Gate Valves

Why do you want to change some valves? Bored? Need work for the guys? Have extra money in the budget?

Some explanation of your intent is in order.

Lacking any further information, I would:

1. Ask the maintenance engineer.

2. Ask the facility engineer.

3. Ask your supervisor.

4. Using the same skills that got you here, contact the manufacturer of the gate valve and ask them what the mystery numbers mean, and what you should do. They will sell you the valves and make money, they should answer your questions.

Dear Lyn,

Those valves are leaking. I am confusing about this number, because Class 300 GV dose not need for this work. Thanks for the advice.

Contact the company who will sell you the new valves, or contact three, or more, companies who may sell you valves.

GlobalSpec.com

I don't know what valve you have but it could well be a series 300 control valve....Here's a video demonstrating the proper valve for control operation....↓

http://www.youtube.com/watch?v=mqJ5ppRjmcY&feature=plcp

http://www.henrypratt.com/news/plunger.aspx

What is "MIV"? How high is the dam? At what relative elevations are the various valves located? Are any of them fast-closing?

The "300" probably (but not certainly) means Class 300.

I strongly suggest you call a valve supplier and have a sales engineer visit your site. consulting an internet forum is the wrong place to begin your project.

I know nothing about the operation of such facilities... but... they are not to be trifled with. The power of water is staggering. Get an expert involved.

Why... Read this...

Tilan-

You don't say what MIV means, nor the height of the water source so this is all based on what is normal for other types of piping. I have only toured Hydro Power Stations, not get into the "guts" other than a very intensive guided tour.

Check with the engineers who are responsible for the station.

If no engineers in house, get a consultant on Hydro Power Station piping. Have him look at it.

Check any prints of the plant. These should say on them. They should give some details.

Bring in a salesman or tech rep from a manufacturer or distributor who sells the appropriate size and type gate valves or just size of valve.

The money for outside consultants is well worth the investment!

DO NOT PURCHASE OR ATTEMPT TO DO ANYTHING WITH ANY VALVES UNTIL YOU DEFINITELY HAVE THE CORRECT INFORMATION.

In chemical processing and many other systems the 300 on the side, for the sizes of 1/4" to 12" and maybe above, means that the valve is rated for 300 psi. I include this only as information. As said before I'm not a Hydro Power Station Engineer and not very familiar with them just smaller valves. Get someone in there to help you. If you get the wrong one it will be a very costly mistake, $X,xxx,xxx.00

Good Luck, Old Salt

The questions you are asking, contain only little information, which can be a perfect recipe for disaster if you proceed as is.

A Gate valve is typically designated by size and rating / Class. To know the size, check the isometric drawings, it will have Bill of material which will give you some more additional information on the size and rating of the valve. This will also help you to discuss with supervisor as well as in contacting original valve manufacturer to go for an replacement or upgrade.

High possibility that a 40 year old isometric would have disappeared by now. Fancy your chances.

Post some pictures of installation with perspective.

Dear Mr.Tilan,

In my opinion, it should be the CLASS of the valve, and the Pressure rating will be 150 psi.

DHAYANANDHAN.S

Don't forget that, on closing, there will be a velocity head resulting from inertia of the water.

A gate valve, used as a penstock (inlet for hydro turbine) will need to withstand a very high transient pressure - a shock - when shutting off the flow. That is what determines the class of the valve. An alternative would be to provide a surge relief column.

As I said, this is serious; there are so many things to consider eg. closing the penstock flow can cause cavitation; it happens all too often and is VERY expensive and potentially very dangerous.

What's to cavitate? Hydraulic hammer, maybe.

Confirm that the 300 imprinted on the valves is the valve class; and that at normal room temperatures the pressure rating would be 720 psi.

Your provided numbers for (measured ? ) pressure at the penstock (inlet ? ):

10 bars x 14.5 => 145PSI (This value is dependent on the reservoir height and can vary.)

Your stated MIV (Maximum Inlet Value ? ) at 60 bars yields:60 x 14.5 => 870PSI (If true this would be the maximum expected pressure generated when the reservoir height is at maximum value.)

By your own admission the valve must be capable of safely handling 870 PSI.

Are you sure that these valves are not plug valves? Normally gate valves are not used for throttle control and instead are used for isolation only.

I would strongly suggest you find out exactly what type of valve you are dealing with, contact a major valve manufacturer, provide them with all of the needed, correct information, and follow their recommendations very closely.

More than likely you read 300 WOG?? valve rating is 300 psi and valve is suitable for water, oil or gas.

Simple enough??

Agree.

Tilan,

I EPC hydopower systems. This is not a small question. Please get hydro engineering involved.

Gene

And the commissioning records? Where are they?

And the maintenance records? Where are they?

And the Process Description document? Where is it?

And the Control Philosophy document? Where is it?