Installation principle of pneumatic control valve 【 Yonglong 】 Shanghai Valve Factory
Time: 2018-10-06 15:45:01 Source: Yonglong Valve Reading: zero second
Installation principle of pneumatic control valve 【 Yonglong 】 Shanghai Valve Factory
Pneumatic control valve is a kind of commonly used control element, which drives the valve with the aid of valve positioner, converter, solenoid valve, retaining valve, gas tank, gas filter and other accessories. It is one of the industrial process control instruments widely used in petroleum, chemical, electric power, metallurgy and other industrial enterprises. This article specifically introduces the installation principles of pneumatic control valves, hoping to help everyone.
Installation Principles of Pneumatic Control Valve
● The installation position of the pneumatic control valve shall be at a certain height from the ground, and a certain space shall be reserved at the top and bottom of the valve to facilitate the disassembly and repair of the valve. For control valves equipped with pneumatic valve positioners and hand wheels, easy operation, observation and adjustment must be ensured.
● The regulating valve shall be installed on the horizontal pipeline and perpendicular to the pipeline. Generally, it shall be supported under the valve to ensure stability and reliability. For special occasions, when the control valve needs to be installed horizontally on the vertical pipeline, the control valve should also be supported (except for small caliber control valve). During installation, avoid bringing additional stress to the regulating valve).
● The operating ambient temperature of the control valve shall be no more than 95% and 95% respectively at (- 30~+60) relative humidity.
● There shall be straight pipe sections at the front and back of the regulating valve, and the length shall not be less than 10 times the pipe diameter (10D), to avoid that the straight pipe section of the valve is too short and affects the flow characteristics.
● If the diameter of the regulating valve is different from that of the process pipe, the reducing pipe shall be used for connection. When installing small diameter control valve, thread connection can be used. The fluid direction arrow on the valve body shall be consistent with the fluid direction.
● Bypass pipe shall be set. The purpose is to facilitate switching or manual operation, and the regulating valve can be overhauled without shutdown.
● Before installation of the regulating valve, completely remove the foreign matters in the pipeline, such as dirt, welding slag, etc.
How to prevent the regulating valve from leaking? (6 methods)
1. Add sealing grease method
For valves without sealing grease, it can be considered to increase sealing grease to improve valve stem sealing performance.
2. Adding filler method
In order to improve the sealing performance of the packing to the valve stem, the method of increasing the packing can be adopted. Usually, double-layer and multi-layer mixed fillers are used, and the effect is not obvious if the number of fillers is increased from 3 to 5.
3. Replacing graphite packing method
As the working temperature of the widely used tetrafluoro filler is within the range of - 20~+200 ℃, when the temperature is at the upper and lower limits and changes greatly, its sealing property will decline significantly, and its aging is fast and its service life is short. Flexible graphite packing can overcome these shortcomings and has a long service life. As a result, some factories have changed all the PTFE packing into graphite packing, and even the newly purchased control valve has changed the PTFE packing into graphite packing for use. However, the use of graphite filler has a large return difference, and some of them have creepage at the beginning, which must be considered.
4. Change the flow direction and place P2 at the valve rod end
When △ P is larger and P1 is larger, sealing P1 is obviously more difficult than sealing P2. Therefore, the flow direction can be changed from P1 at the valve stem end to P2 at the valve stem end, which is more effective for valves with high pressure and large differential pressure. For example, seal P2 should be considered for bellows valves.
5. Lens gasket sealing method
For the sealing of upper and lower covers, the sealing of valve seat and upper and lower valve bodies. If it is a plane seal, under high temperature and high pressure, the sealing performance is poor, causing leakage. Lens gasket can be used instead, and satisfactory results can be obtained.
6. Replace the sealing gasket
Up to now, most of the sealing gaskets are still made of asbestos board. Under high temperature, the sealing performance is poor and the service life is short, causing leakage. In this case, spiral wound gaskets and "O" rings can be used instead, which have been adopted by many factories.
Diaphragm pneumatic control valve
"YongLong" Shanghai Yonglong Valve Factory pneumatic control valve related products include: Fluorine lined pneumatic control valve Electronic fluorine lined electric control valve Fluorine lined pneumatic diaphragm regulating valve
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