Actuator Operation û Without Power Supply.

[BRIS]

We have a major water pipeline (diameters up to 2.0 m (10 ft)) crossing mountainous terrain. We need to install automatic shut down valves which will close in the event of a downstream burst. The valve must detect a high velocity and close automatically. It must operate automatically without electrical power and with only infrequent maintenance.

The water is raw water with a high biological content so small pilots are not acceptable..

My first thoughts are for a knife gate type valve with a water filled hydraulic actuator. The actuator would trip by an actuator drain valve opening from a paddle flow switch in the main pipeline. Once the valve closes it will remain closed until an operator opens it manually. We will need a small diameter bypass around the valve for pipeline refilling and equalizing of pressure before the knife gate valve can be opened.

I am sure that this must have been done before but I cannot find any examples.—any suggestions on where to look before I go on re-inventing wheels.

Brian

 

[BRIS]

further to above - it has been suggested that I use a butterfly valve actuated by a weight which is tripped on high flow by pressure tappings on a downstream orifice. This does not sound very practicle to me for large diameter valves.

If we do have a burst/pipe failure situation velocity through the valve will be som 12 m-sec.

Any comments/ideas.

Brian

 

[MortenA]

An associated remark: Your system is going to see a lot af water hammer/cavitation problems - but I guess you are allready aware of this.

Since pilot are out of question i dont have anything that might help.

Best regards

Morten

 

[zdas04]

How about an idea that is so far outside the box that it isn't clear there really is a box?

Could you transfer some of your pumping-station power to the remote valves by putting a small (capacity, big diameter), low speed turbine in the line at the valve? Use the turbine to generate enough electricity to charge batteries to drive an electric actuator on a knife valve, gate valve, or ball valve (anything that gets out of the way of the flow, I wouldn't put a butterfly valve in this service). You could sense overspeed on the turbine for your failure condition.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

 

[BRIS]

MortenA and Zdas04

Thanks for your response. Cavitation will occur but since this is an emergency closure situation it is acceptable. I have to control the rate of closure to control waterhammer - no point in blowing up the upstream pipeline in trying to protect the downstream pipeline.

The pipeline is gravity fed from a dam - we have already specified reversible pumps as turbines in locations where we have high head losses. The locations we are looking at now are where the pipeline crosses deep valleys. Pressure at the bottom of the valley is some 40 Bar. The areas are rural but valley bottoms are heavily populated. Under normal operation we have no excess head and no energy to lose.

 

[frankeng9]

Hi BRIS,

What you are basically describing is a device called a "Velocity Fuse". I don’t believe I’ve ever seen anything in the size or capacity that you need, but a quick search on google produced 826 references. Start there and you may find someone or learn how to solve your problem. Good luck!

 

[BRIS]

Frankeg9 - thanks for the terminolgy - I quess it would take an electrical engineer to give me the word fuse.

Cheers Brian