Common Valve Problems 2

Common Valve Problems 2

For More Information, Please Read Common Valve Problems 1

6. Why double seating valve is easy to oscillate in small opening?
For single-core valve, when the medium is in open-flow type, the valve will have good stability; on the contrary, when the medium is the in closed-flow type, the valve will have bad stability. Double seating valve has two spools, upper spool is in flow-closed while the lower spool is in flow-open. Thus, when in small opening working situation, the flow-closed type spool will be easy to cause vibration.

7. Why double sealing valve can’t be used as shut-off valve?
Double sealing valve can have large differential pressure, but its highlighted shortcoming is leakage problem caused by the poor contact between the two sealing surfaces. If it is used for cutting off occasion compulsively, obviously, it would have bad result.

8. What straight trip regulating valve has poorer anti-blocking performance than rotary valve?
The spool of straight trip regulating valve is vertical throttle while the medium flows horizontally. Therefore, it will make the flow path complex (shaped like inverted "S" type) and result in many dead zones, providing a space for the medium precipitation and causing blockage over time. Different from straight trip regulating valve, the throttling direction of rotary valve is same with the medium, easy to clean away dirty medium. Also, simple flow path and small media precipitation space will make rotary valve have good anti-blocking performance.

9. Why straight trip regulating valve has small stem?
It involves a simple mechanical principle: sliding friction is big while rolling friction is small. When stem of straight trip regulating valve moves ups and downs, compressing the packing slightly will make a very tight package on stem and have a great backlash. To this end, valve stem is designed to be very small so as to reduce backlash.

10. Why rotary type valve has large cut pressure?
Rotary type valve has large cut pressure. This is because the resultant produced on the spool or valve plate by media has a small torque influence on the axis of rotation, so it can withstand greater pressure.
Common Valve Problems 2