Matters needing attention in engineering application of API 660-2015
Precautions for engineering application:
1.4.2 TEMA R is generally used if there is no special case. TEMA heat exchanger is divided into TEMA RCB, class R refers to petroleum and process industry applications, class C refers to commercial and general process applications, and class B refers to chemical industry applications. Generally speaking, R needs the minimum thickness and the thickest, which is the most expensive.
2.4.1 for single pass floating head heat exchanger and all fixed tubesheet heat exchangers, the purchaser shall indicate the data required to determine the expansion joint. These data can be filled in according to Appendix C.
5.4 overlapping heat exchanger, which shall be provided by the manufacturer
- a) Bolt, nut and gasket of intermediate connecting pipe.
- b) Thin backing plates or distance plates and fasteners between intermediate supports.
6.1.2 the manufacturer needs to provide fluid induced vibration analysis. (this is generally considered in the process calculation. For example, the process calculation software will remind that there may be fluid induced vibration, and the vibration can be avoided by not arranging pipes between baffles. It is difficult for the equipment specialty to consider whether it is necessary to strictly follow this, which is questionable.)
6.2.4 the mechanical design should follow the pressure design specification, and TEMA can be used as a reference. (it can be considered that the tubesheet calculation should be based on the tubesheet calculation of uhx and TEMA as a reference.)
7.2.3 the cladding or surfacing on the tube side of tube sheet shall not be less than 10 mm when it is only expanded, and shall not be less than 5 mm when it is welded. (TEMA rb-7.8 is not less than 7.8mm when only expanding, not less than 3.2mm when welding, C-7.8 is not less than 4.8mm when only expanding, not less than 3.2mm when welding).
7.2.4 cladding or surfacing on shell side of tube sheet shall not be less than 10 mm. (the thickness of TEMA rcb-7.8 is not less than 10 mm, and the thickness of the expanded part is not less than 3.2 mm. The consideration of TEMA should be appropriate. If there are multiple layers on the shell side, it is generally necessary to expand to the multiple layers. Otherwise, the medium on the shell side will contact with the tubesheet substrate, which will cause corrosion of the substrate.)
7.2.5 if the sealing surface of tubesheet is overlaid, the overlaying thickness shall be 6 mm.
7.3.1 if the support of the heat exchanger of the removable tube bundle is fixed on the shell, the support shall be designed to bear the lateral force in the direction of the centerline of the tube bundle equal to 150% of the weight of the tube bundle. The allowable shear stress of the bearing shall not exceed 40% of the yield strength of the material. (the bearing should bear the extraction force of the tube bundle, but how to use software or formula to carry out this is a troublesome thing. In pvelite, there is a gload option, which can input acceleration in all directions to check transportation or core pulling. If you want to calculate by hand, you can think of a way to divide 1.5 times the weight of the tube bundle by the bending modulus of the bearing in the direction of the center line.)
7.3.2 the material of bearing base plate shall be consistent with that of the cylinder, and shall be continuously welded on the cylinder; the base plate shall have a 6 mm air hole on the vertical center line; the minimum thickness of the base plate shall be 6 mm, and the chamfer shall be at least 25 mm.
7.3.4 for overlapped heat exchanger, the manufacturer needs to provide about 6 mm intermediate saddle adjustment plate. (according to GB / t151-2014 126.96.36.199, the minimum adjustment plate between supports is 13mm, the height difference between nozzle and support is 5 * 2 + 3, and the gasket thickness is 13mm)
7.3.5 there is a long round hole in the support base plate of the heat exchanger. The width of the long round hole is w = DB + 8, and the length is L = DB + thermal expansion length + 8
7.4.1 it is not allowed to use stiffeners to reduce the thickness or deflection of the cover plate. (flat cover reinforcement is not allowed, blocking the edge ball)
7.4.2 the thickness of split diaphragm is calculated according to the differential pressure of TEMA rcb9.132, and the differential pressure is at least twice of the pressure drop of each split diaphragm. The thickness of split diaphragm shall be at least 2 times of the pipe side corrosion allowance + 3mm. (the detailed requirements for the calculation of the strength of the split diaphragm and the pressure difference method are put forward. The calculated pressure difference can be obtained from the inlet and outlet pressure difference given by the process. The pressure on both sides of diaphragm in 188.8.131.52 of GB / t151 can be calculated according to this method. In addition to TEMA, the minimum thickness of split diaphragm should also meet the requirements of 2 * Ca + 3
7.4.11 when specified by the purchaser, additional machining allowance of 3mm gasket shall be provided for all equipment flange, pipe box cover plate and floating head flange. These additional thicknesses cannot be used to calculate MAWP.
184.108.40.206 the bending radius of U-shaped pipe shall not be less than 1.5 times the nominal outer diameter. For martensitic steels, super austenitic steels, dual phase steels, titanium and high nickel alloys, the bending radius shall not be less than twice the nominal outer diameter. (GB / t151 adopts not less than 2 times of nominal outer diameter. In fact, it is too large. If this value is a little lower, there is no need for cross routing in many cases. According to the communication with the bending unit, there is no problem for ordinary carbon steel and stainless steel with 1.5 times the nominal outer diameter.)
220.127.116.11 the number of pipes in any layer shall not deviate from the average number of each layer by 10%, unless it is confirmed by the purchaser. (ensure that the number of pipes in each layer is basically the same, so that the flow at the inlet can be normal.)
18.104.22.168 when the tube sheet is expanded, the distance between the edge of the tube sheet hole and the edge of the gasket groove (including the split diaphragm groove) shall not be less than 1.5mm; when the tube sheet is welded, it shall not be less than 3mm. (GB / t151) the spacing is controlled according to the spacing SN of the adjacent pipes on both sides of the pipe limiting circle and the split diaphragm groove. Taking 19 as an example, the width of split plate groove is 12, Sn = 38, and the distance between pipe edge and split plate groove is (38-19-12) / 2 = 3.5, which is basically the same as api660.)
22.214.171.124 when specified by the purchaser, additional machining allowance of 3mm shall be provided for the tube sheet sealing surface. These additional thicknesses cannot be used to calculate MAWP. (the fixed tubesheet is 3mm, and the U-tube is 6mm.)
126.96.36.199 in order to promote shell side drainage, baffle and support plate need to have V-shaped opening. The OD of the equipment is less than 406, and the height of V-shaped opening is 6 mm. When od > 406, the height of V-shaped opening is 10 mm. (GB / t151 figure 6-26, V-shaped opening height is 15 ~ 20mm.)
188.8.131.52 if it is necessary to set the baffle, the diameter of the baffle shall be greater than max (nozzle diameter + 50mm, 1.2 * nozzle inner diameter)
184.108.40.206 the thickness of the baffle shall not be less than 6 mm. (GB / t151 220.127.116.11.2 carbon steel, low alloy steel 4.5mm, stainless steel 3mm)
7.6.4 flange connection can be in the following forms:
- a) Integral forging flange.
- b) Weld wn flange with nozzle or forged pipe.
- c) Forging so flange, except 7.6.5.
7.6.5 so flange cannot be used under the following conditions:
- a) The design pressure is greater than 2.1MPa.
- b) The design temperature is not more than 400 ° C.
- c) The corrosion allowance is more than 3 mm.
- d) Hydrogen, acid, wet H2S environment.
- e) Cyclic load.
7.6.9 except for vent hole, drain hole and cleaning hole, other nozzle loads shall be calculated according to figure 4 and table 2. (if the nozzle load is not specified in the engineering specification, it can be calculated according to table 2 of 660.)
7.6.11 the reinforcing ring shall not be used for cyclic load, hydrogen exposure and operating temperature greater than 230 ° C, or operating temperature greater than 400 ° C (the specification is operating temperature) Temperature refers to whether the design temperature will be followed during execution. Generally, the operation temperature should be followed for hydrogen exposure. Because the operation temperature is very low, hydrogen corrosion will not occur. Sometimes, the design temperature considers special conditions, such as pipe rupture, which will lead to temperature rise. At this time, it is a short-term process, and the time of hydrogen corrosion is very short, which will not cause impact. But in the process of six in one and actual implementation, it is generally the design temperature.)
7.6.12 MAWP cannot be limited by nozzle reinforcing ring. (it should be limited by the main member)
7.7.1 through bolt connection structure shall be used for equipment flange connection, and screw in bolt connection shall be approved by the buyer. (this is not very common, but the original manufacturer used screw in stud connection, in order to reduce the flange thickness. This one avoids the edge ball
7.7.2 the equipment flange shall be wn type, and other types shall be confirmed by the buyer. (if 660 is used, then wn flange must be used. Trust me, unless it is special material, the buyer will not agree.)
7.7.3 nubbins are not allowed to be used (nubbin means small bumps, the protrusion on the sealing surface of special flange, which is generally used to support the covering connection part when using the covering gasket, and is generally not allowed to be used)
7.7.4 the designed clearance between the outer circles of the mating flange shall not be greater than 3mm, and the actual clearance shall not be less than 1.5mm after assembly and tightening. (domestic flange can do it, mainly to avoid the flange outer ring bumping together after tightening.)
7.7.6-9 some regulations on hydraulic stretcher
7.7.11 the same gasket shall be used at the shell side of flange and tube sheet. (if the same gasket is used, the preload of bolt load will be the same on both sides.)
7.7.12 the allowable stress of equipment flange, tube sheet with gasket and flat cover material shall be the value of low stress (low stress forging shall be used for those with gasket contact, and high stress forging can be used for those without gasket, such as welded tube sheet)
7.7.14 MAWP cannot be limited by flange bolts. (obviously)
7.7.15 when specified by the purchaser, additional machining allowance of 3mm gasket shall be provided for all equipment flanges. These additional thicknesses cannot be used to calculate MAWP.
7.7.16 the mortise face structure shall not be used unless agreed by the buyer. (there is no mortise face yet)
7.8.3 one half of the gasket area at the split diaphragm shall be included in the peripheral gasket area AG. (it’s better to follow TEMA, and it’s easier to implement in the software, because there’s no half of the area available in the software. The new SW6 also takes into account the gasket area at the divider plate.)
7.9.1 thin wall or thick wall expansion joint can be used for shell side expansion joint.
7.9.2 thin wall expansion joint has the following provisions:
- a) In order to protect the inner part from damage, a smooth metal draft tube is set inside the cylinder. The material of the draft tube is consistent with the base metal. The carbon steel draft tube shall be at least 6 mm, and the stainless steel and other alloy draft tube shall be at least 3 mm. For the vertically installed bellows expansion joint, the guide tube is welded on the upper part, and the lower part is open for liquid drainage. (because most of the expansion joints are thin-walled when the pressure is low, the calculation of thin-walled expansion joints is easy to pass, but there is no mandatory requirement in GB for all the expansion joints with draft tube.)
- b) Set metal cover to avoid external damage and ensure the integrity of the equipment during transportation, movement and operation.
- c) According to the corresponding pressure design specifications. When calculated according to EJMA, the cycle life shall not be less than 1000 times in any case.
- d) Only one longitudinal seam is allowed when the shell is processed into thin-wall expansion joint, and 100% radiographic inspection is required before forming.
- e) The weld of thin-walled expansion joint (including its accessory weld) needs 100% penetrant testing.
- f) For expansion joint with protective support, the support shall be removed or adjusted before operation. (conducive to the free expansion of the expansion joint).
- g) The inner floating head expansion joint shall be provided with permanent support to avoid damage during maintenance and hydrostatic test when the shell cover is removed. The support shall be designed to allow the expansion joint to move throughout.
7.10.6 if the outer diameter of the gasket is less than or equal to 610, the gasket is not allowed to be spliced. If the outer diameter of the gasket is greater than 610, only one splicing weld is allowed. (one is a bit strange. Shouldn’t the splicing be two? Maybe nonmetallic gasket.)
7.11.1 the dynamic load coefficient of the lifting lug is 2. (the national standard is 1.65, the foreign standard is 1.5, and the heat exchanger is 2, which is special)
8.1.5 if fillet weld is used for tube sheet welded with adjacent shell side cylinder or tube side cylinder, forging or plate can be used for tube sheet. If the plate is used, the lamination of the plate and the defects at the welding position with the cylinder need to be detected by 100% ut. (100% ut plate can be used as tubesheet under low pressure, saving a lot of money.)
8.2 carbon steel requirements in acid and wet H2S environment
8.2.1 materials need to be normalized, otherwise, it needs to be approved by the purchaser. Hot formed materials need to be approved by the purchaser.
8.2.2 the pressure bearing original shall provide material identification test report, which shall include elements Cr, CB (or Nb), Ni, V, Mo and cu. the equivalent carbon content CE shall be calculated according to nacemr0175 or nacemr0103 formula
8.4.1 the overall fin heat exchanger of copper alloy shall be supplied in annealed tempering state. See astmb359/b359m for details.
8.4.2 the welding heat exchange pipe needs to be eddy current tested one by one in full length.
9.1.1 in order to install and draw out the tube bundle flexibly, the longitudinal circumferential weld of heat exchanger subject other than kettle heat exchanger shall be processed as the inner surface is even. If the weld of the kettle heat exchanger is not at the lower part of the shell, this requirement is not applicable to the weld with larger section. (weld is arranged on the middle side)
9.2 for split partition, except for special design determined by the buyer, the forged or welded pipe box and the split diaphragm in floating head cover shall be welded in full length on both sides or full penetration weld. In case of double-sided welding, 50mm from the beginning of gasket surface shall be fully welded through. (this is not specified in the national standard, in fact, to avoid the gap corrosion caused by the medium entering the gap between the split partition and the cylinder. See the following figure for welding nodes here)
9.3 the nozzle and pipe joint shall not exceed the inner surface of the shell, pipe box or head connected with them.
9.4 unless agreed by the buyer, all heat exchange pipes including U-shaped pipes shall be formed by one pipe without circumferential weld.
9.5.6 at least two passes of full penetration welding of tube and tube plate shall be conducted. (generally, add: the difference between the starting points of two courses is 180 degrees)
9.5.8 in addition to the thermal insulation support, the external non pressure bearing accessories (lifting lugs or structural supports) need continuous welding.
9.5.10 if exposed to hydrogen environment, full penetration is required for all internal accessories. (full penetration of split partition, internal eddy current plate, slide, etc.)
9.6.2 the Seller shall indicate whether heat treatment is required after bending U-shaped pipe bending section.
9.6.3 unless specified by the buyer, heat treatment is required after bending under the following circumstances.
- a) Carbon steel, U-shaped pipe with CMO steel and low Cr steel, in acidic or wet H2S environment.
- b) Brass bend (eg. As per ASME SB-395/395m).
- c) For unstable austenitic stainless steel, the outer diameter of heat exchanger pipe with bend radius less than 5 times.
9.6.9 the steel and low alloy steel pipe boxes and glands formed below shall be post weld heat treated.
- a) 6-way or more tube boxes and glands (GB151 is 2-way).
- b) The tube box and gland with the ratio of the inner diameter of the nozzle to the cylinder are ≥ 0.5, except for the cone tube box.
9.6.11 all carbon steel and low alloy steel floating head flange and arch cover shall be post weld heat treatment.
9.6.13 in acid and wet H2S environment, the minimum heat treatment requirements of carbon steel shall be in accordance with nacesp0472. the minimum heat preservation time shall be in accordance with the pressure design specification and not less than 1 hour.
9.7.2 overlapping heat exchanger shall overlap in workshop and check connection alignment.
9.9.1 the groove of pipe hole shall be 90 ° edge, concentric and deburring shall be removed.
9.9.2 austenitic stainless steel, duplex steel, titanium, copper nickel alloy heat exchange pipe, control shall be in accordance with column 7.21 (b) (special tight fit) (the tight fit of austenitic stainless steel is used since the beginning)
9.10.6 if heat treatment is needed for the joint of tube and pipe plate used for expansion welding, expansion joint shall be carried out after heat treatment.
Source: China Flange Manufacturer – Yaang Pipe Industry (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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