exh-ms-1826-h

Chevron Specification EXH-MS-1826-H

AIR COOLED HEAT EXCHANGERSCommented Copy Not for Vendor/Contractor Distribution

December 1989 Page 1 of 13

SPECIFICATION EXH-MS-1826-HAIR COOLED HEAT EXCHANGERS

NOTE: This document is the "Commented" version of Specification EXH-EG-1826-H. The comments, based on Company experience, provide background for therequirements stated in the Specification. These comments are for Company use only, notfor distribution to Vendors/Contractors.

Copies of the EG Specification (without comment) are available in both hard copy(paper) and electronic (MS Word for Windows) format. To order, contact CRTCTechnical Standards at either (510) 242-7232 or -7241. Copies of the MS Specificationare available only electronically. To order, contact CRTC Technical Standards at (510)242-7241.



Page 2 of 13 December 1989

CONTENTS1.0 GENERAL............................................................................................................................3

2.0 PROPOSALS........................................................................................................................3

3.0 DOCUMENTATION............................................................................................................3

4.0 GUARANTEE (EXCEPTION) .............................................................................................4

5.0 DESIGN ...............................................................................................................................4

6.0 MATERIALS........................................................................................................................8

7.0 FABRICATION..................................................................................................................10

8.0 INSPECTION, EXAMINATION, AND TEST ...................................................................10

9.0 PREPARATION FOR SHIPMENT....................................................................................12

11.0 COMPANY REFERENCE DOCUMENTS (ADDITION) ..................................................13




1.0 GENERAL

1.1 Scope

(Addition) This specification supplements the requirements of the latest edition of APIStandard 661 (referred to hereafter as API 661) and its Appendices. An accompanying datasheet for each unit describes further requirements for performance and construction.

1.1.1 Nomenclature.

An exception, as noted, to an API paragraph deletes the entire API paragraph. An addition, as noted, to an API paragraph expands the requirements or selects

options. If an API 661 paragraph is not discussed, then its contents are accepted.

1.6 Conflicting Requirements

1.6.1 (Exception) In order of precedence, the unit shall conform to the followingdocuments:

Purchase Order/List Sheets Air Cooled Exchanger Data Sheet (EXH-DS-1826) This Specification Referenced Specifications Referenced Standard Drawings API 661, Air Cooled Heat Exchangers for General Refinery Services

2.0 PROPOSALS

2.2.1 (Exception) The Vendor's proposal shall include a completed data sheet,EXH-DS-1826 for each unit.

2.2.8 (Exception) The proposal shall include a completed noise data sheet, NCM-EF-594.

3.0 DOCUMENTATION

3.1 Approval Information

3.1.1 (Addition) In addition to the items listed in Paragraph 3.1.1 of API 661, Vendorshall include the following information on the outline drawings.




14. Cross-section drawings of all major components and tube bundle detailssufficiently complete so that Company can fabricate and assemble areplacement bundle.

3.1.2 (Addition) Vendor shall not start fabrication until Company has approvedpreliminary or final shop drawings submitted in accordance with Paragraph 3.1.1.

3.1.4 (Addition) All proposed welding procedures and qualifications shall be submittedfor approval prior to start of fabrication.

3.2 Final Records

3.2.1 Information Required Prior to Shipment

2. (Addition) Report separately in the manufacturer's data report any thicknessof steel in the header that is in excess of required minimum thickness, plusspecified corrosion allowance.

Comment 3.2.1, No. 2 Thicker materials have a greater tendency to bebrittle at low temperatures. The purpose here is to alert the Company to theneed to review Minimum Pressurizing Temperatures if the Vendor increasesthe metal thickness.

9. (Addition) A characteristic performance curve for the fans shall befurnished.

12. (Addition) Copies of certified test reports or certificates of compliancecovering pressure-containing material (except as excluded by Code ParagraphUG-11) and any low and high alloy material used for internals.

4.0 GUARANTEE (EXCEPTION)

Vendor shall guarantee each unit in accordance with GAM-EG-3042.

5.0 DESIGN

5.1.6 Headers - Removal Cover Plate and Removable Bonnet Type

5.1.6.7 (Addition) Stud closures in lieu of through-bolting are not permitted.




5.1.9 Gaskets

5.1.9.2 (Addition) Where compressed asbestos gaskets are used or where gasketsare not confined, 450F shall be given as maximum allowable temperature.

Comment 5.1.9.2 This is consistent with Company piping standards.

5.1.10 Nozzles and Other Connections

5.1.10.1 (Addition) Inlet/Outlet nozzles shall be flanged 2-inch NPS or larger.

Comment 5.1.10.1 Most Company locations require 2-inch minimumnozzles for added strength.

5.1.10.4 (Addition) Cast transition nozzles are acceptable only when specificallyapproved by Company.

Comment 5.1.10.4 Castings can have poor properties and poor quality.Their use should be limited to noncritical and nonhazardous services, andthen only when a significant incentive (availability, cost, etc.) exists.

5.1.10.8 and 5.1.10.9 (Addition) Nozzles of each unit shall be equipped with atemperature and pressure connection.

Comment 5.1.10.8 and 5.1.10.9 Even if these connections have noimmediate need, they generally are used by process engineers for checkingprocess conditions.

5.1.12.7 (Addition) The fin types listed in Paragraph 5.1.12.7 of API 661 shall havethe following temperature limits:

Maximum InletType of Fin Fluid Temperature

1. Embedded 750F2. Integral 550F3. Overlapped Footed 250F4. Footed 250F




5.2 Air-Side Design

5.2.2 Noise Control

5.2.2.1 (Exception) The Vendor's base proposal shall include his standard soundlevel control features, if any. Unless otherwise specified, maximum soundpressure levels at any location 3 feet from any air cooler surface shall notexceed 85 dBA.

For the basic offering, the Vendor shall furnish the guaranteed A-weightedsound pressure level at 3 feet from the unit. If the sound pressure level of thebasic offering exceeds 85 dBA, the Vendor shall separately quote specialdesigns and/or acoustic treatment that would be required for the Vendor toguarantee 85 dBA. Details of specific designs and/or acoustic treatment shallbe furnished with the proposal.

Comment 5.2.2.1 The noise level for several identical fans operating inparallel is only slightly greater than the noise of one fan operating at thesame tip speed. The extensive use of air coolers contributes significantly toplant noise level. Reduction of fan speed is the principal means of reducingdecibel level.

5.2.3 Fans and Fan Hubs

5.2.3.5 (Exception) Fan tip speed shall not exceed 10,000 fpm.

5.2.5 Lubrication Facilities

5.2.5.1 (Addition) Length of lines supplying grease to bearings shall be held to theminimum consistent with good accessibility.

5.2.5.2 (Addition) Gear box oil level shall be capable of being checked and oiladded if necessary without hazardous exposure of the operator or shutdownof the equipment.

5.2.8 Electric Motor Drivers (Exception) Electric Motors shall be furnished inaccordance with Specification DRI-EG-1824.

5.2.11 Belt Drives

5.2.11.1 (Exception) Belt drives shall be Uniroyal High Torque Drive (HTD) synchronous belts and pulleys or Company-approved equivalent.




5.2.11.9 (Exception) HTD synchronous belts shall have a minimum service factor of 2.2 for fixed speed drivers and a minimum service factor of 2.4 for two speed drivers, based on driver-rated brake horsepower.

5.2.12 Gear Drives (Addition) All gear selection is subject to the Company's specificreview and approval.

5.2.14 Vibration Cutout Switches

5.2.14.1 (Addition) Units shall be furnished with vibration shutdown devices(Robertshaw Vibraswitch or equal approved by Company) suitable forClass 1, Division 2 location. The placement and orientation of the sensorshall be determined by the Vendor and shall be a point which is known tothe Vendor to vibrate with sufficient amplitude to activate the shutdownwhenever the machine becomes unbalanced.

5.3 Structural Design

5.3.2 Structural Design Loads and Forces

4. (Addition) Air cooled heat exchangers must be structurally and thermallydesigned to accept maximum fluid inlet temperature throughout the coolingcoils during power failure conditions without warping or pulling of tubes orany other mechanical damage or any leakage of the fluid in the tubes.

Comment 5.3.2, No 4 When a power failure occurs, the entire tube bundlewill heat up quickly to the inlet temperature. Because this temperatureincrease can be large, the tubes may experience significant expansion.Section 6.1.8.3 of this specification lists other operating conditions that cancause significant structural load changes.

5.3.4 Access Facilities

Comment 5.3.4 For designs where the air cooler sits above a pipeway orstructure, the engineering contractor will be responsible for platforms to access theunit. When the platform is required from the Vendor, the Vendor should design theplatform, ladders, etc., to Company standards. Be especially aware of supportcross members interfering with access to the fans and fan drivers.

5.3.4.1 (Addition) Full platform access to fan motors, gears, vibration shutdownswitches, and piping flanges is required. Where plug access is the onlymaintenance requirement, permanent supports for temporary scaffolding areacceptable.




5.3.4.3 (Addition) Grating is acceptable material for use as floor plates.

5.3.4.5 (Addition) Ladders, cages, and guards shall be designed in accordance withStandard Drawings GD-M13909, GF-M88575, and GF-M99645.

6.0 MATERIALS

6.1 General Requirements (Addition) Materials shall comply with requirements of DataSheet EXH-DS-1826.

6.1.1 (Addition) Tube material shall be specified as follows:

Carbon Steel SA-179 or SA-192 Low-Alloy Steel SA-209 or SA-213 Austenitic Stainless Steel SA-213 Ferritic Stainless Steel SA-268

6.1.1.1 Tubes shall be seamless.

Comment 6.1.1.1 Seamless tubes are preferred for air coolers becausetubes are pressure containing parts and seamless tubes are more reliable.This provision could be deleted in noncritical or nonhazardous servicessuch as water.

6.1.8 (Addition) Fan materials, construction, and maximum diameter shall be as follows:

MaximumAcceptable Materials and Construction Fan Diameter

a. One piece cast aluminum blades. 12 feetMarley is an acceptable supplier.

b. Aluminum blades, extruded or fabricated 18 feetfrom sheet metal, with either cast,wrought, or fabricated shanks. ChittomEquipment Co. and The Moore Co. areacceptable suppliers.

c. Chrome-nickel stainless steel, Type 304 18 feet

d. Reinforced Plastic. Hudson Products Co. 18 feetis an acceptable supplier.




6.1.8.1 (Addition) Copper content of aluminum blades shall not exceed 0.4% toexclude aluminum alloys with poor corrosion resistance.

Comment 6.1.8.1 Some aluminum alloys contain copper deliberately addedto make them stronger or easier to coat. However, it causes seriousdegradation of corrosion resistance especially in a coastal or marineatmosphere.

6.1.8.3 (Addition) All components of the fan assembly including the nonmetallicparts such as plastic fan blades, blade mounting bushings, variable pitchcontrols shall meet the following conditions:

1. Fans in induced draft service may be shut down for extended periods,and will then be subjected to the inlet temperature of the fluid beingcooled. They shall be suitable to be re-started from this condition.

2. During turnaround, the cooling coils will be subject to steam flow at a temperature specified by the Company. The fans will not beoperated during or immediately following this period. Fans and othercomponents above the bundle in induced draft services will besubjected to the saturation temperature of the steam.

3. For air cooled heat exchangers with provisions for air recirculation,due consideration shall be given to the temperature to which the fansmay be subjected during abnormal operation.

Comment 6.1.8.3 Plastic fan blades are especially sensitive totemperature. or example, a common type of blade construction uses afiberglass shell with a plastic foam filling. The Company has experiencedfailure of these fans under the conditions described above. Accidentaloverheating caused the plastic foam to expand, splitting the fiberglass outershell. It is very important for the engineer to allow for these situations. Forinstance, a power outage can lead to a situation similar to #1.




7.0 FABRICATION

7.1 Welding

7.1.1 General

7.1.1.5 (Addition) Weld rod or wire shall be selected to ensure that the depositedweld metal in the finished header will not exceed 100,000 psi tensile strength.This shall be verified by hardness testing in accordance with Section 8.2.13.

Comment 7.1.1.5 Weld metal stronger than 100,000 psi tensile strengthwill be susceptible to sulfide cracking in sour service. Cracking can occurquickly. It may result from normal H2S levels in the process fluid, or fromshort term exposure during transient conditions (i.e., upsets, startups,shutdowns).

7.2 Postweld Heat Treatment

7.2.1 (Addition) Carbon steel shall receive a postweld heat treatment when required byCode or when specified by the Company.

Preheat and postweld heat treatment requirements for carbon steel shall be as follows:

Thickness and Minimum Postweld Heat TreatmentPreheat Temperature Temperature Holding Time

To 1-1/2 in.: 70F 1100-1200F Per CodeOver 1-1/2 in.: 250F

8.0 INSPECTION, EXAMINATION, AND TEST

8.2 Quality Control

8.2.2.1 (Addition) Fine grain, high definition, high contrast film (Kodak Type AA orequivalent brands) shall be used. Fluorescent intensifying screens shall notbe used.

Comment 8.2.2.1 Using this type of film enables the viewer to see morefine detail.

8.2.3 (Addition) Company shall be notified sufficiently in advance so that it maydesignate the locations at which the spot radiographs shall be taken.




8.2.13 Hardness Examination

Comment 8.2.13 Weld metals which are harder than the limits specified hereinmay fail in service from sulfide stress cracking. If exposed to conditions whichpromote cracking, failure can occur quickly. Because the incidence of sulfidecracking in the industry is high and cracking-resistant (i.e., soft) weld metal is easilyobtained, these precautions are justified as a general requirement.

The following are additions or exceptions to the items listed in Paragraph 8.2.13 ofAPI 661.

1. (Addition) Hardness readings need not be taken on a carbon steel header ifdemonstrated to Company that it is welded with a brand of rod or wire whichhas been proven to have an acceptable maximum hardness.

2. (Addition) Tests shall be made with a Telebrineller or Bitzen hardnesstester.

3. (Addition) Tests shall be made after any required postweld heat treatmentand before hydrostatic testing.

4. (Exception) Any carbon steel joint with a hardness over 200 Brinell or low-alloy joint with a hardness over 215 Brinell shall be rejected.

5. (Exception) Hardness shall be verified by one spot hardness test of weldmetal on each circumferential and each longitudinal joint.

6. (Addition) Proposed corrections to lower hardness of rejected joints shallbe submitted in writing to Company for approval.

8.3 Pressure Tests

8.3.1 (Addition) The tube side shall be hydrostatic tested to 1-1/2 times the maximumallowable pressure at the test temperature calculated for the nominal thickness asconstructed in accordance with Code Paragraph UG-99(b).

8.3.3 (Addition) The minimum fluid temperature for hydrostatic testing shall be higherthan the Minimum Pressurizing Temperature listed on the Data Sheet EXH-DS-1826.

Comment 8.3.3 The exchanger materials are selected to avoid brittle fracturedown to the Minimum Pressurizing Temperature. If hydrotested at lowertemperatures than this, brittle fracture could occur during the hydrotest.

8.3.7 (Addition) Normal service gaskets shall be used for all hydrostatic tests.




Comment 8.3.7 The ability of a gasket joint to pass a pressure test depends on thegasket used. This paragraph prevents the Vendor from using something other thanthe normal service gasket to make it easier to pass the hydrotest.

8.3.8 (Addition) The purchaser's inspector shall witness the final required tests asdescribed above.

8.4 (Addition) Shop Run In

A shop run of the completely assembled exchanger is required. The Purchaser's inspectorshall witness this test.

Comment 8.4 This shop run verifies that everything fits and vibration levels areacceptable.

8.5 Nameplate

8.5.3 (Addition) In addition to the data required by the Code and API 661, the nameplateshall give the following information:

a. Maximum allowable working pressureb. Maximum allowable temperaturec. Company's order numberd. Stamp of Company's inspector

9.0 PREPARATION FOR SHIPMENT

9.1 General

9.1.4 (Exception) Company will specify coating system to be used and surfacepreparation requirements. Vendor may submit alternate coating proposals forCompany review and approval.

Comment 9.1.4 On major construction projects, use the project paintingspecification if one exists. Otherwise, select the appropriate coating system fromthe Coatings Manual, use the table in Drawing COM-EF-68A or 68B (Section 210)to select the proper coating system. Then refer to the data sheet for that specificcoating system, which can be found in Section 1120. It will give the exchangermanufacturer the information he needs to coat the exchanger the way you want. Also, give the exchanger manufacturer a list of acceptable coatings; these can befound in COM-EF-872A or B of the Coatings Manual.




For example, in an inland location, Section 210 (COM-EF-68A) will tell you to useCoating System 2.3 for uninsulated surfaces which are below 300F and/or mustwithstand steamout. In Section 1120, you will find the data sheet for System 2.3,which tells you what surface preparation and film thickness are required. It alsogives you a Chevron code number for the coating (in this case P9). The acceptablebrands list COM-EF-872-A or B in Section 1100 tells you what P9 really is and whomakes brands that have a good performance record.

Vendor's standard coating systems will generally not perform as well as the onesthe Coatings Manual recommends. However, they can be used and will save moneywhen the environment where the exchanger is to be used is only mildly corrosive. Vendor's standard is also a useful option when a coating is not needed for theservice conditions, but only to protect the exchanger from rust which might occurbefore it is placed in service.

In severe environments (i.e., offshore), the header tubesheets may require painting. In this case, the tubesheet face must be painted prior to tubing the unit using carenot to paint welds or other parts of the header. The reason for this is that thetubesheet is impossible to clean and paint after the tubes are installed. Theremainder of the header is painted after the hydrostatic test.

9.1.5 (Addition) Connections equipped with permanent blind flanges or covers shall bebolted up with specified gaskets in place, ready for service. All other flange facesshall be protected by applying a stiff grease and bolting on wooden or steel coverswith at least four bolts.

Threaded connections on outside of heat exchanger shall be protected from damageby installing carbon steel bar stock plugs.

Tell-tale holes in reinforcing pads shall be plugged with stiff grease only.

11.0 COMPANY REFERENCE DOCUMENTS (ADDITION)

The following drawings and specifications are referenced in and are part of this Specification:

EXH-DS-1826 DRI-EG-404 DRI-EG-1824 GAM-EG-3042 NCM-EF-594 GD-M13909 GF-M88575 GF-M99645

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