The strength performance of a valve is its ability to withstand medium pressure. Valves are mechanical products that withstand internal pressure, so they must have sufficient strength and stiffness to ensure long-term use without rupture or deformation. The sealing performance of a valve refers to the ability of each sealing part of the valve to prevent medium leakage, which is the most important technical performance indicator of the valve.

There are three sealing parts of the valve: the contact between the opening and closing parts and the two sealing surfaces of the valve seat; The matching between the packing and the valve stem and packing box; The connection between the valve body and the valve cover. The previous leakage is called internal leakage, which is commonly referred to as not being tightly closed, and it will affect the valve's ability to cut off the medium.

For block valves, internal leakage is not allowed. The last two leaks are called external leaks, which means that the medium leaks from the inside of the valve to the outside. Leakage can cause material loss, pollute the environment, and even cause accidents in severe cases. For flammable, explosive, toxic, or radioactive media, external leakage is not allowed, so the valve must have reliable sealing performance. After the flowing medium passes through the valve, there will be a pressure loss (i.e. the pressure difference before and after the valve), which means that the valve has a certain resistance to the flow of the medium. To overcome the resistance of the valve, the medium needs to consume a certain amount of energy.

From the perspective of energy conservation, when designing and manufacturing valves, it is necessary to minimize the resistance of the valve to the flowing medium as much as possible. Opening and closing force and torque Opening and closing force and torque refer to the force or torque that must be applied to open or close a valve. When closing the valve, it is necessary to form a certain sealing pressure ratio between the sealing surfaces of the opening and closing parts and the valve seat. At the same time, it is also necessary to overcome the friction between the valve stem and packing, the threads of the valve stem and nut, the support of the valve stem end, and other friction parts. Therefore, a certain closing force and closing torque must be applied. During the opening and closing process of the valve, the required opening and closing force and torque are variable, Its limit value is at the final moment of closure or the initial moment of opening.

When designing and manufacturing valves, efforts should be made to reduce their closing force and torque. The opening and closing speed is expressed in terms of the time required for a valve to complete an opening or closing action. There are generally no strict requirements for the opening and closing speed of valves, but some working conditions have special requirements for the opening and closing speed. For example, some require quick opening or closing to prevent accidents, while others require slow closing to prevent water hammer. This should be considered when selecting valve types.

Action sensitivity and reliability refer to the sensitivity of the valve to respond to changes in medium parameters. For valves such as throttle valves, pressure reducing valves, and regulating valves used to regulate medium parameters, as well as valves with specific functions such as safety valves and drain valves, their functional sensitivity and reliability are very important technical performance indicators. The service life represents the durability of the valve, is an important performance indicator of the valve, and has great economic significance.

Usually expressed in terms of the number of opening and closing times that can ensure sealing requirements, or in terms of usage time. The valve model should usually indicate factors such as valve type, driving method, connection form, structural characteristics, sealing surface material, valve body material, and nominal pressure. The standardization of valve models provides convenience for the design, selection, and sales of valves. Nowadays, there are more and more types and materials of valves, and the model designation of valves is becoming increasingly complex.

Although there is a unified standard for valve model designation in China, it is increasingly unable to meet the needs of the development of the valve industry. At present, valve manufacturers generally adopt a unified numbering method; Where a unified numbering method cannot be used, each manufacturing plant shall develop a numbering method according to their own needs.

1. The method of valve model designation: JB308-75 "Valve Model Designation Method" is applicable to gate valves, throttle valves, ball valves, butterfly valves, diaphragm valves, plunger valves, plug valves, check valves, safety valves, pressure reducing valves, and drain valves used in industrial pipelines. It includes the model designation of the valve and the naming of the valve.

(1) The valve model is composed of 7 units, with their meanings (1 unit representing the type code; 2 units representing the transmission mode code; and so on). For example, taking Q941F-16P as an example, Q represents 1 unit (i.e. the valve type is ball valve); 9 represents 2 units (i.e. the electric mode in the transmission mode); 4 represents 3 units (i.e. flange connection in the connection method); 1 represents the structural form of 4 unit valves; F represents 5 units (i.e. PTFE sealing ring in the sealing material); 16 represents 6 units (i.e. one of the nominal pressures, this demonstration is 1.6MPa); P represents 7 units (this demonstration is made of stainless steel 1cr18Ni9Ti material); The model designation is shown in Table 1. Table 1:1 Unit 2, Unit 3, Unit 4, Unit 5, Unit 6, Unit 7 represents the type code, transmission method code, connection form code, structural form code, valve seat or lining material code, nominal pressure code, valve body material code.

(2) Type code (i.e. Unit 1 of Table 1): The type code is represented by Chinese pinyin letters. As shown in Table 2: Type code Type code Gate valve Z Diaphragm valve G Globe valve J Check valve and bottom valve H Plunger valve U Safety valve A Throttling valve L Pressure reducing valve Y Ball valve Q Drain valve S Butterfly valve D Plug valve X

(3) Transmission mode code (i.e. Unit 2 of Table 1): The transmission mode code is represented in Arabic numerals. As shown in Table 3: Table 3: Transmission mode code Electromagnetic 0 Bevel gear 5 Electromagnetic hydraulic 1 Pneumatic 6 Electric hydraulic 2 Hydraulic 7 Worm gear 3 Pneumatic hydraulic 8 Spur gear 4 Electric 9 Note: ① Handwheel, handle, and wrench transmission, as well as safety valves, pressure reducing valves, and drain valves, omit this code. ② For pneumatic or hydraulic systems: the normally open type is represented by 6k or 7k; Normally closed type is represented by 6B and 7B; The pneumatic belt is manually represented by 6S; Explosion proof electric is represented by "9B".

(4) Connection form code (i.e. 3 units in Table 1): As shown in Table 4: Connection form code Internal thread 1 Pair clamp 7 External thread 2 Clamp 8 Flange 4 Clamp sleeve 9 Welding (including butt welding and socket welding).

(5) Structural form code (i.e. the 4 units in Table 1): The structural form code is represented in Arabic numerals

Table 11: Structural form codes for check valves and bottom valves: Structural form codes for check valves and bottom valves: Lifting straight type 1 vertical lift 2 swing single disc type 4 multi disc type 5 double disc type.

Table 12: Safety Valve Structural Form Code: Safety Valve Structural Form Code: Spring Closed with Heat Sink Full Open 0 Micro Open 1 Full Open 2 Full Open with Wrench 4 Unclosed Double Spring Micro Open 3 Micro Open 7 Full Open 8 Micro Open 5 Full Open 6 Pulse 9 Table 13: Pressure Reducing Valve Structural Form Code:

Table 14: Structural Form Code of Steam Trap: Structural Form Code of Steam Trap: Floating Ball Type 1 Bell Float Type 5 Bimetal Plate Type 7 Pulse Type 8 Thermodynamic Type 9 Pressure Reducing Valve Structural Form Code: Membrane Type 1 Spring Membrane Type 2 Piston Type 3 Bellows Type 4 Lever Type

(6) Valve seat sealing surface or lining material code (i.e. Unit 5 in Table 1): The valve seat sealing surface or lining material code is represented by Chinese pinyin letters, As shown in Table 15: Table 15: Valve seat sealing surface or lining material code: Valve seat sealing surface or lining material code: Copper alloy T hard alloy Y rubber X rubber lining J nylon plastic N lining lead Q fluoroplastic F enamel C tin metal bearing alloy (Babbitt alloy) B boronized steel P alloy steel H graphite SM nitrided steel D Note: The sealing surface material is directly processed by the valve body and is represented by "W"; When the sealing surface materials of the valve seat and disc (gate) are different, use a low hardness material code (excluding diaphragm valves).

(7) Nominal pressure code (i.e. Unit 6 of Table 1): The nominal pressure code is represented in Arabic numerals, and its value is 10 times the nominal pressure value in megapascals (MPa). For valves used in the power plant industry, when the maximum temperature of the medium exceeds 530'C, its value is 10 times the working pressure value in megapascals (MPa).

(8) Valve body material code (i.e. Unit 7 of Table 1): The valve body material code is represented by Chinese pinyin letters, as shown in Table 16. This code is omitted for cast iron valves with PN less than 1.6MPa and carbon steel valve bodies with PN greater than 2.5MPa. Table 16: Valve Body Material Code: Valve Body Material Code: Gray Iron Z 1Cr5MoZG1Cr5Mo I Malleable Iron K 1Cr18Ni9Ti, ZG1Cr18Ni9Ti P Ductile Iron Q 1Cr18Ni12Mo2Ti, ZG1Cr18Ni12MoTi R Copper and Copper Alloy T 12CrMoV Carbon Steel C ZG12CrMoV.