Manufacture of Shell and Tube Heat Exchangers PDF

Document Responsibility: Heat Transfer Equipment Standards Committee 32-SAMSS-007 Issue Date: 26 June 2017 Next Planned Update: 26 June 2020 Manufacture of Shell and Tube Heat Exchangers shall contain a minimum of four tubes a...

Document Responsibility: Heat Transfer Equipment Standards Committee 32-SAMSS-007 Issue Date: 26 June 2017 Next Planned Update: 26 June 2020 Manufacture of Shell and Tube Heat Exchangers shall contain a minimum of four tubes and shall be prepared using the same materials and fabrication procedures (including heat treatment) as are to be used in actual production. Approval from the Saudi Aramco Inspector is required prior to start of production. No need to repeat the test if similar joint design was done in the past 6-months. 9.12 Forming and Heat Treatment 9.12.1 General a) Cold forming for carbon steels shall be performed at temperatures within the range of above 20°C (68°F) and below 120°C (248°F). b) Hot forming is any forming performed above the austenite phase start temperature of 740°C (1364°F). c) All tempering heat treatments for all carbon steels must be at least 25°C (45°F) above the nominal PWHT temperature as given in the applicable ASME code for the respective material. The tempering temperature must not exceed the temperature stated in the steel manufacturers Material Test Certificate. d) There are no restrictions for tempering temperature of 1 Cr- ½ Mo, 1 ¼ Cr- ½ Mo, 2 ¼ Cr-1 Mo, 2 ¼ Cr-1 Mo- ¼ V, 3 Cr-1 Mo and 3 Cr-1 Mo- ¼ V steels, provided that the requirements of paragraph 8.1.15 are met. e) Forming and rolling of plates of 1 Cr- ½ Mo, 1 ¼ Cr- ½ Mo, 2 ¼ Cr-1 Mo, 2 ¼ Cr-1 Mo- ¼ V, 3 Cr-1 Mo and 3 Cr-1 Mo- ¼ V steels shall be performed with a minimum through-thickness temperature of 177°C (350°F). Forming at ambient temperature is prohibited. 9.12.2 Cold Forming a) Heat treatment requirements for Carbon Steels (P-1), Low Alloy Steels (P-3, 4, 5, 9A and 9B), High Alloy Steels and Non-ferrous Materials shall be as follows: Material Fiber Elongation Strain εf (%) Heat Treatment Requirement None Less than or equal to 5 (Exception: PWHT per the applicable Code shall be performed for cold spun heads) Carbon Steels P-1 Greater than 5 & equal to or less than 10 PWHT per the applicable Code Normalizing, Normalizing and tempering or Greater than 10 quenching and tempering, as required to maintain original material properties. Low Alloy Steels P-3, None Less than or equal to 3 P-4, P-5, P-9A, & P9B (Exception: PWHT per the applicable Code Page 41 of 59 Document Responsibility: Heat Transfer Equipment Standards Committee 32-SAMSS-007 Issue Date: 26 June 2017 Next Planned Update: 26 June 2020 Manufacture of Shell and Tube Heat Exchangers Material Fiber Elongation Strain εf (%) Heat Treatment Requirement shall be performed for cold spun heads) Greater than 3 & equal to or less than 10 PWHT per the applicable Code Normalizing, normalizing and tempering or Greater than 10 quenching and tempering, as required to maintain original material properties. Table 6.2 of ASME SEC VIII D2 (Exception: Austenitic stainless steel High Alloy Materials Table 6.2 of ASME SEC VIII D2 formed heads shall be solution annealed irrespective of the calculated fiber elongation strain εf) Non-ferrous Materials Table 6.3 of ASME SEC VIII D2 Table 6.3 of ASME SEC VIII D2 b) Calculation of forming fiber elongation strain εf (%) shall be according to the following: Type of Part Being Formed Fiber Elongation Strain εf (%) For double curvature heads that are formed from one- piece or welded multi-piece blanks by any process that εf = 100 ln [Db/(Df -2t)] includes dishing or cold spinning (e.g., dished heads or cold spun heads) For heads that are assembled from formed segments (e.g., spherical dished shell plates or dished segments εf = 100 t / Rfd of ellipsoidal or torispherical heads) Cylinders and cones formed from plate εf = (50 t / Rfc) [1-(Rfc / Ro)] Where: ln is the natural logarithm Db is the diameter of unformed blank plate or diameter of intermediate product Df is the outside diameter of the finished product Rfd is the smallest mean radius of curvature of formed segment (mean radius of spherical segment, mean knuckle radius of knuckle segment of multi sectional semi-ellipsoidal or torispherical heads) Rfc is the mean radius of curvature of finished product (mean radius of cylinder, mean radius of the smaller diameter of cone) Ro is the mean radius of initial product (flat plate) or the intermediate product (in case of unformed initial product equals to infinity) t is the nominal thickness of the plate before forming or intermediate product Page 42 of 59 Document Responsibility: Heat Transfer Equipment Standards Committee 32-SAMSS-007 Issue Date: 26 June 2017 Next Planned Update: 26 June 2020 Manufacture of Shell and Tube Heat Exchangers Commentary Notes: i) Cold spun heads with nominal thickness exceeding 50 mm shall be heat treated by normalizing, normalizing and tempering or quenching and tempering, as required to maintain original material properties), irrespective of the calculated fiber elongation strain. ii) Need for heat treatment of all double curvature circular products (e.g., spherical crowns, semi-ellipsoidal and torispherical heads) formed from one-piece or welded multi-piece blank, shall be based on fiber elongation strain calculated using equation of the above table. iii) Separate calculation of extreme fiber elongation shall be made for each formed segment forming multi-sectional heads (torispherical or ellipsoidal) or spheres (excluding spherical crown). Need for heat treatment shall be determined for each segment individually using equation of the above table based on the greatest measured thickness and smallest radius of curvature after forming. iv) In case of different forming steps without intermediate heat treatment are employed, extreme fiber elongation is the total amount of elongation of the individual forming steps. In case of intermediate heat treatment, the deformation is that elongation achieved after the last previous heat treatment. This is applicable for all types of formed part. v) Filler metal used in items subjected to hot forming temperatures, or normalized, shall satisfy the weld joint design requirements after such heat treatment. This is considering that such welds will generally suffer significant strength reduction. vi) Austenitic stainless steel formed heads shall be solution annealed irrespective of the calculated fiber elongation strain εf 9.13 Bolt tensioning device shall be used for bolting up flanged connections with stud bolts of diameter 1-½ inch and above. Bolt up of flanges, irrespective of bolt diameter shall be according to ASME PCC-1 requirements. 9.14 Correction of fit-up offsets of the closing longitudinal butt joint in a rolled shell ring shall be achieved by only employing rolling machine operation until the deviations are within the specified Code tolerances. 9.15 Alignment of pre-formed sections of multi-piece exchangers head at butt joints, with fit-up deviations exceeding the Code tolerances, shall be achieved by only reforming (employing pressing machine) the head segments until the deviations are within the specified limits. 9.16 Alignment of completely fabricated sections at girth joints (shell ring-to- shell ring and head-to-shell ring), with fit-up deviations exceeding the Code tolerances, shall be achieved by only reforming the shell (using rolling machine) or head (employing pressing machine), whichever is out-of-true, until the deviations are within the specified limits. 9.17 All hot forming procedures require simulated production test coupons per paragraph 9.5.25 of this specification. Page 43 of 59 Document Responsibility: Heat Transfer Equipment Standards Committee 32-SAMSS-007 Issue Date: 26 June 2017 Next Planned Update: 26 June 2020 Manufacture of Shell and Tube Heat Exchangers 9.18 Welds Encroachment 9.18.1 It is the responsibility of the Exchanger Manufacturer to ensure that the outer edge of welds attaching manways, nozzles (with and without reinforced pads) and other structural attachments (with and without reinforced pads), except those in paragraph 9.18.4, to pressure-retaining components shall not be closer than 1 inch from the adjacent edge of any other weld. It is the responsibility of the manufacturer to ensure that requirements of paragraph 7.17.3 of this specification are met in the vicinity of the welds. Commentary Note: Weld spacing requirements for nozzle/ manway welds in exchangers under the scope of API RP 934-A constructed of 2 ¼ Cr-1 Mo- ¼ V and 3 Cr-1 Mo- ¼ V shall be according to paragraph 9.18.4 of this specification. 9.18.2 NDE per paragraph 10.1.45 shall be performed, where the optimized fabrication layout and/ or process design requirements do not absolutely allow meeting the spacing requirement in paragraph 9.18.1 of this specification. 9.18.3 It is prohibited to cover butt welds in wall of exchangers that will undergo PWHT by structural attachments (with or without reinforcing pads). 9.18.4 Nozzle/ manway welds in exchangers under the scope of API RP 934-A constructed of 2¼ Cr-1 Mo- ¼ V and 3 Cr-1 Mo- ¼ V steels shall be located without intersecting any circumferential or longitudinal welds. Adjacent edges of circumferential or longitudinal welds and welds attaching nozzles / manways shall not be closer than the greater of 50 mm (2 in.) and one thickness of head or shell. 10 Inspection and Testing 10.1 Quality Control 10.1.19 The responsibility for examination rests with the Exchangers Manufacturer in accordance with the applicable Code and the requirements of this specification. 10.1.20 Exchangers manufactured in accordance with this specification are subject to verification by the Saudi Aramco Inspector in accordance with Saudi Aramco Inspection Requirements Form 175-323100. 10.1.21 All required Nondestructive Examination (NDE) shall be performed in accordance with inspection procedures that are in complete compliance with ASME SEC V and this specification. This written procedure shall address each inspection method and technique used including acceptance criteria. Page 44 of 59 Document Responsibility: Heat Transfer Equipment Standards Committee 32-SAMSS-007 Issue Date: 26 June 2017 Next Planned Update: 26 June 2020 Manufacture of Shell and Tube Heat Exchangers The procedure(s) shall be submitted to Saudi Aramco Inspection Department for approval. 10.1.22 All Nondestructive Examination, including Magnetic Particle and Liquid Penetrant examinations, shall be performed by personnel certified in accordance with ASNT CP-189, or equivalent National Certification Programs that has been approved by the Saudi Aramco Inspection Department. Personnel responsible for interpretation of Nondestructive Examination results shall be certified to a minimum of Level II. 10.1.23 All required NDE for final acceptance of the exchanger shall be performed after the completion of all welding and repairs and prior to pressure testing. In exchangers requiring PWHT, all NDE for final acceptance shall be performed after the final PWHT. 10.1.24 Use of fitness-for-service assessment methodology to qualify exchanger welding joints that do not satisfy the applicable construction code acceptance criteria is prohibited. 10.1.25 Magnetic particle examination or liquid penetrant examination per the applicable Code shall be performed on the surfaces of hot formed and reheat treated parts. 10.1.26 All pressure and non-pressure welds in exchangers that are not required to undergo PWHT shall be visually inspected where accessible. All segments of longitudinal, circumferential or built-up head pressure weld seams covered or rendered inaccessible by internals, lifting lugs or other attachments shall be fully radiographed over the entire affected length plus minimum 50 mm (2 in.) either side prior to installation of the attachment. 10.1.27 Additional examination of any weld joint at any stage of the fabrication may be requested by the Saudi Aramco Inspector, including re-examination of previously examined joints. The Saudi Aramco Inspector also has the right to request or conduct independent NDE of any joint. If such examination should disclose nonconformance to the requirements of the applicable Code or this specification, all repair and NDE costs shall be done at the Exchanger Manufacturer's expense. 10.1.28 All necessary safety precautions shall be taken for each examination method. 10.1.29 Surface irregularities, including weld reinforcement, inhibiting accurate interpretation of the specified method of nondestructive examination shall be ground smooth. 10.1.30 Examination of all welds shall include a band of base metal at least one inch Page 45 of 59