TWP & BWP - Pipe Level

The abbreviations I've usually seen are BOP, COP, and TOP; for bottom/center/top of pipe. I don't know what your W stands for, but it might be for "wrapped" if the pipe is insulated and you are measuring to the outside of the insulation rather than the pipe itself. It is best to ask whoever did the drawing, because such abbreviations may not be uniform world-wide.

I am just guessing but I think the "WP" may mean "Work Point".

I have no idea what the "T" and "B" mean.

Check on the DEOTD.

_{Drawing Explanation of Terms Document.}

I agree with pennpiper. The "PFI" defines workpoint. I guess t = top and b = bottom. When laying out pipe, we will use TOS (top of steel), BOP (bottom of pipe), WP (theoretical center line intersection) and invert for burried pipe. But, any sort of configuration will be out there, and one must investigate the company's standards.