

e. Gauges

Pressure and temperature gauges may be reused if they are calibrated, but the cost of

calibration may exceed the replacement cost of the gauges. Level gauges can normally be

reused after they are refurbished.

• Consider removing pressure gauges from a skid and shipping them separately to

protect against vibration failure.

• Consider replacing pressure gauges in pulsating services with liquid filled gauges.

• Protect pressure and temperature gauges that are shipped on a skid from roaddebris by taping them up with a cardboard cover.

• Level gauges should have their packing replaced and the gauge glass should be

cleaned.

• Refurbished level gauges should be pressure tested for leaks.

• Old level gauge valve cocks are often difficult or impossible to operate; consider

replacing the cocks.

f. Tubing

On process skids, instrument tubing usually does not need to be replaced. Off skid tubing

is rarely worth the effort to reuse at the new plant.

Most tubing in gas plants is stainless steel with either plated carbon steel or stainless steel

fittings. When on a skid, tubing runs from these materials should be reusable. However,

if the plated carbon steel fittings have rusted, they should be replaced. This could require

replacement of the ends of each run, if not the whole run itself.



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September 200241

A few older plants were built with bare copper tubing, PVC-coated copper tubing or

carbon steel tubing. The plant designer should consider replacing these runs with stainless

steel tubing.

Tubing should be inspected and blown clear to make sure no foreign material such as dirt

or insect debris has blocked it. When possible, each run should be pressure tested toensure its integrity. Since this is often not possible before the project is completed, the

plant designer should be prepared to replace a significant number of tubing runs during

this testing.

11. Electrical

a. Equipment

Electrical equipment, such as breakers, motor starters, transformers, etc., can often be

reused with little or no refurbishing. The biggest problem facing the plant designer can

often be integrating this equipment into an existing electrical system.

Case in Point: A company was designing the installation of a process skid into anexisting plant. The skid had several motors with explosion proof starters mounted on

the skid itself, which was to be installed several hundred feet from the existing MCC

building. These starters needed to be integrated with the shut-down control system

that was also located in the MCC building. After comparing the costs of a new

breaker, power wiring and control wiring against new equipment in the existing MCC

building, the company decided to replace the on-skid starters with new equipment that

matched their existing equipment. They were able to sell the old starters which

partially offset the cost of the new equipment.

The technology of electrical equipment has improved over the years, with items like

electronic breakers replacing fuses, etc. As with used process equipment, spare parts aresometimes difficult to obtain for the older equipment.

Electrical equipment should be opened and inspected for corrosion, dirt, debris and

insulation condition. If there are signs of rodent infestations, the plant designer should

take steps to ensure that none of the equipment’s insulation has been damaged by the

rodents, as they have been known to chew on electrical insulation.

Oil in older transformers should be tested to make sure no PCB’s are present. Transformer

oil should be inspected and changed if necessary.

b. Wiring/Conduit

On-skid wiring in a used plant can normally be reused successfully, especially if the wiring

is in a conduit, is terminated in a junction box with good labeling, and wiring drawings are

available. Off skid wiring is difficult if not impossible to reuse.

The main concern about wiring is the condition of the insulation, especially if it is in

conduit. Each run of wiring should be checked for continuity at each end and lack of

continuity between the conduit and the wiring.



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September 200242

On occasion, the company doing the plant dismantling will just chop off the conduit and

wiring at the skid edge. It saves time and money in the dismantling but often ruins the

conduit run.

Conduit can normally be reused if it is on a skid, even if the wiring requires replacement.The conduit should be inspected for damage and corrosion and repaired or replaced as

necessary.

12. Structural Steel

Structural steel in gas plants can normally be placed in two categories: process skid support

steel, and off-skid equipment and pipe supports. In many cases, any savings gained from

reusing the off-skid pipe supports is usually not worth the difficulties involved. Skid steel is

usually refurbished in a shop, while off skid pipe supports are often refurbished at the job site

as part of the construction work.

Pipe and equipment support steel should be thoroughly inspected for bent flanges, crackedwelds and external corrosion. The steel’s protective coating should also be examined and

repaired or renewed. Painted, free standing steel is relatively simple to sandblast and repaint.

Galvanized coatings on steel are more difficult but not impossible to repair.

Process skid structural steel is more difficult to refurbish. The most effective, and most costly,

method of refurbishing this steel is to disassemble the skid completely and treat the steel in the

same manner as free standing steel. The least effective method is to apply a new coat of paint

with minimal preparation.

The plant designer should decide what level of refurbishment is appropriate for the project and

communicate these expectations to the refurbishing shop before the work begins.

13. Insulation

One of the advantages of skidded plants is that they can be moved without damaging the

insulation that is already in place. Unfortunately, this insulation can be a hidden drawback.

The insulation makes it impossible to make a visual inspection of the entire piping run, and

makes it difficult to do thickness testing. The insulation can also provide a false sense of

thermal economy, since some insulating materials have a definite service life.

Case in Point: A company installed a skid-mounted cryogenic unit without checking or

replacing the insulation on the stainless piping. When the plant was first started, much of

the cold piping developed large ice accumulations on the insulation jackets. Although the

insulation had sufficient thickness for the new conditions, the insulation itself had failed

under the jacket. The company replaced the insulation and jacketing, eliminating the

problem.

Case in Point: A company purchased a used skid-mounted refrigeration plant and moved

it from the Gulf Coast area it to a new location. Although the plant was fully insulated,

the insulation on the chiller was damaged in transit. When the damaged insulation was






September 200243

being prepared for repair, the plant designer noticed that the surface of the chiller shell

was extremely pitted. The insulation was completely removed and the shell was inspected.

It turned out that the chiller had not been primed or painted before it was insulated. At

some point, the insulation’s vapor barrier had failed and moisture had condensed on the

shell’s surface. This had caused such severe rusting and pitting that the shell’s revised pressure rating was below the plant’s requirements. The chiller was replaced, and the

remaining insulation was removed and all other piping and equipment was inspected

without incident.

The plant designer should consider the following points when determining the scope of

refurbishment:

• Before completing the purchase of the plant, check that the plant contains no asbestos

insulation. If asbestos is present, consider all the costs and risks associated with taking

the responsibility to remove the insulation. The associated costs and risks may be so

expensive as to eliminate the candidate from further consideration.

• Confirm the proper insulation thickness for the new conditions. Process and ambienttemperatures that are colder or warmer than original design may require thicker

insulation.

• Remove the insulation jacketing and inspect the insulation. Replace damaged or

suspect insulation. Replace the moisture barrier and reapply or replace the jacketing.

• Install inspection plugs to provide access to the piping for long term piping thickness

checks (these will be required for OSHA PSM compliance).

• Insulation does not have an indefinite life span. Consider replacing cold insulation if it

is 10-20 years old, as expanded glass foam may have “powdered” and urethane foam

may have degenerated over the years.

14. Paint

In most used plants and equipment, the paint is usually in poor condition. Normally one

should expect to clean, sandblast and repaint all uninsulated surfaces. In damp climates, such

as the Gulf coast, consider removing all insulation and applying primer to the insulated

equipment and piping.

Some older plants may be painted with lead-bearing paint or primer. Before completing the

purchase of the plant, confirm that the plant contains no lead paint or primer. If lead paint or

primer is present, consider all the costs and risks associated with taking the responsibility to

remove the paint.

VI. Dismantling/Installing the Plant

A. Differences in Construction Techniques

1. Dismantling

The plant dismantling effort can require work techniques not normally used on a construction

site. Basically, the concept is to reverse the construction procedure, but there may be

circumstances that require new procedures. For example, the dismantled plant may be part of



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September 200244

an operating plant, and there may be newer piping and equipment that limit or block access to

the unit. In a plant that has been shut down, the unit being dismantled may be in the middle of

other idle equipment that cannot be moved.

Case in Point: A company decided to move a stabilizer system from an idle plant to a new

location. The system included an off-skid tower and skid mounted exchangers. Accesswas blocked by a compressor building on one end, a piperack on the other end and several

other process skids on the sides. The nearest spot for the cranes to set up was about 80’

from the stabilizer tower, and the nearest laydown area was 50’ away on the other side.

The company had to use oversized cranes that would be able to reach over the piping and

equipment to remove the system. After careful planning and coordination, the system was

successfully removed without damage to the surrounding items.

A special construction technique will be needed when an existing block mounted plant is

moved to a new site. The exact dimensions of the equipment foundations and vessel

installation can be critical to the fitting of the used piping, and the original system must be

measured and marked accurately to facilitate reassembly. This was discussed in detail in a prior section of this monograph.

One problem that can arise is the lack of information on an item. This could be information

on the item’s weight or center of gravity, making foundation design or crane lifting difficult.

It could also be the lack of manufacturer’s literature, including shipping, installation,

maintenance or calibration procedures.

The plant designer should consider the following points when dismantling plant and

equipment:

• Piping should be unbolted wherever possible and cold cut where necessary. Cutting

torches should only be used on piping where no other technique can be used, and onlyafter careful planning and attention to safety has been considered.

• Carbon steel studs and bolts can be reused, but often are not worth the time and effort

required to sort, store and ship them to the new site. However, it may be cost effective to

reuse high allow studs and bolts such as those made of low temperature carbon steel or

stainless steel.

• Electrical conduit and wiring should not be cut at skid edge. If the conduit does not

terminate at an on-skid junction box, enough wiring should be pulled from the off skid

conduit to facilitate reconnection in the field. The extra wiring should be coiled on-skid

and secured for shipping.

• If thermocouple wires will be reused, consider pulling thermocouple wires from the off-skid end point to the skid edge to eliminate cutting the wire.

• Off-skid control valve assemblies can often be dismantled and moved as a single unit.

• Gauges should be removed and packed for shipping or supported and protected from

potential shipping damage, including vibration and impacts from road debris.

• If a system had contained water before the unit was dismantled (such as a steam system or

a system that had been recently hydrotested) and is planned to be moved to an area that is



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September 200245

experiencing sub-freezing ambient temperatures, consider adding methanol to the system

to prevent freezing and damage.

Case in Point: A company had a stabilizer skid refurbished in a west Texas shop.

After refurbishing, the skid was hydrotested. The shop drained out the test water and

shipped the skid to the job site in the Rocky Mountain area. The skid was installed under winter conditions. Just prior to start-up, the skid’s reboiler failed a leak test.

The reboiler bundle was pulled and found to have broken tubes. The refurbishing

company had not drained the reboiler completely and the freezing in the reboiler shell

had bent and broken the tubes. The bundle was replaced, but the incident delayed

start-up.

• Review the risks and benefits of keeping insulation on the piping and equipment being

moved. Insulation “bands” can be stripped from towers and off-skid vessels to prevent

insulation damage by handling and by setting the equipment on trucks. Open insulation

ends should be protected from the weather, especially on calcium silicate insulation.

The plant designer should consider using a construction group and supervisory personnel who

are well experienced in plant disassembly. This is no place for rookie construction groups to

get “on the job” training. The plant designer should also consider having a company

representative on the job site that is familiar with the equipment and new project design to

help make decisions on the worth of removing certain equipment items prior to loading and

shipment to the new site.

Case in Point: A company was dismantling a cryogenic plant that had been shut down. A

company engineer was monitoring the dismantling effort. He noticed that there were

several high pressure vessels in a different section of the plant that the company had not

purchased from the plant owner. The engineer realized that some of these vessels would eliminate the need to purchase similar new vessels for the project and for other projects

that the company was developing. The plant owner was contacted, and the vessels were

included in the purchasing agreement for no extra cost to the company.

Care taken in the dismantling efforts can significantly reduce refurbishing and construction

costs. The plant designer should always take extra time and effort to do a good job up front.

2. Installation

For the most part, used plants and equipment can be installed in the same manner as new

plants and equipment. On occasion, some unusual piping configurations are required to fit

existing nozzles on vessels and heat exchangers that may not be located in a convenient

position.

In all cases, the plant designer needs to recognize that there may be unforeseen difficulties in

the construction activities.



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3. Safety/Environmental

Safety is one of the last items discussed in this monograph, but it should be the top priority of

the plant designer. This includes the dismanlting, refurbishing, construction and operation of

the reused plant and equipment. In marginal cases (those in which an item may or may not be

considered safe to reuse), the plant designer should ALWAYS err on the side of safety. No plant or piece of equipment is worth reusing if it risks personnel injury or environmental

damage.

The plant designer should consider the following points to ensure a safe project:

a. Dismantling

• Make sure the plant has been completely emptied of all hydrocarbons, treating

solutions, lubricating oils, etc. Any equipment that is shipped with foreign

material still resident will required permits, MSDS sheets, etc., that could cause

delays and/or extra costs.

• Even if the contract calls for the seller to remove all internal fluids from a plant or

equipment, the job may not have been completely successful. Be prepared tohandle leftover fluids during the dismantling operation.

• Do not take anybody’s word that equipment is safe to dismantle. Verify

everything. Don’t assume that a pressure gauge that is registering no pressure

actually means that there is no pressure in the system; the gauge may be plugged

up, blocked in or just plain broken. Check for liquids in vessels and piping before

opening the system.

• Always have fire fighting equipment available and manned during dismantling

operations, and at all welding or flame cutting sites.

• Isolate as many systems as possible before opening systems. Install skillet blinds

where prudent. Remember that liquids vaporizing in one part of the plant may

flow through long piping runs to an open connection, surprising the workers in that

area.

Case in Point: A company was modifying an existing 100’ long compressor

header prior to installing a larger compressor. The discharge gas from the

compressor cooler contained liquid hydrocarbons and water. The company

shut down the compressor, installed skillets to isolate the compressor, blew

down the header and drained the liquids out of the header. They cold-cut one

end of the header using proper safety procedures. They put a nitrogen purge

on the header and shut down for the day.

The next morning, a welder used a cutting torch to cut off a header support

near the open end of the header. As soon as the flame got near the open pipe,

a fireball ignited and blew out about 30’. Fortunately, no one was in the path

of the flame.

A review of the incident showed that the header had a subsurface drip pot at

the opposite end from the open pipe. The hydrocarbon liquid in the pot had

weathered off all night long, and the nitrogen purge was insufficient for the



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September 200247

extra vapors. The drip pot was not known to the plant operators, did not show

up on any of the plant drawings and was hidden behind a pipe support.

• Be careful opening equipment or piping that had been handling fluids containing

hydrogen sulfide. Even if these systems have been blown down and purged with

inert gas, they may contain pyrophoric iron sulfide or other chemicals that couldspontaneously ignite on contact with air.

b. Refurbishing

As per the suggestions above, do not assume that any equipment received from the

field is completely free of process fluids. Consider following all the same procedures

described above.

c. Construction

Used plants and equipment that have been fully refurbished present the same safety

hazards and challenges as new equipment, except as mentioned above. Normal

construction safety procedures should be adequate. Items that have not beencompletely refurbished should be treated in the same manner as described above:

assume nothing, verify everything.

B. Training

Training for a plant with used equipment will normally be the same as that for a new plant. As

mentioned above, though, the lack of manufacturer’s literature for a piece of equipment may

require the plant designer to develop new procedures for taking care of the equipment. Prior

operating experience with the plant can be used to help develop new procedures, but the plant

designer should be careful to consider all the new conditions that may cause a change in the

original procedures.

VI. Summary

Successful plants have been built with used equipment and systems for many years without following

many of the recommendations included in this monograph. The plant designer that follows these

recommendations, though, will be able to avoid many of the problems mentioned and may also be

able to avoid other similar problems not documented here.

Following all the recommendations, procedures and techniques in this monograph will not guarantee

the success of a project with used plants and equipment. Hopefully, it will get the plant designer

asking a few key questions:

• Will this item bring time and/or cost value to the project?

• Will it refurbish well enough to minimize future problems?

• Can the item be reused safely?

• Are there any hidden process, project, capital or safety risks to using the items?

• When all is said and done, will it really be worth the effort to reuse?






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These questions and the contents of this monograph should help the plant designer reduce or

eliminate some of the problems that others have seen before, and help prepare for any new problems

that may happen. This will result in a project that incorporates used plants and equipment being

safely completed on time, on budget and on performance.



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References:

• Personal Correspondence

• “Cost Effective Utilization of Surplus Equipment”, by Marc Peters; Proceedings of the 67th GPAAnnual Convention (1988)

• “The Merits of Experienced Equipment”, by Jack N. Burch; Proceedings of the 67th

GPA Annual

Convention (1988)

• “Guidelines for Acquisition of Used and Surplus Process Equipment”, by Bryan S. Watt; Proceedings

of the 67th

GPA Annual Convention (1988)

• Untitled paper, by Dave Morrow, given at a GPA Regional Convention

• Notes on Panel Discussion; Rocky Mountain GPA Regional Meeting; Breckenridge, CO, August 1997

• “The Ideal Amine Treating Facility Compared to What You Get with What You Got”, by Marc Peters

and Tom Bacon; Gas Conditioning Conference, 1996

• “Tips and Traps for Reapplying Used Process Plants”, by Michael W. Conder, P.E.; Proceedings of the 78

thGPA Annual Convention (1999)

• various OSHA rulings and interpretations

• API RP-520 and RP-521, “Recommended Practice for the Design and Installation of Pressure-

Relieving Systems in Refineries: Part 1 – Design” and “Part 2 – Installation”.

• API-510 and API-570

• Various private correspondences describing company experiences with used plants and equipment

• Private company documents concerning centrifugal compressor rerating

T4lJKurl GPA Standard - Guide Lines on Reapplying a Used Plant & Equipments

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Transcript of T4lJKurl GPA Standard - Guide Lines on Reapplying a Used Plant & Equipments