NPT Thread Pressure Rating Calculation According to ASME B31.3 Code

Maffoud....

NPT or National Tapered Pipe Threads are NOT pressure rated like ASME flanges.

The experienced pipe fitter simply ensures that he has a well cut pipe thread, removes metal burrs, uses a lubricant (or PTFE pipe tape)....then snugs up the joint. Because these are tapered threads, once the joint begins to engage, it quickly tightens in a fraction of a turn.

Cutting threads in pipe requires a Schedule 40 or higher rated pipe. Schedule 10 or 10S piping is not suitable.

The pressure rating of the system us determined BY THE THREADED FITTING..... NOT BY THE NPT JOINT.

More information can be found in Wikipedia under NPT pipe thread.

You do have an experienced piping engineer to answer your questions in your organization ..... right ?