MINIMUM/MAXIMUM HYDROSTATIC LEAK TEST 2

[Lebpower]

CASE 1:
I NEED TO CALCULATE THE VALUE OF THE MINIMUM AND MAXIMUM TEST PRESSURE FOR A HYDROSTATIC LEAK TEST FOR A NEW PIPE SYSTEM.
THE SERVICE IS GAS NATURAL.
SHOULD I USE ASME B-31.3 OR ASME B-31.8?

ASME B-31.3 PARA. 345.4.2 MENTION THAT THE MINIMUM VALUE SHALL BE NOT LESS THAN 1 1/2TIMES THE DISIGN PRESSURE. SO, WHAT FORMULA CAN I USE TO CALCULATE THE MAXIMUM VALOR?


CASE 2:

WHAT'S THE FORMULA TO CALCULATE THE VALUE OF THE MINIMUM AND MAXIMUM TEST PRESSURE FOR A HYDROSTATIC LEAK TEST FOR AN OLD PIPE SYSTEM.

GIVEN THAT ASME B-31.3 APPLIES FOR NEW PIPE SYSTEMS, HOW CAN I CALCULATE THOSE VALUES FOR A PIPESYSTEM THAT HAVE BEEN OPERATIVE?



THANKS IN ADVANCE.

 

[DSB123]

First of all Lebpower turn your CAPS LOCK off since Capitals is seen as the equivalent of shouting at people and that is not very polite. Secondly calculate the test pressure in accordance with the Design Code you are using. If the Design Code is ASME B31.8 then you do not calculate the test pressure in accordance with ASME B31.3 and vice versa.

For case 2 you need to gather all of the inspection reports to obtain the minimum actual thickness and then perform a calculation to say API 579.

 

[XL83NL]

Re case 1; you mention para 345.4.2. So assuming the design is acc. B31.3, there's no formula for the max pressure.
B31.3 doesnt state the max, only that yield shall not be excdeeded. Refer to 345.2.1(a).

 

[zdas04]

Selecting maximum test pressure is a code issue that has been discussed above. Minimum test pressure is a matter for ENGINEERING JUDGEMENT. It is still required in the proscriptive days. The way I do it is to include in the test procedure that the operator can drain water, but may not add water, and if the final pressure is above MAWP then the test passed. Other engineers do it differently.

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[SNORGY]

There are ceiling pressures for the maximum acceptable hydrostatic test pressures for ASME B16.5 flanges; they are probably as good an "upper limit" as any. I think in 150# / 300# its a bit tight but it's workable. Is there any reason to suspect that 1.5 x Design Pressure, measured at the highest elevation in the test, would not be the minimum pressure?

Who is right doesn't matter. What is right is all that matters.

 

[zdas04]

SNORGY,
The codes state a minimum duration of a test, but companies can set their required duration at any arbitrary time longer than the minimum. Many companies still require a 24 hour test. In 24 hours the likelihood of zero temperature fluctuation is about zero. Smart operators begin their tests in the hottest part of the day and then hold their breaths while the temperature drops through the night. Some procedures allow adding some (very small) amount of fluid, others don't. A procedure that doesn't allow adding fluid AND requires the final pressure on a multi-hour test to remain constant is doomed to fail. Successful test procedures allow for the compensation of temperature change in some way, either specify a volume of water that can be added or specify a minimum pressure for a successful test somewhere below the test pressure.

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[SNORGY]

Thanks, zdas04, and agreed. You've been up here, so you know what kinds of issues exist in trying to achieve a reasonable hydrostatic test with temperatures that *can* swing by 100 F in a 24 hour period. I thought the OP was only concerned about the pressure limits, though. Now reading what you said in your post, however, I get it - it's not as simple as just that. Once again...kudos...

Who is right doesn't matter. What is right is all that matters.

 

[LittleInch]

Case 1 - Max pressure as XL8 states is pressure equivalent to yield stress, so insert yield stress into the stress equation and solve for pressure. However you should not exceed the pressure rating of any attached flange or valve body by more than 1.5 times its rating and that will normally limit your test pressure. If this is pipe designed to B 31.3 then use B 31.3. If this a pipeline designed to B 31.8 then use B 31.8.

Read 345.4.2 (d)

Case 2.
It is unusual to do a full leak test for an existing pipe system unless you have replaced or repaired a section or added a new part. If you do then the same rules apply.

An "inservice" test undertaken at a set interval ( one year, five years, whatever) is usually done at 1.1 times design pressure.



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

 

[GD2]

Lebpower,
ASME B31.3 is a process piping and B31.8 is a for pipeline code. Both are two different design codes and follows different equations, limits etc.
First make sure what is the construction/design code the new piping or the replacement piping. I will talk about what is required by the B31.3 code.
You said the service is natural gas which is for gas service and want to do a hydro test. If it is not a pipeline but part of facility piping and short run, you might go for a pneumatic test. Per B31.3, test pressure will be 1.10P, P=design pressure. Para 345.5 gives some basic rules for pneumatic test.
If you plan to go for a hydro test, the test pressure would be 1.5P x (temp. Correction factor), which is ST/S. See the nomenclature in para 345.4.2. You will need to dry the piping after the test. This test pressure is the minimum test pressure.
The max. Test pressure is calculated by taking the pressure upto 0.9 of SMYS of the pipe material. This is done by Using the hoop streets equation P=2St/D, where P will be the test pressure, S will be 0.9 SMYS, t is pressure design thickness with no tolerance. However, one very important thing to follow if you are testing a piping with flange and other piping component. The test pressure must be lowered if it exceeds the SMYS for the pipe and 1.5 times the flange/component rating at test temperature.

CASE 2:
B31.3 is for construction of new piping. For old piping, industry follows a ASME standard called ASME PCC-2. Unfortunately, ASME PCC-2 don't give any credit for old or used piping. It uses the same test pressure equation as B31.3.

Hope it throws some light on the testing questions.




Ganga D. Deka, P. Eng
Canada

 

[Lebpower]

Thank you so much GD2.

I didn't know about the 0.9SMYS.

Giving you more information about my cases.

CASE 1:

We have an old pipeline and we are evaluating if we can use it to supply natural gas to the refinery due to the main pipeline is about to get into a major maintanance. So we're thinking about using this as a temporary alternative while the maintenance of the main pipeline is done.

Before using it I have to check the integrity of the old pipeline by performing a hydrotest, plus I have to desing some short run pipings to interconect the old alternative pipeline with the main pipeline.

So what codes can I use to the design of the new facilities? and what code can I use to hydrotest the old alternative pipeline? (I dont have any information of what was the design code for the old pipeline but I'm asumming it was B31.8)


CASE 2

It's very similar than case one but in this case is not a pipeline but a piping process inside a plant.

It's an old pipe that haven't been operating since long time ago and they're planning to use it again so we have to evaluate the mechanical integrity by performing a hydrotest.

For this case I already cheked API 570 and for the hydrotest it says that I have to perform it according to the design code which in this case is B31.3

So I could say that this case was resolved.


Thank you so much

 

[curtis2004]

Lebpower,

Nothing is resolved yet. You shall not assume anything. Get all information about the line in question:

1. Design code.
2. Year of construction.
3. Size and wall.
4. Design pressure.
5. Is this underground or above ground line?
6. What commodity is it used for?
7. When it was used last time? Why is it not used afterwards?
8. Inspection and repair records? Hydro test records.

That's only starting point for your investigation project...

Regards,
Curtis

 

[GD2]

Lebpower,

CASE 1: Follow ASME 31.8 to design the new short-run pipes.
Follow the rule of para 817 to re-use the old pipe. ASME B31.8 allows use of old/used pipes. Understanding the rules are not easy but there is no easy route. The service is for natural gas and therefore exposes the line to more hazard than a liquid service pipeline due to more energy carried by the gas.

CASE 2: Normally the fence of the facility determines the transition of design code from Pipeline to facility piping. Most likely, the refinery will follow ASME B31.3. If it is so, follow this design code. ASME B31.3 does not give too much info about usage of unused/old pipe but if you follow the rules of ASME B31.8 it should suffice you. Both codes are written by ASME and for piping.

By the way, have you found the specification of the old pipes that you want to use?

Ganga D. Deka, P. Eng
Canada

 

[Lebpower]

Good Morning Mr. Deka.

I have made the research to get as much information as I can.

CASE 1:
Didn't have any luck. I'm almost starting over with this, doing the isometric drawings (no exist/couldn´t find them), I'm performing a flexibility analysis with CAESAR II to see if I'm gonna need to add expansion loops, plus I requested the inspection dept. to evaluate the integrity of the pipeline according to ASME B31.8 (the para you mentioned above) and also the hydro test, which leaded me here.
But I'm much more clear now with your help.

CASE 2:
I found the P&ID and the piping class and that helped me a lot.

I already recommended to hydrotest the pipe @51Barg (Design P=34Barg)


Thanks for your time.

 

[GD2]

Lebpower,
One place to find the design code is the project documents by the EPC company. Look for a document called DBM (Design Basis Memorundum). Your library should have all the project documents when they first constructed the Pipelie/Facilty.

For the pressure test requirement by B31.8 have a look at the table 841.3.2-1.

Ganga D. Deka, P. Eng
Canada

 

[GD2]

Lebpower,
The hydro test pressure required by B31.3 and B31.8 will be different. So depending on the applicability, the two old pipes should be tested.

As for where to find the original iso drawings, look the project folder documents called As-built' drawings in your library.

Ganga D. Deka, P. Eng
Canada

 

[LittleInch]

GD2,

I don't agree with a couple of things you're stating here - please back up your statements on code issues with the code reference number.

"The max. Test pressure is calculated by taking the pressure up to 0.9 of SMYS of the pipe material."

Errr no - the relevant clause in B 31.3 states don't exceed yield (345.2.1(a)) No mention of 0.9.
90% of SMYS is used in some pipeline codes as the basis of the minimum test pressure, but the ASME codes all use a factor on Design pressure.

" Normally the fence of the facility determines the transition of design code from Pipeline to facility piping."

Maybe in your experience, but not mine. The design code of a pipeline can extend a long way into the plant or be the entire plant, but certainly as far as the end of the pipeline / pig trap. Transitioning at the fenceline simply creates an artificial break in a line for no benefit.

Adding new connections and pipework to existing systems always causes these sorts of issues and often either needs a golden weld or a golden flange.

Be aware even in B 31.8, 817.3 (i) requires a pressure test.

Using old pipes and pipelines that you appear to have few details on is fraught with issues. Probably the only way you're going to get approval to use it from any authority / internal sign off will be to hydrotest to a pressure of at least 1.25 times your MOP for > 4 hours to confirm its strength capabilities. You will probably also need a longer period at 1.1 to demonstrate leak tightness.

You can use the existing pipe and apply a different design code, but then you need to use all the parts of that code and apply it to the existing pipe, e.g. proximity distances, location class etc and not just the bits you would like to.

Don't use words like "temporary". These imply a lower standard of quality and safety than not. There are many "temporary" systems in use many years later. Design it like it will be there for 20 years and you won't go wrong.

LI


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

 

[GD2]

Hi Li,
I will try to clarify my stand as below:
1. Max test pressure per ASME B31.3 code: Yes. The code allows to go up to SMYS but many Owner' won't allow for the simple reason that , the material will start seeing deformation at or above the SMYS. Many project standard and Owners limit this to 0.9SMYS. Most likely, you will never see it because the test pressure will be limited by the flange rating.
2. I don't disagree with your view on this. Yes, the mainline extends up to the traps but I am not sure it it extends to an entire plant. In my opinion, it's all about the designers perspective. ASME gives a scope diagram in Fig. Q.2 under Appendix Q.



Ganga D. Deka, P. Eng
Canada