Actuator:Sluice gate

[PersianEng]

Hi there,

We are specifying 84" x 144" sluice gates in one of our projects and we expect very high torque and thrust required for the actuator to pull up the gate under a head of 40ft water. What type/brand of electric actuators do you suggest?

Thanks

 

[unclesyd]

I would take a look at the Limitorque Company, now part of Flowserve.

http://www.flowserve.com/eim/Products/HeritageBrands/Limitorque

 

[leecoop]

PersianEng,

Have you considered a hydraulic piston actuator? Or does the spec require electric?

 

[Ashereng]

It may help is you gave the torque needed for the actuator, and also opening/closing speed.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[leecoop]

Ashereng is right. Speed can be an important spec. Electrics usually operate at only 12-15" per minute. If this stroke is 144", it might take 10 minutes to open. Likewise, if there is a power failure it may be necessary to maintain control of the valve. A hydraulic accumulator can handle multiple strokes after power is lost. This accumulator would push fluid into the hydraulic actuator.

However, hydraulic actuators can be tall. If there is a height issue, electrics may be the way to go.

 

[PersianEng]

Valid point. However we do not know the actual operating speed and only know that it does not have to be fast; since the gate is operating rarely upon plant shut down or startup.

Hydraulic actuators are not allowed in most water treatment application because of the possibility of contamination and housekeeping considerations. Therefore we are bound to use electric actuators.

 

[Ashereng]

If there is no need for speed, then almost any actuator can be geared to do the work.

What actuator are you using now?

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[leecoop]

If hydraulic fluid is not acceptable, you could also use air.

 

[PersianEng]

Ashereng,

I see what you are saying; that's true.Thanks.

aticooper,
Air is clean but the air cylinder to handle huge thrust load has to be very big.

 

[leecoop]

PersianEng

What is the thrust required?

 

[JimCasey]

The height of the cylinder actuator (either pneumatic or hydraulic) will be within inches of the height of the electric actuator.
With the valve open, the lead screw will have to pass through the electric actuator and stick up into the air. (probably inside a fixed protection tube)
So you can have a 144" stroke cylinder, or a 144" long ACME- threaded actuating screw.

A pneumatic cylinder will presumably run on your plant air system, so typically that means you can have 80 psi you can count on.

A hydraulic actuator typically draws from a 1500 psi system,
So the relative areas of the pneumatic vs hydraulic are almost 20:1 (or a 4.3:1 diameter ratio, neglecting the (important) cross-sectional area of the actuating rod)

If you need fail action, you can use a pneumatic accumulator about the size of a tank car, or a hydraulic accumulator which would be much smaller, or you could use an electrical failsafe which would be basically batteries and an inverter, and comparatively quite compact.

 

[abscott]

PersianEng
I agree that hydraulics are a housekeeping problem but that relates to "hydraulic systems". One option you may want to consider is a hybrid unit where the controls and power to the unit is electrical and the actuator is a sealed self-contained hydraulic unit. Check out

http://www.rexa.com

Regards,
ABScott

 

[ScottyUK]

abscott,

We're fitting a Rexa unit to one of our gas turbines as a trial replacement for the pneumatic IGV actuator. Do you have any experience of the Rexa products? I'm looking for any operation pitfalls or weaknesses which Rexa clearly won't be publicising.

----------------------------------

I don't suffer from insanity. I enjoy it...

 

[abscott]

ScottyUK

We mount them on large globe valves for power plants and pipelines where large pneumatic actuators do not provide the precise control necessary. They are expensive -- but provide very accurate control. We haven't had any problems as far as I know.
Regards,
ABScott