looking for "constant volume" valve

[maxmech]

i'm looking for a valve that doesn't change the volume of the system on activation (i.e. which prevents hydraulic shock), can be operated remotely and has short activation time
i'd use ball valves but their pressure/temperature charts are unsuitable
also i've heard of some kind of piston valve there the stem is located in the middle of piston - this valve is better solution (at least simple) but i don't know the name

any suggestions?
thanks

 

[ALEXFV]

MaxMech:
IMHO, selection of a valve depends on basically 8 parameter (there's more of course, but these could apply on the majority kind of valves):
Type. 2,3 or 4 ways
Operation: NC, NO, universal, on/off service, modulating service, etc.
Medium: Oil?, water?, gas? other?
Size. (Diameter connetion type)
Presure(maximum, minnimum, normal or differential)
Atmosphere (explosive, general purpose, corrosive, etc)
V: Voltage, in case you are using solenoid valves or motorized valves
Extra: Temperature, vibration, special materials, etc.

As large as I can see (you must have to include more information!!), maybe you are looking for a 2ways/2position, normally closed valve. Depending on your specs., you can try with series 8290 os ASCO. This is a piston valve, very very reliable. Is a battle-horse.

If you send more information (please follow above suggestions) of your application I will be pleased to help you.

Regards.

 

[maxmech]

thanks for advice, Calfersoporte
you've mentioned very important parameters but for now i'm rather looking for specific types of valves than specific models

i've checked ASCO's 8290 but they seem not a "constant volume" valves
this property is the main property i'm looking for

thanks again

 

[sailoday28]

What is a constant volume valve?
In "hammer" problems, time of opening/closing is significant.
In a simple length of fixed ID pipe, if sound speed*time of opening/length <2 for small temp and highly incom fluids, there should be small if any hammer.

 

[maxmech]

Sailoday, you've opened my eyes saying hammer is connected with closing time, many thanks

hammer happens only then valve closed while fluid is moving
so i think i've used the term "hydraulic shock" incorrectly
sorry for mislead

seems i need to somehow describe the problem
i have a pump and two valves (for fluid input and output)
pump is filled with fluid and pumping it out by piston
then it reaches the end the pump is stopped so fluid don't move
after that the output valve is closed so pump can take new fluid from input
common piston valve closed by inserting it's piston into fluid
thus the valve displaces the fluid with piston's body and the volume of fluid trapped between the pump and the valve is increased slightly
because of low fluid compressibility i've got strong pressure leap here

that is why i need the valve which would have a constant volume of steel and fluid in it's internal chamber

 

[sailoday28]

MAJOR CORRECTION to my pr4evious post.
In a simple length of fixed ID pipe, if sound speed*time of opening/length >>2 for small temp and highly incom fluids, there should be small if any hammer.

NOTE the ">>" correction.
A long line with a "seemingly"relatively slow closing valve can cause significant hammer problems---- IF

sound speed*time of opening/length <2

 

[MikeHalloran]

You've probably already figured out that you need a "shear-seal" valve.

http://www.barksdale.com

Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA