Working principle diagram of pneumatic membrane double seat regulating valve

- Nov 20, 2018-

Pneumatic two-seat regulating valve, as its name implies, has two spools and two seats in the body of the valve. It adopts a dual-guide structure. It is mainly composed of a multi-spring straight-stroke pneumatic actuator and a straight-through two-seat regulating valve body. It is generally used under the requirement of pressure compensation. It is realized by using two sealing lines on the core barrel to seal at the same time. Pressure compensation and valve turn off.

Pneumatic two-seat control valve has the characteristics of compact structure, large valve capacity, accurate flow characteristics, and can be used in harsh dry working conditions. The rated flow coefficient is bigger than the single seat valve with the same caliber, but the leakage page is larger than the single seat valve. It is suitable for clean media occasions where the leakage requirement is not strict and the pressure difference between front and back of the valve is large. It is widely used in industrial control departments such as petroleum, chemical industry, pharmacy, metallurgy, power station, etc. It mainly controls gas, liquid, steam and other media.

The pneumatic two-seat regulating valve seat has two upper and lower spools. Fluid flows into the left side of the valve body and flows out from the right side after passing through the seat and spool. It can flow more media than the one seat valve with nominal diameter, and its circulation capacity is increased by 20%~25%. The force acting on the upper and lower spool can be offset by each other, so the imbalance force is small and the operating pressure difference is large.

However, due to the complex medium flow path of the valve, the erosion and cavitation damage of the valve body are serious when used in high pressure difference; it is not suitable for the adjustment of high viscosity medium and medium containing fibers. In addition, because the upper and lower two spool valves are not easy to be closed at the same time, the leakage is large when closing. However, it has strong flow capacity, allowing the use of large differential pressure, larger than the same caliber of single seat valve flow capacity, suitable for leakage requirements and large differential pressure occasions.