pressure test piping of natural gas 150 Barg by N2 2

[Suradach]

I am worried about the PNEUMATIC TESTING piping of natural gas 150 Barg by N2 or Air because of the many dangers of exploding to person.
Detail : PIPE ASTM A671-CC65 CL.22, 24" x STDx 1000 m
Please help to recommend for performing this test

 

[LittleInch]

Why is this needed compared to a hydrostatic pressure test.

Can you remove people for about 100m around the pipe?

What other NDT are you doing?

150 barg sounds quite high. What is the design pressure, and design code?

 

[HTURKAK]

I am worried about the PNEUMATIC TESTING piping of natural gas 150 Barg by N2 or Air because of the many dangers of exploding to person.

I would refrain the pneumatic testing of the PL with 150 Barg . Huge amount of potential energy will be build up and is a real potential danger. Suggest you hydrostatic test .
You may look ,
- ASME B31.8
-EN 1594
and NFPA for details .

 

[pierreick]

Hi,
This is "crazy", perform hydrotest if needed. Check with relevant authorities in Thailand.
I'm aware of a mechanic passing away in Indonesia during pneumatic test of HX.
Pierre

 

[Dhurjati Sen]

Pneumatic test has been suggested due to subsequent drying issues for the pipe after hydotest. However, there are many techniques in vogue for drying of piping after hydrotest. Convince the client regarding the hazards of pneumatic test and furnish the procedures that you would perform to dry the piping after hydrotest. That would solve your problem.

 

[weldstan]

What are the design condditions? 72% of SMYS? >40% of SMYS? Where is the location? Heavily popolated or rural? Inside a plant or outside? Is the pipe in the trench during the test and prior to burial? All of these isssues pertain to the efficacy of pneumatic testing. I have written inspection and test plans for pneumatic testing that insured personnel safety many times during my carreer.

 

[GD2]

I am worried about the PNEUMATIC TESTING piping of natural gas 150 Barg by N2 or Air because of the many dangers of exploding to person.
Detail : PIPE ASTM A671-CC65 CL.22, 24" x STDx 1000 m
Please help to recommend for performing this test

yes, there is danger of stored energy in pneumatic test but you can do it. Follow ASME 31.8 pressure test (if you follow the Code). It will give you min and max test pressure and also max permissible hoop stress by Location class.

 

[GBTorpenhow]

Also see ASME PCC-2 for stored energy calculations (they use equivalent lb of TNT which can be eye opening) and recommended setback distances for pneumatic testing.

 

[LittleInch]

Maybe suradach has already been ejected into space?

not seen since asking the question.

You need to eb careful with the energy equation for pipelines as it doesn't all release in the same instance like say a tank or vessel.

The biggest issue is usually some small bore valve or piece of pipe which breaks off and flies a long way like a bullet.

 

[Suradach]

Pneumatic test has been suggested due to subsequent drying issues for the pipe after hydotest. However, there are many techniques in vogue for drying of piping after hydrotest. Convince the client regarding the hazards of pneumatic test and furnish the procedures that you would perform to dry the piping after hydrotest. That would solve your problem.

Thank you. I will persuade the owner to proceed with the hydrostatic pressure test and then dry the piping. Could you please suggest a suitable drying method?

 

[Suradach]

Maybe suradach has already been ejected into space?

not seen since asking the question.

You need to eb careful with the energy equation for pipelines as it doesn't all release in the same instance like say a tank or vessel.

The biggest issue is usually some small bore valve or piece of pipe which breaks off and flies a long way like a bullet.

Thank you, bro

 

[LittleInch]

There are many drying methods.

First swabbing, then possibly water absorbent liquids (e.g. MEG), vacuum drying, hot dry air blowing, Nitrogen blowing (very low dewpoint when re gasified from a cryogenic supply).

Depends on what water dewpoint yu want or need to get down to?

-20C is quite common.

 

[akpipelineengr]

Am I missing something? That hydrotest pressure on that grade of low yield pipe results in hoop stress almost double the yield strength. This looks like a bomb to me.

What is the design pressure? What is the basis for the test pressure?

 

[Dhurjati Sen]

Thank you. I will persuade the owner to proceed with the hydrostatic pressure test and then dry the piping. Could you please suggest a suitable drying method?

You need to contact me directly.

 

[LittleInch]

Am I missing something? That hydrotest pressure on that grade of low yield pipe results in hoop stress almost double the yield strength. This looks like a bomb to me.

What is the design pressure? What is the basis for the test pressure?

Good spot. I hadn't actually checked, but 150 bar is double the max pressure this pipe can withstand at yield pressure.

Something is not right even for hydrostatic test. You will have a 25inch pipe and never reach test pressure.

 

[GD2]

Am I missing something? That hydrotest pressure on that grade of low yield pipe results in hoop stress almost double the yield strength. This looks like a bomb to me.

What is the design pressure? What is the basis for the test pressure?

It looks to me you have missed a lot. Which Code allows you to do a hydrotest beyond the Yield Strength? The SMYS of the ASTM A671-CC65 CL.22 is same as ASTM A106 Gr. B pipes. How many times we have tested these pipes? All over the place.

Follow the Code rules for the hydrostatic/pneumatic tests.

Yes, I understand, we are talking of a pipeline test but then we have to adjust the test pressure based on the elevation profile so that you don't shoot off the YS of the pipe at the bottom most point considering the hydrostatic head. This is part of a pressure test plan.

For a pneumatic test, the hoop stress limit will be well below the YS.

 

[akpipelineengr]

@GD2 What am I missing?

Try running the numbers here.

If we assume this is a B31.8 pipeline, the maximum design pressure is ~875 psig, assuming the highest allowable design factor of 0.8. That results in a hydrotest pressure of 1094 psig, which is about half of the proposed test pressure here (150 barg = ~2175 psig). The proposed test pressure and resulting hoop stress condition are way out of the bounds of any code I'm familiar with.

 

[GD2]

@GD2 What am I missing?

Try running the numbers here.

If we assume this is a B31.8 pipeline, the maximum design pressure is ~875 psig, assuming the highest allowable design factor of 0.8. That results in a hydrotest pressure of 1094 psig, which is about half of the proposed test pressure here (150 barg = ~2175 psig). The proposed test pressure and resulting hoop stress condition are way out of the bounds of any code I'm familiar with.

You are right.
Lets make it simple to understand by OP.

We can find the design pressure for the selected pipe: ASTM A671-CC65 CL.22, 24" x STD.
Assume Location 1 Division. F=0.80, S = 34,800 psi, E=1.00, T=1.00, D = 24", t=0.375"
P=2St/D (FET) = [2 (34,800)(0.375)/24](0.80 x 1.00 x 1.00) = 870 psig (60 Barg)

Hydrotest pressure = 1.25 x 60 Barg = 75 Barg.

OP has two options to deal with his requirement - either reduce the design pressure or select a thicker wall pipe.
What is not allowed is to exceed the YS of the pipe during the pressure test.

In summary, OP can't use the given pipe for 150 Barg test pressure.