On the terminology of valves
Time: 2019-05-31 21:30:51 Source: Yonglong Valve Reading: zero second
A Brief Talk on the Professional Terms of Valves - Shanghai Yonglong Valve Factory
The valve is used to open and close the medium flow in the pipeline, Emergency shut-off valve For pipe accessories that control the flow direction, adjust and control the parameters (temperature, pressure and flow) of the transmission medium, please edit some professional terms in the valve industry!
Basic technical terms
1. Strength performance
The strength performance of the valve refers to valve Ability to withstand medium pressure. The valve is a mechanical product subject to internal pressure, so it 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 each sealing part of the valve to prevent medium leakage, 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 two sealing surfaces of the valve seat; The matching position of packing, valve rod and stuffing box; The connection between the valve body and the valve cover. The leakage at the first place is called internal leakage, that is to say, it can not be closed tightly, which will affect the ability of the valve to cut off the medium.
For block valves, internal leakage is not allowed. The latter two leaks are called external leakage, that is, the medium leaks from inside the valve to outside the valve. Leakage will cause material loss, environmental pollution, and even accidents in serious cases.
For flammable, explosive, toxic or radioactive media, leakage is not allowed, so the valve must have reliable sealing performance.
3. Flowing medium
After the medium flows through the valve, there will be 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, and the medium will consume a certain amount of energy to overcome the resistance of the valve.
In consideration of energy conservation, when designing and manufacturing the valve, the resistance of the valve to the flow medium should be reduced as much as possible.
4. Hoisting force and moment
Opening and closing force and opening and closing torque refer to the force or torque that must be applied to open or close the valve.
When closing the valve, it is necessary to form a certain sealing pressure between the opening and closing parts and the two sealing surfaces of the hair seat, and to overcome the friction between the valve stem and the packing, between the threads of the valve stem and the nut, at the end support of the valve stem 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 hoisting force and moment are variable, and the maximum value is at the final instant of closing or the initial instant of opening. The valve shall be designed and manufactured to minimize its closing force and 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 action. Generally, there are no strict requirements on the opening and closing speed of valves, but some working conditions have special requirements on the opening and closing speed. For example, some require rapid opening or closing to prevent accidents, and some require slow closing to prevent water hammer, which should be considered when selecting valve types.
6. Action sensitivity and reliability
This refers to the sensitivity of the valve to respond to changes in medium parameters. For throttle valve, pressure reducing valve, regulating valve and other valves used to regulate medium parameters, as well as safety valve, drain valve 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 opening and closing times that can ensure the sealing requirements, or by the service time.
8. Type
Classification of valves according to use or main structural characteristics
9. Model
Number the valves according to type, transmission mode, connection type, structural characteristics, valve seat sealing surface material and nominal pressure.
10. Connection dimensions
Size of valve and pipe connection
11. General dimensions
Valve opening and closing height, handwheel diameter, connection size, etc.
12. Type of connection
Various methods (such as flange connection, threaded connection, welding connection, etc.) used for the connection of valves with pipes or machinery equipment.
13. Seal test
Test to check the performance of the hoist and valve body sealing pair.
14. Back seal test
Test to check the sealing performance of valve rod and bonnet sealing pair.
15. Seal test pressure
The pressure specified during the valve sealing test.
16. Suitable medium
Medium applicable to the valve.
17. Applicable temperature
Temperature range of media applicable to the valve.
18. Sealing face
The hoist is closely fitted with the valve seat (valve body) and serves as two contact surfaces for sealing.
19. Hoist (disc)
A general term for a part used to cut off or regulate the flow of medium, such as the gate in a gate valve, the disc in a throttle valve, etc.
20. Packing
The packing material that is installed into the stuffing box (or stuffing box) to prevent the medium from leaking from the valve stem.
21. Packing seal
The part that supports the packing and maintains the packing seal.
22. Gland
The part used to compress the packing to seal.
23. Yoke
On the bonnet or valve body, it is used to support the stem nut and parts of the transmission mechanism.
24. Dimension of connecting channel
The structural dimension of the connection part between the hoist and the valve rod assembly.
25. Flow area
It refers to the minimum sectional area between the inlet end of the valve and the sealing surface of the valve seat (but not the "curtain" area), which is used to calculate the theoretical displacement without any resistance effect.
26. Flow diameter
The diameter corresponding to the runner area.
27. Flow characteristics
When the inlet pressure and other parameters are constant, the outlet pressure of the pressure reducing valve is a function of the flow rate under the steady flow state.
28. Flow characteristics derivation
Under the stable flow state, when the inlet pressure and other parameters remain unchanged, the outlet pressure change value caused by the change of the pressure reducing valve flow.
29. General valve
The valves commonly used on pipelines in various industrial enterprises.
30. Self acting valve
The valve operates by itself depending on the capacity of the medium (liquid, air, steam, etc.).
31. Actuated valve
Valves operated manually, electrically, hydraulically or pneumatically, such as pneumatic emergency shut-off valve, liquid ammonia emergency shut-off valve, electric emergency shut-off valve, Hydraulic emergency shut-off valve 。
32. Hammer blow handwheel
The handwheel structure uses the impact force to reduce the valve operating force.
33. Wormgear actuator
A device that uses a worm gear mechanism to open and close or adjust valves.
34. Pneumatic actuator
The driving device for opening and closing or regulating the valve with air pressure.
35. Hydraulic actuator
Use hydraulic pressure to open and close or adjust the driving device of the valve.
36. Hot condensate capacity
Maximum amount of condensate that can be discharged from drain valve I under given pressure difference and temperature
37. Steam loss
Amount of fresh steam leaked from drain valve in unit time.
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