Zero leakage means the good sealing performance of the valve. Under the allowable pressure difference, the leakage of the valve is almost zero. Valve sealing decide to the size of valve leakage
User should determine the maximum operating leakage, or determine the degree of sealing required within the desired valve life range before replacement of the valve trim. This can be used as the basis for selecting the appropriate valve type to meet these requirements. Some valves maintain the leakage amount tested by the valve factory for a long time on site. Other valves are quickly scratched or slightly damaged due to repeated closing or corrosion, so that the leakage is higher than in normal use.
Stem packing material
There are many types of packing available for regulating valves. There are the lowest frictional resistance,smallest valve deterioration, and the seal is extremely tight for PTFE packing. Graphite asbestos packing is suitable for higher operating temperature. When the valve usage environment becomes worse, the leakage of graphite asbestos packing is much higher than that of PTFE packing. When the graphite asbestos packing is close to the smoke density of the PTFE packing, it will be greatly deteriorated and the valve operation will be unstable. The polytetrafluoroethylene packing used in the electric control valve and pneumatic control valve produced by Zhejiang huizheng Valve can extend the service life of the valve in a wide range of applications.
Bellows stem seal
Bellows seals are used where hazardous fluids or fluids will lose the filler material normally used. They are often used in radioactive or vacuum applications to prevent air pollution in pipelines. Bellows seals are relatively expensive, with limited travel, and require high actuator thrust to overcome the elasticity of the bellows. This bellow seals should be avoided in non-essential situations. The service life of the bellows seal's cyclic change depends on the full stroke or partial throttle stroke. Electric bellows sealed regulating valve is composed of 3810 series (PSL series) electronic electric actuator and low flow resistance regulating valve body. Electric actuator is an integrated structure with a servo amplifier and input control signal (4-20mADC or 1-5VDC) and power supply can control the opening of the valve to achieve the adjustment of industrial parameters such as pressure, flow, liquid level and temperature. The spool of the electric bellows sealed regulating valve adopts an upper guide structure, which is compact in structure and has an S-shaped flow channel, which makes the pressure drop loss .Small flow rate is large, Adjustable range is wide, and flow rate accuracy is high, which conforms to IEC534-1-1976 standard. The upper bonnet adopts a bellows sealed structure valve. The tightness of the valve is very important. It is suitable for the adjustment of extremely literate, flammable, explosive, volatile and rare precious metal media. In addition, the valve can also be used in vacuum applications.
