Pipe EOL....

[mashjones]

I am looking for a little validation on this as I haven't thought of it this way. So you use CA, mill tol, pressure, etc to calculate a required thickness per B31.3. Using this you select a schedule that has a nominal thickness. An API inspector is telling me that end of life for the pipe would be nominal - CA. From this you can then perform FFS API579 techniques to extend life if so desired. Seems to me like this could lead to premature replacement. Particularly if you do not have beginning of life UT readings to know pipe thickness from the mill. Ideas, thoughts on this would be apreciated.

Regards

 

[StevenHPerry]

Ask the inspector what he would do with 12" sched XS (0.5") that comes in 12.5% under from the mill but was designed with a 0.05" C.A..

- Steve Perry

http://www.linkedin.com/in/stevenhperry

 

[Berndt]

The way I have it is that FFS would only be called upon if the remaining thickness is less than the minimum specified by the code of construction.

Your inspector seems overly conservative.

 

[ferdy]

When you design by B31.3, you have a design thickness for the pressure at the operating temperature, then you add the CA if you have, then you goes to the nominal thickness from where you multiply by 0.875 to have the useful thickness for your pipe, so, you have enough thickness for many years of operation, for this reason many projects do not take in account the CA because normally is minimal regarding the 0.875 nominal thickness.

 

[StevenHPerry]

Ferdy,

The approach you describe sounds like a bet that corrosion/erosion will never appear when the mill delivers the minimum wall allowed per specification.

Murphy is betting against the projects which take this approach.

- Steve Perry

http://www.linkedin.com/in/stevenhperry

 

[dcasto]

You have the beginning mill thickness, it's 87.5% of the published thickness. Next, you don't use the corrosion allowance, because during the testing, you are looking for an actual corrosion.