Piston type valves 1

[BRIS]

A specification for control valves on water pipes (600mm to 800mm dia) working to control flow into a tank with up to 100m upstream pressure (cavitating conditions) calls for "Piston Type Valves" (this refers to valve type not the actuator type). What is a "Piston Type Valve" ?

For this application I would expect to use a ported sleeve valve with anti cavitation gage.

 

[europipe]

Maybe a ramtype?

http://www.strahmanvalves.com/Front_End/Product.asp?ProductID=56&ProdLineID=28&CategoryID=2

 

[dcasto]

Water doesn't cavitate very easily unless you have high temperatures or vacuum.

I'd guess that the piston type means a plug and seat valve (globe) versus a rotary valve.

 

[JimCasey]

Could mean something like the Cla-Val products.
They have a Y-Pattern body, Cage, and a free piston. The volume above the piston is controlled by a pilot valve. Depending upon the nature of the pilot the valve can perform different functions.

Piston valves such as this have Fl values in the mid .9s so they are more resistant to cavitation than an equivalent size (but tiny fraction as costly) butterfly valve.

 

[UNSR60001]

It never ceases to amaze me the denominations that people use for valves, it seems that people out there just pick arbitrarily names to describe valves or they use a non technical dictionary to traduce a valve name into English.

Fortunately the valve industry in America is well developed and has standardized on generic names for all types of valves.

A piston valve has its rooters in a piston pump and later developed into a valve.

Today this design, originally developed in 1922, by Richard Klinger who invented the piston valve by replacing the disk and seat of a conventional globe valve with a cylindrical piston and two resilient, replaceable sealing rings.

To my knowledge the above design of Piston valves are not manufactured above 12" (300mm.)

In waterworks sometimes Plug or Cone valves are referred as piston valves. The most recognize manufacturer for this type of applications is Henry Pratt, they make both a Cone and a Plug valve. Although in my opinion their Cone valve is a plug and their Plug valve is relay not a True Plug, but more like a C-Ball Valve or you can call it a C-Plug.

http://www.henrypratt.com/

BTW: Ram Type Drain Valves or any type of drain valve design are NOT used to supply a tank. That is why they are called "Drain Valves". Further more I can not imagine a tank that would require a 24" Drain valve, not to mention a 32" one. Not to say that there are not 24" or larger drain valve's out there, but the applications are very rare. In the old Crane Valve catalog they had Y-Pattern globe valves in a drain design, all the way up to 36"

 

[BRIS]

Thanks for the responses.

By tank I mean reservoir. The pipeline is a major trunk main for water supply. The valve controls flow into the reservoir under high upstream pressure. We do have cavitating conditions. From the response it would appear that the specification we have is a cut and paste job.


I don't have a problem selecting an appropriate valve - now that I am convinced that I can ignore the specified "piston Valve"

 

[terje61]

Hi Bris,

Quite often 'axial flow control valves' are referred to as 'piston valves', because they have a piston moving inside the valve body. The advantage is that the flow does not need to make several turns inside the valve. This makes quite some difference compared to the globe style control valves, especially in severe service (e.g. cavitation, erosion, high pressure drops). They are also available in larger sizes.

Regards,
Terje

 

[caihui]

I think the piston it's same function as the by-pass valve to reduce operation torque.