Maximum pressure allowed at ASTM A53 SCH40 GR B pipe. 4

[sv879]

Dear Experts,
Does anyone share info about maximum allowable pressure at ASTM A53 SCH 40 GrB pipe?
Is this as per manufactures recommendation? I was looking for such kind of info from manufactures data sheet unfortunately I could not find anything pertains to max allowable pressure. Any help would be much appreciated.

Thanks in advance.

 

[mk3223]

The max allowable pressure of A53-B Sch.40 pipe may be depended on the several factors. such as design temperature, C.A., pipe mill and machining tolerance, as well as the applicable Codes, etc.
The Excel sheet may help to calculate it with changing these parameters with the fixed Sch.40 pipe thickness for the maximum allowable pressure.

 

[LittleInch]

vinod,

As per MK3223, there is no thing as there are too many variables. Many companies create piping specifications and in them define for a particular duty such as fire water, the required pipe schedule for each type of pipe or type of material.

The original intent of schedule numbers was to provide for the same pressure "rating" for each diameter of pipe, but by the time they did this (the 1930's) there were simply too many existing thicknesses as "schedule XX" for this to be able to be implemented. So all they did was normalize and codify the what schedule 40 meant in different pipeline sizes. Here endeth the history lesson....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[sv879]

LittleInch & mk3223, Thank you for your response.
To clarify further, I shall put my question in a different way. Is SCH40 pipe is suitable for a system riser which is constrained by 20 bar static pressure? or SCH80 must be used.

 

[LittleInch]

To answer that you need to define size, material strength and design code being used.

Assuming this is steel and not very big (<12"), sch 40 should be good enough for 20 bar, but there are many issues to be considered.

A very similar question is being asked here at the moment and my response applies equally well. Also for things like risers, the issue of mechanical strength needs to be considered looking at tall the possible forces on the pipe, support loads, clamp locations etc. So sch 40 might be good enough for the pressure containment, but for practical purposes Sch 80 might be preferred. This is more common at the smaller pipe sizes.

https://www.eng-tips.com/viewthread.cfm?qid=447926

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[sv879]

I forgot to mention pipe size, yes it is 6" dia.
How do we substantiate that SCH 40 pipe will suffice the requirement to withstand 20 Bar pressure.

 

[JGard1985]

Choose your governing code...say B31.1 for power piping....

Go to section 104.1 Pressure Design of Components...straight pipe

Calculate deisgn pressure based on Tm (minimum wall) equal to the nominal thickness, using material allowable stress, joint efficiency factor (Probably 1.0) and "A" an additional thickness" of material credited for (grooving, corrosion, threading).




Jeff
Pipe Stress Analysis
Finite Element Analysis

http://www.xceed-eng.com

 

[sv879]

Choose your governing code...say B31.1 for power piping....

Go to section 104.1 Pressure Design of Components...straight pipe

Calculate deisgn pressure based on Tm (minimum wall) equal to the nominal thickness, using material allowable stress, joint efficiency factor (Probably 1.0) and "A" an additional thickness" of material credited for (grooving, corrosion, threading).

Thank you for your valuable input.

 

[DavidCR]

I´d also choose B31.1 (2007) as an aprox. reference point.
For a 6" inch pipe with an arbitrary 2mm corrosion allowance, the required thickness for 20bar at room temp is 4.02mm and 6"Sch40 is actually 7.1mm, so no problem with your pressure with SCH40. Smaller diameter same Sch are safe too and also 10" is safe.

So I´d say no problem with Sch40, the margin is obvious. But I wouldn´t sign it since may be a B31.1 criteria or specific detail that may not be applicable for your case.

Notes:
- Some use the corrosion allowance as a way to get a longer life against internal corrosion.
- Sch may deal with issues on type of joint.

 

[sv879]

Thank you for your comments DavidCR,
I presume that, based on your computation, 4.02mm is without considering the applicable lower limit of manufacturing tolerance at out side dia and applicable lower limits of manufacturing tolerance at wall thickness of sch40 pipe. Could you please clarify.

 

[DavidCR]

Yes, without the CA the required thickness would be 2.02mm.
With a ca of =0, 6-Sch40 holds 1150psi aprox.
With a ca of =2mm, 6-Sch40 holds 810psi aprox.
This is approximate, many variables: check on respective ASTM if mill tol. is 12.5%, allowable stress is still 4.6kpsi on the current code, y=0.4, etc. etc.

As others said it is not an "easy" question, but my point is showing some example B31.1 numbers using an old spreadsheet I had in hand to support you are on a safe zone with Sch40.