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I have a P&ID that shows a spec break at the control valve. The control valve is 150# CS and it is connecting to a 300# Inconel spec. In my short piping experience, I always see the control valve to be the higher rating. Any suggestion on how to make this work without changing the CV because it has already been purchased.
I suggest you talk to the Instrumentation Engineer and point out that he (or she) now needs to spec and purchase a Pressure Safety Valve to protect the Class 150 material that will be required to fit-up to the "out-of-spec" control valve.
Someone needs to find out who made the mistake that resulted in the wrong flange class on the control valve.
Also:
A DCN (Design Change Notice) package needs to be created for review by the Project Manager and the Client before any real action is taken.
- The P&ID needs to be marked up to show the new PSV and the additional piping
- A sketch of the new (more complex) configuration needs to be made
- A material take-off needs to be done and given to the Estimators
- A cost analysis needs to be done on the total impact of these new requirements
- A cost comparison needs to be evaluated between the cost of returning the class 150 PSV and the cost of the new PSV and additional piping
Now get the Project Manager and Client approvals
Thanks JOP
Just curious, how did you resolve the problem?
Jop,
First, our process people designed the line to be 150# and our instrument engineer prepared the requisition for the 150# CV. But during client review of the P&ID, the client decided and marked-up the P&ID to have the spec break, 300#, after the valve, which is after we issued the PO for the 150# CV.
We asked and got approval from Client to use a 150# flange for a 300# spec only for that connection.