Double line with check valve and ball valve for Spill over system in tank

[VladimirWH]

Hello!
I'm piping designer and preapre P&ID.
So,I made spill over system with check valve but customer want to add ball valve in parallel line,and now it looks like double line one with cheack valve and another with ball vavle. Tank - 0,6 m3, atm. press., methanol. I can't understand why need ball valve?

 

[1503-44]

I dont know why you need a check valve. Once something "spills over" it is probably not coming back anyway. A designer should know the purpose of what he/she is trying to design. Suggest you ask someone that knows the details about that. We don't.

Reality used to affect the way we thought. Now we somehow believe that what we think affects reality.

 

[LittleInch]

I can't understand either as a description like that is about 5% of the information needed to make a response.

A snapshot oft he P&ID MAY help, but we're not the process engineer - Ask him or her would be much better.

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

 

[VladimirWH]

A snapshot oft he P&ID MAY help

Here snapshot

 

[1503-44]

Like I said.

Hard to imagine why you need spillover to go back into that vessel, especially from a drain. If you use it, put a lock closed device on it. And Why is there a valve without a check valve on the low drain. Seems to be somewhat inconsistent requirements. They want to be able to introduce drain vapors into the tank? Really? Very strange.

And Please ask your process engineer to reconsider the need for it. Looks like a no, but we can't be sure.

Reality used to affect the way we thought. Now we somehow believe that what we think affects reality.

 

[georgeverghese]

With the limited info provided, the ball valve is probably for reactor maintenance isolation from the drain system. It should be a normally locked open valve and should be marked so on the PID, since it has HSE implications. If you have some concern of backflow from the drain system, the check valve should be in series and upstream of this ball valve. If there is no backflow concern, then delete the check valve. A check valve is NOT an isolation valve.