Double Piston Effect and Single Piston Effect 6

[bmoorthy]

Just came across the following terms

1) Double Piston Effect
2) Single Piston Effect

This terminology is used by European Ball Valve Manufacturer and use this a marketing tool and claim various levels of superiority over other valves.

Although i understand the concept of Duble Piston Effect, i am not able to understand the rationale of single Piston effect.

None of the valve standards (Including API, ANIS, ISO BS) seem to describing this trait and yet this seem to be the prime parameter in selection of a type of valve.

Question 1:

Under what circumstance would some one prefer Single Piston Valve over the double piston Effect Ball Valve


Question 2: Is the floating valve design always Single Piston Effect valves

Question 3: Is turnion type Ball Vlave always Double Piston effect valve

Question 4: Where can one get an animation of SINGLE PISTON EFFECT AND a comparision with Double Piston effect.

 

[hydtools]

Williams Valve Engineeering has a description of both effects in this document.

http://www.cesare-bonetti.it/Catlgs/HTB - WVE ball valves/B 05-20.pdf

Ted

 

[277Peter]

You can also find a very good description of both single and double piston effect in the Velan API 6D ball valve catalogue

http://www.velan.com/products/pdfs/vel-bv6d-web.pdf

Good luck

:-D

 

[BValve]

Hi Bmoorthy,

To respond to your 4 queries:

Question 1: Single piston is usually the standard design for trunnion mounted ball valves. It works in one direction only.
Trunnion mounted valves having in most of cases two seats, overpressure between upstream and downstream seats (body cavity) shall be released, in case of thermal expansion for example.
Single piston seat being pressure energized in one direction only, will automatically release overpressure.
Double piston effect seats are pressure energized in both direction. They will not release valve body cavity overpressure, a pressure relief design shall be added then.
However, double piston effect seats offer valve sealing redundancy.
If upstream seat fails, downstream seat can still insure valve tightness. Interesting in specific applications (high integrity required) or for some pipe testing issues during construction.
Finally, you can also combine on valves having two seats, single and double piston effect designs.

Question2: No piston effect for floating valve design. Seats are usually locked into their respective pocket, ball is floating against one or other seat upon flow/pressure changes.

Question 3: No, trunnion mounted valves are usually single piston effect type as standard.

Question 4: hydtools and 277 Peter already provided illustrations.

Regards.