VGZ Valve Terminology

Basic professional terms

1. Strength Performance

Valve strength performance refers to the ability of the valve to withstand medium pressure. Valves are mechanical products withstanding internal pressure, so they must have sufficient strength and stiffness to ensure long-term use without cracking or deformation.

2. Sealing performance

The sealing performance of the valve refers to the ability of the sealing parts of the valve to prevent medium leakage. It 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 two sealing surfaces of the valve seat; the matching place between the filler and the stem and the filling box; and the connecting place between the valve body and the valve cover. The former leakage is called internal leakage, which is commonly referred to as lax closure, and it will affect the ability of the valve to cut off the medium.

Internal leakage is not allowed for truncation valves. Leakage at the last two places is called leakage, i.e. medium leaks from inside to outside of the valve. Leakage can cause material loss, pollution of the environment, and serious accidents.

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

3. Flow media

When the medium flows through the valve, it will cause pressure loss (the pressure difference between the front and the back of the valve), that is, the valve has 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.

Considering energy saving, when designing and manufacturing valves, the resistance of valves to flow media should be reduced as much as possible.

4. Opening and closing force and moment

Opening and closing forces and opening and closing moments refer to the forces or moments that must be applied when the valve is opened or closed.

When closing the valve, it is necessary to form a certain specific sealing pressure between the opening and closing parts and the sealing surfaces of the seat. At the same time, it is necessary to overcome the friction between the stem and filler, between the threads of the stem and nut, at the end of the stem support and other frictional parts. Therefore, a certain closing force and closing moment must be applied to the valve during the opening and closing process. The required opening and closing force and moment are variable, and the maximum value is at the final closing moment or the initial opening moment. Valves should be designed and manufactured to reduce their closing force and closing moment.

5. Opening and closing speed

The opening and closing speed is expressed by the time required for the valve to complete an opening or closing operation. Generally, there is no strict requirement for the opening and closing speed of valves, but some working conditions have special requirements for the opening and closing speed, such as some requirements for quick opening or closing, in order to prevent accidents, some requirements for slow closing, in order to prevent water hammer, etc., which should be considered when selecting valve types.

6. Action sensitivity and reliability

This refers to the sensitivity of the valve to the change of medium parameters and the corresponding response. For throttle valves, pressure relief valves, control valves and other valves used to regulate 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 represents the durability of the valve, is an important performance index of the valve, and has great economic significance. Usually, it can be expressed by the number of times of opening and closing that can guarantee the sealing requirements, or by the use time.

8. Type

Classification of valves by use or main structural characteristics

9. Model

Number the valve according to type, transmission mode, connection form, structural characteristics, seating material and nominal pressure.

10. Connection dimensions

Dimensions of connecting parts of valves and pipes

11. General dimensions

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

12. Type of connection

Various ways of connecting valves to pipes or machine equipment (such as flange connection, threaded connection, welding connection, etc.).

13. Seal test

Tests to test the performance of hoists and body seals.

14. Backseal test

Test of sealing performance of stem and cover sealing pair.

15. Seal test pressure

Pressure required for sealing test of valves.

16. Applicable medium

The medium that the valve can be used.

17. Applicable temperature

Temperature range of medium applicable to valve.

18. Sealing face

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

19. Disc

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

20. packing

Packing box (or packing box) to prevent medium leakage from the valve stem.

21. packing seat

Supporting packing, keep packing sealing parts.

22. gland

It is used to press the filler to seal the parts.

23. Yoke

On the bonnet or body, parts used to support stem nuts and drive mechanisms.

24. Dimension of Connection Channel

The structural dimension of the assembly connection part between the opening and closing parts and the valve stem.

25. Flow area

The minimum cross-sectional area (but not the "curtain" area) between the inlet end of the valve and the sealing surface of the seat is used to calculate the theoretical displacement without any resistance effect.

26. Flow diameter

The diameter corresponding to the area of the runner.

27. Flow characteristics

Under steady flow condition, when the inlet pressure and other parameters remain unchanged, the function relationship between outlet pressure and flow rate of pressure relief valve is obtained.