mcop11

PETRONAS/UCC JVMALAYSIA PROJECT

TECHNICAL STANDARD

MECHANICAL HEAT EXCHANGERS

GENERAL REQUIREMENTS FORDESIGN AND CONSTRUCTION OF

SHELL-AND-TUBE HEAT EXCHANGERS

MCOP-11

SEPTEMBER 1998

MCOP-11MECHANICAL PAGE 0 OF 70HEAT EXCHANGER PETRONAS/UCC JV - MALAYSIA PROJECT SEPTEMBER 1998

Revision 2

GENERAL REQUIREMENTS FOR DESIGN AND CONSTRUCTIONOF SHELL-AND-TUBE HEAT EXCHANGERS

NOTE: Revisions in subsequent issues will be noted on Page 0 of this standard.

REVISION DATE PAGE(S) REVISED

A 1-Dec-97 Review and Comments

0 27-Feb-98 Issue for Engineering(Pre-Endorsement)

1 06-Apr-98 Issue for Engineering(Endorsement Issue)

2 15-Sept-98 Revised Para. 25.2.1.2Per comment from UCC.

PMC APPROVAL

SIGNATURE ON FILE SIGNATURE ON FILEName: Title: Originating Engineer/Engineering Manager Title: Engineering Representative

(PMC) (PMT)

PMT AUTHORISATION

SIGNATURE ON FILE SIGNATURE ON FILEName: Title: Skills Area Lead Engineer Title: Engineering Representative

(Union Carbide Corporation) (PETRONAS)


Revision 2


TABLE OF CONTENTS

1. GENERAL

1.1. Scope

1.2. Exceptions Policy

1.3. Design Requirements

1.4. Vessel Specifications

1.5. Definitions

1.6. Bid Proposals

2. REFERENCE CODES AND STANDARDS

2.1. ASME Code

2.2. TEMA Standards

2.3. Other Codes

2.4. Effective Dates

2.5. Laws of Malaysia

3. WORKING DRAWINGS AND CALCULATIONS

3.1. Information Required

3.2. Special Notes

3.3. Language

3.4. CONTRACTOR/OWNER Review

3.5. Units

3.6. Calculations

4. MATERIALS

4.1. Unspecified Materials

4.2. Tubing

4.2.1. Tubing Thickness

4.2.2. Welded Tubing

4.2.3. Stainless Steel Welded Tubing

4.3. Flange Gaskets

4.3.1. Service Gaskets

4.3.2. Test Gaskets

4.3.3. Spare Gaskets

4.4. Solution Anneal

5. FABRICATION DETAILS

5.1. Backing Strip Removal

5.2. Weld Metal

5.2.1. Clad Materials

5.3. Nozzle Attachment Welds

5.4. Nozzle Location


Revision 2


5.4.1. Examination Of Intersected Weld Joints

5.5. Segmental Nozzle Reinforcing Pads

5.6. Nozzle Reinforcing Pad Test

5.7. Nozzles For Safety Relief And Drainage

5.8. Bore Of Welding Neck Flanges

5.9. Flange Drilling

5.10. Grounding Clip

5.11. Gasket Contact Surfaces

5.11.1. Surface Finish

5.11.2. Flatness Tolerance

5.12. Thickness Of Fixed Tubesheets

5.13. Heat Treatment Of Expanded Joints

5.14. Tolerances

5.15. Welding

5.15.1. Welders and Welding Procedures

5.15.2. Subcontracted Fabrication Work

5.16. Welding Or Grinding

5.17. Prevention Of Stress Raisers In Impact Tested Materials

5.18. Postweld Heat Treatment

5.18.1. Exchangers In Ammonia Service

5.18.2. Welding After Heat Treatment

5.18.3. Alternative PWHT

5.19. Flanged Joint Assembly

5.20. Painted Components That W ill Be In accessible After Assembly

6. NONDESTRUCTIVE EXAMINATION

6.1. Applicable Code

6.2. Examination After Heat Treatment

6.3. Miscellaneous Examinations

6.3.1. Weld Examination

6.3.2. Welded Pressure Joints That Will Be In accessible After Assembly

6.3.3. Base Material Examination

6.3.4. Tube-To-Tubesheet Joints

6.4. Examination Of Repairs

7. HYDROSTATIC TESTING

7.1. Vertically Mounted Exchangers

7.2. Horizontally Mounted Exchangers

7.3. Individual Compartment Tests

7.4. Stacked Exchangers

7.5. Expansion Joints


Revision 2


7.6. Holding Time

7.7. Metal Temperature

7.8. Water Quality

7.9. Blind Flanges For Test

7.10. Leakage During Test

7.11. Retesting Repaired Exchangers

7.12. Disassembly Of Flanged Joints After Testing

7.13. Painting

7.14. Shot Peening

8. NAMEPLATES

8.1. Manufacturer's Nameplate

8.1.1. Mounting Clip

8.2. OWNER'S Nameplate

9. REQUIRED INFORMATION

9.1. Retention

9.1.1. Retention of Radiographs

9.2. Reports

9.3. Calculations

10. CLEANING, PAINTING, AND SHIPPING PROTECTION

10.1. Drying And Cleaning

10.2. Painting

10.3. Machined Surfaces

10.3.1. Assembled Joints

10.3.2. Exposed Surfaces

10.4. Exchanger Openings

10.5. Warning Signs

10.5.1. Heat Treated Exchangers

10.5.2. Fragile Components

10.6. Welded Attachments

11. REFERENCES

11.1. American Society Of Mechanical Engineers (ASME)

11.2. American National Standards Institute (ANSI)

11.3. Military Specifications

11.4. OWNER’s Engineering Standards:

11.5. Not Used

11.6. Welding Research Council (WRC)


11.8. Attachments

11.8.1. Figure 2 - Expanded Tube to Tubesheet Joint


Revision 2


11.8.2. Figure 3 - Expanded and Seal Welded Tube to Tubesheet Joint

12. ARTICLE NOT USED








20. DESIGN CRITERIA

20.1. Equivalent Design Pressure

20.1.1. Equivalent Design Pressure For Shop-Fabricated And Shop-Tested Exchangers

20.2. Design Temperature

20.2.1. Maximum Design Temperature

20.2.2. Minimum Design Temperature

20.3. Operating Liquid Head

20.4. Allowable Stress Values

20.4.1. Low Allowable Stress

20.5. Designing For Vacuum Service

20.5.1. Internal Pressure Rating of Exchangers Designed for VacuumService

20.5.2. Stiffening Rings

20.6. Butt Joints Required

20.7. Radiographic Examination

20.7.1. Seams In Formed Heads

20.8. Corrosion Allowance

20.8.1. Tubes

20.8.2. Nonpressure Parts

20.9. Common Components

20.10. Clad Components

20.11. Wind Or Earthquake Loads

20.11.1. Wind Loads

20.11.2. Earthquake Loads

20.11.3. Article Not Used

20.11.4. Wind Excitation

20.12. Design Pressure And Additional Loadings

20.12.1. Design Loads

20.12.2. Load Combinations


Revision 2


20.13. Torispherical Heads

20.14. Local Shell/Formed Head Stresses

20.15. Combined Primary Stress For Elevated Temperature Service (>427 °C)

20.16. Exchangers In Cyclic Service

21. HYDROSTATIC TEST (SEE ARTICLE 7)

21.1. Test Pressure Determination

21.1.1. Test Pressure

22. PNEUMATIC TESTS


23.1. Magnetic Particle And Liquid Penetrant Examination

23.1.1. ASME Code Categories A and B, and Categories C and D Butt-Type Joints

23.1.2. ASME Code Categories C and D Non-Butt-Type Joints

23.1.3. Corner Joints

23.1.4. Nonpressure Attachment Welds

23.2. Ultrasonic Examination

23.2.1. Rolled Plate

23.2.2. Forgings

23.2.3. Integrally-Bonded Clad Plate

23.2.4. Reports

24. MATERIAL SELECTION

24.1. Carbon And Low-Alloy Steels

24.1.1. Restriction of Code Provision

24.2. Other Than Carbon Or Low Alloy Steels

24.3. Pressure Bolting

24.3.1. Piped Nozzle Flanges

24.3.2. Swing Bolts

24.4. Exchanger Supports

24.5. Attachments To Pressure Parts

24.5.1. Internal Attachments

24.5.2. External Attachments

24.6. Welded Parts Of Dissimilar Metals

24.6.1. External Nozzle Reinforcing Pads for Austenitic Stainless SteelExchangers

24.6.2. External Nonpressure Attachments, Excluding ExchangerSupport Skirts, Welded to Austenitic Stainless Steel Exchangers

24.6.3. Support Skirts Welded To Austenitic Stainless Steel Exchangers

24.6.4. Nozzle Necks For Clad And Unclad Steel Exchangers

24.6.5. External Stiffening Rings Welded to Austenitic Stainless SteelExchangers


Revision 2


24.6.6. Tubesheets Welded To A Carbon Steel Shell

24.7. Flanged Joints Of Dissimilar Metals

25. MISCELLANEOUS DESIGN REQUIREMENTS

25.1. Flanged Pressure Joints

25.1.1. Confined Joints

25.1.2. Gasketed Pass-Rib Joints

25.1.3. Unconfined Joints

25.1.4. Lap Joints

25.1.5. Limitations On The Use Of Slip-On Flanges

25.1.6. Asbestos Gaskets

25.1.7. Spiral-Wound Gaskets

25.1.8. Gasket Selection, Design Factors, and Contact Width

25.1.9. 3-Ply and Single-Ply Corrugated Metal Gaskets

25.1.10. External Moments

25.1.11. Flange Rigidity

25.1.12. Minimum Bolt Size

25.1.13. Bolt Spacing Factor

25.1.14. Indicator-Type Bolting

25.1.15. Additional Flange Design Criteria For ElevatedTemperature (>427 °C)

25.2. Tubesheets

25.2.1. Minimum Tubesheet Thickness

25.2.2. Cladding Thickness

25.2.3. Stationary Tubesheets for Removable Tube Bundles

25.2.4. Tubesheet-to-Shell Weld Joints

25.2.5. Tube-to-Tubesheet Joints

25.3. Tubes

25.3.1. Minimum Wall Thickness

25.3.2. Plain Ends for Low-Finned Tubes


25.4.1. Design Basis

25.4.2. Type of Construction

25.4.3. Location

25.4.4. Other Considerations

25.5. Vapour Belts



25.5.3. Use as Expansion Joint

25.6. Baffles And Support Plates


Revision 2


25.6.1. Minimum Thickness

25.6.2. Baffle Cuts

25.6.3. Drain or Vent Notches

25.6.4. Slides for Removable Tube Bundles

25.6.5. U-Tube Bundles

25.6.6. Tie Rods And Spacers

25.7. Channels, Covers, And Bonnets

25.7.1. Pass Partition Plates

25.7.2. Mitered Reducing Elbows

25.7.3. Flanged Joints

25.8. Nozzles And Manways

25.8.1. Projection

25.8.2. Minimum Manway Size

25.8.3. Integral Reinforcement

25.8.4. Type Of Nozzle Connection

25.8.5. Nozzle Flanges

25.8.6. Minimum Nozzle Neck Thickness

25.8.7. Pipe Tap Connections

25.8.8. Studding Outlets

25.8.9. Gussets

25.8.10. Shell Side Nozzles and Vents and Drains

25.8.11. Flange Connections

25.8.12. Nozzles in or Passing Through Skirts

25.8.13. Tubesheet Vents and Drains

25.8.14. Manway Davits

25.9. Internal Parts

25.9.1. Clad Exchangers

25.9.2. Integrally-Clad Plate

25.9.3. Weld Overlay

25.9.4. Loose Lining


25.10.1. Design Stresses

25.10.2. Skirt Supports

25.10.3. Saddle Supports

25.11. Anchor Bolting


25.11.2. Spacing and Location

25.11.3. Supplier

25.12. Lifting Lugs


Revision 2


25.12.1. Exchanger Lifting Lugs

25.12.2. Lugs for Removable Parts

25.12.3. Tailing Lugs

25.13. Flow-Induced Tube Vibration


Revision 2


PREFACEMCOP-11 (OWNER Technical Standard) publication reflects the views, at the time ofpublication, of:

PETRONAS /UNION CARBIDE Malaysia Joint Venture

It is based on the experience acquired during the involvement with the design, construction,operation and maintenance of processing units and facilities. Where appropriate in MCOP-11 is based on, or reference is made to, national and international standards and codes ofpractice.

The objective is to set the recommended standard for good technical practice applied byOWNER in oil and gas production facilities, oil refinery, gas processing, chemical plants,marketing facilities or any other such facility, and thereby to achieve maximum technicaland economic benefit from standardisation.

When CONTRACTORS or Manufacturers use MCOP-11, they shall be solely responsiblefor the quality of work and the attainment of the required design and engineeringstandards. In particular, for those requirements not specifically covered, the OWNER willexpect them to follow those design and engineering practices which will achieve the samelevel of integrity as reflected in the MCOP-11. If in doubt, the CONTRACTOR orManufacturer/SUPPLIER shall, without detracting from his own responsibility, consult theOWNER or its technical advisor.

The right to use MCOP-11 rests with three categories of users:

1) OWNER and its affiliates.

2) Other parties who are authorised to use MCOP-11 subject to appropriatecontractual arrangements.

3) CONTRACTORS / subcontractors and Manufacturers under a contract with usersreferred to under 1) and 2) which requires that tenders for projects, materialssupplied or -generally - work performed on behalf of the said users comply with therelevant standards.

Subject to any particular terms and conditions as may be set forth in specific agreementswith users, OWNER disclaims any liability of whatsoever nature for any damage (includinginjury or death) suffered by any company with the use, application or implementation of anyMCOP-11 combination of MCOP-11 or any part thereof.

The benefit of this disclaimer shall inure in all respects to OWNER and/or any companyaffiliated to OWNER that may issue MCOP-11 or require the use of MCOP-11.

Without prejudice to any specific terms in respect to confidentiality under contractualarrangements, MCOP-11 shall not, without the prior written consent of OWNER, bedisclosed by users to any company or person whomsoever and MCOP-11 shall be usedexclusively for the purpose it has been provided to the user. MCOP-11 shall be returnedafter use, including any copies which shall only be made by users with the express priorwritten consent of OWNER. The copyright of MCOP-11 vests in OWNER. Users shallarrange for MCOP-11 be held in safe custody and OWNER may at any time requireinformation satisfactory to OWNER in order to ascertain how users implement thisrequirement.


Revision 2


1. GENERAL

1.1. Scope

This standard designates general requirements for design and construction1

of welded shell-and-tube heat exchangers having maximum allowableworking pressures (MAWP) greater than 1.034 barg but not exceeding 138barg, and those subject to external pressure, or for vacuum service (internalpressures less than atmospheric pressure). Special requirements arecovered in the Vessel Specification (see Article 1.4). This standard doesnot provide coverage of air- cooled heat exchangers (see EngineeringStandard MCOP-12). Shell-and-tube heat exchangers within the scope ofthis standard satisfy all applicable requirements of the ASME Boiler andPressure Vessel Code including inspection and Code symbol stamping.

1.1.1. The technical intent of this standard is to establish minimum "base

case" requirements for the construction1 of shell-and-tube heatexchangers, irrespective of specific service fluid-relatedrequirements. The bases/sources for the statements are regulatoryrequirements, safety, environmental protection, and recognised andgenerally accepted good engineering practices for exchangers inchemical service.

1.2. Exceptions Policy

Any exception to or deviation from any statement of this standard and thereferenced documents herein, and which meets the technical intent of thestandard, requires written approval by the OWNER, who shall be responsiblefor interpreting the technical intent of the statement. Exceptions or deviationsto the statements which have been properly approved and listed in theVessel Specifications (see Article 1.4) shall be the Manufacturer’sauthorisation to deviate from the statements in this Standard. Otherwise theManufacturer shall not deviate from this Standard and the referenceddocuments herein without written approval by the OWNER (see Article 1.5).

1.3. Design Requirements

Exchangers or exchanger parts shall comply with applicable parts of theDesign Requirements of Articles 20 through 25. Mechanical design providedin the Vessel Specifications shall not relieve Manufacturer of his ASME

Code-defined responsibility regarding Code construction1.

1.4. Vessel Specifications

The term "Vessel Specifications" shall be understood to include anydrawings, specifications, data, and listings of approved deviations (see

1 Construction is an all-inclusive term comprising materials, design, fabrication, examination,

inspection, testing, certification and pressure relief.


Revision 2


Article 1.2) designated by OWNER (see Article 1.5) for a particularexchanger or group of exchangers. In case of disagreement between theVessel Specifications and MCOP-11, Article 1.2 applies.

1.5. Definitions

The OWNER is the party which initiates the project and ultimately pays for itsdesign and construction. The OWNER will generally specify the technicalrequirements.

The OWNER may also include an agent or consultant, authorised to act forthe OWNER.

The CONTRACTOR is the party which carries out all or part of the design,engineering, procurement, construction and commissioning for the project.The OWNER may sometimes undertake all or part of the duties of theCONTRACTOR.

The Manufacturer is the party which manufactures or supplies equipmentand services to perform the duties specified by the CONTRACTOR.

1.6. Bid Proposals

All quotations shall be submitted in strict accordance with this standardand/or the Vessel Specifications. Proposed exceptions or alternatives tothese requirements may be quoted as options for OWNER's considerationprovided such exceptions or alternatives are clearly and completelydescribed in the proposal.

2. REFERENCE CODES AND STANDARDS

2.1. ASME Code

Exchangers shall be constructed1 in accordance with the ASME Boiler andPressure Vessel Code, Section VIII, Division 1 (hereafter referred to as theASME Code). Each ASME Code U-symbol- stamped exchanger shall beregistered with the National Board of Boiler and Pressure Vessel Inspectors.National Board registration is not applicable for exchangers stamped with theASME Code UM-symbol.

2.2. TEMA Standards

Exchangers shall comply with the mechanical standards of the TubularExchanger Manufacturers Association (TEMA) for Class "B" exchangers,except as otherwise or additionally specified herein or in the VesselSpecifications.


Revision 2


2.3. Other Codes

Requirements for exchangers constructed in accordance with rules otherthan specified in Articles 2.1 and 2.2 shall be by written agreement betweenOWNER and Manufacturer.

2.4. Effective Dates

References to codes, standards, and other specifications are to the latestedition or addenda issued at the date of the exchanger purchase contractaward.


Factories and Machinery Act 1967 (Act 139) & Regulations and Rules (As at25th January 1997).

2.5.1. Exception

2.5.1.1. Paragraph 61, Item 2 (Factories and Machinery (SteamBoilers and Unfired Pressure Vessel) Regulations, 1970, PartIII)

"The distance between any two supports of anyhorizontal unfired pressure vessel shall not begreater than sixteen feet and each supportshall extend over not less than one-third of thecircumference of the vessel except whereauthorised in writing by the Chief Inspector"

Exception: Article 25.10.3.3 of this standard"Saddle Design" shall be used as anapproved exception to Paragraph 61,Item 2 of the Factories and MachineryRegulations, 1970.

2.5.1.2. Paragraph 72. (Factories and Machinery (Steam Boilers andUnfired Pressure Vessel) Regulations, 1970, Part III)

(1) "Every steam boiler and unfired pressurevessel shall, before being put into service forthe first time, be subjected to a hydrostatic test-

a) of twice the authorised safe workingpressure where such pressure is notmore than one hundred pounds persquare inch:

and


Revision 2


b) of one and a half times the authorisedsafe working pressure plus fifty poundswhere such pressure exceeds onehundred pounds per square inch".

Exception: Pressure Vessels conforming to thisstandard, shall be hydrostatic tested inaccordance with Article 21.

3. WORKING DRAWINGS AND CALCULATIONS

3.1. Information Required

Manufacturer shall provide certified assembly and working drawings andapplicable design calculations (see Article 3.6) for all exchangers. Drawingsshall be complete and shall include, but not necessarily be limited to, thefollowing information:

1. OWNER's item number, purchase order number, work order number,and property number.

2. Reference to specifications. Manufacturer shall include on hisdrawings a reference to all applicable codes, ASME Code Cases,standards, and specifications, including date of issue. Referencesshall include all applicable OWNER specifications and standards,and any applicable Manufacturer standards. When reference ismade to Manufacturer’s own standards, copies of such standardsshall be included with the submitted working drawings.

3. Applicable ASME Code paragraphs for impact test exemption [e.g.,UG-20(f), UCS-66(a), UCS-66(b), UCS-66(c)] or for impact testrequirements (such as UHA-51 or UHT-6).

4. National Board registration number (U-symbol stamped exchangers;see Article 2.1).

5. Maximum allowable working pressures (MAWP) for shell side andtube side and coincident maximum design temperature (see Article20.2). (Internal and external if applicable).

6. Minimum design metal temperatures (MDMT) for shell side and tubeside and coincident maximum allowable working pressure (see Article20.2).

7. Design specific gravity (see Article 20.3).

8. Joint efficiency for each butt welded joint (or seamless equivalent) inthe exchanger, including nozzles and communicating chambers. Ajoint efficiency map may be required.

9. Corrosion allowance. If none, so state.

10. Relevant fabrication, inspection, nondestructive examination, testing,and painting requirements, including postweld heat treatment, degreeof radiographic or other nondestructive examinations, etc.

11. Hydrostatic or pneumatic test pressures for the shell side and thetube side, as applicable:


Revision 2


a. Horizontal position (referenced to compartment centreline)

b. Vertical position (referenced to top of compartment)

12. Minimum permissible test temperature and holding times for the shellside and the tube side.

13. Sensitive leak tests, if any.

14. Estimated weight of exchanger, empty, operating, full of water, anderection weight with platforms, insulation, piping, and otherattachments which will be in place during the erection. Also showestimated weight of removable tube bundles.

15. Capacity of shell side (or each compartment) and tube side, in litres.

16. Gross tube surface area on shell side, in mm2.

17. Thickness of all components. For formed heads, the specifiedminimum thickness after forming shall be shown.

18. Tube bending schedule for u-tube bundles. (Center-to-centredimensions of bends.)

19. Material specifications for all components (including ASME standardspecifications for product forms, as applicable).

20. Weld details including weld contour requirements, if applicable. Allwelds shall be either detailed or identified by use of the standardwelding symbols of the American Welding Society, ANSI/AWS A2.4.

21. Surface preparation and painting or other protective coatingspecifications.

22. All pertinent dimensions, including location of weld seams, nozzlelocation and projection, location of exchanger supports, insulationsupports, and any other information necessary for a completedescription of the exchanger.

23. Manufacturer's drawings shall have the same designation for nozzles,manways, and skirt openings as shown in the Vessel Specifications.For nozzles located normal to a cylindrical shell, the exchangerassembly drawings shall include dimensions from the centreline (axis)of the shell to the nozzle faces.

24. Complete description of all exchanger flanges (including bothstandard and custom design), pressure bolting, and gaskets.

25. Facsimiles of Manufacturer's and OWNER's nameplates as stampedby Manufacturer.

26. Special service notes (e.g., "for cyclic service" followed by adescription of the cyclic loadings and number of cycles used in thedesign).

27. Exchanger support details.


Revision 2


3.2. Special Notes

Manufacturer's drawings shall also include the following notes as applicable:

1. Stainless Steel or Nickel-Alloy Exchangers

The following note: "Zinc-coated (galvanised or painted) componentsshall not be in contact (welded, bolted, or loose) with any alloy partsof the exchanger."

2. Hastelloy, Monel, Nickel, or Nickel-Alloy Exchangers

The following note: "Substances containing sulphur (e.g., lubricantsto aid machining) shall not be applied to alloy parts of theexchanger."

3. All Exchangers

The following note: "Substances containing chlorine or which willdecompose to hydrogen chloride (e.g., coatings to prevent adhesionof weld spatter) shall not be applied to any part of the exchanger."

4. Clad-Steel Exchangers

Drawing notes shall specify whether or not the thickness of claddingmetal has been included in the design calculations for strength.Inclusion of cladding requires OWNER's approval (see Article 20.10).

5. Balance Point Location

For horizontal exchangers, the balance point location shall be notedand dimensioned from a permanent reference point (e.g., main shellflange, tubesheet, etc.).

6. Exchangers for which Fatigue is a Controlling Design Requirement

The following note: "Each shell section shall be corrected for peakingof the longitudinal seam(s) prior to assembly to mating shell sectionsor other components."

3.3. Language

The language of all drawings and calculations shall be English or the Englishtranslation of the language used shall also be shown.

3.4. CONTRACTOR/OWNER Review

Manufacturer's drawings shall be reviewed by CONTRACTOR prior to startof fabrication unless release to proceed is obtained from CONTRACTOR inwriting. OWNER may also require review/audit of Manufacturer’s drawings.


Revision 2


3.5. Units

Dimensions, pressure, stress, volume, temperature and area shall be in thefollowing metric units:

Dimensions mm Pressure bar

Stress kg/cm2 Volume litre

Temperature oC Area mm2

3.6. Calculations

Calculations are required for each item in sufficient detail to demonstratecompliance with the requirements of this standard and the referenceddocuments (see Article 9.3).

4. MATERIALS

4.1. Unspecified Materials

Materials not completely defined in the Vessel Specifications shall conformto the requirements of the ASME Code.

4.2. Tubing

4.2.1. Tubing Thickness

Average wall tubing (tubing with a plus-or-minus variation fromspecified wall thickness) may be used provided the under-tolerance will not permit wall thicknesses less than the requiredminimum for design conditions. The tolerance for average walltubing shall not be more than the smaller of the allowabletolerance for average (nominal) wall given in the applicable tubespecification or plus-or-minus 10% of the specified wall thickness.Tubes having a wall thickness different than specified in theVessel Specifications shall not be substituted without OWNER'sapproval.

4.2.2. Welded Tubing

Welded tubing shall be examined by the electromagnetic (eddycurrent) nondestructive examination technique after final heattreatment in accordance with applicable ASME Boiler andPressure Vessel Code material specifications.


Revision 2


4.2.3. Stainless Steel Welded Tubing

The weld metal of molybdenum bearing grades of stainless steelwelded tubing shall be cold worked prior to final heat treatment inaccordance with applicable ASME Boiler and Pressure VesselCode material specifications.

4.3. Flange Gaskets

Gaskets shall be continuous, except that metal gaskets made integral by

welding (e.g., single or 3-ply corrugated gaskets) and GRAFOIL® GTTMHgrade tape gaskets (or surface treatment for single or 3-ply corrugatedgaskets) with overlapped ends are acceptable. Means shall be provided forpositioning (centring) the gasket during joint make-up. Gaskets cut fromsheet stock shall be 1.6 mm thick.

4.3.1. Service Gaskets

When service gaskets are designated to be furnished byManufacturer (e.g., for main shell joints, manways, blind flangednozzles), the gaskets shall be as specified in the VesselSpecifications (see Article 25.1.6).

4.3.2. Test Gaskets

Any flanged joint for which the service gasket is to be furnishedby Manufacturer and which will not be disassembled after testingshall be tested with the specified service gasket (see Article4.3.1). If the joint is to be disassembled after testing and employsflanges per ASME/ANSI B16.5, the test gasket may be selectedby Manufacturer subject to the limitations in Article 4.3.2.1. If thejoint is to be disassembled after testing, employs non-standardflanges (other than ASME/ANSI B16.5), and the service gasket isnot specified, the test gasket shall be approved by OWNER.

4.3.2.1. Limitations

In no case shall the nominal thickness of sheet orlaminate gasketing be greater than 1.6 mm. No jointsealing compound, gasket adhesive, or lubricant shallbe used unless specified for the service condition.

4.3.2.2. Flanged Joints Disassembled After Testing

Flanged joints specified to be furnished with servicegaskets (e.g., main shell joints, manways, blindflanged nozzles) and which are disassembled followingtests shall be reassembled using new service gaskets.If such joints are shipped unassembled, new service


Revision 2


gaskets for field installation shall be suitably packaged,marked, and shipped with the exchanger.

4.3.3. Spare Gaskets

For flanged joints specified to be furnished with service gaskets, aspare gasket (in addition to any required for initial field assemblyin Article 4.3.2.2) shall be furnished and suitably packaged,marked, and shipped with the exchanger for the following joints:Flanged joints having other than ASME/ANSI B16.5 flanges withother than commercially available sheet or laminate gaskets.

4.4. Solution Anneal

All formed heads fabricated from austenitic (Type 304 and Type 316 only,including low-carbon and stabilised grades) or duplex stainless steel shall besolution annealed, per SA-480 of ASME Boiler and Pressure Vessel CodeSection II, Part A, after forming.

5. FABRICATION DETAILS

5.1. Backing Strip Removal

Permanent weld joint backing strips are not permitted (see Article 20.6).

5.2. Weld Metal

Deposited weld metal shall be essentially of the same strength, ductility, andchemical composition as the material joined.

5.2.1. Clad Materials

For weld joints in clad material, the final pass on the clad sideshall be of the same nominal composition as the cladding. Theweld shall not be ground smooth or flush unless specified in theVessel Specifications. Corrosion resistant weld overlay shall bein accordance with Engineering Standard MMOC-616.

5.3. Nozzle Attachment Welds

Non-butt joints connecting nozzles (includes manways, couplings, studdingoutlets, and sight glasses) to exchanger wall (ASME Code Category D joints)shall be full penetration welds. Unless otherwise approved by OWNER, allCategory D joints shall be full penetration welds extending through the entirethickness of the exchanger wall. Reinforcing pads shall not be located onthe inside surface of the vessel. Nozzles designated to extend beyond theinside surface of the exchanger wall shall have a fillet weld at the insidecorner.


Revision 2


5.4. Nozzle Location

Nozzles or other openings shall be located so that no part of the nozzle,added reinforcement, or attachment welds intersects any welded joint in theexchanger wall, except, if necessary, they may be located in ASME CodeCategory B joints. They shall not be located in other exchanger joints.

5.4.1. Examination Of Intersected Weld Joints

Welded joints in the exchanger wall which are to be intersectedshall be radiographed using acceptance standards as set forth inASME Code Paragraph UW-51 for full radiography. When thewelded joint is to be covered by a reinforcing pad, the weld shallbe radiographed and ground flush before pad attachment.Except as required by ASME Code Paragraph UW-14 for smallopenings, the length of weld seam to be radiographed shall bethe greater of the nozzle inside diameter each side of the axis ofthe nozzle or the portion of the weld seam to be covered by areinforcing pad and its attachment weld plus 25 mm on each side.

5.5. Segmental Nozzle Reinforcing Pads

Nozzle reinforcing pads constructed in segments shall have the segmentsjoined with full penetration butt welds, the location of which shall be at least45° from the longitudinal axis of the exchanger (see ASME Code Figure UG-37).

5.6. Nozzle Reinforcing Pad Test

External nozzle reinforcing pads shall have one NPT 1/4 telltale hole in eachpad segment. The pad shall be tested with 1.724 barg dry air or nitrogenand application of a bubble forming solution (soaps, detergents, and/orindustrial compounds that are designed specifically to be used as cleaningagents are not permitted) to all pad welds and accessible surfaces of insidenozzle-to-exchanger wall weld. Telltale holes shall be plugged with a roomtemperature vulcanising (RTV) silicone sealer.

5.7. Nozzles For Safety Relief And Drainage

Nozzles intended for use with a safety relief device and nozzles serving asexchanger drains shall be trimmed flush inside the exchanger wall.

5.8. Bore Of Welding Neck Flanges

The bore of welding neck flanges shall match the inside diameter of theattached pipe.


Revision 2


5.9. Flange Drilling

Bolt holes in all fixed flanges and studding outlets shall straddle the naturalcentrelines. For nozzles in heads, the bolt holes shall straddle centrelinesparallel to or coincident with the natural exchanger centrelines. Bolt holes inflanges shall be 3.2 mm larger than the diameter of the bolts.

5.10. Grounding Clip

Provide each exchanger with a grounding clip in accordance withEngineering Standard MEQ-19.

5.11. Gasket Contact Surfaces

For all tubesheets, shop-fabricated flanges, and lap rings, the gasket contactsurface shall be checked and machined as required after completion of alloperations that can affect flatness tolerance.

5.11.1. Surface Finish

Except for ASME/ANSI B16.5 flanges and factory-made lap-jointstub ends, the gasket contact surface shall be 3.175 - 6.350microns with spiral or concentric circular serrations.

5.11.2. Flatness Tolerance

When specified in the Vessel Specifications, the gasket contactsurface flatness tolerance, in both the radial and circumferentialdirections, shall be 0.152 mm total indicator reading.Measurement shall be made by a dial indicator after all otheroperations with regard to the fabrication of the tubesheet, flange,or lap ring and its attachment to the shell or nozzle neck havebeen completed. The total circumferential tolerance shall notoccur in less than 20 degrees of arc.

5.12. Thickness Of Fixed Tubesheets

Tubesheet thickness in excess of 3.2 mm greater than the specifiedthickness is not acceptable for fixed tubesheets.

5.13. Heat Treatment Of Expanded Joints

Expanded tube-to-tubesheet joints shall be rolled (expanded) after anyrequired postweld heat treatment in which the temperature of the expandedjoint exceeds 204°C.

5.14. Tolerances

Dimensional tolerances shall apply to the completed exchanger after finalpressure test, and shall conform to Engineering Standard MEQ-182. For


Revision 2


exchangers for which fatigue is a controlling design requirement, theallowable peaking distortion, shall be specified by OWNER.

5.15. Welding

5.15.1. Welders and Welding Procedures

All welds, including those attaching non-pressure parts topressure parts, shall be made by welders (or welding operators)and welding procedures qualified under the provisions of SectionIX of The ASME Boiler and Pressure Vessel Code.

5.15.2. Subcontracted Fabrication Work

Approval must be obtained from CONTRACTOR before anywelding or preparation for welding is subcontracted to anothershop or supplier. Such approval shall require knowledge byCONTRACTOR of the qualifications of the subcontractor who isperforming the work.

5.16. Welding Or Grinding

Welding or grinding (including cosmetic grinding) will not be allowed on thepressure resisting components of exchangers after pressure testing andASME Code symbol stamping unless approved in writing by OWNER.

5.17. Prevention Of Stress Raisers In Impact Tested Materials

Special care shall be taken to prevent stress raisers which might cause lowimpact strength due to notch effect or abrupt change in section. Referencelines shall not be stamped on the material. Welder's and welding operator'ssymbols may be stamped on the material in accordance with the provisionsof ASME Code Paragraph UW-37, provided that a round-nose stamp isemployed and the symbol is located at least 25 mm from the edge of theweld.

5.18. Postweld Heat Treatment

When postweld heat treatment is required, a sufficient number ofthermocouples shall be firmly attached to the exchanger to assure that it isbeing heated and cooled evenly during the heat treatment operations. Amulti-point recording type instrument shall be used to record thetemperatures during the heat treatment cycles. (See Article 5.13 forexpanded tube joints.)

5.18.1. Exchangers In Ammonia Service

Ferritic steel exchangers in anhydrous ammonia service shall bepostweld heat treated.


Revision 2


5.18.2. Welding After Heat Treatment

No welding shall be performed on the exchanger after postweldheat treatment.

5.18.3. Alternative PWHT

Requirements of Code Table UCS-56.1 for carbon and low alloysteels shall not be employed.

5.19. Flanged Joint Assembly

5.19.1. Joints shall be assembled and tightened in accordance with thefollowing:

1. All "working" surfaces must be cleaned and inspectedbefore assembly is started.

a) Clean gasket seating surfaces to remove all greaseand dirt. Gasket seating surfaces shall be freefrom any scratches, nicks, burrs, weld spatter, andsimilar defects.

b) External and internal threaded surfaces offasteners shall be inspected for damage: replacequestionable parts.

c) Inspect nut bearing surfaces for scores, burrs, etc.:Remove protrusions, spot face if required.

2. Place new gasket in position following examination fordefects or damage. Handle gaskets carefully to avoiddamage. Do not remove any gasket shipping/handlingprotector until ready to use the gasket. Make sure that thegasket is in proper alignment with the gasket surfaces onthe flanges or lap joint stub ends.

3. Liberally coat all external and internal threaded surfaces offasteners with the lubricant specified in the VesselSpecification. If the lubricant is not specified in the VesselSpecification, the lubricant shall be approved by OWNER.

4. Align flange or stub end faces carefully before bolting up.Fasteners shall fit loosely in bolt holes. Do not usefasteners to spring flanges for alignment.

5. Install fasteners with nuts hand tight, then snug up at 1.38to 2.77 kg-m.

6. Tighten fasteners carefully using a cross-bolting techniqueand incremental tightening to increase loading about 1/4to 1/3 of total preload per step.


Revision 2


5.19.2. Joints requiring custom assembly procedures shall be as required bythe Vessel Specification.

5.20. Painted Components That W ill Be In accessible After Assembly

The surfaces of painted components that will be inaccessible after assemblyshall be non-destructively examined and painted prior to assembly andhydrostatic testing (see Articles 6 and 10.2).


6.1. Applicable Code

When weld examination by the magnetic particle (MT), liquid penetrant (PT),or ultrasonic (UT) method is required, the examination shall be inaccordance with Appendix 6, 8, or 12, respectively, of the ASME Code.

6.2. Examination After Heat Treatment

When completed welds are required to be examined by the MT, PT, or UTmethod and the exchanger or part is to be postweld heat treated, theexamination shall be made after heat treatment for the following:

1. Carbon or low-alloy steel exchangers for which impact testing isrequired.

2. Welds joining non-impact-tested low-alloy steels over 32 mm thick.

3. Welds joining carbon steels over 51 mm thick.

4. When required by the ASME Code.

6.3. Miscellaneous Examinations

6.3.1. Weld Examination

The root pass, after back-chipping to sound metal, and allaccessible surfaces of the completed weld shall be examined byMT or PT for the following:

1. Category A, B, C, and D butt-type joints when jointthickness exceeds 51 mm.

2. Category C and D nonbutt-type joints when design isbased on a joint efficiency of 1.00.

6.3.2. Welded Pressure Joints That Will Be In accessible After Assembly

Welded joints that will be inaccessible after assembly shall beexamined by PT (see Article 6.1), and repaired as required, priorto painting and assembly as follows:

1. Examine the root pass and its opposite side after back-chipping to sound metal.


Revision 2


2. Examine the finished surfaces of the weld, after anyrequired machining or grinding, with the followingadditional requirement: all indications on the finished weldsurfaces shall be removed by grinding or welding prior tothe required pressure test.

6.3.3. Base Material Examination

When nozzles are attached with a full penetration weld throughthe nozzle wall, the cut edge of the openings in exchanger wallsthicker than 13 mm shall be examined by MT or PT before nozzleattachment and, when accessible, after attachment.

6.3.4. Tube-To-Tubesheet Joints

Any specified sensitive leak testing of seal-welded or strength-welded tube-to-tubesheet joints shall be performed prior to anytube-to-tubesheet joint rolling or hydrostatic testing.

6.4. Examination Of Repairs

When an examination reveals an unacceptable imperfection, it shall berepaired and the repair shall be examined by the same method, to the sameextent, and by the acceptance criteria that revealed the condition.Additionally, all repairs made by welding shall be made prior to any requiredpostweld heat treatment.

7. HYDROSTATIC TESTING

7.1. Vertically Mounted Exchangers

Vertical exchangers shall be tested in their operating position if practicable.If a vertical exchanger is shop-tested in the horizontal position, Manufacturershall be responsible for determining the need for and providing anytemporary supports to prevent distortion or other damage to the exchangerduring the test. All supporting lugs, rings, legs, or other permanentlyattached supports shall be attached to the vessel before the test.

7.2. Horizontally Mounted Exchangers

Horizontal exchangers shall be tested on their operating supports withoutadditional temporary supports or shoring. The saddles or other permanentlyattached supports shall be attached to the exchanger before the test.

7.3. Individual Compartment Tests

The shell side and tube side shall be given a separate and individual testwith atmospheric pressure in the adjacent compartments (see Article 20.9).


Revision 2


7.4. Stacked Exchangers

Stacked exchangers with integrally connected nozzles shall be assembledand tested as a single unit by Manufacturer.


Temporary ties or supports which restrict the normal movements ofexpansion joints shall be removed or loosened during hydrostatic tests.

7.6. Holding Time

The test pressure shall be maintained for one hour per 25 mm of maximumshell or formed head thickness, with a one hour minimum and a five hourmaximum.

7.7. Metal Temperature

The exchanger metal temperature, for the entire duration of the test, shallnot be colder than the minimum design metal temperature (MDMT) plus17°C (see Article 20.2).

7.8. Water Quality

Unless otherwise approved by CONTRACTOR in writing, the hydrostatic testliquid shall comply with the following:

1. Hydrostatic test liquid shall be potable water, condensate, ordemineralised water.

2. Hydrostatic test liquid shall have a chloride content not greater than250 ppm. For exchangers with austenitic stainless steel or aluminiumcomponents, the chloride content shall not exceed 50 ppm unless thevessel is drained and rinsed with condensate or demineralised waterhaving a chloride content less than 50 ppm.

3. Hydrostatic test liquid shall not remain in contact with exchangercomponents longer than 72 hours.

7.9. Blind Flanges For Test

Manufacturer shall furnish all blind flanges, gaskets, and bolting (or othertypes of blanking covers as may be required) necessary for testing. Forconnections not specified to be furnished with blind flanges, the blind flangesand bolting (or other type covers) may be removed after testing and remainthe property of Manufacturer (see Article 10.4 for shipping covers).

7.10. Leakage During Test

Except for leakage that might occur at temporary test closures for thoseopenings intended for weld connections, leakage is not allowed during theduration of the test (see Article 7.6). Leakage form temporary seals shall bedirected away so as to avoid masking leaks from other joints.


Revision 2


7.11. Retesting Repaired Exchangers

Repairs to eliminate rejectable imperfections revealed during pressuretesting shall be tested by reapplying the original pressure test(s).

7.12. Disassembly Of Flanged Joints After Testing

Main shell joints, manways, and nozzles specified to be furnished with blindflanges shall be left undisturbed and assembled after testing if practicable. Ifnecessary to disassemble for shipping, drainage, or other purposes, newgaskets shall be furnished as specified in Article 4.3.2.2.

7.13. Painting

Except for surfaces to be painted but which will be inaccessible afterassembly (see Article 10.2), painting shall be performed after the Codepressure test (and any sensitive leak test) has been completed.

7.14. Shot Peening

Unless approved by OWNER in writing, controlled shot peening and othersimilar methods, which are intended only to enhance surface properties ofexchangers or exchanger parts, shall be performed after the Code pressuretest (and any sensitive leak test) has been completed.

8. NAMEPLATES

8.1. Manufacturer's Nameplate

Each exchanger shall be furnished with a Manufacturer's nameplate inaccordance with ASME Code Paragraph UG-119. Where stamping directlyon the exchanger in lieu of a nameplate is unavoidable, a round-nose stampor punch shall be employed. Nameplate stamping directly on impact testedmaterial is not permissible. For exchangers designed for vacuum operation,the nameplate shall also include the maximum allowable external pressureand coincident maximum temperature.

8.1.1. Mounting Clip

Material, style, and projection for mounting clips shall be the sameas shown on Engineering Standard MEQ-15A for the OWNER’snameplate (see Article 8.2). Engineering Standard MEQ-15Aprovides for mounting the Manufacturer's nameplate and theOWNER nameplate on the same clip where adequate exchangerspace is available.

8.2. OWNER'S Nameplate

Each exchanger shall be furnished with a separate OWNER’s standardnameplate for the shell side and the tube side. The nameplate(s) will be


Revision 2


furnished by CONTRACTOR for stamping and installation by Manufacturer.Stamping shall be per Engineering Standard MEQ-16, and attachment to theexchanger per Engineering Standard MEQ-15A.

9. REQUIRED INFORMATION

9.1. Retention

Copies of drawings, calculations, reports, and other pertinent data requiredby this standard and the referenced documents shall be submitted byCONTRACTOR to OWNER.

9.1.1. Retention of Radiographs

All radiographs (full RT only), including the location marker mapwhen location markers are not permanently marked on theexchanger, shall be forwarded to CONTRACTOR. Radiographsand location marker maps shall be identified by the equipmentpurchase order and exchanger item number.

9.2. Reports

Manufacturer shall furnish CONTRACTOR with a minimum of four copies ofeach of the following data as applicable:

1. Manufacturer's Data Report (U-symbol stamped exchangers; seeArticle 2.1). For exchangers which are designed for overpressureprotection by system design, Manufacturer shall include the followingstatement in the Remarks section of the Manufacturer's Data Report:"Code Case 2211; Prior jurisdictional acceptance of this Code Casemay be required."

2. Manufacturer's Certificate of Compliance (UM-symbol stampedexchangers; see Article 2.1).

3. Certified mill test reports or certificates of compliance for materialsused, including forgings to other than the dimensional andidentification marking requirements of an ASME/ANSI flange or fittingstandard.

4. Charts of recorded heat treatment temperatures.

5. Rub-offs of Manufacturer's and OWNER’s nameplate stampings.

9.3. Calculations

Manufacturer shall furnish CONTRACTOR with complete certified exchangerdesign calculations (see Article 3.6).


Revision 2


10. CLEANING, PAINTING, AND SHIPPING PROTECTION

10.1. Drying And Cleaning

The exchanger shall be completely drained and immediately dried after thehydrostatic test. It is preferred that the residual water be wiped from theinterior of the exchanger heads; however, blowing with nitrogen, or dry air ifan adequate source of nitrogen is unavailable, is acceptable provided thatthe gas pressure in the exchanger is not greater than essentiallyatmospheric pressure.

10.2. Painting

Surfaces that are required by the Vessel Specification to be painted andwhich will be inaccessible after assembly (e.g., mating surfaces between lap-joint flanges and nozzle necks, shells, lap rings or stub ends, bolt holes, andwelded joints) shall be painted prior to assembly and hydrostatic testing.Welded joints that will be inaccessible after assembly shall be examined byPT, and repaired as required, prior to painting (see Article 6).

10.3. Machined Surfaces

All gasket seating, threaded, or other machined surfaces shall be protectedfor shipment as follows:

10.3.1. Assembled Joints

Main shell joints, manways, blind-flanged nozzles, pluggedcouplings, and other connections specified to be furnished withservice covers shall be shipped assembled if practicable (seeArticle 4.3.2.2).

10.3.2. Exposed Surfaces

For carbon and low alloy steels, all exposed machined orthreaded surfaces shall be cleaned with solvent and coated withtemporary rust preventive grease conforming to MilitarySpecification MIL-G-10924. The following products meet thisdesignated specification; other equivalent products areacceptable: Ashland Oil-Tectyl 858C, Sanchem No-Ox-Id-A,Exxon-Beacon 325, Houghton-Rust Veto Heavy. Furnishshipping covers per Article 10.4.

10.4. Exchanger Openings

Openings shall be covered with durable and damage-resistant covers (e.g.,wood or metal) to prevent entrance of dirt, water, and debris. Protectmachined and threaded surfaces from damage.


Revision 2


10.5. Warning Signs

The following types of exchangers shall be conspicuously marked onopposite sides of the exchanger identifying the need for caution:

10.5.1. Heat Treated Exchangers

Exchangers which have been postweld heat treated shall be soidentified and marked with a notice prohibiting the welding of anyattachments.

10.5.2. Fragile Components

Exchangers having fragile parts (e.g., glass lining, HAVEG,KARBATE) shall be so identified and marked with the need forcareful handling.

10.6. Welded Attachments

Welding attachments to exchangers for shipping purposes is not permitted(see Article 10.5.1).

11. REFERENCES

This standard contains references to the following documents (see Article 2.2):

11.1. American Society Of Mechanical Engineers (ASME)

ASME Boiler and Pressure Vessel Code

Section II, Part A, Ferrous Material Specifications

Section II, Part B, Non-ferrous Material Specifications

Section VIII, Division 1, Pressure Vessels

Section IX, Welding and Brazing Qualifications

ASME Code for Pressure Piping

B31.3, Chemical Plant and Petroleum Refinery Piping

B1 Screw Threads (formerly ANSI B1)

ASME/ANSI B1.1, Unified Inch Screw Threads (UN and UNR ThreadForm)

B16 Standardisation of Valves, Flanges, Fittings, and Gaskets (formerlyANSI B16)

ASME/ANSI B16.5, Pipe Flanges and Flanged Fittings

ASME/ANSI B16.9, Factory-Made Wrought Steel Buttwelding Fittings


Revision 2


ASME/ANSI B16.47, Large Diameter Steel Flanges

B18 Standardisation of Bolts, Nuts, Rivets, Screws, Washers, and SimilarFasteners (formerly ANSI B18)

ASME/ANSI B18.2.2, Square and Hex Nuts (Inch Series)

11.2. American National Standards Institute (ANSI)

American Society of Civil Engineers (ASCE)

ANSI/ASCE 7, Minimum Design Loads for Buildings and Other Structures

American Welding Society (AWS)

ANSI/AWS A2.4, Symbols for Welding, Brazing, and NondestructiveExamination

11.3. Military Specifications

MIL-G-10924, Grease, Automotive and Artillery

11.4. OWNER’s Engineering Standards:

MEQ-15A, Nameplate Mounting Clip for OWNER’s Nameplate.

MEQ-16, OWNER’s Nameplate for Process Vessels.

MEQ-19, Grounding Clip for Process Vessels.

MEQ-180, Locking Studs for Stationary Tubesheets.

MEQ-182, Fabrication Notes and Dimensional Tolerances for Shell-and-Tube Heat Exchangers.

MCOP-12, General Requirements for Design and Construction of Air-CooledHeat Exchangers

MMOC-615, Application of XYLAN 1014 Coating to Carbon Steel and Low-Alloy Steel Threaded Fasteners

MMOC-616, Corrosion Resistant Overlays on Steel Base Metal

11.5. Not Used

11.6. Welding Research Council (WRC)

Bulletin 107, Local Stresses in Spherical and Cylindrical Shells due toExternal Loadings


Revision 2


Bulletin 297, Local Stresses in Cylindrical Shells due to External Loadings onNozzles


Factories and Machinery Act 1967 (Act 139) & Regulations and Rules (As at25th January 1997).

11.8. Attachments

11.8.1. Figure 2 - Expanded Tube to Tubesheet Joint

11.8.2. Figure 3 - Expanded and Seal Welded Tube to Tubesheet Joint










Revision 2


DESIGN REQUIREMENTS

LIMITATIONS

The design of shell, tubes, tubesheets, and expansion joints (if used) for fixed tubesheetexchangers having any of the following design conditions shall either be performed byOWNER, or Manufacturer's proposed design shall be reviewed by OWNER prior topurchase:

1. Tube side design pressure exceeding 42 barg.

2. Shell side design pressure exceeding 69 barg.

3. Shell inside diameter larger than 1219 mm with carbon steel, low-alloy steel, or cladtubesheet material; or larger than 762 mm with high-alloy or non-ferrous tubesheetmaterial.

4. Any exchanger requiring a shell expansion joint(s).

20. DESIGN CRITERIA

20.1. Equivalent Design Pressure

FOREWORD

These design requirements for determining exchanger thicknesses arebased on the criteria that exchangers shall be designed to withstand, in thecorroded condition if a corrosion allowance is required, the more severe ofthe following design conditions:

1. The "Equivalent Design Pressure" at 38°C. This design conditionprovides for full hydrostatic test of all pressure components of shop-fabricated vertical exchangers while in the horizontal position, andpermits future hydrostatic testing of vertical exchangers in theoperating position. Article 20.1 defines the design procedure to beused for the "Equivalent Design Pressure" condition for ASME Codeexchangers (see Article 2.1).

2. The design pressure plus any applicable additional loadings (e.g.,wind pressures, seismic loadings) at both the maximum and minimumdesign metal temperatures (considering: start-up and start-upfollowing an emergency shutdown; normal, temporary, andemergency operation; and, normal and emergency shutdown).

In addition to the requirements of Articles 20.2 through 20.13, the thicknessof all pressure components shall be further checked and increased, ifnecessary, to conform to the following requirements:

20.1.1. Equivalent Design Pressure For Shop-Fabricated And Shop-Tested Exchangers

The thickness of all pressure components (before any corrosionallowance is added), regardless of elevational position in theexchanger, shall be adequate to withstand the larger of the


Revision 2


equivalent design pressures PED or PET determined by formulas(1) and (2) below. In computing thickness required to withstandequivalent design pressures, the ASME Code allowable tensilestresses at 38°C and the applicable welded joint efficiency shallbe used, and no additional loadings other than those inherent inthe equivalent design pressure formulas need be considered. Forthe purpose of computing equivalent design pressures only,where two ASME Code allowable stress values are given for amaterial, the higher value shall be used (see Article 20.4).

PED = SaSd

( PD + HO + V ) (1)

PET = SaSd

( PD + V ) + 2HT

3 (2)

where: PED = Equivalent design pressure at 38°C based ondesign (operating) liquid head, in barg

PET = Equivalent design pressure at 38°C basedon test liquid head, in barg

PD = Internal design pressure at top of compartmentin its operating position at maximum designtemperature (nameplate rating), in barg

HO = Hydrostatic head at the bottom of thecompartment in its operating position whenfilled to its maximum operating depth with aliquid having a specific gravity equal to thegreater of that of the operating liquid or 1.0, inbarg. Exchangers, except those in non-condensing gas service, shall be assumed tooperate completely filled with liquid

HT = Hydrostatic head at the bottom of thecompartment in its operating position whencompletely filled with water, in barg

Sa/Sd = Highest ratio (for each of the materialsof which the main exchanger shell sections andformed heads are constructed) of the ASMECode allowable tensile stress at 38°C (Sa) tothe ASME Code allowable tensile stress atdesign temperature (Sd). Tubesheets andtubes shall not be included in the calculation ofthis ratio


Revision 2


V = Design vacuum on adjacent chamber, if any, inbarg

20.2. Design Temperature

The shell side and the tube side shall have both maximum and minimumdesign metal temperature ratings, and both shall be marked on theexchanger nameplates. Except when specified in the Vessel Specifications,maximum and minimum design temperatures shall be determined as follows:

20.2.1. Maximum Design Temperature

Exchangers for warm service (0°C to 400°C, inclusive) shall havea maximum temperature rating at least equal to the maximumanticipated temperature (considering: start-up and start-upfollowing an emergency shutdown; normal, temporary, andemergency operation; and, normal and emergency shutdown)plus 14°C, but in no case less than 66°C.

20.2.2. Minimum Design Temperature

Exchangers shall have a minimum design metal temperaturerating equal to or lower than the minimum anticipated temperature(considering: start-up and start-up following an emergencyshutdown; normal, temporary, and emergency operation; and,normal and emergency shutdown), but in no case warmer thanminus 1°C. For exchangers whose metal temperature in normalservice is dependent on ambient temperature, the minimumdesign metal temperature shall be minus 1°C..

20.3. Operating Liquid Head

The hydrostatic head considered to apply in addition to and coincident withthe design pressure shall be the hydrostatic pressure on each componentwhen the compartment is filled to its maximum operating depth with a liquidhaving a specific gravity equal to the greater of that of the operating liquid or1.0. Exchangers, except those in non-condensing gas service, shall beassumed to operate completely filled with liquid, unless otherwise specifiedin the Vessel Specifications.

20.4. Allowable Stress Values

Allowable design stress values for all operating temperature conditions shallbe taken at the maximum nameplate (rated) temperature for the componentunder consideration.

20.4.1. Low Allowable Stress

Where two allowable stress values are given in the ASME Codefor a material, use the lower value only in the design of


Revision 2


tubesheets and gasketed flange joints or other applications whereslight distortion can cause leakage or malfunction.

20.5. Designing For Vacuum Service

Exchangers subjected to partial vacuum operating pressures of 0.259 bargor more shall be designed and ASME Code stamped for full vacuum.Maximum design temperature shall be per Article 20.2.

20.5.1. Internal Pressure Rating of Exchangers Designed for VacuumService

Exchangers designed primarily for vacuum service shall bedesigned for an internal pressure rating not less than 1.724 bargat the maximum design temperature specified for the vacuumrating.

20.5.2. Stiffening Rings

Stiffening rings for shells under external pressure shall have athickness not less than 9.5 mm and a ring width-to-thickness rationo greater than 10. Stiffening rings shall be located on theoutside of the exchanger and shall be attached with a continuousfillet weld on both sides of the ring.

20.6. Butt Joints Required

Welded joints of ASME Code Categories A and B, and when used, butt-typeCategories C and D, shall be Type No. (1) of ASME Code Table UW-12.Butt welds with one plate edge offset [ASME Code Figure UW-13.1(k)] andpermanent weld joint backing strips are not permitted (see Article 5.1). SeeArticle 25.10.2.3 for butt welded joints in vessel support skirts.

20.7. Radiographic Examination

The minimum degree of examination of welded butt joints shall be spotradiography per ASME Code Paragraph UW-52. In applying the rules ofParagraph UW-52, the increments of weld shall be selected so as to includeall Category A, B, and C butt welds, except Category B or C butt welds innozzles and communicating chambers that exceed neither 254 mm nominalpipe size nor 28.6 mm wall thickness may be excluded.

20.7.1. Seams In Formed Heads

The flat plate from which formed heads are made shall be eitherseamless or made equivalent to seamless ; i.e., all Category Awelds shall be Type No. (1) and fully radiographed per ASMECode Paragraph UW-51. After forming, the spin hole, if itremains in the final exchanger construction, shall be repaired witha metal plug which is butt-welded in place with a Type No. (1)


Revision 2


weld and radiographed to meet the requirements of the VesselSpecifications and the design basis.

20.8. Corrosion Allowance

Add corrosion allowance specified in Vessel Specifications to all pressureparts in contact with the service fluid.

20.8.1. Tubes

Corrosion allowance shall be added to tubes only when specifiedin the Vessel Specifications.

20.8.2. Nonpressure Parts

Design welded-in, nonpressure, internal components ofnoncorrosion resistant materials to include a corrosion allowanceon all wetted surfaces of 75% of that for pressure parts to permitthe components to function in the corroded condition. Removablenonpressure, internal parts of noncorrosion resistant materialshall include a corrosion allowance on all wetted surfaces of 50%of that for pressure parts..

20.9. Common Components

Tubesheets, tubes, and other components subjected to both shell side andtube side conditions shall be designed for the most severe combinations ofpressure, temperature, and other loadings which may occur during operationand test conditions. Design solely on the basis of simultaneous loading ofinternal pressure in adjacent compartments is not acceptable.

20.10. Clad Components

Except for austenitic stainless steel and nickel alloy clad components (thisexclusion does not apply to clad tubesheets), the thickness of cladding metal(includes weld overlay) shall not be included in the design calculations forstrength.

20.11. Wind Or Earthquake Loads

Exchangers shall be self-supporting and designed to resist the specifiedwind pressures.

20.11.1. Wind Loads

Design wind loads shall be the greater of those determined inaccordance with ANSI/ASCE 7(95), using data for classificationCategory II, Exposure C structures, or other code or standard ifinvoked by jurisdictional regulation. The basic wind speed at 10mshall be 40.3 m/sec.


Revision 2


See Article 20.11.4.2 for force coefficients to be used for thelength of vertical exchangers for which spoilers are added.

Apply wind load to the total projected area of the exchangerincluding insulation, ladders, platforms, attached piping, and otherappurtenances.

20.11.2. Earthquake Loads

Earthquake loads are not a design consideration for this project.

20.11.3. Article Not Used

20.11.4. Wind Excitation

Vertical exchangers having a height-to-diameter ratio (h/d, where"h" is the total exchanger height and "d" is the exchangerdiameter measured to the mid-thickness of the exchanger wall) of15 or greater and which do not have a significant number ofeffective external exchanger attachments (attachments such asladders and piping where the maximum circumferential distancebetween them is not greater than 108°) shall be investigated fordynamic behaviour due to wind excitation. [One paper coveringthe analysis of vessels for vibration due to vortex shedding is"Dynamic Response of Tall Flexible Structures to Wind Loading"by Joseph Vellozzi, PhD, P.E.; available through the NationalInstitute of Standards and Technology (formerly the NationalBureau of Standards)].

20.11.4.1. Wind Spoilers - Corrective Action

When it has been determined that an exchanger mayvibrate and the attributes of the exchanger (e.g.,normal attachments) cannot be changed such thatvibration will not occur, wind spoilers in accordancewith one of the following shall be added to the upperthird of the exchanger:

1. Helical Spoilers

Use a three-start system of spoilers in a helicalpattern. An optimum configuration consists ofspoilers with an exposed width (beyond insulation,if applicable) of 0.09d and a pitch (height of onehelical wrap) of 5d, where "d" is the exchangerdiameter at the top. The spoiler system may beinterrupted to provide clearance at exchangerattachments.

2. Vertical Spoilers

Use a three-start system of short vertical spoilersarranged in a helical pattern. An optimum


Revision 2


configuration consists of spoilers with an exposedwidth (beyond insulation, if applicable) of 0.09dand a pitch of between 5d and 11d. There shouldbe a minimum of 8 spoilers over the pitch distance(each complete helical wrap) and a minimum of 1.5helical wraps over the top third of the exchanger.The spoiler system may be interrupted to provideclearance at exchanger attachments.

20.11.4.2. Additional Sail Area

When spoilers as described in Article 20.11.4.1 areadded to a exchanger, the column projected areanormal to the wind, Af, and the corresponding force

coefficient, Cf, for very rough surfaces for the column

height where spoilers have been added shall be usedin the calculation of the overturning load whendesigning the exchanger and supporting structure.The column projected area shall be calculated usingthe projected diameter taken at the outside edge of thespoilers times the height of the section underconsideration.

20.12. Design Pressure And Additional Loadings

The shell side and tube side shall be designed to withstand the specifieddesign pressure at both the maximum and minimum design metaltemperatures, including any additional loadings as specified in ParagraphUG-22 of the ASME Code, and as required by this standard and the VesselSpecifications. The design pressure applies to the top of the exchanger inits operating position, and in its corroded condition when a corrosionallowance is required by applicable codes or the Vessel Specifications.

20.12.1. Design Loads

Design loads are defined and classified as follows:

1. Dead Load (L1) - Dead load is the installed weight of theexchanger including internals, catalyst, platforms,insulation, piping, and other permanent attachments.

2. Operating Live Load (L2) - Operating live load is theweight of the liquid at the maximum operating level.

3. Pressure Load (L3) - Pressure load is the MAWP (internalor external at the coincident maximum or minimum designmetal temperature) load, including the pressure dropthrough the exchanger. See Article 20.9 and ASME CodeParagraph UG-19(a).

4. Thermal Loads (L4) - Thermal loads are the loads causedby the restraint of thermal expansion/contraction of the


Revision 2


exchanger and/or its supports and connected piping orother equipment.

5. Test Load (L5) - Test load is the weight of the testmedium, usually water.

6. Wind Load (L6) - Wind load shall be determined inaccordance with Article 20.11.1 and 20.11.4.2.

7. Piping Loads (L7) - Loads caused by piping other than thedead load shall be considered as applicable.

20.12.2. Load Combinations

Exchangers and their supports shall be designed to meet themost severe of the load combinations below. Except as permittedin Item 5 below, ASME Code allowable stresses and factors [seeParagraph UG-23(d) of the ASME Code] shall be used forexchangers and attachments such as supports outside the scopeof the ASME Code (see Article 20.4).

1. L1 + (0.11)L6 Lift condition with 33% of design windvelocity (11% of design wind load). L1 may be reducedfor weight of materials not installed at the time of lift.

2. L1 + L6 Erected condition with full wind load.

3. L1 + L2 + L3 + L4 + L6 +L7 Design condition with fullwind load [include both full and zero pressure conditions(L3) for check of maximum longitudinal tensile andcompressive stress].

4. L1 + L2 + L3 + L4 + L7 Design condition with seismicload [include both full and zero pressure conditions (L3)for check of maximum longitudinal tensile andcompressive stress].

5. L1 + (F)L3 + L5 + (0.25)L6 Future test condition with50% of design wind velocity (25% of design wind load)."F" is the required design pressure or MAWP multiplier fora hydrostatic test, defined as 1.5(Sa/Sd), where (Sa/Sd) isdefined in Article 20.1.1. For exchangers having acorrosion allowance, L1, (F)L3, and L5 shall be based onthe exchanger in the corroded condition.

20.13. Torispherical Heads

For the prevention of internal pressure-induced plastic buckling oraxisymmetric yielding of large diameter, thin, formed (torispherical) heads(diameter-to-thickness ratio greater than 300), a design check of the ASMECode required thickness shall be performed. One acceptable method(among several that have been published) is by G. D. Galletly, “DesignEquations for Preventing Buckling in Fabricated Torispherical ShellsSubjected to Internal Pressure”, published in Proceedings, Institute ofMechanical Engineers, London, Volume 200, No. A2.


Revision 2


20.14. Local Shell/Formed Head Stresses

When there is concern that an overstress condition may exist, the localmembrane and surface stresses due to local loads, such as piping loads,platform loads, etc., shall be determined using the WRC-107. For localloads and internal pressure, the allowable stresses are 1.5Sd for local

primary membrane stress and 3.0Sd for primary membrane plus secondary

bending stress, respectively at the design temperature.

20.15. Combined Primary Stress For Elevated Temperature Service (>427 °C)

For evaluating the effect of external loads on exchanger appurtenances,(nozzles, clips, etc.) and other discontinuities (cone/cylinder junctions havinghalf-apex greater than 30°, etc.), as permitted by ASME Code Paragraph U-2(g), combined local membrane stress plus primary bending stress shall belimited to 1.25 Sd for temperatures greater than 427°C.

20.16. Exchangers In Cyclic Service

The required service for all exchangers shall include consideration of cyclicservice. When an exchanger is identified in the Vessel Specifications asbeing in cyclic service, the applicable cyclic conditions provided in the VesselSpecifications shall be used to perform a fatigue analysis.

21. HYDROSTATIC TEST (SEE ARTICLE 7)

21.1. Test Pressure Determination

Test pressures for the shell side and the tube side shall be determined asfollows:

21.1.1. Test Pressure

For testing in the horizontal position, the test pressure referencedto the centreline of the compartment shall be 1.5 times (the largerof PED or PET) minus (the hydrostatic head of the testing liquidbelow the compartment centreline). If a vertical exchanger istested in a vertical position (as for a field test), the test pressurereferenced to the top of the compartment shall be 1.5 times (thelarger of PED or PET) minus HT (see Article 20.1.1).

22. PNEUMATIC TESTS

Except for preliminary low-pressure leak tests (e.g., see nozzle reinforcing pad testin Article 5.6), pneumatic tests (air, nitrogen, etc.) shall be performed only whenspecified in the Vessel Specifications.


Revision 2



This Article defines the minimum degree of nondestructive examination required inaddition to radiographic examination specified in Article 20.7. Additionalnondestructive examination may be required by the ASME Code and theVessel Specifications. All nondestructive examination shall be performed inaccordance with ASME Code methods (see also Article 6.2 for postweld heattreated exchangers).

23.1. Magnetic Particle And Liquid Penetrant Examination

Examine the following weldments by magnetic particle or liquid penetrantexamination:

23.1.1. ASME Code Categories A and B, and Categories C and D Butt-Type Joints

When the joint thickness exceeds 2 inches (51 mm), examine theroot pass and all accessible surfaces of completed weld.

23.1.2. ASME Code Categories C and D Non-Butt-Type Joints

Except as required in Article 15.1.2.1 for tubesheet-to-shell joints,when the exchanger shell sections and heads have beendesigned on the basis of a joint efficiency of 1.00, examine allCategory C and D non-butt type joints, including those in nozzlesand communicating chambers, as follows:

1. After back-chipping or gouging root pass to sound metal,examine the back-chipped or gouged surface.

2. All accessible surfaces of completed weld.

23.1.2.1. Joints Attaching Tubesheets

For exchangers larger than 610 mm nominal diameter,or for any size having design pressure on thetubesheet attachment side exceeding 20.68 barg, non-butt-type joints attaching tubesheets shall beexamined as follows:

1. Before welding, examine the cut surfaces perASME Code Paragraph UG-93(d)(4).

2. For joints per ASME Code Paragraph UW-13.2(f), (j), or (k), examine the depositedgroove weld surfaces after machining weldflush with tubesheet.

3. For double-welded joints, after back-chippingthe reverse side of weld metal first depositedand before additional welding, examine thebackchipped surfaces.


Revision 2


4. Examine all accessible surfaces of completedweld.

5. After welding, re-examine all cut edgesexamined per Item 1 above that remainexposed.

23.1.3. Corner Joints

For nozzles and communicating chambers attached with a fullpenetration weld through the nozzle or communicating chamberwall (see Article 5.3), examine the cut edge of the openings inexchanger walls thicker than 13 mm. The examination shall bemade before nozzle attachment, and a re-examination made afterattachment when accessible.

23.1.4. Nonpressure Attachment Welds

Examine accessible surfaces of completed welds attachingnonpressure parts to pressure parts as follows:

1. All welds (internal and external) when the thickness of thepressure part exceeds 51 mm.

2. Welds attaching exchanger supports (e.g., skirts, lugs,legs, etc.).

3. Welds attaching exchanger lifting (erection) lugs.

23.2. Ultrasonic Examination

Examine the following materials ultrasonically in accordance with the ASMEmaterial specifications shown:

23.2.1. Rolled Plate

Rolled plate for flat covers and blind flanges (blind flanges perASME/ANSI B16.5 excluded) exceeding 76 mm in thickness shallbe examined after cutting to final size per SA-578, acceptancelevel I. Rolled plate for tubesheets exceeding 76 mm inthickness shall be examined after cutting to final size per SA-578,acceptance level I, supplementary requirement S1. Note: ThisArticle shall apply to carbon, low alloy, and high alloy steel plates.

23.2.2. Forgings

Forgings exceeding 76 mm in thickness (flanges per ANSI/ASMEB16.5 excluded) shall be examined per SA-745 with the followingrequirements. Note: This Article shall apply to carbon, low alloy,and high alloy steel forgings:

1. Quality levels for straight beam examinations from flatsurfaces shall be:

Thickness, mm Quality Level


Revision 2


over 76 through 203 QL-2

over 203 through 305 QL-3

over 305 QL-4

2. Quality level for straight beam examinations from curvedsurfaces shall be QL-5.

3. Quality level for all angle beam examinations shall be QA-1. Notch depth shall be per QA-1 or 6.4 mm, whichever isless.

23.2.3. Integrally-Bonded Clad Plate

Except as provided in Article 23.2.3.1, clad plate, excludingtubesheets, for exchangers designed for vacuum service and forexchangers whose design calculations include the cladding (seeArticle 20.10) shall be examined per SA-578, acceptance level I,supplementary requirement S6. Clad plate for tubesheets shallbe examined per SA-578, acceptance level I, supplementaryrequirement S7.

23.2.3.1. Manufacturer's Specifications

Where the clad plate Manufacturer's specificationsinclude ultrasonic examination which differs from thatin Article 23.2.3 (e.g., proprietary explosion-bondedclad), such specifications shall be submitted forOWNER's review.

23.2.4. Reports

A report of examination results shall be submitted toCONTRACTOR and shall include the following:

1. Component identity.

2. Drawing, purchase order, and Manufacturer’s serialnumbers (if applicable).

3. Examination equipment used (including couplant).

4. Instrument settings and calibration data.

5. Location and dimensions of reportable and unacceptableindications.

6. Location of areas not inspected due to geometricconfiguration.

7. Names and certification levels of examination personnel.

8. Date of examination.


Revision 2


24. MATERIAL SELECTION

24.1. Carbon And Low-Alloy Steels

Except as required in Article 24.1.1, impact testing exemptions for carbonand low-alloy steels shall be established in accordance with ASME Coderequirements.

24.1.1. Restriction of Code Provision

When Paragraph UCS-66 of Section VIII, Division 1 of the ASMECode is used to establish impact testing exemptions, all weldedattachments shall be considered essential to the structuralintegrity of the exchanger and shall also be in compliance withrules of ASME Code Paragraph UCS-66.

24.2. Other Than Carbon Or Low Alloy Steels

Materials other than carbon steel or low alloy steel shall be as specified orapproved by CONTRACTOR.

24.3. Pressure Bolting

Except as required in Article 24.3.1 bolting materials for pressure-resistingflanged joints shall be selected from Table 1. Bolting shall be studs with onenut at each end unless otherwise specified in the Vessel Specifications. Forexchangers with maximum nameplate temperature ratings ≤ 232 °C, lowalloy steel bolting shall be coated per Engineering Standard MMOC-615

TABLE 1

Materials For Pressure Bolting(1)(9)

Design Temperature Range(2) ASME Boiler and Pressure Vessel Code Material

SpecificationMinimum Maximum Bolting

Material(3) Nut Material

(4)(5)(6)

FERRITIC STEELS-40°C 399°C SA-193, Gr B7 SA-194, Gr 2 or 2H-40°C 427°C SA-193, Gr B7 SA-194, Gr 3 or 4-29°C 538°C SA-193, Gr B16 SA-194, Gr 3 or 4

-101°C 204°C SA-320, Gr

L43(7)SA-194, Gr 7, Suppl. Requirement S4

-101°C 371°C SA-320, Gr L7(7) SA-194, Gr 7, Suppl. Requirement S4

AUSTENITIC STEELS(8)(9)

-198°C 260°C SA-193, Gr B8,Cl 2

SA-194, Gr 8 or 8A

-198°C 538°C SA-453, Gr 660 Same as bolting

NICKEL ALLOY(8)(9)

-198°C 621°C SB-637(10) Same as bolting


Revision 2


NOTES:

(1) Bolt coating (e.g. galvanised or fluoropolymer coated), shall be per Article 24.3.

(2) Exchanger nameplate temperature rating.

(3) Both ends of studs shall have a flat and chamfered point. Stud length shall bemeasured from first thread to first thread. Studs 25 mm and smaller shall becoarse-thread series and studs over 25 mm shall be 8-pitch thread series. All studsshall have ASME/ANSI B1.1 Class 2A threads.

(4) Nuts shall conform to the dimensions of Heavy Hex Nuts per ASME/ANSI B18.2.2.

(5) Nuts produced from sintered, powder metal are not acceptable.

(6) Washers specified for use with these nut materials shall be through-hardened andshall meet the chemical and mechanical property requirements of ASTM F-436 fortemperatures not exceeding 204°C. For temperatures greater than 204°C, washersshall be in accordance with SA-540 of ASME Section II [any grade having aminimum yield strength of 8437 kg/cm2 or higher].

(7) For diameters 50.8 mm and smaller, the impact requirements of SA-320 of ASMESection II may be applied. For diameters larger than 51 mm, the requirements ofASME Code Paragraph UG-84 shall apply.

(8) Austenitic stainless steel and nickel alloy bolting shall be lubricated with one of thefollowing products, or with a Buyer-approved equal:

Stainless Steel Nickel Alloy Lubricant Maximum Temperature Maximum Temperature

Jet-Lube 550 288°C 260°C

GRAFOIL Tape 454°C 260°C

TEFLON Tape 204°C 204°C

Jet-Lube is manufactured by Jet-Lube, Inc., Glendale, CA. For temperaturesexceeding 454°C, lubricants shall be approved by OWNER.

(9) Because of possible incompatibility, bolt lubricants shall not be used on internalcomponents exposed to process fluids.

(10) ASME Code Case 1993.

24.3.1. Piped Nozzle Flanges

Bolting for piped nozzle flanges, if furnished by Manufacturer,shall be according to applicable Valve and Piping MaterialsSpecifications.

24.3.2. Swing Bolts

Swing bolts (eye bolts) shall be of one-piece construction withoutwelding. Hinge pins shall be solid (not rolled) and of the samematerial as the swing bolts.


All components of skirts, saddles, lugs, legs, and other exchanger supportsshall be ASME Code approved material.


Revision 2


24.5. Attachments To Pressure Parts

Attachments welded to pressure parts shall be ASME Code approvedmaterial (see Item 3 of Article 9.2). Carbon and low-alloy steel materialsshall be selected per Article 24.1.

24.5.1. Internal Attachments

Internal attachments shall be of the same type material as thepressure part to which attached.

24.5.2. External Attachments

External attachments shall be of the same type material (ASMECode P-Number) as the pressure part to which attached, exceptas provided in Article 24.6. When austenitic stainless steelexternal welded attachments are required, any 300-seriesstainless steel may be used.

24.6. Welded Parts Of Dissimilar Metals

Pressure parts or attachments welded to pressure parts shall be of amaterial having essentially the same coefficient of expansion as theexchanger material, except as permitted in Articles 24.6.4, 24.6.5, 25.1.5Item 4, and as follows:

24.6.1. External Nozzle Reinforcing Pads for Austenitic Stainless SteelExchangers

External nozzle reinforcing pads for austenitic stainless steelexchangers may be of carbon steel provided that:

1. The maximum design temperature is not greater than232°C .

2. The minimum design metal temperature is not colder thanminus 29°C and the carbon steel material satisfies therequirements of Article 24.1.

3. The total number of cycles in which the range oftemperature fluctuation exceeds 69°C does not exceed5000.

4. The exchanger is not postweld heat treated.

5. The exchanger is not for lethal service.

24.6.2. External Nonpressure Attachments, Excluding ExchangerSupport Skirts, Welded to Austenitic Stainless Steel Exchangers

External nonpressure attachments, excluding exchanger supportskirts, welded to austenitic stainless steel exchangers may be ofcarbon steel subject to the limitations specified in Items 1 through


Revision 2


4 of Article 24.6.1. Exchanger support skirts shall be per Article24.6.3.

24.6.3. Support Skirts Welded To Austenitic Stainless Steel Exchangers

Support skirts welded to austenitic stainless steel exchangersshall be of austenitic stainless steel, except as follows:

1. For exchangers having a design temperature betweenminus 29°C and 66°C, and having a height-to-diameterratio of 5 or less, the entire skirt may be carbon steelsubject to the requirements of Article 24.1.

2. For exchangers having a design temperature greater than66°C but not exceeding 232°C, the skirt shall be stainlesssteel for a minimum distance of 1.5 Rt (where R = meanskirt radius, and t = skirt thickness) below the attachmentweld, but not less than the dimensions shown below. Theremainder of the skirt below this stainless steel portionmay be carbon steel.

Minimum Dimension Exchanger Diameter 203 mm up to 1981 mm, inclusive

305 mm over 1981 mm through 3505 mm

457 mm over 3505 mm

3. For exchangers having a design temperature greater than232°C, the minimum length of stainless steel skirt belowthe attachment weld shall be 457 mm.

24.6.4. Nozzle Necks For Clad And Unclad Steel Exchangers

Nozzle necks for steel exchangers clad with austenitic stainlesssteel shall be of similarly clad material for nozzles larger thanNPS 12 nominal diameter. For unclad steel exchangers and forsteel exchangers clad with austenitic stainless steel, nozzles NPS12 nominal diameter and smaller may be of solid stainless steelsubject to the limitations specified in Items 1 through 4 of Article24.6.1. Weld overlay in accordance with Engineering StandardMMOC-616 in lieu of clad may be used. Loose liners shall not beused.

24.6.5. External Stiffening Rings Welded to Austenitic Stainless SteelExchangers

External stiffening rings welded to austenitic stainless steelexchangers may be of carbon steel for exchangers designed forfull vacuum and a maximum internal pressure rating of 1.724 bargat a minimum design metal temperature not colder than minus12°C and a maximum design temperature not exceeding thatpermitted by Figure 1, but in no case greater than 232°C. Use ofcarbon steel rings on stainless steel exchangers outside these


Revision 2


limitations or geometries not covered by Figure 1 shall be justifiedby a complete stress analysis and approved by OWNER.Additionally, the material for carbon steel rings shall satisfy therequirements of Article 24.1.


Revision 2


FIGURE 1:Maximum Permissible Temperature

Carbon Steel Stiffening Ring On Austenitic Stainless Steel Shell

Note: Maximum permissible temperature is equal to the lesser of the temperaturesdetermined for both the corroded and non-corroded conditions, but shall in no casebe greater than 232°C.

24.6.6. Tubesheets Welded To A Carbon Steel Shell

Tubesheets welded to a carbon steel shell shall be of carbonsteel or clad carbon steel except that solid stainless steeltubesheets may be used provided:

1. The intended use of tubesheets of stainless steel (or othermaterials having a coefficient of expansion which differsfrom that of the shell material by more than 15%) isjustified by a complete stress analysis and approved by

HtR

t Stiffening Ring

CL

D

(Shell ID)

300310320330340350360370380390400410420430440450460

400

380

360

340

320

300

280

260

240

220

200

180

160

140

120

100806040

D/t

Q=5

Q=10Q=15

Q=20

Q=30

Q=40

Q=(tR x H)/t 2

149

160

171

182

193

204

216

227232

MA

XIM

UM

PE

RM

ISS

AB

LE T

EM

PE

RA

TU

RE

°F


Revision 2


OWNER, or the tubesheet is welded to a relatively shortshell section of the same material and the junction of thealloy and carbon steel shell sections is justified by acomplete stress analysis and approved by OWNER.

2. The tubesheet material is approved by OWNER.

24.7. Flanged Joints Of Dissimilar Metals

Austenitic stainless steel or non-ferrous alloy flanges may be bolted tocarbon steel flanges provided that the differential diametrical expansion willnot result in diametrical interference of recessed (e.g., tongue and groove)joints and does not exceed 0.80 mm. Bolting joining a carbon steel flangeto a stainless steel or non-ferrous alloy flange shall be of low-alloy steel (seealso Article 24.3).

25. MISCELLANEOUS DESIGN REQUIREMENTS

25.1. Flanged Pressure Joints

25.1.1. Confined Joints

For any of the following conditions, gasketed flange joint designs(main shell and nozzle joints) larger than 610 mm nominaldiameter shall provide outer confinement of the gasket:

1. Design pressure 20.68 barg or higher.

2. Design temperature hotter than 260°C.

3. Design temperature colder than minus 29°C.

4. Joint requires metallic gasket. 3-ply and single-plycorrugated metal gaskets are exempted.

5. Cyclic pressure or temperature service.

25.1.2. Gasketed Pass-Rib Joints

Confining grooves shall be provided for gasketed pass-rib jointswhere the nominal diameter of the joint exceeds 305 mm, or themaximum anticipated differential pressure across the passpartition exceeds 2.07 barg.

25.1.3. Unconfined Joints

Flanges for unconfined gasket joints shall have a raised face of atleast 1.6 mm, except that a raised face is not required on atubesheet mating with a lap-joint type flange.

25.1.4. Lap Joints

In exchangers having a nameplate temperature rating greaterthan 300°F, flanged joints for stainless steel and non-ferrous alloyshells or nozzle necks shall be of the lap-joint type with carbon or


Revision 2


low-alloy steel flanges (see Article 24.7). Flanges for aluminiumlap joint stub ends shall be galvanise. Except for ASME/ANSIClass 150 NPS 12 and smaller and Class 300 NPS 8 and smaller,modified slip-on welding flanges shall not be substituted forASME/ANSI B16.5 lapped flanges. This note shall appear in allVessel Specifications that permit lap-joint flanges.

25.1.4.1. Lap Ring Dimensions

The nominal outside diameter of shop-fabricated lapsshall correspond to ASME/ANSI B16.9 standarddiameters when used with ASME/ANSI standardflanges. When shop-fabricated laps are to be usedwith custom designed flanges, the nominal outsidediameter of the lap shall not exceed the flange boltcircle diameter minus one bolt diameter, and thefinished radial width of the lap shall comply with thefollowing:

Minimum Radial

Exchanger OD (mm) Lap Width (1) (mm)up to 914.4, inclusive 38

over 914.4 through 1524 44over 1524 51

(1) Radial lap width shall be measured from the toeof the lap-to-shell attachment weld to the outeredge of the lap ring (see Article 25.1.8.5).

25.1.4.2. Lap Ring Thickness

The minimum finished thickness of shop fabricated laprings shall be the nominal thickness of the shell towhich it is attached plus 4.8 mm. The lap rings shallbe machined after welding on both the front and backsurfaces in one "set-up" so that the planes of the twosurfaces are parallel after machining.

25.1.4.3. Lap-Type Flange To Shell Clearance

The difference between the flange ID and the OD ofthe shell shall not exceed:

1. 1.6 mm for nominal diameters up to NPS 12,inclusive.

2. 3.2 mm for nominal diameters over NPS 12through 1219 mm OD.

3. 4.8 mm for nominal diameters over 1219 mmOD.


Revision 2


25.1.4.4. Flange Bevel And Lap Ring Weld

The fillet weld attaching the lap ring to the shell shallbe an equal leg fillet weld with the leg dimension equalto the nominal shell thickness (+1.6 mm, -0 mm). Theflange bevel for lap ring-to-shell weld clearance shallbe 45 ° x 1.6 mm greater than fillet weld leg size.

25.1.4.5. Stop Rings

Where needed to hold the lap-joint flange in positionfor bolt-up (such as lap-joint type manways), threesmall, equally spaced flange stops shall be used belowthe flange.

25.1.5. Limitations On The Use Of Slip-On Flanges

Slip-on type flanges are limited to use under the followingconditions:

1. ASME/ANSI standard forged flanges for design pressuresand temperatures not exceeding the pressure-temperatureratings for Class 150 standard flanges as specified inASME/ANSI B16.5.

2. Custom designed flanges per ASME Code MandatoryAppendix 2, Fig. 2-4 (8), (8a), (9), (9a), (10), or (10a) fordesign temperatures not exceeding 343°C; and for flangethickness not exceeding 76 mm.

3. Corrosion allowance does not exceed 1.6 mm. In specialcases and when approved by OWNER, slip-on flangesmay be considered for corrosion allowance exceeding 1.6mm, or for use on necks of clad material; however, in suchcases, the flanges shall be provided with a telltale holedrilled radially through the flange. The hole shall betapped from the outside NPT 1/8 for flange sizes NPS 4and smaller; NPT 1/4 for larger flange sizes.

4. Carbon or low-alloy steel flanges attached to solid high-alloy necks are limited to sizes NPS 12 and smaller, and todesign temperatures no greater than 232°C; unless ahigher temperature is justified by a complete stressanalysis and approved by OWNER.

5. Minimum design metal temperature is not colder than -29°C.

6. Exchanger is not for lethal service.

7. Exchanger is not for cyclic pressure or temperatureservice; or subjected to cyclic loadings from associatedequipment.


Revision 2


25.1.6. Asbestos Gaskets

Gaskets containing asbestos are not acceptable. Compressedasbestos-substitute gaskets shall not be used without OWNER’sapproval, except as permitted in Article 4.3.2 for test gaskets only.

25.1.7. Spiral-Wound Gaskets

25.1.7.1. Spiral-wound gaskets shall not be used in customdesigned flanges.

25.1.7.2. All spiral-wound gaskets for raised f ace or otherunconfined gasket joints shall be furnished with aninner and an outer compression limiting ring.

25.1.7.3. Spiral-wound gaskets shall not be used for joints largerthan 610 mm nominal diameter.

25.1.8. Gasket Selection, Design Factors, and Contact Width

25.1.8.1. Pass-Rib Area

The total gasket area in contact with pass partitionsshall be included in the gasket area used in flange jointdesign calculations.

25.1.8.2. Gasket Selection

Gaskets for main shell joints, custom designedflanges, and blind flanged nozzles shall be asspecified in the Vessel Specification.

25.1.8.3. Gasket Design Factors

Gasket design factors "y" and "m" shall be according tothe ASME Code or, if not listed in the Code, inaccordance with manufacturer's recommendations.

Factors for GRAFOIL® gaskets and corrugated metal

gaskets with GRAFOIL® tape on both sides shall beas follows:

GASKET MATERIAL/TYPE y m

GRAFOIL®, Grade GHTM

E, 1.6 mm 2500 2.0

GRAFOIL®, Grade GHTM

R, 1.6 mm 2500 2.0

3-ply corrugated stainless steel with GRAFOILoverlay

6500 3.5

1-ply corrugated stainless steel with GRAFOILoverlay

3700 2.75


Revision 2


25.1.8.4. Gasket Seating Stress

The design of all custom flanges shall include thefollowing check: After designing the flange per ASMECode rules, the actual seating stress over the full

seating area of the gasket, based on 11/2 x allowable

bolt stress at ambient temperature (11/2 x Sa), shall be

equal to or greater than the "y" value, but shall notexceed 2460 kg/cm2. If it is not, then bolting and/orgasket width adjustments shall be made and theflange redesigned.

25.1.8.5. Gasket Contact Width

The minimum gasket contact width for gaskets incustom designed joints shall not be less than thefollowing:

Minimum Gasket

Vessel OD (mm) Contact Width (1).(mm)up to 914, inclusive 25

over 914 through 1524 32over 1524 38

(1) Gasket contact width is the recommendedwidth of the gasket in contact with both flangeor lap faces. Note: For 3-ply corrugated metalgaskets, the gasket OD shall be a minimum of6.4 mm smaller than the gasket contact facingOD. For all other gaskets, the contact OD shallbe the gasket contact facing OD.

25.1.9. 3-Ply and Single-Ply Corrugated Metal Gaskets

3-ply and single-ply metal corrugated gaskets, when required,shall be as specified in the Vessel Specifications.

25.1.10. External Moments

The design of custom and ASME/ANSI B16.47 flanges (otherthan flanges per ASME/ANSI B16.5) shall include the effects ofexternal moments. When calculating the required bolt loads forthe operating condition, the hydrostatic end force, H, shall bemodified as follows:

H = 0.785G2 PM

G+

163π

Where: P and G are as defined in ASME Code Appendix 2,Paragraph 2-3 and M = moment applied across fullsection at flange, in.-lb.


Revision 2


Note: Experience has shown that axial forces resulting froma properly designed piping system have no significanteffect on the flange design and hence are not includedin the equivalent pressure.

25.1.11. Flange Rigidity

The rigidity of custom flanges and flanges per ASME/ANSIB16.47 (other than flanges per ASME/ANSI B16.5) shall bechecked, and redesigned if necessary, in accordance with ASMECode Appendix S, Paragraph S-2. KI shall be 0.30 and KL shallbe 0.20.

25.1.12. Minimum Bolt Size

The diameter of bolts for custom designed pressure-resistingjoints (other than flanges per ASME/ANSI B16.5 or B16.47) shallnot be smaller than 19 mm.

25.1.13. Bolt Spacing Factor

The design of custom flanges and flanges per ASME/ANSIB16.47 (other than flanges per ASME/ANSI B16.5) shall includethe effect of bolt spacing in accordance with the following:

1. Maximum bolt spacing = 2a + 6t

m + 0.5

2. If bolt spacing exceeds (2a + t), the design moment (MO)

acting on the flange shall be multiplied byBS

2a + t

where: MO, and m are as defined in ASME Code Appendix 2,Paragraph 2-3; a = nominal bolt diameter; BS = actualbolt spacing, and t = minimum finished flangethickness, exclusive of corrosion allowance.

25.1.14. Indicator-Type Bolting

Flanged joints requiring 51 mm diameter and larger bolting (alsosee Item 6 in Article 25.1.15) shall be furnished with bolts havingan indicator rod through the bolt centre for measuring installedbolt elongation (using a depth gauge). Every bolt in the jointassembly shall be an indicator-type bolt. The indicator rodmaterial for low alloy steel bolting shall be nickel alloy UNS10276. The indicator rod for other bolting materials shall be thesame as the bolts or a material having essentially the samecoefficient of expansion and a composition suitable for welding tothe bolts. All bolts in the assembly shall have a through-hardened


Revision 2


flat washer under each nut. (see Table 1, Note 6 andEngineering Standard MEQ-1B).

25.1.15. Additional Flange Design Criteria For Elevated Temperature(>427°C)

The use of flanged joints in high temperature service shall beavoided when possible. When flanged joints are required, thefollowing requirements shall be met:

1. The flange type shall be lap-joint construction with wroughtflanges. Integral type flanges shall not be used.

2. The coefficients of expansion of flange and boltingmaterials shall be nominally the same.

3. The required gasket for custom designed flanges is a 3-ply corrugated metal gasket.

4. External pipe reactions on flanged joints shall be held byCONTRACTOR to a minimum practical value (see Article25.1.10).

5. Flanged joints that are designed on the basis of noinsulation require administrative controls to assure thatinsulation will not be added during their use in the future.These joints shall be provided with a shield to protect themfrom thermal shock due to rain. The design of rain shieldsand personnel protection cages shall be such that thedesign temperature will not be exceeded.

6. Indicator-type bolting shall be used when the bolt size is38 mm diameter or larger.

7. Buyer shall be involved in the preparation of a jointassembly and bolt tightening procedure when indicator-type bolting is required.

25.2. Tubesheets

25.2.1. Minimum Tubesheet Thickness

25.2.1.1. The effective tubesheet thickness shall not be less than 25mm.

25.2.1.2. For all fixed tubesheet exchangers greater than 762 mmID, the Manufacturer shall calculate the value of Xa asdefined in ASME Code Paragraph AA-2.4. Thesecalculations shall be submitted with the mechanical designcalculations. If the value of Xa is less than 3.0, then thetubesheet shall be designed in accordance with ASMECode, Appendix AA rules, or the methods provided in thereferences in TEMA, RGP-RCB-7. For values of Xa equalto or greater than 3.0, the tubesheet may be designed inaccordance with TEMA, ASME Code, or the RGP-RCB-7


Revision 2


references. Tubesheets exceeding the scope of TEMAshall be designed in accordance with ASME Code Rules orRGP-RCB-7 references regardless of the value of Xa.

25.2.2. Cladding Thickness

The minimum thickness of cladding, when required, shall be thegreater of 4.8 mm or that required to provide 3.2 mm claddingunder pass partition and gasket grooves.

25.2.3. Stationary Tubesheets for Removable Tube Bundles

Stationary tubesheets for removable tube bundles shall have adiameter and bolt hole drilling to match the mating flange. Thetubesheet shall be designed to permit hydrostatic test of the shellside with the channel removed; and test of the tube side with thebundle removed from the shell.

25.2.3.1. Locking Studs

Flanged joints for stationary tubesheets for removabletube bundles shall be furnished with locking studs perEngineering Standard MEQ-180.

25.2.3.2. Pulling Eyes

The stationary tubesheet of exchangers withremovable tube bundles shall be provided with at leasttwo tapped holes in the tube side face for pulling eyes.Furnish service plugs of a material similar to thetubesheet material.

25.2.4. Tubesheet-to-Shell Weld Joints

Except as required in Article 25.2.4.1, or by the ASME Code (forlethal service), tubesheet-to-shell (or channel) weld joints may beany full penetration weld permitted by ASME Code Figure UW-13.2 [excluding Figures (d) and (i)] that does not employ apermanent backing strip.

25.2.4.1. Limiting Design Conditions

Exchangers having any of the following designconditions shall employ tubesheet-to-shell (or channel)weld joints per ASME Code Figure 13.2 (a), (f), or (k);

1. Tube side design pressure exceeding 42 barg.

2. Shell side design pressure exceeding 69 barg.

3. Design temperature colder than minus 29°C.


Revision 2


4. High-alloy tubesheet or adjoining shell (orchannel) material with the weld joint exposed toprocess fluid.

5. Shell inside diameter larger than 1219 mm withcarbon steel, low-alloy steel, or clad tubesheetmaterial; or larger than 762 mm with high-alloyor non-ferrous tubesheet material.

25.2.4.2. Determination of Weld Sizes

For the purposes of determining required weld sizes inaccordance with ASME Code requirements, atubesheet shall be considered supported (not less than80% of the pressure load is carried by the tubes,stays, or braces) if:

A EA E

t t

s s≥ 4

where: At = total cross-sectional metal area oftubes, in mm2

Et = modulus of elasticity of tubematerial at design temperature, inkg/cm2

As = cross-sectional metal area of shellbased on actual thickness lesscorrosion allowance, in mm2

Es = modulus of elasticity of shellmaterial at design temperature, inkg/cm2

25.2.4.3. Clad Tubesheets

Remove cladding from clad tubesheets as required topermit welding directly to the base material. Aftercompletion of the strength weld, exposed basematerial shall be covered with weld overlay of thesame composition and thickness as the cladding.

25.2.5. Tube-to-Tubesheet Joints

Tube-to-tubesheet joints for single tubesheets shall be as follows.When the type of tube joint is not designated in the VesselSpecifications, expanded joints shall be used for tubesheets ofsolid material; expanded and sealed-welded tube joints shall be


Revision 2


used for tubesheets having integrally-clad material on the outerface:

1. Expanded tube-to-tubesheet joints per Figure 2.

2. Expanded and seal-welded tube-to-tubesheet joints perFigure 3.

25.2.5.1. Strength Welded Tube Joints

Requirements for strength welded joints with the totaltube load carried by the weld shall be as specified inthe Vessel Specifications or otherwise approved byOWNER.

25.2.5.2. Double Tubesheets

Requirements for tube joints for double tubesheetsshall be as specified in the Vessel Specifications orotherwise approved by OWNER.

25.3. Tubes

25.3.1. Minimum Wall Thickness

Except as provided in Articles 25.3.1.1 and 25.3.1.2, tubing shallhave an average wall thickness (see Article 4.2.1) not less than16 BWG (1.65 mm).

25.3.1.1. Titanium Tubes

Tubes of titanium material for welded tube-to-tubesheet joints shall have an average wall thicknessnot less than 20 BWG (0.89 mm).

25.3.1.2. Low-Finned Tubes

The wall thickness under the fin of low-finned tubesshall be not less than 18 BWG (1.25 mm) averagewall.

25.3.2. Plain Ends for Low-Finned Tubes

Plain ends for low-finned tubes shall have a wall thickness notless than 16 BWG (1.65 mm) average wall and a length not lessthan 102 mm or the tubesheet thickness plus 25 mm, whicheveris greater.


Revision 2




The need for and design of expansion joints shall be based onthe following design conditions:

1. Operating or upset temperatures rather than nameplatetemperatures.

2. Metal temperatures rather than process fluidtemperatures.

3. Design (nameplate) pressures rather than operatingpressures.


Expansion joints shall be of the external type constructed offlanged-and-flued or flanged only heads. Bellows type joints shallnot be used without Buyer's approval.

25.4.3. Location

The expansion joint-to-shell weld shall not be located less than2.5 Rt from the back of the tubesheet; where R = outside radiusof the shell and t = actual thickness of shell less corrosionallowance.

25.4.4. Other Considerations

The flexibility of the joint(s) shall be considered in the design ofthe exchanger shell, tubes, and tubesheets.

25.5. Vapour Belts


The design of vapour belts shall include the effect of pressureloads and loads resulting from expansion contraction. Forexchangers of other than fixed tubesheet type, the design shallalso consider the hydrostatic end load under both the operatingand test conditions.


Vapour belts shall be constructed of flanged-and-flued or flangedonly heads.


Revision 2


25.5.3. Use as Expansion Joint

Vapour belts may be used as expansion joints provided allrequirements of Article 25.4 are met. Whether or not vapour beltsare used as expansion joints, their flexibility shall be considered inthe design of exchanger shell, tubes, and tubesheets.

25.6. Baffles And Support Plates

25.6.1. Minimum Thickness

The minimum thickness of carbon steel traverse baffles andsupport plates shall be 1.6 mm greater than required by TEMA,Class B.

25.6.2. Baffle Cuts

Segmental traverse baffles shall be cut on the centreline of a rowof tubes. For tubes on a triangular pitch, the baffle cut shall notbisect the apex angle of the pitch.

25.6.3. Drain or Vent Notches

Traverse baffles shall not be furnished with drain or vent notches.

25.6.4. Slides for Removable Tube Bundles

Removable bundles for exchangers larger than 610 mm nominaldiameter shall be furnished with slides or runners welded to thebaffles and tubesheet.

25.6.5. U-Tube Bundles

The baffle adjacent to the tube bends shall be located in thestraight portion of the tubes not more than 51 mm from thetangent line of the bends.

25.6.6. Tie Rods And Spacers

Peripheral tie rods and spacers for positioning baffles shall belocated so that the outside of the spacers coincides with the outerperiphery of the baffles. The inside diameter of the spacer shallnot be larger than the tie rod diameter plus 3.2 mm.

25.7. Channels, Covers, And Bonnets

25.7.1. Pass Partition Plates

Pass partitions shall be designed for the maximum anticipateddifferential pressure across the partition and coincident


Revision 2


temperature during operation and test conditions, but in no caseshall the pressure be less than 2.07 bar.

25.7.2. Mitered Reducing Elbows

Mitered 90° reducing elbows for thermosyphon reboiler outletheads shall conform to the following requirements:

1. The minimum number of section shall be 5, with not lessthan 3 changes in direction at the inside and outsidecontour.

2. Meridianal (change of direction) angles between adjacentsections shall be approximately equal for gradual flowtransition.

3. The general contours shall be similar to those ofcommercial forged reducing elbows.

4. Cyclic loading is not a governing design requirement.

25.7.3. Flanged Joints

Removable channels or bonnets, channel covers, and floatinghead covers shall be attached with through-bolted flanged joints.(see Article 25.2.3.1 for required locking studs for removable tubebundles.)

25.8. Nozzles And Manways

25.8.1. Projection

The minimum distance from the outside of the exchanger wall tothe nozzle face shall be:

1. 152 mm for nozzles up to NPS 3, inclusive.

2. 203 mm for nozzles larger than NPS 3.

25.8.2. Minimum Manway Size

Manways, when required, shall be no smaller than 610 mmnominal size.

25.8.3. Integral Reinforcement

Nozzles and manways shall be integrally reinforced for thefollowing conditions:

1. When located in shells greater than 51 mm thick.

2. The exchanger is designed for cyclic service.

3. The maximum design metal temperature is hotter than399°C.

4. Radial nozzles exceeding the limits in ASME CodeParagraph UG-36(b)(1). The design shall comply with


Revision 2


ASME Code Appendix 1-7(a) & (b). Code Case 2236 shallnot be used without written approval by OWNER.

25.8.4. Type Of Nozzle Connection

External nozzles NPS 1-1/2 nominal size and larger shall beflanged-type connections. Couplings shall neither be less thanClass 6000 nor smaller than NPS 3/4.

25.8.5. Nozzle Flanges

External nozzle flanges for nozzle sizes NPS 24 and smaller shallbe per ASME/ANSI B16.5. Threaded flanges and socket-weldtype flanges shall not be used.

25.8.6. Minimum Nozzle Neck Thickness

For nozzle sizes NPS 2 and smaller, the nominal neck thicknessshall not be less than Schedule 80 or 80S.

25.8.7. Pipe Tap Connections

Pipe tap connections per TEMA B-10.32 and RB-10.33 (pressureand temperature) shall not be located on nozzle necks unlessspecified in the Vessel Specifications.

25.8.8. Studding Outlets

The use of studding outlets is discouraged. However, if studdingoutlets must be used, they shall have tapped bolt holes, threadrelief on studs, and coated bolts and studs as specified in theVessel Specifications. A spacer ring of the same material as thenozzle flange shall be provided for each studding outlet. Thethickness of the spacer ring shall be sufficient to provide aneffective stud bolt stretching length equal to or greater than thatresulting from a through-bolted joint of two identical nozzleflanges.

25.8.9. Gussets

The use of gussets on nozzle necks to increase external loadcapacity is prohibited. Alternatives such as thicker exchangerwall, reinforcing pads, and larger or thicker nozzles shall beconsidered.


Revision 2


25.8.10. Shell Side Nozzles and Vents and Drains

25.8.10.1. Location

Shell side nozzles or vent and drain couplings whenrequired for horizontal exchangers shall be located onthe top and bottom of the shell.

25.8.10.2. Minimum Distance from Tubesheets

Shell side nozzles shall not be closer to integraltubesheets than tn+t or 1.5 Rt , whichever is greater;where R = mean radius of the shell; t = thickness ofshell; and tn = thickness of the nozzle.

25.8.10.3. Vents and Drains

Shell and channel vents and drains shall be NPS 1Class 6000 couplings with plugs. The couplings shallbe omitted for lethal or hydrogen-rich services, or CSCClass II and III services as specified in the VesselSpecifications.

25.8.11. Flange Connections

Flanged connections shall not be located within the confines ofthe exchanger skirt.

25.8.12. Nozzles in or Passing Through Skirts

Nozzles (including attached piping) within or passing throughexchanger support skirts shall be adequately supported for theoperating conditions and for protection during shipping andhandling.

25.8.13. Tubesheet Vents and Drains

Three or four tubesheet vents/drains are required for verticalexchangers to permit venting and draining of the shell side.

25.8.14. Manway Davits

When required by Vessel Specifications, exchanger manwaysshall be provided with davits for the cover plates in accordancewith Engineering Standard MEQ-206.

25.9. Internal Parts

Internal nonpressure parts attached to exchanger wall shall be welded withcontinuous fillet welds all around the part. The size of weld shall include


Revision 2


allowance for corrosion when a exchanger corrosion allowance is required(see Article 20.8.2).

25.9.1. Clad Exchangers

Pass partitions, sealing strips, and other parts shall normally bewelded directly to the cladding. Unusual conditions requiringremoval of cladding for welding to the base metal (e.g., heavilyloaded parts) shall be reviewed with OWNER.

25.9.2. Integrally-Clad Plate

All integrally-clad plate, whether cladding is included in designcalculations or not (see Article 20.10), shall satisfy therequirements of ASME Code Paragraph UCL-11 for shear andbond strength.

25.9.3. Weld Overlay

Weld overlay shall be in accordance with Engineering StandardMMOC-616. Weld overlay alloy designation shall be as specifiedin the Vessel Specifications.

25.9.4. Loose Lining

Loose type applied lining material shall not be used, except as aliner for flat cover plates and blind flanges. Plug welds shall notbe used to attach liners to blind flanges.


The type of exchanger support (skirt, legs, saddles, lugs) shall be asspecified in the Vessel Specifications (see Article 25.11 for anchor bolting).


Except as provided in Article 25.10.1.1, allowable design stressesfor all exchangers support components shall be the same asspecified in the ASME Code for pressure parts. The totallongitudinal compressive stress due to the combined action ofoverturning moment and weight in a cylindrical support skirt shallnot exceed that permitted in ASME Code Paragraph UG-23 forcylindrical shells.

25.10.1.1. Anchor Rings

Stresses resulting from direct bending in anchor ringbase plates shall not exceed 1.5 times the ASMECode allowable tensile values. Compressive stressesin anchor ring gussets and other compression


Revision 2


members shall not exceed 1.25 times the Code tensilevalues.

25.10.2. Skirt Supports

Support skirts for vertical exchangers with either a torispherical,semi-ellipsoidal, or toriconical bottom head shall be welded to thebottom head with a continuous weld sized so as to provide for themaximum imposed loadings.

25.10.2.1. Access Openings

Skirt supports shall be provided with two round accessopenings spaced 180 degrees apart. The openingsshall not be smaller than the following:

Opening Diameter

Exchanger OD(1) mm mm

610 through 762, inclusive 203over 762 through 914 254

over 914 through 1219 381over 1219 through 1524 457

over 1524 610(1) Skirt access openings for exchangers less than

610 mm OD shall be as specified in the VesselSpecifications.

25.10.2.2. Vent Openings

Skirt supports shall not be provided with ventopenings.

25.10.2.3. Weld Joints

All welds within the skirt shall be Type No. (1) of ASMECode Table UW-12. Alignment tolerance at plateedges shall be per ASME Code Paragraph UW-33.Skirts made up of two or more courses shall have thecentres of the welded longitudinal joints of adjacentcourses staggered or separated by a distance of atleast five times the thickness of the thicker plate.

25.10.3. Saddle Supports

Exchangers to be horizontally installed shall be mounted on twosaddle-type supports. Supports shall extend over at least one-third (120 degrees) of the circumference of the exchanger shell.Wear plates shall be provided and shall have radiused corners,be welded to the shell with a continuous fillet weld, and beprovided with two telltale holes. The holes shall be plugged with


Revision 2


a room temperature vulcanising (RTV) silicone sealant. Thebottom of the supports shall extend at least 25 mm below nozzlesor other projecting exchanger components.

25.10.3.1. Slide Plates

One of the two saddles shall be designated as thefixed saddle and holes shall be provided to receive theanchor bolts. The other saddle shall be designated asthe sliding saddle and slotted holes of sufficient lengthto permit the maximum anticipated expansion orcontraction shall be provided. Except where greased

slide plates are permitted, TFE [(Teflon®) limited to107°C] or graphite slide plates shall be furnished (byCONTRACTOR) under all sliding saddles. The designstatic coefficient of friction for the slide plate shall betaken as 0.1 for TFE and 0.15 for graphite. Greasedslide plates may be used when all of the followingapply:

1. Exchanger does not exceed 610 mm OD.

2. Support load does not exceed 3400 kg.

3. Outside shell-to-base plate of saddle does notexceed 356 mm.

4. Operating temperature does not exceed 107°C.

25.10.3.2. Clearance Of Shell Seams

The minimum distance from the toe of fillet weldsattaching either saddle or lug-type supports, or theirwear plates, to the centreline of either a longitudinal orcircumferential shell seam shall be Rt (where R =shell inside radius and t = shell thickness exclusive ofcorrosion allowance).

25.10.3.3. Saddle Design

The effect of the saddles on the shell shall beanalysed using the method developed by L. P. Zickand published by John Wiley and Sons, ProcessEquipment Design by Brownell and Young, 1959,Chapter 11, "Design of Horizontal Vessels with SaddleSupports".

25.11. Anchor Bolting

Carbon steel anchor bolts shall not be smaller than 19 mm nor larger than 38mm. When larger anchor bolts (carbon steel) would be required, low-alloysteel bolts shall be used. The minimum size for low-alloy steel bolts shall be25 mm. Anchor bolts shall be hot-dipped galvanised per ASTM A 153.


Revision 2



Allowable design tensile stresses, as calculated using the tensilestress area of the threaded portion, shall not exceed thefollowing:

1. Carbon steel, 1055 kg/cm2

2. Low-alloy steel, 1757 kg/cm2 for bolt diameters 63.5 mmand smaller, and 1617 kg/cm2 for bolt diameters over 63.5mm through 101.6 mm.

25.11.2. Spacing and Location

Anchor bolts for skirt supported vertical exchangers shall beselected in multiples of four bolts. Orientation will be furnished byCONTRACTOR. The anchor bolt circle shall be selected toprovide radial clearance for the bolt tensioning device when low-alloy steel bolting is required.

25.11.3. Supplier

Unless otherwise specified in the Vessel Specifications, anchorbolting will be furnished and installed by CONTRACTOR.

25.12. Lifting Lugs

Lifting lugs shall be furnished as follows:

25.12.1. Exchanger Lifting Lugs

Vertical exchangers having a nominal diameter 1524 mm orlarger, or a height greater than 1981 mm shall be furnished withlifting lugs designed to permit erecting the exchanger from ahorizontal position. The crevice between the lug and the tophead dish surface shall be sealed by a bead of room temperaturevulcanising (RTV) silicone sealant after painting. Usually, twoear-type lugs spaced 180 degrees apart and welded to thestraight flange portion of the top head and shell are adequate.For unusually tall exchangers, it may be necessary to providetrunnion-type lugs located about two-thirds the height of theexchanger from the base. The effect of handling and erectionshall be considered in the design of the exchanger and the liftinglugs.

25.12.2. Lugs for Removable Parts

Removable components weighing more than 27 kg shall beprovided with lifting lugs.


Revision 2


25.12.3. Tailing Lugs

Provide tailing lugs for vertical exchangers greater than 6000 mmin height and/or greater than 4535 kg in weight.

25.13. Flow-Induced Tube Vibration

Flow-induced vibration shall be considered. Damaging vibration (resonanceat natural frequency) as a result of fluid-elastic excitation, vortex shedding,acoustic resonance, or turbulent buffeting shall be avoided. The effect ofany axial loading on the tubes shall be considered when determining naturalfrequencies. Regions of high velocity, such as inlet and outlet nozzles, shallbe properly considered. Baffle and tube bundle types which reduce oreliminate the potential for flow-induced tube vibration should be selected.Detuning baffles shall be provided when required.


Revision 2


(See drawing MCOP-11.DGN)

mcop11

Documents

postweld heat treated

postweld heat treatment

room temperature vulcanising

straight beam examinations

sensitive leak test

mechanical heat exchanger

combined primary stress

final heat treatment