First, the valve industry

1, strength performance

The strength of the valve refers to the ability of the valve to withstand the pressure of the medium. The valve is a mechanical product that is subjected to internal pressure, so it must have sufficient strength and stiffness to ensure long-term use without rupture or deformation.

2, sealing performance

The sealing performance of the valve refers to the ability of the sealing parts of the valve to prevent the leakage of the medium, which is the most important technical performance index of the valve.

There are three sealing parts of the valve: the contact between the opening and closing parts and the sealing surface of the valve seat; Packing with the valve stem and stuffing box; The connection between the valve body and the valve cover. The leakage in the first place is called internal leakage, which is usually referred to as lax closing, which will affect the ability of the valve to cut off the medium.

For cut-off valves, internal leakage is not allowed. The latter two leaks are called external leaks, that is, the medium leaks from inside the valve to outside the valve. Leakage will cause material loss, pollute the environment, and cause accidents in serious cases.

For flammable and explosive, toxic or radioactive media, leakage is not allowed, so the valve must have reliable sealing performance.

3, the flow medium

After the medium flows through the valve, there will be a pressure loss (the pressure difference before and after the valve), that is, the valve has a certain resistance to the flow of the medium, and the medium will consume a certain amount of energy to overcome the resistance of the valve.

From the perspective of energy conservation, when designing and manufacturing valves, the resistance of the valve to the flowing medium should be reduced as much as possible.

4. Opening and closing force and torque

Opening and closing force and opening and closing moment refers to the force or moment that must be applied to open or close the valve.

When closing the valve, it is necessary to form a certain specific pressure seal between the opening and closing parts and the head sealing surface, and at the same time to overcome the friction between the valve stem and the packing, the valve stem and the screw thread between the valve stem and the nut, the valve stem end support and other friction parts, so a certain closing force and closing torque must be applied, the valve in the opening and closing process, the required opening and closing force and opening and closing torque are changed. Its maximum value is at the last instant of closing or the first instant of opening. The valve should be designed and manufactured to reduce its closing force and closing torque.

5. Opening and closing speed

Opening and closing speed is expressed by the time required for the valve to complete an opening or closing action. Generally, there are no strict requirements for the opening and closing speed of the valve, but some working conditions have special requirements for the opening and closing speed, such as some requirements for rapid opening or closing, to prevent accidents, and some requirements for slow closing, to prevent water strikes, etc., which should be considered when selecting the valve type.

6, action sensitivity and reliability

This refers to the sensitivity of the valve to changes in medium parameters. For throttle valves, pressure reducing valves, regulating valves and other valves used to adjust medium parameters, as well as safety valves, traps and other valves with specific functions, their functional sensitivity and reliability are very important technical performance indicators.

7. Service life

It indicates the durability of the valve, is an important performance indicator of the valve, and has great economic significance. It is usually expressed by the number of opening and closing times that can ensure the sealing requirements, and can also be expressed by the use time.

8. type

Classification of valves by use or major structural features

9. model

According to the type, transmission mode, connection form, structural characteristics, sealing surface material and nominal pressure of the valve number.

10. connection dimensions

Dimensions of valves and piping connections

11. Main dimensions (general dimensions)

Valve opening and closing height, handwheel diameter and connection size, etc.

12. type of connection

Various ways of connecting valves to pipes or machines (such as flanged connections, threaded connections, welded connections, etc.).

13. seal test

Test to check the performance of opening and closing parts and valve body seals.

14. back seal test

Test to check the sealing performance of stem and cover seals.

15. seal test pressure

The pressure specified when the valve is tested for sealing.

16. suitable medium

The valve can be applied to the medium.

17. suitable temperature

The temperature range of the medium for which the valve is applied.

18. sealing face

The opening and closing parts are closely fitted with the valve seat (valve body) and act as two contact surfaces for sealing.

19, opening and closing parts (disc)

A general term for a part used to cut off or regulate the flow of media, such as a disc in a gate valve, a valve disc in a throttle valve, etc.

20. packing

A packing material packed into a stuffing box (or stuffing box) to prevent media from leaking from the valve stem.

21. packing seat

Parts that support the packing and keep the packing sealed.

22, packing gland

A part used to press the packing to seal.

23. yoke

Part for supporting the stem nut and drive mechanism on the valve cover or body.

24. dimension of connecting channel

The structural dimensions of the opening and closing parts and the connecting parts of the valve stem assembly.

25. flow area

Refers to the small cross-sectional area between the valve inlet end and the sealing surface of the valve seat (but not the "curtain" area), used to calculate the theoretical displacement without any resistance influence.

26, flow diameter

The diameter corresponding to the area of the flow path.

27. flow characteristics

In the stable flow state, when the inlet pressure and other parameters are unchanged, the outlet pressure of the pressure reducing valve is a function of the flow.

28. flow characteristics derivation

In the stable flow state, when the inlet pressure and other parameters are unchanged, the outlet pressure change value caused by the change of the pressure reducing valve flow.

29. general valve

Valves commonly used on pipelines in various industrial enterprises.

30, Automatic (Self-acting valve)

A valve that operates by itself depending on the ability of the medium (liquid, air, steam, etc.).

31, Actuated valve

Valves operated manually, electrically, hydraulically or pneumatic.

32, hammer blow handwheel (hammer blow handwheel)

A handwheel structure that uses impact forces to reduce valve operating forces.

33. wormgear actuator

A device for opening, closing or adjusting a valve with a worm gear mechanism.

34. pneumatic actuator

A drive device for opening, closing or adjusting a valve with air pressure.

35. hydraulic actuator

A drive device that opens, closes or adjusts a valve with liquid pressure.

36. Hot condensate capacity

The maximum amount of condensate that can be discharged from a trap at a given pressure difference and temperature

37. Steam loss

The amount of fresh steam leaking from the trap per unit time.