1、 General requirements
1. The valve specification and type shall meet the requirements of pipeline design documents.
2. The model of the valve shall indicate the national standard number requirements. If it is an enterprise standard, the relevant description of the model should be indicated.
3. The working pressure of the valve is required to be greater than or equal to the working pressure of the pipeline. On the premise of not affecting the price, the working pressure that the valve can bear should be greater than the actual working pressure of the pipeline; Any side of the valve under closed condition shall be able to bear 1.1 times the working pressure of the valve without leakage; When the valve is open, the valve body shall be able to withstand 1.5 times the working pressure of the valve.
4. The valve manufacturing standard shall state the national standard number. If it is an enterprise standard, the enterprise document shall be attached to the purchase contract.
2、 Valve standard quality
1. The material of the valve body should be determined according to the working conditions, and the brand and the actual physical and chemical test data of the material should be indicated.
2. The material of stem is stainless steel stem (2Cr13). The material of the valve stem can be determined according to the working conditions.
3. The nut is made of cast aluminum brass or cast aluminum bronze, and its hardness and strength are greater than those of the valve stem.
4. The hardness and strength of the valve stem bushing material should not be greater than that of the valve stem, and there is no electrochemical corrosion with the valve stem and valve body under the condition of water immersion.
5. Material of sealing surface
① Different types of valves, sealing methods and material requirements;
② The material, fixing method and grinding method of ordinary wedge gate valve, 13Cr alloy and copper ring should be explained;
③ Physicochemical and hygienic test data of soft seal gate valve and valve plate rubber lining materials;
④ The material of sealing surface on valve body and butterfly plate shall be marked on butterfly valve; Their physical and chemical test data, especially the hygienic requirements, aging resistance and wear resistance of rubber. Generally, NBR and EPDM are used, and recycled rubber is strictly prohibited.
6. Valve shaft packing
① As the valves in the pipe network are usually opened and closed infrequently, the packing is required to be inactive for several years, and the packing is not aging, so as to maintain the sealing effect for a long time;
② Valve shaft packing should also bear frequent opening and closing, good sealing effect;
③ In view of the above requirements, the valve shaft packing shall not be replaced for life or more than ten years;
④ If the packing needs to be replaced, the valve design should consider the replacement measures under the condition of water pressure.

Types of valve applications
In the application of valve types, machinery, metallurgy, petrochemical, chemical, urban construction and other industries application valve classification is the most. Especially in the machinery industry, all kinds of valves are basically applied. In addition to the machinery industry, safety valves are mainly used in chemical industry; Butterfly valve is mainly used in petrochemical and metallurgy; Diaphragm valve is mainly used in metallurgy, electric power and chemical industry; Check valve is mainly used in metallurgy, chemical industry and petrochemical industry; Stop valve is mainly used in petroleum and chemical industry; Shut off valve is mainly used in metallurgy, petrochemical, chemical and electric power; Blowdown valve is mainly used in petrochemical and chemical industry; Ball valves are mainly used in petroleum, chemical industry and metallurgy; Gate valves are mainly used in chemical industry, electric power and urban construction; The control valve is mainly used in chemical industry, metallurgy, electric power and food industry; Plunger valve is mainly used in petrochemical and metallurgy; Plug valves are mainly used in chemical industry and metallurgy; Pressure reducing valve is mainly used in petrochemical, chemical and metallurgical industry; Steam trap is mainly used in chemical industry and petrochemical industry.
Industry scope of valve application
The users of valves have a wide range of industries, including petroleum, petrochemical, chemical, metallurgy, electric power, water conservancy, urban construction, machinery, coal, food and others. Among them, the mechanical and chemical industry users are most concerned about the valve market, and their requirements for valves are also higher. The largest users of valves are petrochemical industry, electric power sector, metallurgical sector, chemical industry and urban construction sector.

1. The general structure and principle of all kinds of vacuum valves should be understood clearly.
2. For the same kind of vacuum valve, the valve type should be selected by comparing the structure, performance, parameters, scope of application, leakage rate, seal material, use method and other comprehensive factors.
3. When installing the vent valve on the vacuum chamber, the model of the vent valve should be selected according to the amount of gas in the vacuum chamber and the time needed to open the door of the vacuum chamber.
4. There are three driving modes of vacuum valve: manual, electric and pneumatic. The valve with that driving mode should be considered from the needs of vacuum system.
5. Ultra high vacuum valve is often used in ultra-high vacuum system.
6. The vacuum valve can be used alone, and can be configured between the vacuum chamber and the vacuum pump or on the vacuum chamber. It is a necessary component of general vacuum system. But most vacuum valves are used in vacuum pumping unit.
7. Because of its simple structure, small volume, light weight and good sealing performance, vacuum diaphragm valve is suitable for pre pumping pipeline and non corrosive gas with temperature of - 25 ℃～ 80 ℃.
8. The types and basic parameters of the electromagnetic vacuum valve have been standardized in China.
9. Glass vacuum piston, calibration system and glass vacuum system for vacuum measurement.

Heat treatment of sealing surface of carbon steel gate valve refers to heat treatment of sealing surface of cobalt chromium tungsten carbide welded on carbon steel valve body and gate. After the sealing surface of cobalt chromium tungsten carbide is overlaid by carbon steel gate valve, the stress annealing is to remove the residual stress and improve the machining performance.
The overlay materials can be divided into two types according to the different effects of heat treatment. A kind of cemented carbide is represented by cobalt chromium tungsten, whose hardness can not be changed by heat treatment generally, and the hardness of sealing surface is guaranteed by surfacing material. The other is Cr13 Stainless steel, whose hardness can be changed by heat treatment, and the hardness of sealing surface (generally 38-44hrc) can be achieved by heat treatment.
The valve with carbon steel base is overlaid with CoCrW cemented carbide, sf-4 (137) alloy, and WF330 or fe30 parts are spray welded. The temperature of stress annealing heating is selected according to the carbon steel of the base material, and generally 600-650 ℃. The heat preservation time depends on the effective thickness of the parts, generally, it is 1 / 25mm and at least 2 hours. After heat preservation, it will be cooled to 300 ℃ with the furnace and then it will be discharged to air cooling.
Because of the different medium for carbon steel gate valve, different surfacing sealing material can be selected. It is suitable for gate valves of water, steam, oil and its products. Cr13 Stainless steel is generally overlaid, but some factories are also covered with Cr Mn alloy (85 alloy or 137 alloy), copper alloy and iron base alloy.

1. the welding parts of the solenoid valve include the welding of valve cover, magnetic isolation pipe, magnetic isolation pipe and fixed core. The original self fusion welding is changed to wire filling welding to increase the welding strength to prevent fatigue cracking. After welding, the pressure strength test and air tightness test shall be conducted to ensure the welding quality.
2. the seal of high temperature solenoid valve generally adopts hard seal. In order to ensure the sealing performance meets the specified requirements, the sealing surface of valve seat and valve core seal must be ground. The sealing surface of valve plug and seat is matched with grinding technology, which can make the roughness of sealing surface reach 0.2 μ It is more than 5 m.
3. the finishing of screw cover, valve plug and valve body is the key part of solenoid valve. The key points are the inner hole of the screw cap, the outer circle size of the valve plug and the roughness of the sealing surface. The surface treatment of the plug is identified as a key process. Because of the high hardness, high precision and easy deformation of the valve plug surface, it is necessary to screen the surface treatment of the plug. The key parts shall be analyzed by process capability, personnel, equipment, fixed point and regular inspection shall be carried out, and data statistics and analysis shall be collected to ensure the processing quality of parts.

1、 General requirements
1. The valve specification and type shall meet the requirements of pipeline design documents.
2. The model of the valve shall indicate the national standard number requirements. If it is an enterprise standard, the relevant description of the model should be indicated.
3. The working pressure of the valve is required to be greater than or equal to the working pressure of the pipeline. On the premise of not affecting the price, the working pressure that the valve can bear should be greater than the actual working pressure of the pipeline; Any side of the valve under closed condition shall be able to bear 1.1 times the working pressure of the valve without leakage; When the valve is open, the valve body shall be able to withstand 1.5 times the working pressure of the valve.
4. The valve manufacturing standard shall state the national standard number. If it is an enterprise standard, the enterprise document shall be attached to the purchase contract.
2、 Valve standard quality
1. The material of the valve body should be determined according to the working conditions, and the brand and the actual physical and chemical test data of the material should be indicated.
2. The material of stem is stainless steel stem (2Cr13). The material of the valve stem can be determined according to the working conditions.
3. The nut is made of cast aluminum brass or cast aluminum bronze, and its hardness and strength are greater than those of the valve stem.
4. The hardness and strength of the valve stem bushing material should not be greater than that of the valve stem, and there is no electrochemical corrosion with the valve stem and valve body under the condition of water immersion.
5. Material of sealing surface
① Different types of valves, sealing methods and material requirements;
② The material, fixing method and grinding method of ordinary wedge gate valve, 13Cr alloy and copper ring should be explained;
③ Physicochemical and hygienic test data of soft seal gate valve and valve plate rubber lining materials;
④ The material of sealing surface on valve body and butterfly plate shall be marked on butterfly valve; Their physical and chemical test data, especially the hygienic requirements, aging resistance and wear resistance of rubber. Generally, NBR and EPDM are used, and recycled rubber is strictly prohibited.
6. Valve shaft packing
① As the valves in the pipe network are usually opened and closed infrequently, the packing is required to be inactive for several years, and the packing is not aging, so as to maintain the sealing effect for a long time;
② Valve shaft packing should also bear frequent opening and closing, good sealing effect;
③ In view of the above requirements, the valve shaft packing shall not be replaced for life or more than ten years;
④ If the packing needs to be replaced, the valve design should consider the replacement measures under the condition of water pressure.