Manufacturing specifications for spiral plate heat exchangers

The manufacturing process specifications for heat exchangers can be found at http://bbs.hcbbs.com/thread-211191-1-1.html for the original poster’s reference~

Reposting this here in the hope it will be helpful to the original poster! Manufacturing procedures for heat exchangers: Heat exchangers are a common type of heat exchange equipment among pressure vessels, and during their manufacture, it is necessary to strictly comply with the \"Regulations on Safety Supervision of Pressure Vessels\", GB151 \"Shell and Tube Heat Exchangers\", as well as other relevant standards. In addition, the heat exchanger should be manufactured, inspected, and accepted in accordance with the following process requirements. 1. When the housing 1.1 is rolled from steel plate, the allowable deviation of the inner diameter can be controlled through the outer circumference; the allowable upper deviation for this outer circumference is 10 mm, while the allowable lower deviation is zero. 1.2 On the same cross-section of the cylinder, the difference between the maximum and minimum diameters is e ≤ 0.5%DN. Furthermore: when DN≤1200mm, its value is not greater than 5mm ； When DN > 1200 mm, the value shall not exceed 7 mm. 1.3 The allowable deviation for the straightness of the cylinder is L/1000 (where L is the total length of the cylinder), and when L ≤ 6000 mm, this value shall not exceed 4.5 mm ； When L > 6000 mm, its value shall not exceed 8 mm. The straightness inspection should be conducted in the horizontal and vertical planes passing through the center line, that is, by measuring at the four positions of 0°, 90°, 180°, and 270° around the circumference. 1.4 Any welds on the inner wall of the shell that may affect the proper insertion or removal of the tube bundles should be ground to be level with the surface of the base material. 1.5 When the installation of nozzles or other attachments on the shell causes significant deformation, thereby affecting the proper installation of the tube bundle, measures should be taken to prevent such deformation. 1.6 For plug-in nozzles, unless specified in the drawings, the pipe fittings shall not protrude from the inner surface of the tube box or shell; moreover, the inner fillet welds should be welded first before the pipes are inserted. To prevent deformation of the cylinder, the outer fillet welds shall be welded after the tube bundle has been assembled. 2. Heat exchange tubes 2.1 The outer surface of the tube ends of the heat exchange tubes shall be rust-removed and cleaned. For welding, the cleaning length at the pipe end should be no less than the outer diameter of the pipe, and also no less than 25 mm ； For expansion jointing, the pipe end should have a metallic luster, and its length should be no less than twice the thickness of the tube sheet. 2.2 The splicing of heat exchange tubes shall meet the following requirements: 2.2.1 A welding procedure qualification shall be carried out for the butt joints; the number of test pieces, their dimensions, and the testing methods shall comply with the provisions of JB4708. 2.2.2 For the butt welds of the same heat exchange tube, there shall be no more than one such weld on a straight section of tube ； There shall not be more than two U-tubes ； The minimum pipe length shall not be less than 300 mm; there shall be no welds at the joints within the U-shaped bend section, which includes at least a 50 mm straight pipe section ； 2.2.3 The pipe end groove shall be machined mechanically and cleaned thoroughly before welding ； 2.2.4 The misalignment amount at the mating surfaces shall not exceed 15% of the wall thickness of the heat exchange tube, and shall not be greater than 0.5 mm ； The straightness deviation shall be such that it does not prevent smooth tube insertion ； 2.2.5 After docking, the corresponding steel ball diameter should be selected first (for d≤25, the diameter of the steel ball is 0.75di) ； 25＜d≤40 Steel ball diameter: 0.8di ； d＞40, steel ball diameter 0.85di ； di is the inner diameter of the pipe. According to 2.2.6, butt joints shall be subject to radiographic inspection; the number of samples inspected shall be no less than 10% of the total number of joints, and at least one sample per joint, with grade III as specified in JB/T4730 considered acceptable ； If one item is found to be non-compliant, random inspections should be doubled ； If non-conformities occur again, a 100% inspection should be carried out ； 2.2.7 The heat exchange tubes after connection shall be individually subjected to a hydraulic test, with the test pressure being twice the design pressure. 2.3 Bending of U-tubes: The roundness deviation of the bent section of the U-tube shall not exceed 10% of the nominal outer diameter of the heat exchange tube ； However, U-shaped bend sections with a bending radius of less than 2.5 times the nominal outer diameter of the heat exchange tube can be accepted at 15%. 3. Tube sheet: 3.1 The butt joints of the welded tube sheet shall be subject to 100% radiographic or ultrasonic inspection; according to JB/T4730, a radiographic inspection result of grade II or above, or a grade I result in ultrasonic inspection, is considered acceptable ； 3.2 Except for stainless steel, the gasketed tube sheet shall undergo stress-relief heat treatment. 3.3 Clad Composite Tube Sheets 3.3.1 A cladding process qualification shall be carried out prior to cladding ； 3.3.2 The surface of the area on the base material to be welded, as well as the surface of the cladding material after processing (but before drilling), shall be inspected according to JB/T4730 ； The test results must show no cracks or vent holes, and should meet the criteria for Grade II defect indications ； 3.3.3 Welding of the tube sheet by welding the heat exchange tubes to it and then filling the gaps between them with welds is not permitted for tube sheet cladding. 3.4 Surface roughness of tube holes in the tube sheet 3.4.1 When the heat exchange tubes are welded to the tube sheet, the Ra value of the surface roughness of the tube holes shall not exceed 25 mm ； 3.4.2 When the heat exchange tubes are joined to the tube sheet by expansion jointing, the surface roughness Ra value of the tube holes shall not exceed 12.5 mm ； 3.5 When the heat exchange tubes are joined to the tube sheet by expansion bonding, the tube holes must not have any defects that could affect the tightness of the expansion bond, such as through-going longitudinal or spiral grooves. 3.6 The sealing surface of the tube sheet partition groove should be level with the annular sealing surface, or slightly lower than it (within 0.5 mm), to ensure that when the tube box is sealed to the tube sheet, the hard contact between the partitions and the partition grooves does not compromise the seal. 4. Connection between heat exchange tubes and tube sheet 4.1 The surfaces of the heat exchange tubes and the holes in the tube sheet at the connection site must be cleaned thoroughly; no burrs, iron shavings, rust spots, oil stains, or other substances that could affect the quality of the expansion jointing or welding connection should remain ； 4.2 In the case of expansion joint connections, the length of the expansion joint shall not extend beyond the back side of the tube sheet (the shell side). There should be a smooth transition between the expanded and unexpanded sections of the heat exchange tubes, with no sharp corners. 4.3 During welding, slag and weld beads protruding from the inner wall of the heat exchange tube must be removed. For pipe end welding, automatic TIG welding, manual TIG welding, and manual arc welding should be given priority. However, regardless of the welding method used, two passes are required to eliminate pores on the weld metal and defects at the joints resulting from the first pass, thereby ensuring the quality of the pipe end welding. For the repair of weld defects, the defect should be removed first and then repaired by welding. 5. Baffles and support plates 5.1 The surface roughness Ra of the outer circular surface of baffles and support plates shall not exceed 25 mm, and the sharp corners on both sides of the outer circular surface should be rounded off. 5.2 Any burrs on the baffle plates and support plates shall be ground and removed by a riveter in the vessel shop before the tube bundle is assembled. 6. Assembly of the tube bundle 6.1 The baffle plates should be arranged in accordance with their sequence numbers; be sure not to disrupt this order, as it may cause difficulties when inserting the tubes ； 6.2 The nuts at the ends of the tie rods should be tightened to prevent the heat exchange tubes from being damaged due to the movement of the baffle plates when the tube bundle is inserted or removed. The size of the spacers between each layer of baffle plates should be consistent. For those spacers that are too small and cause looseness, measures should be taken to weld them to the baffle plates, in order to prevent vibration of the spacers due to air flow impacts during the operation of the heat exchanger. 6.3 When threading pipes, a hammer should not be used to strike the pipe end face; for those pipes that are difficult to thread, a wooden hammer or a copper hammer should be used, ensuring that no dents or scratches appear on the pipe end face. 6.4 Except for the welded connection between the heat exchange tubes and the tube sheet, no other components shall be welded to the heat exchange tubes. 7. Tube box fabrication 7.1 When marking lines and making holes in the shell and tube box, it is essential to ensure that the orientation of the partition grooves on the tube sheet matches that of the partitions on the tube box (or that the arrangement of the flange screw holes on the tube box corresponds to that of the screw holes on the tube sheet, which are generally arranged at the mid-span) ； 7.2 For tube boxes made of carbon steel or low-alloy steel that have partition plates welded in them, as well as those with lateral openings exceeding 1/3 of the cylinder’s inner diameter, stress-relief heat treatment shall be carried out after welding; the sealing surfaces of the equipment flanges shall be processed after this heat treatment. 8. Kettle-type reboiler 8.1 Welded joints on the support guides that obstruct the passage of the slide rails should be ground smooth ； 8.2 The support guides shall be parallel to the longitudinal center line of the equipment; the deviation in parallelism shall not exceed 2/1000, and shall also not be greater than 5 mm ； 8.3 The upper surface of the overflow plate shall be level, with a tilt not exceeding 3 mm. 9. The sealing surface of the heat exchanger must be protected; it must not be damaged by impacts, scratches, arc damage, weld spurs, splashes, etc. After machining the sealing surfaces, their surfaces should be coated with butter to prevent rusting. 10. The gasket shall be a single-piece gasket; in special cases, splicing is permitted, but the spliced joints of the gasket must not affect its sealing performance. 11. Compressed air at a pressure of 0.4~0.5 Mpa should be introduced into the signal hole of the reinforcement ring prior to the pressure test to check the quality of the welded joint. 12. The overlapping heat exchangers must be pre-assembled during manufacturing. The adjustment plates between the overlapping supports should be spot-welded to the overlapping supports of the lower heat exchanger after passing the pressure test, and permanent markings should be applied to the outside of the overlapping supports and adjustment plates for alignment during assembly at the customer’s site. 13. Heat exchanger assembly 13.1 Before assembly, the components of the heat exchanger should be carefully inspected and cleaned; there should be no weld scars, welding spatter, rust, or other debris remaining ； 13.2 When lifting the tube bundle, care should be taken to prevent deformation of the bundle and damage to the heat exchange tubes, as well as to protect the welds at the tube ends from being pulled apart; this is especially important in floating-head heat exchangers. 13.3 The tightening of the bolts should be carried out in at least three passes, with the starting point of each pass being offset by 120° from the previous one; if tightening proceeds smoothly, it can be done as shown in the diagram below. 14. Pressure testing 14.1 Sequence of pressure testing for fixed-tube-sheet heat exchangers: a. Test the pressure in the shell side, while simultaneously checking the connections between the heat exchanger tubes and the tube sheet ； b、Piping pressure testing ； 14.2 Sequence of pressure testing for U-tube heat exchangers and stuffing box heat exchangers: a. Conduct a shell-side test using a test pressure ring, while checking the joint welds at the same time ； b、Piping pressure testing ； 14.3 Pressure testing sequence for floating-head heat exchangers and kettle-type reboilers: a. Perform pressure testing on the tube ends using a testing pressure ring and special testing tools for floating heads. The batch reboiler should also be equipped with a dedicated housing for pipe end pressure testing ； b、Piping pressure testing ； c. Shell-side pressure testing: For heat exchangers designed based on pressure difference: a. Joint pressure testing (using the maximum test pressure difference specified in the drawings); b. Stepwise pressure testing of the tube side and shell side (using the test pressures and step procedures specified in the drawings). 14.5 For heat exchangers that use special media such as chlorine or liquid chlorine as the working medium, an ammonia penetration test should be carried out during pressure testing to check the quality of the welds at the tube ends

I studied the manufacturing procedures for heat exchangers carefully; thank you for sharing them