Basic Technical Terms of Valves

The valve is a pipeline accessory used to open and close the pipeline. It controls the flow direction, and adjusts the parameters (temperature, pressure and flow) of the conveying medium. Do you know all the technical terms of valves?
 
Basic terminology
 
1. Strength and performance
 
The strong performance of the valve refers to the ability of the valve to withstand medium pressure. The valve is a mechanical product that bears internal pressure, so it must have enough strength and rigidity 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 place with the packing valve stem and stuffing box; The joint of the valve body and bonnet. One of the former leaks is called internal leakage, which is usually called lax closing, and it 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, pollute the environment, and even cause accidents in severe cases.
 
For flammable, explosive, toxic or radioactive media, leakage is not allowed, so the valve must have reliable sealing performance.
 
3. Flowing medium
 
The pressure loss (that is, the pressure difference between the front and back of the valve) will occur after the medium flows through the valve, that is, the valve has a certain resistance to the flow of the medium, and the medium will consume certain energy to overcome the resistance of the valve.
 
Considering energy saving, when designing and manufacturing valves, the resistance of valves to flowing media should be reduced as much as possible.
 
4. Opening and closing force and moment
 
Opening force and moment refer 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 sealing specific pressure between the two sealing surfaces of the valve opening and closing piece and the valve seat. At the same time, it is necessary to overcome the friction between the valve stem and packing, the screw thread between the valve stem and nut, the end support of the valve stem and other friction parts, so 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 change, and the maximum value are at the final moment of closing or the initial moment of opening. When designing and manufacturing valves, efforts should be made to reduce their closing force and moment.
 
5. Opening and closing speed
 
The opening and closing speed are expressed by the time required for the valve to complete an opening or closing action. 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 to prevent accidents, and some requirements for slow closing 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 making a corresponding response. For valves such as throttle valves, pressure-reducing valves and regulating valves that are used to adjust medium parameters, and valves with specific functions such as safety valves and steam traps, their functional sensitivity and reliability are very important technical performance indicators.
 
7. Service life
 
It indicates the durability of the valve, which is an important performance index of the valve and has great economic significance. It is usually expressed by the opening and closing times that can guarantee the sealing requirements, and it can also be expressed by the service time.
 
8. Type
 
It refers to the classification of valves according to their use or main structural characteristics
 
9. Model
 
Number the valve according to its type, transmission mode, connection form, structural characteristics, sealing surface material of valve seat and nominal pressure.
 
10. Connection dimensions
 
It is the size of the valve and pipeline connection parts.
 
11. Main dimensions (general dimensions)
 
It refers to the opening and closing height of the valve, the diameter of the handwheel and the connection size, etc.
 
12. Type of connection
 
It refers to various methods (such as flange connection, threaded connection, welded connection, etc.) used to connect valves or machinery and equipment.
 
13. Seal test
 
It refers to the test to check the performance of opening and closing parts and valve body sealing pair.
 
14. Back seal test
 
It refers to the test to check the sealing performance of the valve stem and bonnet sealing pair.
 
15. Seal test pressure
 
It refers to the pressure specified during the sealing test of the valve.
 
16. Suitable medium (suitable medium)
 
It refers to the medium to which the valve can be applied.
 
17. Applicable temperature (suitable temperature)
 
It refers to the temperature range of the applicable medium of the valve.
 
18. Sealing face
 
It refers that two contact surfaces of the opening piece and the valve seat (valve body) closely adhere to each other and play a sealing role.
 
19. Opening and closing parts (disc)
 
It is a general term for a part used to cut off or regulate the flow of the medium, such as gates in gate valves, the disc in throttle valves, etc.
 
20. Packing
 
A filler is put into the stuffing box (or stuffing box) to prevent the medium from leaking from the valve stem.
 
21. Packing seat
 
Parts that support packing and keep packing sealed.
 
22. Gland
 
It refers to parts used to compress packing to achieve sealing.
 
23. Stand (yoke)
 
On the bonnet or valve body, it is used to support the valve stem nut and the parts of the transmission mechanism.
 
24. Dimension of the connecting channel
 
It refers to the structural dimensions of the assembly and connection parts between the opening piece and the valve stem.
 
25. Flow area
 
It refers to the minimum cross-sectional area (but not the "curtain" area) between the valve inlet and the sealing surface of the valve seat, which is used to calculate the theoretical displacement without any resistance.
 
26. Flow diameter
 
It refers to the diameter corresponding to the flow passage area.
 
27. Flow characteristics
 
In the steady flow state, when the inlet pressure and other parameters are constant, the functional relationship between the outlet pressure of the pressure-reducing valve and the flow rate.
 
28. Deviation of flow characteristics
 
In the steady flow state, when the inlet pressure and other parameters are constant, the outlet pressure change value is caused by the change of the pressure reducing the valve flow rate.
 
29. General valve
 
It refers to valves commonly used in pipelines in various industrial enterprises.
 
30. Automatic valve (Self-acting valve)
 
A valve that acts by itself depending on the capacity of the medium (liquid, air, steam, etc.).
 
31. Actuated valve
 
A valve operated by hand, electricity, hydraulic pressure or air pressure.
 
32. Hammer blow handwheel
 
It refers to the handwheel structure using impact force to reduce valve operating force.
 
33. Wormgear actuator
 
A device that opens and closes or adjusts a valve with a worm gear mechanism.
 
34. Pneumatic device (pneumatic actuator)
 
A driving device for opening, closing or regulating a valve by pneumatic pressure.
 
35. Hydraulic actuator
 
A driving device for opening, closing or regulating a valve by hydraulic pressure.
 
36. Hot condensate capacity
 
Under the given pressure difference and temperature, the maximum amount of condensate that can be discharged by the trap in one hour.
 
37. Steam loss
 
It refers to the amount of fresh steam leaked from the steam trap per unit time.
 
 
Definition terms of valves
 
1. Valve
 
The totality of mechanical products with movable mechanisms are used to control the flow of medium in pipelines.
 
2. Gate valve (slide valve)
 
The valve whose opening (gate) is driven by the valve stem and moves up and down along the valve seat (sealing surface).
 
3. Globe valve (stop valve)
 
It refers to the open-close valve (valve disc), which is driven by the valve stem and moves up and down along the axis of the valve seat (sealing surface).
 
4. Throttle valve
 
A valve that changes the cross-sectional area of the passage through the opening and closing piece (valve flap) to adjust the flow rate and pressure.
 
5. Ball valve
 
It refers to the on-off (ball) valve that rotates around a curve perpendicular to the passage.
 
6. Butterfly valve
 
It refers to the open-close valve (butterfly plate) rotating around a fixed shaft.
 
7. Diaphragm valve
 
It refers to the open-close (diaphragm) valve driven by the valve stem, which moves up and down along the axis of the valve stem and separates the actuating mechanism from the medium.
 
8. Cock valve
 
A valve whose opening and closing (plug) rotates around its axis.
 
9. Check valve (non-return valve)
 
It refers to the open-close (valve flap) valve that automatically prevents the reverse flow of the medium by the force of the medium.
 
10. Safety valve (relief valve)
 
It refers to the open-close type (valve flap) that automatically opens and discharges when the pressure of the medium in a pipeline or machinery exceeds the specified value; A valve that automatically closes when it is lower than the specified value to protect the pipeline or machine.
 
11. Pressure-reducing valve
 
A valve that reduces the medium pressure by throttling the opening and closing piece (valve flap) and automatically keeps the pressure behind the valve within a certain range by the direct action of the pressure behind the valve.
 
12. Steam trap
 
A valve that automatically discharges condensed water and prevents steam leakage.
 
13. Draining Valves
 
It refers to valves for blowdown of boilers, pressure vessels and other equipment.
 
14. Low-pressure valve
 
It refers to all kinds of valves with nominal pressure PN≤1.6MPa.
 
15. Middle-pressure valve
 
It refers to all kinds of valves with a nominal pressure of PN ≥ 2.0, and PN < 10.0 MPa.
 
16. High-pressure valve
 
It refers to all kinds of valves with nominal pressure PN≥10.0MPa.
 
17. Ultra-high pressure valve
 
It refers to all kinds of valves with nominal pressure PN≥100.0MPa.
 
18. High-temperature valve
 
It refers to various valves with medium temperature > 450℃.
 
19. Low-temperature valve (sub-zero valve)
 
It refers to various valves with medium temperatures from -40℃ to -100℃.
 
20. Cryogenic valve
 
It refers to various valves with medium temperature <-100℃.