SSV closing time 1

[godel123]

hi
What is the maximum time expected for SSV to close (by de-energize the hydraulic control of actuator) ?

 

[LittleInch]

By SSV I think you mean sub surface valve?

Closure should be around 15 seconds?

No more than 30.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

SSV = surface safety valve ?

On a hydraulic actuator, time to close is much better than for an air operated valve - it also depends on the size of the return hydraulic line - if there are many SSVs' and they all close at the same time, then closing time would be slower than for a single SSV only. If you have a slow closing SSV, then one of more of the return lines or the return manifold may be the bottleneck.

 

[godel123]

ssv : surface safety valve

15 s : is there a standard or is it a best practice or a company specification ?

 

[georgeverghese]

Little Inch , Godel123

In the absence of a company standard:

For an air op SDV, typical closing speed is about 1inch to 1.5inch of nominal size per second, so would guess that for a single acting, fail close SSV, you should get approx 2inch of nominal bore per sec or better.

So, for an SSV on a 6inch line, closing time = 3sec or better.

 

[godel123]

it's a hydraulic actuator
the distance between the Christmas Tree and the control-panel is 50 meters

 

[LittleInch]

Gödel,

Now we know valve you're talking about, no, there is no set figure AFAIK, only guidelines and perhaps company standards and targets.

The oft quoted 1 inch per second is just a guide. 50 m of tubing - closure will depend on tubing size and size of the return spring, but max time for say a 6inch valve 10 to 15 seconds. In reality most of the time it would be probably about 5 or less.

I got a 16" class 600 ball valve to close in 3 seconds to 5 seconds - needed two air ports and a BIG spring, but it did it.

Why are you asking??

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[godel123]

Thank you for your answers.
as we only have values ​​without Reference to any standard , i'm looking for a document that gives an explanation.

 

[LittleInch]

Each case is different so there is no document.

If it is safety critical that your valve shuts in 2 seconds, then you design it to shut in 2 seconds. If 10 seconds doesn't result in significant safety issues then it is more economic to design it to shut in 10 seconds (smaller tubing, smaller springs, less complex electronics etc etc). Taking 30 seconds or 60 seconds to close defeats the point of having the valve. All highly variable.

Not everything is prescribed in a standard or design code.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

A 50m long return header can result in a slow closing SSV if it isnt sized correctly. Directionaly speaking, increasing return header size by 2nominal sizes up or so may give you a much better closing time. Run some pressure drop calcs on this return header with the required closing time and then you'll see where and what needs to be done.

 

[godel123]

there is also a maximum velocity of the expansion of the spring when closing the valve, which is insured by limiting device in the control panel

 

[georgeverghese]

Yes, use the max oil displacement rate from the sum total of all actuators that could be activated in the pressure drop calc, and also use the max viscosity of the oil at the lowest ambient operating temp.

 

[godel123]

thanks for all