7500 PSIG Hydro Test w/ 6M SA-105 Fittings (b31.3 and b16.11)

[swiftworks]

Hello -

We have a piping system that has a design pressure of 5000 PSIG w/ hydrotest pressure of 7500 PSIG (1.5x Design per B31.3).

I am working through understanding the testing tree. The valves and gauges all 10,000# rated no problem, but the tee's and couplings, and plugs are stumping me a little bit. I'm familiar with pipe pressure calculations and how to understand pressure rating of the piping used, but since the fittings are 6M, I just wanted to reach out. My understanding of this situation is explained below. Any advise is greatly appreciated.

I'm understanding this is backed up by ASME B16.11

Paragraph 2.3 - Pressure testing is not required by this Standard, but the fittings shall be capable of withstanding a hydrostatic test pressure required by the applicable piping code for seamless pipe of material equivalent to the fitting forging and of the schedule or wall thickness correlated with the fitting Class and end connection of Table 8 (attached).

https://files.engineering.com/getfi...b7-4d73-4845-8d3d-e551da318d5e&file=image.png

Since A-105 (fitting) strength is 36 Yield and SA106B Yield is 35KSI, A-105 is superior. Therefore you would just run threaded pipe pressure calculations for the NPS of interest.

For example 1 NPS - good to 7783 PSI (design - threaded - shown attached). Therefore the fitting for 1 NPS manufactured to B16.11 would have to be able to support this design pressure. Since our hydro pressure is lower than the design pressure, we're alright. Same would follow for 3/4, 1/2 and 1/4 NPS as long as the calculated threaded pipe pressure is above our hydro test pressure of 7500 PSIG, we're good?

https://files.engineering.com/getfi...3ce-4d8e-a22e-14efba2792be&file=image_(1).png

Thanks,

 

[GBTorpenhow]

You have the right idea, but compare design pressure to design pressure, not design pressure to hydrotest pressure. If the fitting design pressure is at least 5000 psig you are good, design pressure at 5000 psig means that it will support a 7500 psig hydrotest, just like pipe with a design pressure of 5000 psig.

 

[swiftworks]

So a 6M fitting (6000# Design) is good to 1.5x MAWP = 9000 PSIG is what you're saying?

 

[swiftworks]

Like a stamped 6M tee or 6m elbow or 6m cross, etc. SA-105. Trying to determine the allowable hydro pressure. Based on 2.3 it states look at an XXS NPS pipe pressure similar

 

[GBTorpenhow]

No, Class 6000 does not have anything to do with 6000 psig. Your approach of calculating the design pressure of a 1" XXH threaded pipe is correct.

I would just correct your statement as below in red:

"For example 1 NPS - good to 7783 PSI (design - threaded - shown attached). Therefore the fitting for 1 NPS manufactured to B16.11 would have to be able to support this design pressure. Since our piping system design pressure is lower than the fitting design pressure, we're alright.

 

[swiftworks]

Thanks man, appreciate it.