PIP VESST002 Supplemental Design and Fabrication Specification for Shell and Tube Heat Exchangers ASME Code Section VIII, Divisions 1 and 2

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1 March 2012 Process Industry Practices Vessels PIP VESST002 Supplemental Design and Fabrication Specification for Shell and Tube Heat Exchangers ASME Code Section VIII, Divisions 1 and 2

2 PURPOSE AND USE OF PROCESS INDUSTRY PRACTICES In an effort to minimize the cost of process industry facilities, this Practice has been prepared from the technical requirements in the existing standards of major industrial users, contractors, or standards organizations. By harmonizing these technical requirements into a single set of Practices, administrative, application, and engineering costs to both the purchaser and the manufacturer should be reduced. While this Practice is expected to incorporate the majority of requirements of most users, individual applications may involve requirements that will be appended to and take precedence over this Practice. Determinations concerning fitness for purpose and particular matters or application of the Practice to particular project or engineering situations should not be made solely on information contained in these materials. The use of trade names from time to time should not be viewed as an expression of preference but rather recognized as normal usage in the trade. Other brands having the same specifications are equally correct and may be substituted for those named. All Practices or guidelines are intended to be consistent with applicable laws and regulations including OSHA requirements. To the extent these Practices or guidelines should conflict with OSHA or other applicable laws or regulations, such laws or regulations must be followed. Consult an appropriate professional before applying or acting on any material contained in or suggested by the Practice. This Practice is subject to revision at any time. Process Industry Practices (PIP), Construction Industry Institute, The University of Texas at Austin, 3925 West Braker Lane (R4500), Austin, Texas PIP Member Companies and Subscribers may copy this Practice for their internal use. Changes or modifications of any kind are not permitted within any PIP Practice without the express written authorization of PIP. Authorized Users may attach addenda or overlays to clearly indicate modifications or exceptions to specific sections of PIP Practices. Authorized Users may provide their clients, suppliers and contractors with copies of the Practice solely for Authorized Users purposes. These purposes include but are not limited to the procurement process (e.g., as attachments to requests for quotation/ purchase orders or requests for proposals/contracts) and preparation and issue of design engineering deliverables for use on a specific project by Authorized User s client. PIP s copyright notices must be clearly indicated and unequivocally incorporated in documents where an Authorized User desires to provide any third party with copies of the Practice. PUBLISHING HISTORY March 2012 Issued Not printed with State funds

3 March 2012 Process Industry Practices Vessels PIP VESST002 Supplemental Design and Fabrication Specification for Shell and Tube Heat Exchangers ASME Code Section VIII, Divisions 1 and 2 Table of Contents 1. Introduction Purpose Scope References Process Industry Practices Industry Codes and Standards Government Regulations Definitions Requirements General Design Fabrication Process Industry Practices Page 1 of 13

4 1. Introduction 1.1 Purpose This Practice provides mechanical design and fabrication requirements for shell-andtube heat exchangers constructed in accordance with TEMA Standards of the Tubular Exchangers Manufacturers Association and ASME Boiler and Pressure Vessel Code, Section VIII, Division 1 or Division 2, henceforth referred to as the Code. Requirements that are specific to Code, Section VIII, Division 2 are shown in braces { }. 1.2 Scope 2. References This Practice describes the mechanical design, fabrication, examination, inspection, testing, and documentation requirements for shell-and-tube heat exchangers constructed in accordance with TEMA Standards of the Tubular Exchangers Manufacturers Association and Code, Section VIII, Division 1 {or 2}. This Practice is supplemental to the requirements of PIP VESV1002, Design and Fabrication Specification for Pressure Vessels, ASME Code Section VIII Divisions 1 and 2. This Practice does not cover the following types of shell and tube heat exchangers: a. Standardized pre-designed (i.e., off-the-shelf) heat exchangers b. Heat exchangers with layered construction Applicable parts of the following Practices, industry codes and standards, and references shall be considered an integral part of this Practice. The edition in effect on the date of contract award shall be used, except as otherwise noted. Short titles are used herein where appropriate. 2.1 Process Industry Practices (PIP) PIP VESV Design and Fabrication Specification for Pressure Vessels, ASME Code Section VIII Divisions 1 and 2 PIP VEDST003 - Documentation Requirements for Shell and Tube Heat Exchangers PIP VEFV Vessel/S&T Heat Exchanger Standard Details PIP VEFV Vessel; Nameplate Bracket PIP VEFV Vessel; Tolerances (Orientation) PIP VEFV Vessel; Grounding Lug PIP VEFV Vessel; Horizontal, Saddles Supported on Concrete PIP VEFV Vessel; Horizontal, Saddles Supported on Steel PIP VEFV Vessel; Manway Hinges PIP VEFV Vessel; Manway Vertical Davit PIP VEFV Vessel; Manway Horizontal Davit Process Industry Practices Page 2 of 13

5 PIP VEFV Vessel; Internal Ladders PIP VEFV Heat Exchanger Fixed Tubesheet Vent and Drain PIP VEFV Vessel Skirt Attachment 2.2 Industry Codes and Standards For each of the following reference documents, if Code Table U-3 {1.1} lists an edition or addenda different than the edition listed in the reference, the edition listed in Code, Table U-3 {1.1} shall be used. American Society of Mechanical Engineers (ASME) ASME Boiler and Pressure Vessel Code (Code) Section II, Part D - Properties Section V - Nondestructive Examination Section VIII - Pressure Vessels, Divisions 1 and 2 Section IX - Welding and Brazing Qualifications ASME B1.1 - Unified Inch Screw Threads (UN and UNR Thread Form) ASME B Pipe Flanges and Flange Fittings, Sizes NPS 1/2 through NPS 24 ASME B Factory-Made Wrought Buttwelding Fittings ASME B Large Diameter Steel Flanges, NPS 26 through NPS 60 ASME PCC-1 - Guidelines for Pressure Boundary Bolted Flange Joint Assembly TEMA Standards for Tubular Exchanger Manufacturers Association 2.3 Government Regulations 3. Definitions The following reference is applicable to U.S. installations or as specified by Purchaser. U. S. Department of Labor, Occupational Safety and Health Administration (OSHA) OSHA 29 CFR (k)(3)(ii) - Permit-Required Confined Spaces for General Industry Code: The ASME Boiler and Pressure Vessel Code, Section VIII, Division 1 {or 2} and its referenced Sections (e.g., Section II, Section V, and Section IX) and any Code Cases permitted by the User. References to Division 2 are shown in braces { }. construction: An all-inclusive term comprising materials, design, fabrication, examination, inspection, testing, certification (i.e., Code stamp and Manufacturer s Data Report), {Manufacturer s Design Report}, and pressure relief. Process Industry Practices Page 3 of 13

6 Manufacturer: The party entering into a contract with the Purchaser to design and construct a heat exchanger in accordance with the requirements in this Practice and the contract documents. In accordance with the Code definition, the Manufacturer is the party that possesses a valid Certificate of Authorization to manufacture pressure vessels with the ASME Mark. Comment: The Purchaser may duplicate portions or all of the exchanger design. National Board: The National Board of Boiler and Pressure Vessel Inspectors, an organization comprised of chief inspectors of various governmental jurisdictions in the United States and Canada. Owner: The party who owns the facility wherein the heat exchanger will be used. The owner is typically also the User. Purchaser: The party who awards the contract to the Manufacturer. The Purchaser may also be the Owner, User, or the Owner s or User s Designated Agent (e.g., engineering contractor). User: The party who establishes construction criteria in accordance with the Code philosophy and service hazards. The User is the operator of the facility wherein the heat exchanger will be installed. Purchaser s Inspector: The person or company authorized by the Purchaser, Owner, and/or User to inspect pressure vessels to the requirements of this Practice and other Purchaser contract requirements. vessel: The pressure boundary components of the heat exchanger, including the shell, heads, tube sheets, nozzles. 4. Requirements 4.1 General Overall Responsibilities Heat exchangers shall be provided in accordance with this Practice and the following: a. PIP VECV1002 for the mechanical design and fabrication of all pressure boundary components and attachments. b. PIP VEDST003 including the following Purchaser s forms: 1) PIP VEDST003-D Data Sheet 2) PIP VEDV1003-T Inspection and Testing Requirements Sheet or equivalent 3) PIP VEDV1003-R Documentation Requirements Sheet 4) PIP VEDST003-F Welded Pressure Joint Requirements c. The Code Process Industry Practices Page 4 of 13

7 d. Design criteria that may supersede the requirements of this Practice but not take exception to the requirements of the Code e. PIP VEFV1100 details: VEFV1101, VEFV1102, VEFV1103, VEFV1105, VEFV1106, VEFV1116, VEFV1117, VEFV1118, VEFV1125, VEFV1127, and VEFV1128 f. Other codes and standards referenced in this Practice g. Local requirements h. Other contract requirements furnished by the Purchaser Heat exchangers shall be in total compliance with the Code, including stamping Unless otherwise specified by the Purchaser, U- {U2-} stamped exchangers shall also be National Board (NB) registered Deviations from this Practice shall be submitted in writing for approval by the Purchaser If a conflict is identified between this Practice, the design drawings, data sheets, referenced codes and standards, or any supplementary specification, written clarification shall be obtained from the Purchaser before proceeding with any work All aspects of the work shall be in accordance with applicable local, county, state, and federal rules, regulations and standards at installation site including but not limited to the rules and standards established by the EPA and OSHA, or equivalent national standards, if applicable, as designated by the Purchaser. See Purchaser s PIP VEDST003-D Data Sheet If the Purchaser furnishes an exchanger or exchanger component design, the Manufacturer shall not be relieved of his responsibility to comply with the requirements of this Practice and the contract documents. Comment: Certain non-code-design functions may be performed solely by the Purchaser (e.g., design of exchanger internals) Release for shipment by Purchaser s inspector shall not relieve the Manufacturer of his responsibility to comply with the requirements of this Practice and the contract documents Documentation Responsibilities Heat exchanger documentation shall be provided in accordance with Purchaser s PIP VEDV1003-R Documentation Requirements Sheet The data required by Part B of Purchaser s PIP VEDST003-D Data Sheet shall be provided with the approval drawings. Process Industry Practices Page 5 of 13

8 4.2 Design General Heat exchanger mechanical design shall be in accordance with this Practice, PIP VESV1002, the Purchaser s PIP VESST003-D Data Sheet in lieu of PIP VESV1003-D, and all other requirements in the contract documents Half-pipe or pipe section jackets shall be designed in accordance with Code Appendix EE {4.11.6} Pressure and Temperature The basis for thermal expansion used in the design, as shown on Purchaser PIP VEST003-D Data Sheet, shall be shown on the fabrication drawings. Comment: Fixed tubesheet exchangers cannot typically be operated at the coincident nameplate temperature-pressure conditions Heat exchangers shall be designed for full pressure on either shell side or tube side with atmospheric (or full vacuum, if specified) on the other side If an exchanger is designed for differential pressure, the nameplate shall so indicate Tubesheets 1. Tubesheets for U tube, fixed tubesheet and floating tubesheet heat exchangers shall be designed in accordance with Code Parts UHX-12, 13 and 14 {4.18.7, and }. 2. Tubesheets shall be designed for full design pressure on either side, with atmospheric pressure or specified vacuum on the other side. 3. Differential pressure design shall only be used if approved by Purchaser. 4. Unless otherwise approved by the Purchaser, tubesheets welded to a carbon steel shell or channel shall be of carbon steel or clad carbon steel. 5. If in accordance with one of the following criteria, solid alloy tubesheets may be welded to a carbon steel shell or channel: a. The thermal coefficients of expansion do not vary greater than 15% from the tubesheet to the shell or channel over the operating temperature range. b. A stress analysis is performed by the Manufacturer and approved by the Purchaser for the joint between the tubesheet and the shell or channel. Process Industry Practices Page 6 of 13

9 4.2.3 Supports 6. If a stress analysis of the junction of the alloy and carbon steel cylindrical section is performed and approved by the Purchaser, a solid alloy tubesheet may be welded to a relatively short cylindrical section of the same alloy material to be welded to a carbon steel shell or channel. 7. Confining gasket grooves shall be provided for exchangers with gasketed pass partition joints Skirt supports for vertical exchangers shall be in accordance with the standard detail on PIP VEFV1128 as specified on Purchaser s PIP VEDST003-D Data Sheet, Page Supports for stacked heat exchangers shall be in accordance with the following: 1. The lower exchanger shells shall be designed to withstand the superimposed load of upper exchangers filled with water or operating fluid, whichever is greater, without distorting the shells in a manner that could cause binding of tube bundles. 2. A 1/2-inch (13 mm) shimming allowance shall be provided between intermediate exchanger supports. 3. Lower fixed exchanger supports shall be designed for the full bundle pulling load for removal of any upper exchanger tube bundle. 4. The design of exchanger supports, including the dimensions of the slots, shall include allowances for differential thermal expansion between exchangers If required for removal of exchanger components (i.e., bonnet, cover, etc.), two or more lifting lugs, located at 45 degrees from the top centerline of the components, shall be provided Internals For multi-pass heat exchangers, the total gasket sealing areas of the pass partition plates shall be included when calculating the minimum initial bolt load required to seat the exchanger gasket If the type of joint is not specified on Purchaser s PIP VESST003-D Data Sheet, expanded joints with grooves shall be used for tubesheets of homogeneous material. Expansion may be by roller, hydraulic pressure, or other Purchaser-approved method Strength-welded tube-to-tubesheet joints shall be used if either of the following applies: 1. Expanded joints cannot carry the expected tube load 2. Residual interface pressure because of expansion (i.e., tube rolling or hydraulic expansion) can be compromised during operation Process Industry Practices Page 7 of 13

10 Comment: Loss of residual interface pressure can occur in high temperature applications, or if significant differential thermal expansion can occur between the tube and tubesheet The special close fit tolerances for tube holes in accordance with TEMA shall be provided for the following applications: a. Austenitic tubes with expanded and grooved tube-to-tubesheet joints b. Seal-welded or strength-welded tube-to-tubesheet joints c. Hydraulically expanded tube-to-tubesheet joints Tube Bundles 1. The minimum mean bend diameter of U-tubes shall not be less than 3 times the nominal tube outside diameter. 2. The end baffle spaces shall be equal to or greater than the central baffle space Cross Baffles 1. Cross-baffle metallurgy and thickness shall be selected considering the corrosiveness of the shell side fluids and the intended design life. 2. Cross baffles that resist corrosion shall have a thickness not less than the greater of that specified by TEMA or 1/8 inch (3 mm). 3. Cross baffles susceptible to corrosion shall have a thickness not less than the greater of the TEMA minimum, 2 times the corrosion allowance, or 3/16 inch (5 mm). 4. The end-baffle spaces shall be equal to or greater than the crossbaffle space Each support plate and baffle in horizontal exchangers shall be provided with a 1/2 inch (13 mm) by 90 degree notch in the bottom for draining Each TEMA Type S and T exchanger (i.e., having a removable shell cover) shall have a floating head support plate located 4 to 6 inches (100 to 150 mm) from the inside face of the floating tubesheet Except for shell side isothermal boiling, isothermal condensing, or kettles, bypass sealing devices shall be provided in accordance with the following: a. Seal strips shall be provided if the radial clearance between exchanger shell and outer tubes is greater than 5/8 inch (16 mm). b. Seal strip thickness shall not be less than the greater of 75% of baffle thickness or 1/4 inch (6 mm). Process Industry Practices Page 8 of 13

11 c. For exchangers with vertical cut baffles (i.e., baffle cut parallel to shell side nozzle centerline), seal strips shall be provided to seal the bypass areas caused by the omission of tubes. Seal strips shall not extend into the inlet or outlet baffle spaces. d. For horizontal cut baffles (i.e., baffle cut perpendicular to shell side nozzle centerline), seal strips shall extend from the front or stationary tubesheet to the last baffle or support plate. e. Dummy tubes, rods, or seal strips shall be provided for any pass partition lanes that are parallel to the shell side flow. f. One pair of seal strips or one dummy tube shall be provided for each five tube rows between baffle cuts. Minor adjustments to this requirement may be made to suit actual tube layout Skid Bars 1. Exchangers with removable tube bundles weighing 20,000 pounds (9070 Kg) or greater shall be provided with bundle skid bars. 2. A minimum of two skid bars shall be provided. 3. Skid bars shall have a thickness equal to or greater than crossbaffle thickness with a minimum thickness of 1/2 inch (13 mm), and a 1-1/2 inches (38 mm) minimum height flat bar. 4. Skid bars shall be located not greater than 30 degrees from the vertical centerline. 5. For TEMA Types S and T heat exchangers, skid bars shall extend from the stationary tubesheet to floating head support plate. 6. For TEMA Types P, U, and W heat exchangers, skid bars shall extend from the stationary tubesheet to end baffle. 7. If skid bars interfere with nozzle openings, the skid bars shall be terminated at the baffle or support plate adjacent to the nozzle. A tie rod/spacer of adequate strength to carry the bundle pulling load shall be located close to the tube field and within 3 inches (75 mm) of the skid bar and shall extend from the tubesheet or baffle/support plate on one side of the nozzle to the baffle/ support plate on the other side of the nozzle Perforated or slotted impingement plates shall not be permitted Multiple exchangers of the same TEMA size and material, either stacked or parallel, shall be provided with interchangeable components to the maximum extent possible Expansion Joints The design of expansion joints shall be performed by any method of stress analysis (e.g., finite element analysis), including TEMA Paragraph RCB-8, which is applicable to expansion joints. The Process Industry Practices Page 9 of 13

12 allowable stresses for design shall be in accordance with Code Appendix 5 { }. Cycle life shall be in accordance with Code U-2(g) Unless otherwise specified on Purchaser s PIP VEDST003 Data Sheet, shell expansion joints shall be of the thick wall flanged and flued type or flanged only type in accordance with Code Appendix 5 { } For the following conditions, thin wall bellows type shell expansion joints shall be provided in accordance with Code Appendix 26 {4.19}: a. If specified on the Purchaser s PIP VEDST003 Data Sheet, the expansion joint welding stubs shall be of the same material as the exchanger shell. b. For single pass floating head heat exchangers, thin wall bellows type joints may be provided. The expansion joint welding stubs shall be of the same material as the tail pipe material The expansion joint-to-shell weld shall not be located less than two times Rt from the back of the tubesheet, where R is the outside radius of the exchanger shell in inches (mm), and t is the actual thickness of the shell less corrosion allowance in inches (mm) Exchanger shell expansion joints shall be ventable and drainable in the operating position Vapor Belts The design of vapor belts shall be based on the following: a. Effect of pressure loads b. Except for fixed tubesheet designs, longitudinal stresses produced by operating and test pressures c. Consideration of flexibility produced when designing the exchanger shell, tubes, and tubesheet d. If a sleeve type vapor belt is used, the design shall be considered flexible and designed in accordance with Section Vapor belts may be used as expansion joints if designed in accordance with Section Whether or not vapor belts are used as expansion joints, vapor belt flexibility shall be considered in the design of exchanger shell, tubes, and tubesheets. Process Industry Practices Page 10 of 13

13 4.2.7 Shell Covers Except for kettle type reboilers, TEMA Type T exchangers shall have removable shell covers Except for TEMA Type D stationary head designs, removable channels or bonnets, channel covers, and floating head covers shall be attached with through-bolted flanged joints If full diameter tubesheets are specified for exchangers with removable tube bundles, the following shall apply: a. Retaining studs shall be provided to maintain the gasket seal on the shell side of the tubesheet with the channel or bonnet removed. b. Retaining studs shall be installed in 25% of the bolt holes or in four bolt holes minimum whichever is greater. c. The tubesheet shall be designed to withstand shell side or tube side hydrostatic test pressure with bonnet/channel or shell removed Mitered 90 degree reducing elbows for thermosyphon reboiler outlet heads shall be in accordance with the following: a. Number of changes in direction at the inside and outside contours shall not be less than three b. Cyclic loading shall not be a governing design requirement c. Meridian (i.e., change of direction) angles between adjacent sections shall be approximately equal for gradual flow transition d. General contours shall be similar to those of commercial forged reducing elbows Pass Partition Plates Drain holes in pass partition plates shall not be permitted Floating Heads Floating heads shall be designed and dimensioned in accordance with Code Figure 1-6(d) {Figure 4.7.5} The use of nubbins shall be approved by Purchaser Floating heads shall be designed with respective corrosion allowance applied to the inside and outside of the floating head and flange Corrosion allowance on the outside diameter of the flange shall be added to the recommended edge distance for the selected bolt size. Process Industry Practices Page 11 of 13

14 Kettle Type Exchangers 4.3 Fabrication Kettle type exchangers shall be provided with either of the following arrangements: a. 3-inch (75 mm) minimum length cylindrical section (includes flanged hub, if any) between the shell flanges and conical transitions b. Other alternative for cone-to-flange fit-up and bolting clearance For kettle type exchangers with tubesheets integral with the shell, the minimum length of cylindrical section between the tubesheet and the conical transition shall be the greater of 3 inches (75 mm) or Rt, where R is the mean radius of the cylindrical section in inches (mm), and t is the thickness of the section in inches (mm) Rails shall be provided to support and guide the tube bundle. Rails shall be welded to the exchanger shell A hold down bar or angle shall be provided directly above the floating head or the last U-tube support plate If a weir plate is required, the weir plate shall be continuously welded all around to the exchanger shell and shall be of sufficient height to flood the top row of tubes with a minimum of 2 inches (50 mm) of process fluid during normal operation. Drains shall be provided to both sides of the weir Tubesheet-to-shell or -channel weld joints shall be a full penetration weld in accordance with Code Figure UW-13.2 {Tables and 4.2.8} or Figure UW 13.3{Table 4.2.7}, except as follows: 1. Weld joints that use a permanent backing strip shall not be permitted. 2. To avoid the potential for crevices forming during fabrication, Code Figures UW-13.2 (d), (e-2), and (i) shall not be permitted {not shown in Division 2}. 3. Exchangers having any of the following design conditions shall use tubesheet-to-shell or -channel weld joints in accordance with Code Figures UW-13.2 (a), (f), or (k){table Details 1 and 3, and Table 4.2.8}, or Figure UW-13.3{Table 4.2.8}: a. Tube side MAWP greater than 600 psig (4 MPa) b. Shell side MAWP greater than 1000 psig (6.9 MPa) c. Minimum Design Metal Temperature less than minus 20 F (29 C) d. High-alloy tubesheet and adjoining shell or channel with the weld joint exposed to the process fluid Process Industry Practices Page 12 of 13

15 e. Shell or channel inside diameter greater than 48 inches (1200 mm) with carbon steel, low-alloy steel, or clad steel tubesheet material f. Shell or channel inside diameter greater than 30 inches (760 mm) with high-alloy or nonferrous tubesheet material For the purpose of determining required tubesheet-to-shell or -channel weld sizes in accordance with Code requirements, a fixed tubesheet shall be considered supported (i.e., not less than 80% of the pressure load is carried by the tubes) if the following equation is satisfied: Where: [(A t E t )/(A s E s )] 4.0 A t = Total cross-sectional metal area of tubes, sq. inches (sq. mm) E t = Modulus of Elasticity of tube material at mean metal temperature, psi (kpa) A s = Cross-sectional metal area of shell based on actual thickness less corrosion allowance, sq. inches (sq. mm) E s = Modulus of Elasticity of exchanger shell material at mean metal temperature, psi (kpa) If vents or drains are specified to be in the tubesheet, installation shall be in accordance with the details shown on PIP VEFV Nameplates shall be located on the exchanger shell in an accessible location. The nameplate location shall be shown on the dimensioned outline drawing. Process Industry Practices Page 13 of 13