DGS-ME-001-R1 Shell and Tube Heat Exchanger Design Criteria

7/25/2019 DGS-ME-001-R1 Shell and Tube Heat Exchanger Design Criteria

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Abu Dhabi Oil Refining Company

SHELL AND TUBE HEAT EXCHANGER DESIGN CRITERIA DGS-ME-001Rev-1 April 2009

Takreer DGS-ME-001-Rev-1 April-2009 Printed 16-Apr-09 14:01:15 Initials Page 1 of 22

SHELL AND TUBE HEAT EXCHANGERDESIGN CRITERIA

Amendment History

No Date Amendment Description Proposed Approved Incorporated

DGS History

1 April 2009 DGS-ME-001-Rev-1 Base Reference Project5578

TH/DDC QAM / MAY

0 March 2006 DGS-ME-001-Rev-0 Previous Project / LessonsLearnt Incorporated

TH/DDC ETSDM / EPDM

No Date Description Source Reviewed Approved

DGS-ME-001 Rev-1


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TABLE OF CONTENTS

1.0 GENERAL ................................................................................................................................31.1 INTRODUCTION.............................................................................................................3 1.2 PURPOSE.......................................................................................................................3 1.3 DEFINITIONS .................................................................................................................31.4 EXCEPTIONS .................................................................................................................3

2.0 CODES AND STANDARDS ..................................................................................................... 33.0 REFERENCE DOCUMENTS ................................................................................................... 44.0 DOCUMENT PRECEDENCE...................................................................................................45.0 SPECIFICATION DEVIATION/CONCESSION CONTROL ......................................................4

6.0 QUALITY ASSURANCE/QUALITY CONTROL ........................................................................ 57.0 DOCUMENTATION ..................................................................................................................58.0 SUBCONTRACTORS/VENDORS............................................................................................5 9.0 HANDLING...............................................................................................................................510.0 DESIGN....................................................................................................................................5

10.1 GENERAL REQUIREMENTS .........................................................................................510.2 TECHNICAL REQUIREMENTS ......................................................................................9

11.0 MATERIALS ...........................................................................................................................2012.0 FABRICATION........................................................................................................................21 13.0 TESTING................................................................................................................................21ADDENDUMSHEET .......................................................................................................................22

List of Authorized Signatures/ Initials

DGS Discipline Committee Member, ADRD ------------------------------

DGS Discipline Committee Member, RRD ------------------------------

DGS Discipline Committee Member Leader, E&PD Taha Hussein (TH)

Engineering & Technical Services Manager, E&PD Quazi Abdul Matin (QAM)

Engineering & Projects Division Manager, E&PD Mohamed Al Yabhouni (MAY)


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1.0 GENERAL

1.1 INTRODUCTION

This Specification establishes the criteria for the thermal design of standard TEMA typeShell and Tube Heat Exchangers for the PROJECT. It also defines the minimum processand mechanical data required for thermal and hydraulic design and completion of HeatExchanger Data Sheets (hereinafter referred to as Data Sheets).

1.2 PURPOSE

The purpose of this specification is to ensure consistency in selection and design of TEMAtype shell and tube heat exchangers for the Project.

1.3 DEFINITIONS

For the purpose of the specification, the following definitions shall apply:

CONCESSION REQUEST A deviation requested by the SUBCONTRACTOR orVENDOR, usually after receiving the contract package or purchase order. Often, it refersto an authorization to use, repair, recondition, reclaim, or release materials, componentsor equipment already in progress or completely manufactured but which does not meet orcomply with COMPANY requirements. A CONCESSION REQUEST is subject toCOMPANY approval.

SHALL Indicates a mandatory requirement.

SHOULD Denotes an action or requirement which is not mandatory but which is stronglyrecommended.

1.4 EXCEPTIONS

This specification does not apply to design of Double Pipe Heat Exchangers, Plate HeatExchangers, Water Cooled Surface Condensers, and Brazed Aluminum Fin HeatExchangers. For other special applications only part of this specification may be relevant,subject to mutual agreement between VENDOR/MANUFACTURER andCOMPANY/CONTRACTOR.

2.0 CODES AND STANDARDS

It shall be the VENDOR'S responsibility to be, or to become, knowledgeable of therequirements of the referenced Codes and Standards.

The following Codes and Standards, to the extent specified herein, form a part of thisspecification. The latest edition in force shall apply:

Tubular Exchanger Manufacturers Association (TEMA) Standards API 660 : Shel l &Tube Heat Exchangers for General Refinery Service


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WRC Bulletin 107 : Local stresses in spherical and cylindrical shells due to externalloadings.

International Organization for Standardization (ISO)

ISO 9001 - 2000 Quality Management System Requirements

ISO 9004 - 2000 Quality Management Guidelines for Performance ImprovementSystem

ISO 9011 Guidelines for Quality and/or Environmental System Auditing

WRC Bulletin 297 : Local stresses in spherical and cylindrical shells due to externalloadings (Supplement to WRC Bulletin No 107).

3.0 REFERENCE DOCUMENTS

The following reference documents, to the extent specified herein, form a part of thisspecification. When an edition date is not indicated for a document, the latest edition inforce at the time of VENDORS/CONTRACTORS proposal submittal shall apply.

Project Specifications

DGS-MU-013 Criticality Rating System

DGS-MU-014 Minimum Shop Inspection and Certification Requirements

Standard Drawings

STD-MD-00020 Nozzles for Apparatus

STD-ME-00001 Brackets for Standard Vertical Reboilers, Nominal Diameter 350up/including 1100 mm

STD-ME-00008 Saddles for Horizontal Shell and Tube Heat Exchangers

4.0 DOCUMENT PRECEDENCE

The VENDOR shall notify the CONTRACTOR of any apparent conflict between thisspecification, the related Data Sheets, the Codes and Standards and any other

specifications noted herein. Resolution and/or interpretation precedence shall be obtainedfrom the CONTRACTOR in writing before proceeding with the design/manufacture.

In case of conflict, the order of precedence shall be stated in the AGREEMENT or otherPROJECT documents as applicable.

5.0 SPECIFICATION DEVIATION/CONCESSION CONTROL


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Any technical deviations to the Purchase Order and its attachments including, but notlimited to, the Data Sheets and Narrative Specifications shall be sought by the VENDORonly through CONCESSION REQUEST format. CONCESSION REQUESTS requireCONTRACTORS and COMPANYS review/approval, prior to the proposed technicalchanges being implemented. Technical changes implemented prior to COMPANYapproval are subject to rejection.

6.0 QUALITY ASSURANCE/QUALITY CONTROL

The Criticality Rating (CR) System outlined in Project Specification DGS-MU-013 shall beused by CONTRACTOR or CONTRACTORS designee to develop the design checkinglevels and minimum requirements for shop inspection, testing and material certificationgiven in Project Specification DGS-MU-014.

7.0 DOCUMENTATION

This section is not applicable to this specification.

8.0 SUBCONTRACTORS/VENDORS


9.0 HANDLING


10.0 DESIGN

10.1 GENERAL REQUIREMENTS

10.1.1 Definitions

Clean Service shall include services where the fouling resistance is less than or equal to

0.00034 m2 hrC/kcal (0.0017 ft2hr F/Btu).

Fouling Service shall include all services not otherwise defined as clean service, orwhere mechanical cleaning is required.

10.1.2 Process Data

In addition to heat duty, fluid identity, flow rates, design pressures and temperatures,operating pressures and temperatures, allowable pressure drops, material of constructionand exchanger type and setting, the process data shall include, but not be limited to, thefollowing:

10.1.2.1 Sensible Heat Transfer Service

a. Vapour and Gas


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Density, thermal conductivity, specific heat and viscosity at two referencetemperatures, molecular weight and hydrogen partial pressure.

b. Liquid

Density, thermal conductivity, specific heat and viscosity at two referencetemperatures. For liquid streams having a high viscosity, a third viscosity datapoint at an intermediate temperature or viscosity/temperature correlation isdesirable, except that when the viscous liquid is being cooled, the third datapoint should be at the average temperature of the opposing stream.

Physical properties of hydrocarbon streams shall be weighted to include theeffect of miscible water, and shall be so specified.

Immiscible or free water shall be shown on the Data Sheet. Fluid propertiesshall not be weighted to include immiscible water.

10.1.2.2 Condensing Service

a. Physical property requirements shall be the same as for sensible heat transfer plusthe bubble point, dew point, latent heat, quantity and molecular weight ofnoncondensible gas and quantity of steam when present. Vapor physical propertiesshall be weighted for the entire vapor phase mixture. For cases where H2content ismore than 10 mol percent, vapor mixture physical properties shall be given underthree referenced temperatures. Latent heat for a steam/hydrocarbon mixture shallbe for the hydrocarbon only.

b. Data Sheets shall state if condensation is linear, unless heat release data isprovided.

c. For nonlinear heat release services, a plot with duty, weight percent vapor andmolecular weight and liquid surface tension versus temperature shall be provided.

d. When fluid entering exchanger is a vapor mixture at its dew point temperature,liquid properties shall also be given at that temperature unless sensible heat is 10percent or less of total duty.

10.1.2.3 Boiling Service

a. Physical property requirements shall be the same as for sensible heat transfer plusliquid surface tension, mixture bubble point and dew point, critical pressure andtemperature and latent heat.

b. The Process Engineer shall provide tables or curves showing vapor temperatureand fraction vaporized at two constant reference pressures between bubble pointand dew point, with three additional points between. The three additional pointsmust be close to the operating range. For pure components or in cases with verynarrow boiling ranges only vapor pressures at two temperatures need be provided.


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c. For non-linear heat release services, a plot with duty, molecular weight and weightpercent vapor versus temperature shall be provided.

d. For kettle reboilers, the required entrainment ratio (kg liq/kg vapor) shall beprovided, including steam purity for steam generators.

e. For thermosyphon reboilers complete piping geometry between the fractionatingcolumn and the reboiler must be analyzed, together with the available static head.

10.1.2.4 Corrosion Allowance

a. For all exchanger parts, except tubes, the materials of construction and corrosionallowance shall be selected to give exchangers a design service life of 30 years, inaccordance with Project Specifications. Corrosion allowance shall be specified onthe Data Sheets.

b. Tubes shall have a design life of ten years, and where necessary to achieve this,corrosion allowance for tubes in high pressure service shall be specified.

10.1.2.5 Fouling

Fouling factors and cleaning requirements shall be specified on the Data Sheets.

10.1.2.6 Nozzle Sizes

Where practical, the exchanger nozzles shall be designed to match the line sizes providedthat the exchanger's thermal, vibration and hydraulic requirements are met, and thatTEMA entrance and exit velocity criteria are met.

10.1.2.7 Excess Heat Transfer Surface

Any requirements for excess surface must be fully explained on the Data Sheet, withinstruction on effect on flow, temperatures and pressure drops if these are to differ fromthose listed on the Data Sheets. It is insufficient to add notes such as provide 10 percentexcess surface.

10.1.2.8 Design Temperature and Pressure

a. All parts of the tube bundle including floating head shall be designed for either fulltubeside internal pressure or full shellside external pressure, whichever condition is

controlling. Differential pressure shall not be used as design basis unless specified.

b. In selecting design temperatures for multiple exchangers in series, considerationshall be given to the maximum or minimum temperature, on each side of eachexchanger, that results from either fouled or clean operation.

c. The differential between the inlet and outlet operating temperatures of a shellside

fluid should not exceed 200C (360F) per shell.


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d. The differential between the inlet and outlet operating temperatures of channels of

multipass exchangers should not exceed 120C (216F) per exchanger.

e. For the determination of the design pressure on the low pressure side, the greaterof the initial design pressure on the low pressure side or 77% of the designpressure on the high pressure side shall be taken.

f. For heat exchangers in series, individual shells of a unit may have different designtemperatures for economy in material selection. Where this applies, measures shallbe taken to prevent incorrect line-up of shells within the unit.

g. The effect of the temperature profile over a thick wall tubesheet not being linearshall be taken into account because this may have a large consequence on the

mean metal temperature as well as on the temperature gradient and stresseswithin the tubesheet.

h. Unless otherwise specified on Data Sheets/drawings, the design pressure shall beas follows:

MAXIMUM OPERATING PRESSURE(kg/cm2 G):

DESIGN PRESSURE(kg/cm2 G):

Full or partial vacuum 1.05 external/3.5 internal

0 (Gauge) - 0.35 0.5 external/3.5 internal

0.36 - 1.8 3.5

1.81 - 17.2 Operating + 1.7

17.3 - 70.0 Operating + 10 %

70.0 - 140.0 Operating + 7.0

140.0 - Up Operating + 5%

i. Both, Design Temperature (DT) and Minimum Design Metal Temperature (MDMT)shall be identified on Data Sheets.

10.1.2.9 Allowable Pressure Drop

Allowable pressure drop shown on the Data Sheet shall be for clean conditions.

10.1.3 Mechanical Data

The complete Data Sheets shall include the following information, as a minimum:

a. Process data (including heat release curves, when applicable).

b. Parameters defining exchangers thermal performance (i.e. heat transfer coefficients,calculated pressure drops, Mean Temperature Difference, etc.).


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c. Definition of exchangers type and orientation.

d. Identification of any special design considerations.

e. Outline drawing, defining overall dimensions, required maintenance clearances,locations of vents, drains and any other non-process connections, process nozzlessize, rating, location and projection, saddles location and projections, location andsizing of the anchor bolts, and flow direction.

f. Definition of internals, like baffle spacing or internal expansion joints.

g. Tube layout including as a minimum: number of tubes, tube diameter, outer tube limit(OTL), baffle cut, baffle orientation, sealing and sliding strips, tie rod location andsize, definition of impingement protection (if required), and schematic identification ofthe shellside nozzle size.

h. Identification of materials and corrosion allowances.

i. Identification of special services and NDE requirements.

j. Identification of PMI requirements.

10.2 TECHNICAL REQUIREMENTS

10.2.1 General Requirements

a. TEMA Class Selection

All shell and tube heat exchangers for this PROJECT shall be in accordance withTEMA classR.

b. The thermal design and rating shall be based on the design methods which havebeen proven in practice. In this respect, the design procedures and computerprograms published by the Heat Transfer Research Institute (HTRI), and HeatTransfer and Fluid Flow Service (HTFS) are considered proven design methods.HTRI Methods are preferred.

10.2.2 Exchanger Type Selection

10.2.2.1 Front/Rear Head Selection

a. Type B front head shall be used for clean service and/or for design pressure above30.0 kg/cm2(G). For fouling service and for design pressure less than or equal to10.15 kg/cm2 (G), Type A front head shall be used.

b. Rear end head Type M should be used for fixed tubesheet designs. However, forheat exchangers with a Type A front end stationary head and an odd number of tubepasses Type L shall be selected.


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c. Rear end head Type S should be used for floating head type heat exchangers with anominal shell diameter of more than DN 250. Alternative construction would need tobe considered for diameters up to DN 250. Rear end head Type T shall be used fora kettle type heat exchanger with floating head.

d. Types P and N are not permitted.

e. High pressure or other design requirements may justify deviation from the guidelinesshown.

10.2.2.2 Use of Fixed Tubesheet (nonremovable bundle) Exchangers

a. Use of fixed tubesheet exchangers requires prior approval by the COMPANY.

b. Nonremovable bundle exchangers may be used in clean shellside service where ashellside expansion joint is not required. The use of shellside expansion jointsrequire prior approval by the COMPANY.

c. The differential expansion between shell and tubes of a fixed tubesheet exchangershall be based on the controlling metal temperatures, either clean or one side fouled.

d. The maximum controlling differential temperature between the tube and shellsideduring operation, start-up, shutdown or steamout shall be stated on the Data Sheetand used to determine the requirement for an expansion joint and tubesheetthickness on a fixed tubesheet heat exchanger. If design consideration result inexpansion joint being required, a removable bundle type exchanger shall beselected.

10.2.2.3 Use of U-Tube Bundles

U-tube bundles shall be used only for the clean service on the tubeside as defined inparagraph 10.1.1. Other design considerations may govern, but require prior approval bythe COMPANY.

10.2.2.4 Shell Selection

The single-pass shell, Type E, shall be selected for general duties, except as indicatedbelow:

a. Where the shellside pressure drop is a restricting factor, the divided flow shell Type Jor cross-flow shell Type X or double-split flow shell Type H, should be considered.

b. For horizontal shellside thermosyphon reboilers, Types G, H, J, or X should beselected.

c. The kettle type shell, Type K, should be selected for boiling where almost 100%vaporization (0-5% entrainment) or where a phase separation is required.


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d. The use of TEMA Type F shells with removable bundles is discouraged unless thereare considerable economic savings or design advantages. Limit shellside pressuredrop to 0.49 kg/cm2 (7.0 psi) per shell and temperature differential between shell

inlet and shell outlet to 140C (252F).

10.2.2.5 Horizontal and Vertical Exchangers

a. Heat exchangers should be of the horizontal type; however, for processrequirements or where cleaning and other maintenance will be infrequent or spacerequirements make it more attractive, the vertical arrangement may be considered.

b. For thermosyphon reboilers, vertical orientation is preferred to horizontal orientation.However, all aspects of design, vibration, maintainability, and performance should be

evaluated when making a selection.

c. When horizontal arrangements are preferred, the stacking of exchangers should beconsidered to conserve space in the structure. Preferred stacking should be 2 (two)shells high.

10.2.3 Tube Bundle

10.2.3.1 Design Considerations

a. Maximum Size

Maximum sizes shall be as shown below. Larger sizes may be considered to realizeeconomic or design advantages. Larger sizes must be approved by the COMPANY.

The maximum straight length for tubes shall be 7315 mm (24 feet).

The maximum bundle diameter for removable bundle exchanges shall be 1524mm (60 inches).

The maximum removable bundle weight shall be 20,000 kg (44,092 lb).

b. Standard straight lengths for tubes shall be as follows:

Millimeters 2438 3048 3658 4877 6096 7315

(Feet) (8) (10) (12) (16) (20) (24)

c. The ratio of tube length to bundle outer diameter for removable bundles shall be lessthan 10:1.

d. The maximum tube length for vertical thermosyphon reboilers shall be 6096 mm(20 ft).

e. Selection of different tube lengths than above for U-tubes may be considered wheneconomically justified.


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10.2.3.2 Tube Diameters and Gauges

The following table specifies bare tube diameters and minimum permissible gauges(BWG):

Tube ODCarbon Steel And Low

Al loysCopper, Copper Alloys

AndHigh Alloys

19.05 mm(0.75 in.)

(Min. Wall)

2.11 mm(0.083 in.)

(Min. Wall)

1.65 mm(0.065 in.)

25.4 mm

(1 in.)

2.77 mm

(0.109 in.)

2.11 mm

(0.083 in.)

*31.75 mm(1.25 in.)

3.40 mm(0.134 in.)

2.77 mm(0.109 in.)

* Use of 31.75 mm OD tubes requires prior approval by COMPANY.

10.2.3.3 Tube Diameter, Pitch and Layout

The following table defines criteria for selection of tube diameter, pitch and layout:

ShellsideService

Tubeside Fouling

m2 hrC/kcal

(ft2 hrF/Btu)

Min. TubeO.D.

mm ( in .)

Pitch, mm (in.)and layout

Clean* Up to and including0.0006 (0.003)

19.05 (0.75) 25.4 (1.0) 30/45/90

Clean* Over 0.0006 (0.003) 25.4 (1) 31.75 (1.25)30/45/90

Fouling* Up to and including0.0006 (0.003)

19.05 (0.75) 25.4 (1) 45/90

Fouling* Over 0.0006 (0.003) 25.4 (1) 31.75 (1.25) 45/90

* As defined in paragraph 10.1.1.

Exceptions to the above table are as follows:

a. The pitch and layout guidelines shown above are the minimum starting points foreconomic design. Larger pitch or different layout patterns may be required tosatisfy pressure drop or boiling flux requirements.

b. Tube pitch for heavy wall tubes shall not be less than the recommended values inTEMA Table R-7.22.


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c. Rotated square layouts (45) are preferable for Laminar Flow. In turbulent flow,especially for pressure drop-limited cases, square layout (90) is preferred.

d. Triangular or rotated triangular pitch shall be used only for nonremovable bundledesigns.

10.2.3.4 Baffles and Support Plates

a. Permissible types of transverse baffles are segmental, double segmental and thesegmental type having no tubes in the window area.

b. Horizontal cut segmental baffles are not acceptable for systems where the shellsidefluid is two phase or contains suspended solids.

c. Baffle cut perpendicular to nozzle centerline (normally horizontal cut) is preferred for

single phase fluids. Where shellside inlet nozzle has 180 rotation from shellsideoutlet nozzle, the number of shellside crosspasses must be odd for segmentalbaffles.

d. The minimum baffle cut for segmental baffles shall be 15 percent of the shell insidediameter.

e. All U-tube bundles shall have full support plate at U-bend. The full support plateshall be trimmed to the extent defined by the baffles outline (on top and bottom) butcovering the full tube layout.

f. All baffles shall have a V-notch at bottom to allow draining. In addition, bafflesused in 2-phase flow shall have a V-notch on top of the baffle.

10.2.3.5 Bundle Rotation

Where possible, without decreasing the thermal performance of the exchanger, the carbonsteel tube bundles shall be designed to allow their operation after being placed back intothe exchanger, following a 180 rotation around the bundle's longitudinal axis.

10.2.3.6 Tubesheet

All removable bundles used with a B type front head shall have their stationary tubesheetsextended to be equal to the shell flange outside diameter. Tubesheet thickness must be

sufficient to eliminate a need for test rings.

Removable bundles used with an A type front head do not need to have full diametertubesheets. Exchangers with extended tubesheets and B type front heads shall be fittedwith 100% collar bolts in order to allow shellside hydrotest with Bonnet removed.

10.2.3.7 Maximum Unsupported Tube Length

The maximum unsupported tube span shall not be more than 0.8 times the values shownon TEMA Table R-4.52.


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10.2.3.8 Finned Tubes

Wolverine type S/T (or equal) low and medium height integral fin tubes are acceptableunder the following conditions, but require COMPANY approval:

a. The shellside fouling resistance using low fin tubes does not exceed 0.00017 m2 hr

C/kcal. Medium height fin tubes are to be used only in gas services with fouling notgreater than 0.00017 m2hr C/kcal.

b. The shellside stream is boiling or in the turbulent flow regime.

c. Their application is economically attractive. As a general guideline finning may befeasible, when the unfinned heat transfer coefficients, corrected for fouling, indicatesthe shellside coefficient controlling by a ratio of 2:1 or more (low fin tubes may befeasible) and 3:1 or more (medium height fins may be feasible). To avoid fretting ofthe tubes in baffle/support plates, the baffle and/or support plates shall have athickness in accordance with TEMA Table R-4.41; however, the minimum thicknessshall not be less than 13 mm.

d. High-finned tubing is not permitted.

e. Longitudinally-finned tubes are not allowed for shell and tube exchangers.

10.2.3.9 U-Tube Bundle Bend Radius

Bends with radius R < 1.5 times nominal tube OD are not permitted.

10.2.4 Water-Cooled Coolers

10.2.4.1 Cooling water shall be placed on the tubeside and should run upwards through the tubesin order to avoid gas build-up. The tubeside velocity should be as specified in thisspecification. The tubeside shall be maintained at a positive pressure so that air cannotseparate from or be sucked into the water.

10.2.4.2 Cooling Water Velocity

a. Tubeside velocity range for seawater or brackish water shall be as follows:

Tube Material Velocity m/s (FPS)

Titanium 1.5 - 4.6 (4.9-15.1)

70-30 Cu-Ni 1.5 - 3.7 (4.9-12.1)

90-10 Cu-Ni 1.5 - 2.7 (4.9-8.9)

Al Brass, Al Bronze 1.5 - 2.0 (4.9-6.6)

Monel 1.5 - 3.7 (4.9-12.1)

Incoloy 825, Carpenter 20 CB3 1.5 - 3.7 (4.9-12.1)

Incoloy 625, Hastelloy C 1.5 - 3.7 (4.9-12.1)

b. Tubeside velocity range for treated/fresh cooling water shall be as follows:


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Tube Material Velocity m/s (FPS)

Carbon and Low Alloy Steel 1.0 - 2.1 (3.3-6.9)

Austenitic Stainless Steel 2.0 - 4.5 (6.6 -14.8)

Titanium 1.0 - 4.5 (3.3-14.8)

Inhibited Admiralty 1.0 - 2.7 (3.3-8.9)

70-30 Cu-Ni 1.0 - 3.0 (3.3-9.8)

90-10 Cu-Ni 1.0 - 2.5 (3.3-8.2)

Aluminum, Brass, Alum. Bronze 1.0 - 2.1 (3.3-6.9)

Monel 1.8 - 3.5 (5.9 -

11.5)

Incoloy 825, Carpenter 20 CB3 1.5 - 3.7 (4.9-12.1)

10.2.5 Tubeside/Shellside Selection

In general, tubeside/shellside selection shall be made to satisfy as many as possible of thefollowing points, unless otherwise indicated on Data Sheets:

Service Shellside Tubeside

Seawater X

Cooling Water X

Condensing Vapors (exceptsteam) X

Lower Allowable P X

Larger Flow and SimilarProperties

X

Higher Pressure Fluids X

Corrosive Fluids/AlloyConstruction

X

*High Fouling Factors X

High Viscosity/Laminar Flow X

* If chemical cleaning can be utilized, the fouling fluid may be placed on the shellside.

10.2.6 Special Applications

10.2.6.1 Slurry Handling

Slurry services shall be routed through the tubeside of the exchanger.


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Minimum tube size shall be 25.4 mm (1 in.) OD at 2.77 mm (0.109 in.) (BWG) minimumwall thickness.

Velocity limits for cycle oil containing catalyst fine shall be as listed below. The optimumvelocity is 1.75 m/sec (5.74 ft/sec).

Velocity m/s (FPS)

Maximum Minimum

Straight tube 2.13 (7.0) 1.14 (3.74)

U-tube 1.75 (5.74) 1.14 (3.74)

Straight tube construction is recommended.

Slurry flow shall be horizontal or downward.

10.2.6.2 HF Acid/Lethal Service

To minimize potential of acid leakage into the process area, exchanger design shallprovide as few joint closures as practical.

10.2.6.3 Pulsating Flow on Shellside

Maximum unsupported tube length for vapor or 2-phase flow shall be 914 mm (36 inches).

Design shall include adequate impingement protection plate or a distributor belt so that

V2into a bundle shall not exceed 744 kg/m-s2(500 lb/ft-s2).

10.2.7 Kettle-Type Reboilers and Evaporators

The shell diameter depends on the required vapor escape area above the tube bundle.Vapor velocities shall nowhere exceed the maximum vapor velocity determined by theentrainment requirements.

These entrainment requirements shall be specified in Data Sheets.

The design shall take into account that frothing is likely to occur above the liquid level. Anallowance 125 mm shall be made for this frothing. The height of the escape area abovethe frothing allowance shall be at least 250 mm.

Minimum of two (2) vapor outlet nozzles shall be used for bundles longer than 4877 mm(16 ft).

The entry for vapor/liquid mixtures shall be above the boiling pool. Provision shall bemade to separate the vapor phase from the liquid phase by using a deflector plate, spiderpipe or other suitable arrangement.

A device recommended for distributing the liquid/vapor mixture above the froth bed is thespider pipe arrangement shown in Figure 1 below:


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Figure 1. SPIDER PIPES

The requirements for spider pipes are as follows:

a. Located at the position of lowest vapor generation

b. The mixed vapor/liquid stream should direct downwards against the shell wall topromote separation of the liquid and vapor

c. No holes in the direct path from the inlet nozzle

d. The velocity head in the inlet nozzle shall be 4000 kg/m-s2maximum

e. The velocity head in the spider header shall be 1000 kg/m-s2maximum

f. The velocity head in the holes shall be 4000 kg/m-s2

maximum

If considered necessary, provision shall be made for cleaning the spider pipes.

A vortex breaker shall be provided for the liquid outlet nozzles.

If the liquid level is to be controlled by instrumentation, a calming baffle shall be installedto prevent boiling turbulence from affecting the level instruments.

The liquid space shall be determined by the liquid hold-up requirements.

A distance of 50 mm minimum shall be maintained between the bottom of the bundle andthe bottom inside diameter of the shell so as not to obstruct liquid recirculation into the

bundle.

Weir plate shall be located behind tube bundle, and it shall be welded tightly to the shell.Weir plate shall have no drain holes and have sufficient height to flood top of top tubeswith a minimum of 50 mm of process fluid during normal operation.

The minimum distance between weir plate and the shell head tangent line shall be1220 mm.


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A hold angle shall be provided and placed above the tube bundle to keep bundle in placeduring shipment and handling. It shall be located directly above and close to the floatinghead flanges (type T) or the full support plate (at u-bend) when u-tube construction isused.

10.2.8 Venting and Draining of Exchangers

All shell and tube exchangers, including vertical units, shall be provided with vents anddrains allowing complete draining and venting of shellside and tubeside of exchangers,after hydrotest in-situ.

For stacked exchangers of the same service, hydrotest in-situ can be performed instacked position, but each shell shall be completely drainable and ventable.

Separate vents and drains on exchangers are not necessary if hydrotest in-situ andsubsequent draining and venting of exchangers can be accomplished through pipingconnections or line breaks.

Vertical units shall have vent and drain passages drilled through their stationarytubesheets (including bottom tubesheet of nonremovable bundle), exiting out the outsideedge and provided with flanged vents and drain nozzles, with blinds and service gaskets.

In total condensing services on the shell side, a non condensibles vent shall be providedat the opposite end to the shell inlet connection. For tubesiede condensing, the vent shallbe located on the highest point of the last tube pass of the exchanger.

10.2.9 Design for Interchangeability

Design of shell and tube heat exchangers for the PROJECT shall target maximuminterchangeability of complete units or components.

10.2.10 Shell Diameter

Up to and including a nominal diameter of 500 mm (20 in.) seamless pipe shall be used.

For shells rolled from plate, the nominal shell diameter is the shell inside diameter.

For shells rolled from plate, inside diameters should be changed in 10 mm incrementsduring thermal design or sizing. This requirement can be deviated from in case of highpressure application and when it is economically justified.

10.2.11 Maximum Number of Tube Passes

The maximum number of tube passes shall be 16 for any given heat exchanger.

10.2.12 Connections

a. The minimum size of any connection shall be 50 mm (2 inches), including vents anddrains.


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b. Threaded connections/drains/vents are not permitted.

c. Vents and drains shall be Class 300 minimum rating.

d. All nozzle flanges, unless specifically noted otherwise on Data Sheets, shall haveRaised Face (RF) and Smooth Finish (SF). Smooth Finish shall be as definedon Project Standard Drawing STD-MD-00020.

e. Test connections on process nozzles are not permitted, except for the following twoconditions:

For vertical thermosyphon reboilers, directly connected to columns,Temperature Indicators (TI) or Pressure Indicators (PI) are permitted orprocess nozzle directly connected to the column (when needed for processreasons).

For stacked exchangers, when TI and/or PI are required to be installed onintermediate nozzles, they shall be placed on intermediate nozzles of lowerexchanger.

f. For stacked S type shells, vent of lower shell cover and drain of top shell covershall be elbowed out 90.

g. Reinforcing pads on shellside nozzles are not permitted, if their use will increaseinlet or outlet baffle spacings by moving the nozzles location away from the bodyflanges.

h. The minimum projections for process nozzles shall comply with Project StandardDrawing STD-MD-00020.

i. All flanged 2 inch connections shall be minimum rating ANSI Class 300# and shallbe braced 90 degrees apart.

10.2.13 Saddles/Supports

a. Saddle design for horizontal exchangers shall comply with Project Standard DrawingSTD-ME-00008.

b. Support design for vertical exchangers shall comply with Project Standard DrawingSTD-ME-00001.

10.2.14 Baffle-to-Shell Clearance

For viscous fluids on shellside, with the dynamic viscosity above 2.0 cP at inlet or outlettemperature, the heat transfer coefficient shall be calculated with the baffle-to-shellclearance specified as large. The shellside pressure drop, however, shall be calculatedwith the baffle-to-shell clearance specified as standard/average.


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10.2.15 Impingement

a. Impingement protection, in form of impingement plate or two rows of impingementrods, shall be specified for:

Steam heaters with steam on shellside

Two phase flow at inlet

b. For noncorrosive, nonabrasive fluids, nozzles shall be sized to avoid necessity ofimpingement protection. For designs with nozzles sized to avoid impingement

protection, the shell entry area shall be sufficient to obtain comparable values of V2

(within 15-40%) through the nozzle and corresponding shell entry area, but with larger

deviations only permitted if V

2

is low, otherwise the preferred margin is 10%-15%.

10.2.16 Vibration

Thermal design and sizing process shall include analysis of all aspects of design to avoidor minimize the possibility of vibration.

10.2.17 Tubeside Performance

For gases and vapors, the V2 in tubes shall be less than 7000 kg/m-s2 (4700 lb/ft-s2).

For water, the maximum velocities shall be as listed in paragraph 10.2.4.2.

For liquids (other than water), the V2 shall not exceed 8900 kg/m-s2 (5980 lb/ft-s2).

For two-phase flow, the V2 in the tubes shall be checked carefully against the danger oferosion of the tube ends. In such a case, the velocity and density shall be based on ahomogenous gas/liquid mixture.

V is the linear velocity in m/s (ft/s) and is the density in kg/m3(lb/ft3).

10.2.18 Enhanced Heat Transfer Technology

Proprietary technology such as helical baffles, twisted tubes, tube inserts etc may beconsidered where a significant economic or technical advantage can be realized with littleof no detrimental impact to operability and maintainability.

The use of proprietary technology of the type described must be approved by theCOMPANY. In such cases, the thermal and hydraulic design and guarantee shall beincluded in the scope of the technology owner, not the equipment manufacturer (exceptwhere the manufacturer is licensed to carry out the design by the technology owner).

11.0 MATERIALS

Materials selection shall be indicated on the Project Equipment Data Sheets.


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12.0 FABRICATION

Project Equipment Data Sheets shall indicate any special fabrication requirements.

13.0 TESTING

Project Equipment Data Sheets shall indicate any special testing requirements.


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ADDENDUMSHEET

All revisions to this DGS subsequent to the issue of Rev Zero shall be recorded in thisaddendum sheet and shall be incorporated into the DGS in the next revision.

Date Proposed Revision Remarks

DGS-ME-001-R1 Shell and Tube Heat Exchanger Design Criteria

Documents

Transcript of DGS-ME-001-R1 Shell and Tube Heat Exchanger Design Criteria