10 replies to this topic

[curious]

Hi all,

How do I select which Pipe Schedule to chose for a given pipe dia to read off the wall thickness?

for example, for size of 24, u have 2 options of either schedule 5S or 10S with each having different wall thickness. how do I know which schedule to use?

thanks heaps!

[Paul S]

Well since there are many uses for pipe, a little more info about what you are asking may be needed to help you!

[SSmith]

Wow.

[Paul S]

I am even more in awe now that I see that in one of your posts you state that you have a Masters in Mechanical Engineering! What are you asking?

[mechie_aggie]

The wall thickness is calculated based on your design pressure inside the piping and corrosion allowance. You can get the procedure to calculate wall thickness in ASME B31.1 (Power piping) or ASME B31.3 (Process Piping) which ever applies to your current job. Apply suitable corrosion allowance on the calculated wall thickness depending upon the nature of the service inside the pipe.

Once you have calculated the above, you should select the nearest (towards the higher side) pipe schedule from your schedule tables.

Hope this is what you wanted to know.

[Supe]

The wall thickness is calculated based on your design pressure inside the piping and corrosion allowance. You can get the procedure to calculate wall thickness in ASME B31.1 (Power piping) or ASME B31.3 (Process Piping) which ever applies to your current job. Apply suitable corrosion allowance on the calculated wall thickness depending upon the nature of the service inside the pipe.

Once you have calculated the above, you should select the nearest (towards the higher side) pipe schedule from your schedule tables.

Hope this is what you wanted to know.

Of course if you want to get really fancy, you can factor in permissible undercut, too. That one's become an interesting topic around the job site as of late with our AI's with all the min wall pipe being ordered...

[mechie_aggie]

Of course if you want to get really fancy, you can factor in permissible undercut, too. That one's become an interesting topic around the job site as of late with our AI's with all the min wall pipe being ordered...

I guess you are talking about mill tolerance.

[Supe]

I guess you are talking about mill tolerance.

Quite a bit of our high dollar pipe is ordered based on minimum wall thickness rather than typical wall schedules (large bore power piping).

[mechie_aggie]

Quite a bit of our high dollar pipe is ordered based on minimum wall thickness rather than typical wall schedules (large bore power piping).

Yes, I think that is generally the case for ID based piping. In one project, I was designing boiler feed water piping and operating pressures was 150 barg on the BFW pump discharge. We used A106 Grade C material for the application, and we just used the minimum wall thickness as the basis.

[mizzoueng]

B31.1 does not actually require you to include corrosion allowances in the MWT calculation, is it recommended, but not required.

B31.3 may be different, I have not read that code yet cover to cover.

Also, 24" pipe comes in more MWT than 5S and 10S, wait, where did OP go?

[Paul S]

I guess I must apologize for my response since I appear to be out of line. There are all good answers here and I am curious if the OP resolved the issue?