Pressure rate for welded steel pipes - SCH40

[sowhatso]

In the past I asked a question about the difference between the schedule and the Grade for the steel pipes,
The answer was:
Schedule is associated with the pipe thickness whereas Grade is normally associated with the material (For Example 8"nb Schedule 40 - Materials API 5L Grade B)

My concern is about the PRESSURE RATE, is it defined through the schedule (for example SCH40) or is it defined by the material grade as (API 5L Grade B). How can I get the pressure rate for welded steel pipes of SCH40 by the schedule information itself or by the material standard (API 5L)???

 

[SNORGY]

Pressure rating is defined through consideration of *both* schedule and grade, since the available thickness directly impacts hoop stress and the "grade" correlates to allowable yield strength and, by association, basic allowable stress in tension.

Be careful about the "rating"; it might or might not account for mechanical thickness allowances and fabrication undertolerances. It is a calculated number.

Regards,

SNORGY.

 

[AllHandlesTaken]

The "pressure rating" is also highly dependant on temperature (and to reiterate, Schedule & Grade as well) - metal strength decreases at higher temperatures (you may also want to look at brittle fracture if low temperatures are involved).

The correct way to get a piping "pressure rating" is to apply the rules of the applicable piping code, for example ASME B31.3.