check valve (FSV) as safety device in API 14C

[Lean Process]

Hello.
I am looking into safe design of an offshore heating medium system using combustible heat transfer medium heated in a power generation turbine exhaust duct.
API 14C recommends a single FSV in the heating medium line downstream the Exhaust-Heated Component, to prevent backflow of combustible fluid into the exhaust heater chamber in the event of tube rupture.
In my experience as a process designer in the North Sea, a single FSV is considered to limit backflow only in an operational context. In the safety context I have specified two dissimilar FSVs in series as primary overpressure protection with a PSV as secondary protection. In this case I have further assumed that when a demand is placed on the FSVs, they will leak at a rate corresponding to 10% of the cross sectional area of the pipe in which they are installed.
In my experience as a process support engineer I have never come across a performance standard for regular verification of FSVs, such as would be applied to ESD valves in hydrocarbon service.
So now I am inclined to specify an ESD valve in the heating medium line instead of FSVs, since backflow of heating medium would risk escalation of a fire event in the exhaust heater chamber.
Any comments please folks?

 

[LittleInch]

Sounds like a good plan to me. I assume you would need one anyway on the inlet side of the tube bundle so another one on the exit is not a big deal IMHO. what size pipe are we talking here and would you add a FSV as well as the ESD or only the ESD valve? I'm thinking about closure speed and activation time for the ESD system to detect a tube rupture and close the valve(s).

I didn't follow the issue about two dissimilar FSVs unless you were talking about a different case.

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

 

[georgeverghese]

You've probably answered your concern yourself : 2 dissimilar FSVs' are preferred when there is a risk of overpressure (and loss of containment) due to reverse flow.

In this case, the loss of containment has already occured with the tube rupture, so you're not really minimising the risk of an overpressure here - all we want to do is to minimise the severity of the potential fire in the waste heat recovery unit.

Adding an SDV on the exit (in addition to the one that would be somewhere on the inlet line) further reduces the severity of the potential fire in the WHRU, but this would be viewed as a supplementary risk reduction device, while the check valve would be the primary.

 

[GasOilEng]

Hi

I want to design a heat recovery system from Exhaust gas of gas turbine ,to heat up oil of hot oil system. can anyone give tips to how size the heat exchanger to be used.
Many thanks in advance for any help.

 

[LittleInch]

Please don't hijack other people's threads. Just start your own one and provide as many details as you can.

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