Main technical standards for power station valves
"Power station valve" is also called power station special valve, which is mainly used for the pipeline of various systems of thermal power station, cutting or connecting the pipeline medium. Applicable medium: non-corrosive medium such as water and steam. Compared with other valve products, power station valves are characterized by high temperature and high pressure and unique self-sealing design. The higher the pressure, the more reliable the seal. Due to the special technical characteristics and working conditions, the products also form features that cannot be replaced by other products.
1. Related standards for power station valves:
General requirements for JBT 3595-2002 power station valves
JB/T 5263-2005 Technical conditions for steel castings of power station valves
JB/T 4018 power station valve type preparation method
DL 959-2005 Application Guidelines for Safety Valves for Utility Boilers
DLT 531-1994 power plant high temperature and high pressure cut-off valve gate valve technical conditions
DLT 641-2005 power station valve electric actuator
DLT 850-2004 power station piping
GB 10869 power station regulating valve technical conditions
GBT 10868-2005 power station temperature reducing pressure reducing valve
2. The design of the power station valves shall comply with the requirements of safety and reliability. In addition to the requirements of JB/T 3595-2002, they shall also comply with the following relevant standards:
a) Steel valves shall comply with the provisions of GB/T 12224-1989;
b) The gate valve shall comply with the provisions of GB/T 12234-1989;
c) The shut-off valve and check valve shall comply with the provisions of GB/T 12235-1989 and GB/T 12236-1989;
d) Ball valves shall comply with the provisions of GB/T l2237-1989;
e) The safety valve shall comply with the provisions of GB/T l2241-1989, GB/T 12242-1989, GB/T 12243-1989 and JB/T 9624-1999;
f) The pressure reducing valve shall comply with the provisions of GB/T 12244-1989, GB/F 12245-1989 or GB/T 12246-1989;
g) The temperature reducing and pressure reducing valve shall comply with the provisions of GB/T 10868-1989;
h) The regulating valve shall comply with the provisions of GB/T 10869-1989;
i) The blowdown valve shall comply with the provisions of JB/T 6900-1993;
j) The valve electric device shall comply with the provisions of JB/T8528-1997ak JB/T8529-1997;
k) Valve electric actuators shall comply with the provisions of JB/T 8219-1999;
l) Valve pneumatic actuators shall comply with the provisions of GB/T 4213-1992.
4. Material requirements of power station valves The power station valve materials should be selected according to the use conditions and manufacturing requirements; the materials of bolts, nuts and other fasteners should be selected according to the use pressure and temperature. When the material of the bearing parts of the casing is selected, the high temperature of the use of the zui is as specified in Appendix C. See Appendix D for guidelines on the selection of surfacing materials and surfacing hardness for sealing surfaces.
The materials and welding materials selected for the pressure parts of the valve shall comply with the material standards specified in the relevant national standards, industry standards or order contracts. The material manufacturer must ensure the quality of the material and provide a certificate of quality. Metallic materials and weld gold shavings shall have specified strength, toughness and elongation and good fatigue and corrosion resistance under the conditions of use.
5. Material inspection and test of power station valves The materials used for power station valves should have material certification or relevant certificates: metal materials should be marked with steel number, furnace number and batch number, and have chemical composition and mechanical property certificate.
The material of the pressure-bearing parts shall be sampled before storage, the chemical composition shall be sampled according to the smelting furnace, the mechanical properties shall be sampled according to the heat treatment batch, and the inspection results shall comply with the provisions of the corresponding material standards.
When one of the mechanical properties of the specimen is unqualified, the double-strength sample shall be retested. If there is still one unqualified, the parts shall be reheated. Before, the number of reheating treatments is not more than two times (excluding the number of tempering). If one sample is not tested after a retest, the batch of materials cannot be used. When the chemical composition index of one of the sampling test results is unsatisfactory but the mechanical properties of the sample are qualified, the disposal measures shall be determined according to the specific conditions or the provisions of the material procurement contract.
6. Assembly and performance inspection of power station valves All parts of the valve shall be inspected by the quality inspection department before assembly, and unqualified parts shall not be assembled. Alloy steel parts are 100% spectrally inspected and marked to ensure they are not confused with parts of other materials.
The sealing surface should be of sufficient hardness, as per the design or see Appendix D. The polished sealing surface is not allowed to have defects such as cracks, dents, pores, spots, scratches, and nicks. The sealing surface shall ensure that the radial fit is not less than 80%.
The threaded surface of the fastener, the surface of the asbestos rubber sheet and the gasket shall be coated with molybdenum disulfide (paste) or a coating of equivalent effect to prevent seizure.
The valve should be assembled and debugged strictly according to the drawings and relevant technical documents, and the movement should be flexible and free from any jamming.
The whole machine valve should be checked for stroke. The electric valve should be adjusted for stroke protection and torque protection, so that all the mechanisms of stroke and torque protection are reliable and accurate. The position of the pointer on the valve such as the regulating valve, pressure reducing valve, throttle valve, butterfly valve, etc. should be consistent with the position of the actual valve opening.
The whole machine valve shall be subjected to pressure strength test and sealing test one by one. However, the integral forged valve with nominal diameter DN≤50mm can be sampled for strength test under the condition of mature production process and stable product quality. The sampling quantity is 10%~15%, but not less than 5; after sampling test In case of failure, the test shall be carried out by double sampling. If there is still one failure, the strength test shall be carried out one by one.
The repaired valve body shall be re-tested for strength and the test shall be carried out after repair welding and heat treatment. For non-destructive testing, the casing shall be subjected to non-destructive testing.
6. Packaging of power station valves Before the valve is packaged, the valve shall be painted according to the provisions of 8.1.5. The unpainted parts or the surface without the anti-rust layer shall be coated with anti-rust oil.
The flange sealing surface, the welding end, the threaded end and the valve cavity at both ends of the valve are protected by a plug or a cover, and should be easy to assemble and disassemble.
Valve products should be packaged and shipped according to the packing list: For larger valves, they can be bare-packed according to the order, but should not be damaged during transportation.
7. Storage of power station valves Power station valve products should be stored in a dry, ventilated room and stacked neatly as required. Open storage or stacking of products is not allowed.
8. Transportation of power station valve During transportation, the valve flap should be closed, the valve flap of the check valve should be fixed; the plug valve should be in the open position; the weight of the lever valve should be removed from the lever and placed separately. And fix the lever. The flanges of the valve passages at both ends or the welding groove of the branch pipe are blocked by a cover or a plug to prevent the intrusion of dust and sewage.
The exposed part of the stem should be protected.
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