hydraulic positioner

[leecoop]

Has anyone ever used a hydraulic positioner for a control valve? Does anything exist?

 

[dcasto]

Are you talking about a valve postioner, like a Fisher Type 3582, or a hydraulic valve actuator Fisher type 350?

 

[leecoop]

A 3582 is for pneumatic actuators, right? I am talking about a positioner for a hydraulic actuator.

 

[pipehead]

Hydraulic actuators are fairly rare and I don't believe I've seen a positioner on one. That said, the unit would serve the same purpose of feedback to the control loop and the ability to not rely on benchsetting the actuator. I use to not spec postioners until I put in a "tight" seal (low packing loss) valve. The hystorisis (sic) was terible, the valve jumped everywhere. The positioner cured it.

 

[ScottyUK]

Hydraulic servos are pretty common in the power generation industry for modulating duty on governors, MSV's and reheat valves. They're also used on valves off the tubine itself in similar applications where a modulating valve is required with very high force, good accuracy, and long service intervals.

One of the more common servo valve manufacturers is Moog. Their servo valves are often seen married to third party cylinders from the likes of Rexroth, Vickers, Parker, etc, although they also produce their own cylinders.

http://www.moog.com/Industrial/

Feedback to close the loop is usually from an LVDT or a magnetostrictive transducer on the cylinder, while the servo controller itself could be either an OEM product embedded within a larger control system, e.g. Emerson's QVP card for their WDPF DCS system, or a stand-alone item from the likes of Moog.

If you are looking for a self-contained package more akin to a traditional valve positioner, have a look at Rexa's offerings. If you give it electrical power and a demand signal it behaves much as a positioner. Failure modes to mimic OAF / CAF / stayput can be designed in as required.

http://www.rexa.com

Finally, forum1083 is probably the best place for your question - get some advice from real pro's instead of me!


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Sometimes I only open my mouth to swap feet...

 

[hydromech]

Backing off slightly from servo valves, you can use proportional valves to get the same result at less than half the cost.

Servo valves have a faster reponse time and lower hysteresis than proportional valves. But if the system is closed loop and the position of the hydraulic cylinder is known, a good proportional valve will do the job.

It will just achieve the correct position slightly slower.

Adrian

 

[terje61]

Hello Leecoop,

Valcontrols from Denmark produces medium independent positioners for the oil and gas industry. See

http://www.valtor.dk

- Control signal is 4-20 mA.
- Valve position feedback to positioner is 4-20 mA.
- Output is 2x 24 VDC (1 solenoid to open / 1 to close)
- Power supply is 24 VDC

M.v.h.
Terje

 

[ScottyUK]

Forgot all about BTG who now appear to be part of CCI these days. Have a look at:

http://www.ccivalve.com/pdf/638.pdf

We use something similar from the BTG days which is reasonably good at its job. It lacks the finesse of the precision servos on the turbines but costs significantly less too.


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Sometimes I only open my mouth to swap feet...

 

[Haeggen]

Hello Leecoop

The CCI Smartrak solution is as close as you can get to a "hydraulic positioner".

See link

http://www.ccivalve.com/pdf/877.pdf

for more info.

BR
Mathias

 

[CToft]

Hi Leecoop

I'm an employe at Val Controls in Denmark. We manufacture and sell a lot of hydraulic positioners.

Our main focus is the oil and gas industry and in the oil and gas industry they use a lot hydraulic actuators.

We manufacture Hydraulic positioners for both Offshore, industry and Subsea. And are able to deliver positioners certified to EEx i or EEx d.

So if you are looking for a positioner for a hydraulic actuator, please give me a call.

Best regards
Carsten Toft
vc@valcontrols.com
Tel. +45 75470600