Need Pilot Scheme for Hyd. Cyl. actuated PR Ball Valve

[jawilke]

Subject: Pressure Reducing Ball Valve with Hydraulic Cylinder Actuator.

Industry: Potable fresh water at 100 psig upstream to 40-50 psig downstream.

Looking for: Hydraulic Cylinder actuation pilot schematic.

Background: Existing valve is a 12" throttling full port Ball Valve in a municipal potable water application. (typical wet dirty vault - cramped for room) Existing actuator is a Limitorque motor actuator, manually adjusted through remote SCADA control. Valve has terrible control due to large BV size relative to the flow rate and pressure drop.

A 16" globe style pressure reducing valve would be perfect for this application, but there is no room to install the new vault such a large valve requires.

So... I'm brainstorming using a 8" V-Port Ball Valve which has excellent Cv range and pressure control capability for this application, but due to the continuous modulating function, and the high probability that electrical power will fail, I am looking a ways to use a hydraulic cylinder actuator, powered from line pressure just like globe style pressure regulating valves (PRVs) do. We do not want pneumatic or electrical battery backup systems due to their maintenance requirements and the valve location.

So, I am looking for a trustworthy pilot system for hydraulic cylinder actuation which would mimic the funtion of a continuously modulating globe style PRV. Has anyone seen this done? If so, how?

- Jim

 

[abscott]

jawilke,
Check out web site rexa.com. They make self-contained electro-hydraulic rotary actuators that provide very accurate control. If they can provide an actuator with enough procision you may be able to drop a new actuator on the existing valve. Good luck.
Hope this Helps,
ABScott

 

[jawilke]

abscott,
I already considered REXA but as I wrote in my introductory problem statement, if the electrical power fails, the REXA would stop working until poer is restored and my system could be over or under pressured in big hurry.

 

[JLSeagull]

I thought about Rexa too. However Rexa requires power. It does not meet the "self-contained regulator" type requirement. Many globe style valves are available in a self-contained arrangement. I think that they are typically in gas service instead of water. Contact your valve sales woman to discuss this application.

 

[EdDanzer]

You may be able to do this with a cylinder with a bore to rod ratio that uses the pressure difference and orifices to modulate the valve.

 

[abscott]

jawilke,
How much room do you have? This may be a design & build to order application.

The US Navy did use water operated valves in the reactor systems of the nuclear submarines but I don't remember who made them.
abscott

 

[terje61]

Hello Jawilke,

I used the following method for a similar application:

1)
The hydraulic cylinder had a piston rod that went through the cylinder cap, to make sure that the volumes were the same on both sides.
2)
The inlet pipeline pressure is connected to two solenoids. The first one to the top of the cylinder. The second one to the bottom of the cylinder. The solenoid 'vents' go to the downstream piping.
3)
To control the cylinder you can buy stand-alone positioners. I used an Orange positioner (

http://www.orangeinstruments.co.uk).

Input is 4-20 mA and 24 VDC power. Output is 24VDC to the solenoids.
4)
To know the actual position of the valve you need a feedback mechanism like a potentiometer or LVDT. The resulting output is also connected to the positioner.

Attention points:
- The size of the solenoids determine the speed of the valve and the accuracy.
- You need 24 VDC power on the positioner
- My project was with oil, yours is with water, which is much more difficult. I have no experience with solenoids and actuators suitable for water.
- The pipeline pressure you have is very low for hydraulics. This means that the size of your actuator will probably be very big. You might reconsider if this is what you want.

Good luck,
Terje

 

[jawilke]

terje61,

Our application can only use system water pressure acting through hydraulic pilots. This is exactly how water utilities control globe valves for water pressure reduction.

No electrical. No pneumatics. No stored energy of any kind.

- jawilke

 

[terje61]

Hi Jim,

It took me a while to understand that you are looking for a water pressure regulator. (I hope that this is indeed what you are looking for).

These regulators normally only work on pressure balanced valves because of the very small available actuation forces. I do not think you can make it work in a ball valve, because of the large forces necessary.

What is the CV you need and face to face dimension you have available?

Terje

 

[EdDanzer]

If you cannot find an off shelf solution we may be able to assist in designing a system to meet your needs.