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Technical condition number of double-ended studs and nuts for medium and low temperature use: SEEQ0315-1999 Catalog 1 General 1.1 Scope of application 1.2 Referenced standard 1.3 Alternative standard 2 Materials and dimensions 3 Processing and inspection of studs and nuts Appendix A Recommended table for stud wrench space and minimum spacing Appendix B Preparation instructions General 1.1 Scope of application This standard is applicable to studs and nuts used in pressure vessels with design temperatures below 300°C in hydrogenation and reforming units of petroleum refineries. Other similar situations can be implemented as a reference. 1.2 Reference standards When using this standard, the provisions of the following standards should also be complied with: a) GB/T90 "Fastener acceptance inspection, marking and packaging" b) GB/T196 "Basic dimensions of ordinary threads (diameter 1-600mm)" c) GB/T197 "Tolerances and fits of ordinary threads (diameter 1-355mm)" d) GB/T699 "Technical conditions for high-quality carbon structural steel" e) GB/T1804 "General Tolerances for Linear Dimensions Unnoted Tolerances" f) GB/T3077 "Technical Conditions for Alloy Structural Steel" g) GB/T3098.2 "Mechanical Properties of Fasteners Nuts" h) GB/T3103.1 "Fastener Tolerances Bolts, Screws and Nuts" i) GB/T5779.2 "Fastener Surface Defects - Nuts - General Requirements" j) GB/T5779.3 "Fastener Surface Defects - Bolts, Screws and Studs - Special Requirements" k) JB4730 "Non-destructive testing of pressure vessels" 2. Dimensions and materials 2.1 30CrMoA and 35CrMoA steel for double-ended studs should comply with the requirements of GB/T3077 for high-grade high-quality steel and comply with the provisions of 2.4. 2.2 The materials used for No. 35 steel nuts should comply with the requirements of GB/T699. 2.3 The material used for 30CrMoA steel nuts should comply with the requirements of GB/T3077 for advanced high-quality steel. 2.4 The mechanical properties of double-ended studs after quenching and tempering treatment should comply with the requirements in Table 24. Table 2.4 Mechanical properties table of double-ended studs after quenching and tempering treatment Steel grade specifications σbMPaσSMPaδ5% AkvJHB30CrMoA≤M22≥M24～56≥700≥660≥550≥500≥15≥15≥61≥61181～242181 ~24235CrMoA≤M22≥M24～80≥M85～105≥835≥805≥735≥735≥685≥590≥13≥13≥13≥54≥54≥47238～304242～318242～318 Note: ① The impact value is the average of three samples, and one of the samples is allowed to be greater than or equal to 70% of the required value. ② Studs should be composed of a batch of the same furnace number, same specification, same forging process, and same furnace heat treatment, and no less than two blanks in each batch should be tested for mechanical properties. At 1/2 radius (for blanks with Ф≤30mm, it should be at the center), cut out one tensile specimen and three impact specimens along the axial direction of each blank. If the test results are unqualified, the spot inspection should be doubled. If the test results are still unqualified, the heat treatment should be repeated. 2.5 At least one nut of each specification from each piece of equipment should be selected for load-bearing testing, and its guaranteed load should not be less than the requirements in Table 2.5. If it is unqualified, double the spot check should be carried out. If it is still unqualified, it should be reheated or remanufactured. For test methods, see GB/T3098.2. Table 2.5 Nut guaranteed load table units: Nd nut guaranteed load 3535CrMoAM16×27441499444M18×297484130273M20×2123663165259M22×2152954204402M24×3152203208518M27×3199390273164M30× 3252938346526M33×3312849428603M36×3379121519396M39×345175561 8904M42×3530751727129M48×3707827969723M56×39835131347413M64×3 1787081M72×3 2288725M80×3 2852347M90×3 3138654 Note: It is recommended to use No. 35 steel nuts with 30CrMoA studs; 30CrMoA nuts with 35CrMoA studs. 2.6 The basic dimensions of the threads on the studs should comply with the provisions of GB/T196. Its tolerance should comply with the requirements of 6g level in GB/T197. 2.7 The basic dimensions of the thread on the nut should comply with the requirements of GB/T196. The tolerance should comply with the requirements of level 5H in GB/T197. 2.8 The dimensions and types of studs are shown in Figure 2.8 and Table 2.8. Except for those noted in the figure, the surface finish is Ra25. When L-2L1≤d2, the stud should be through wire. Figure 2.8 Dimensions and types of studs Figure 2.8 Stud size table units: mmDL1d2RcL single quantity, kg/100mmM16×25013.861.570～3000.157M18×25015.361.5 0.199M20×25017.88270～3000.208M22×25519.88280～3000.256M24×36020.78390～3500.300M27×38023.783100～4000.3 96M30×38526.7103120～4500.474M33×39029.7103130～4500.581M36×39532.7103150～5000.688M39×310035.7123150～6 000.817M42×310038.7123150～6001.015M48×311041.7123170～6001.230M56×313752.7123190～6001.694M64×315360.7 123200～6002.520M72×316968.7123230～6003.200M80×318576.7123240～7003.900M90×320586.7124250～10005.0972.9 Other technical requirements for studs should comply with the requirements for "Grade A" in GB/T3103.1 and the regulations of GB/T5779.3. 2.10 The dimensions and types of nuts are shown in Figure 2.10 and Table 2.10. Except for those noted in the figure, the surface finish is Ra25. 2.11 Other technical requirements for nuts should comply with the requirements for "Grade A" in GB/T3103.1 and the regulations of GB/T5779.2. Figure 2.10 Dimensions and types of nuts Figure 2.10 Nut size table units: mmdDSD1≈H unit weight, kgM16×226.882422.8160.028M18×229.62725.7180.050M20×233.63028.5700.051M22×238.083 432.3220.068M24×340.323634.2240.107M27×345.924139.0270.157M30×351.524643.7300.222M33×356.0504 * * 330.297M36×361.65552.3360.372M39×367.26057.0390.508M42×372.86561.8420.612M48×3847566.5480.929M56×395.28580 .8561.342M64×3106.49590.3642.492M72×3117.610599.8722.527M80×3128.8115109.3803.302M90×3145.6130123.5904.781 3. Processing and inspection of studs and nuts 3.1 Studs and nuts should be delivered in a quenched and tempered state. 3.2 After rough machining, studs and nuts should be subjected to magnetic particle testing in accordance with JB4730 Part 4 piece by piece. The inspection results show that the cumulative length of defects is Level I, which is considered qualified. After the threads of the stud are machined, a magnetic particle inspection is performed. 3.3 The hardness of studs and nuts should be checked piece by piece after rough machining. Inspection results show that the hardness of the studs should comply with the requirements in Table 2.4. The hardness of the nut should be 20~30HB lower than that of the corresponding stud. 3.4 The threads of studs and nuts should be visually inspected and should be free of burrs, rust spots and defects that would prevent the passage of gauges. 3.5 The studs should be straight and the allowable bending is 0.lmm within 100mm. 3.6 The limit deviation of unspecified tolerance dimensions shall be in accordance with the M-level requirements specified in GB/T1804. 3.7 Double-ended studs and nuts should be treated to prevent atmospheric corrosion. 3.8 Acceptance rules, packaging and marking should comply with the provisions of GB/T90. 3.9 30CrMoA steel studs or nuts should be marked with the material identification "CrMo" on their ends. 35CrMoA steel studs or nuts should be marked with the material identification "5CrMo" on their ends. 3.10 Annotation examples: Material 30CrMoA, M30 studs with length 300mm are marked as: M30×300 30CrMoA M30 nut made of No. 35 steel is marked as: M30 35 Appendix A Stud wrench space and minimum spacing recommended table Stud wrench space and minimum spacing recommended table Unit: mm stud diameter, dBLALe minimum stud spacing, LM16241838M18261942M20302046M22322452M24342656M27382862M30443070M33 463375M36483680M39523985M42564290M486048102M567055116M64806 0134M729270150M8010078165M9010884182M9511290194M10011892206 Appendix B Preparation Instructions B1 This standard is based on the reset of B-6066 "Technical Conditions for Double-ended Stud Nuts for Medium and Low Temperatures". After four years of trial, feedback from all aspects was collected and compiled in conjunction with the latest national and industry standards. B2 Since the σb and σs of 30CrMoA bolts have been significantly modified in GB150-1998, the σb and σs in Table 2.4 of this standard have also been modified accordingly. Users should be careful not to use this standard in conjunction with GB150-89. Otherwise problems will occur. B3 During the trial process, we often found that the bolt diameter specifications were too small. This time we increased the specifications from 12 to 17 to meet the user's requirements. B4 The guaranteed load of the No. 35 steel nut in Table 2.5 is calculated by multiplying 0.9 times the os of 30CrMoA and the area of the stud root circle. The guaranteed load of the 3OCrMoA nut is calculated by multiplying 0.9 times the σs of 35CrMoA and the area of the stud root circle. B5 This standard recommends that No. 35 steel nuts be used with 30CrMoA studs. 30CrMoA nuts are used with 35Cr