Summary:
ZJHN pneumatic diaphragm double seats control valve is generally to achieve pressure compensation and valve shut down by the use of the spool barrel on the two sealing lines sealed at the same time in the pressure compensation requirements. Pneumatic diaphragm double seats control valve body has two seats, and it has more than a single seat than single seat. It also increase the amount of leakage because of such a structural form. But its flow capacity is strong, unbalanced force is small, and the allowable pressure difference is bigger. It is larger than the same diameter of a single seat valve flow capacity, so it is usually especially suitable for large flow, high pressure drop and leakage occasions.

Advantages:
The differences between pneumatic double seats control valve and single-seat control valve is the that the body of double seats has two seats, and a single seat body has a seat. Double - seat valve can withstand the pressure difference is large, but the amount of leakage is also large. Single - seat valve can withstand a small pressure difference, but also a small amount of leakage. Pneumatic diaphragm two-seat control valve is widely used in the accurate control of gas, liquid, vaporization and other media process parameters, such as pressure, temperature, flow, liquid level to maintain a given value.

Principle:
Pneumatic double seats control valve has the upper and lower two spools. Fluid flows in from the left side of the body and out from the right side after passing through the seat and spool. It can flow through more media than the same nominal size of a single seat regulator, the flow capacity of about 20% to 25%. Medium action on the upper and lower spool forces can offset each other, so the unbalanced force is small, the operation pressure difference is large.

Due to the valve medium flow path is more complex, in the process of using the high pressure difference, the medium of the valve body erosion and cavitation damage is serious, so the valve is not suitable for high viscosity medium and fiber medium regulation. In addition, the upper and lower spools are not easy to close at the same time, so the leakage is large when closed. But the flow capacity of the valve is strong, allowing the use of large differential pressure, larger than the flow capacity of the same diameter of a single seat valve, suitable for leakage requirements and large differential pressure occasions.