Above ground 4 hour test 1

[Engineer4143]

@Biginch

http://www.eng-tips.com/viewthread.cfm?qid=369443

In this thread you mentioned above ground test for B31.8 piping is not to see for leaks, it is to verify strength.
I have a follow up question on this,
IF a test is done under B31.4 above ground for a manifold with many diameters pipe, during this test the inspector somehow did a continous bleed for 3 hours of the test inorder to nullify the pressure variations due to temperature. I would like to ask if this test is acceptable as per code as an above ground 4 hour test?

What if he had collected the volume of water water he bled?
WHat if the volume was not measured?

Always be a Student

 

[Engineer4143]

Anyone? I guess Mr.Biginch is busy. I could not locate verbiage verifying his statement on either codes B31.8 and B31.4.
If we have the volume bled, we could perform PVT calculations and determine that there were no other leaks apart from the continuous bleed.
IF we do not have the volume bled, we cannot perform calculations.. Does this invalidate the test as per code?



Always be a Student

 

[LittleInch]

I don't have my copy of the code to hand as it's late here but from memory B31.4 is rather vague about what constitutes acceptence. Therefore what you need or needed to do was work out what was good enough and agree it worth the owner or client.

Now for me, a wholly above ground section inspected thoroughly and held at your test pressure will pass the test. It would be much better if you measure the water and can show that the volume drained equals the expansion volume but it's not essential for such a system.

As I said in your previous post B31.4 is really designed for buried systems but you can adapt it so long as you write it down and agree it beforehand.

Does that help?

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

 

[Engineer4143]

Thanks for your input, I would not disagree with you.
But I am intrigued by Mr. Biginch statement, guess we'd have to wait for his engineering explanation.


Always be a Student

 

[KevinNZ]

For above ground B31.1 piping we must have access to all the welds and welds and joints so the inspector can VT every joint and check for leaks and weeps. Checking pressure hold and run down is not required. "The piping system .. shall show no visual evidence of weeping or leaking". A continuous bleed would be allowed.

This not a strength test as the pipe is only held at 1.5 design pressure, which when corrosion allowance etc is considered, can put be quite low stress in the pipe, the pipe would/may see more stress when heated up in service.

 

[BigInch]

That's not a test. That's an untested system running at overpressure.

All of us here know what a "pressure test" is and more or less how it should be done. It doesn't fit our common sense definition of a proper hydrotest, so basically it fails. Normally in a hydrotest both pressure and volume are held behind a closed plug valve and some temperature variation is permitted. Nobody was holding anything there, actually perhaps varying one to offset variations in the other. Actually I'm surprised that an inspector had any desire to pass that point.

Has the inspector done any calculations to show that variations of pressure was the result of temperature change? Those calculations can be problematic enough when only attempting to verify pressure vs. temperature. Continuously bleeding volume adds two more variables, input volume and output volume. Do you have recording charts on all variables? Can you positively verify that the manifold was completely full at all times and that dV corresponds to dP and dT over each reading time interval.

What does API RP 1110 say about that?

 

[Engineer4143]

Strength tests are determined to be successful if no pipe ruptures or leaks occur as per the established
acceptance criteria.
- API RP 1110

It doesn't fit our common sense definition of a proper hydro test, so basically it fails.- Exactly same thoughts but i need something in writing in code or regulations. Calculations are with in the acceptable limits due to temperature changes in the test medium.

I am not exactly sure as to how the tightness of the manifold was tested in this test, somehow i do not feel this is within code, but the code does not categorically specify this. I will conduct more research on this..

Always be a Student

 

[BigInch]

So what is YOUR established acceptance criteria. Can't remember ever seeing "ran at test pressure for 4 hours". Kind of funny actually.

the code does not categorically specify this Magic words.
YES! CORRECT! THAT is YOUR JOB! To specify what is required. Sorry, but your understanding of the purpose of design codes is, shall we say, incomplete. Design codes tell us the minimum requirements. How do you explain that the pipeline code does not require us to provide a liquid pipeline going uphill with pumps! How could they not mention that. There are an infinite number of things that are not mentioned in any code, yet they still could be necessary to make a design perform satisfactorily in strength, intent, function and safety. It is the engineer's responsibility to provide all other things that may be needed. You cannot prove what you do not know yourself just by flashing some code text to your client. That only proves to him what you know is insufficient. To be a good engineer my friend, you need to know what the codes DO NOT require and when you need to have it.

Richard Feynman's Problem Solving Algorithm
1. Write down the problem.
2. Think very hard.
3. Write down the answer.

 

[Engineer4143]

In this case, it is only required to be tested to 4 hours since this is an above ground assembly. During this period you are not allowed to have leaks and all pressure variations should be accounted for using PVT calcs(Acceptance criteria).

I am not sure as to why a 4 hour above ground test is funny. It is a valid test as per code, regulations and RP 1110.

I agree that it is my job to approve or reject this test and have them re-do this. Thanks for your valuable input.



Always be a Student

 

[BigInch]

Funny because IMO no pressure was ever held. It was cleverly balanced.

Maybe it qualifies for operation at high pressure under an alternate demonstrated highest recorded pressure during operation, but I can't agree that it is a pressure test in the classic sense.

Richard Feynman's Problem Solving Algorithm
1. Write down the problem.
2. Think very hard.
3. Write down the answer.

 

[LittleInch]

BI, I think you're going too far and not looking at the specifics here.

This is a wholly above ground test of a manifold where visual inspection is possible, not a buried pipeline.

B31.4 437.4 applies here.

All it says is that the piping system shall be subjected to a hydrostatic proof test not less than 1.25 x design pressure for a min of 4 hours. Nothing about holding it and it specifically allows you to relieve excess pressure.

It states if you can visually examine all the components during the proof test then no further testing (leak testing) is required.

True it does say you should take records of the effect of temperature change, but for a proof test where you can visually examine each component and weld I believe you've satisfied the conditions required. If this was a buried pipeline I would agree with you that it isn't a proper pressure test or more not a proper leak test, but for a manifold??

In future it would be much better to have the testing procedure and acceptance criteria clearly specified and agreed

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

 

[BigInch]

I know. But you have to realize that this has nothing to do with engineering or engineering judgement. However this is a continued risk to operations. You admit it isn't a proper test. The competent authorities aren't going to have a warm and fuzzy feeling about it. You have followed inappropriate testing procedures, have incomplete calculations, no test procedure, no chart recordings, allowed faulty record keeping practices, which will at least get you hearing, a fine, or shut down until you reach compliance, even if things go well. Heck I won't even approve it anonymously over the internet with only my "BigInch" reputation to lose .... and I'm not thinking at all about protecting my cushy government job. Gotta pass two other tests. Will it fly in India and would BP do it today?

Richard Feynman's Problem Solving Algorithm
1. Write down the problem.
2. Think very hard.
3. Write down the answer.

 

[LittleInch]

BI, Hangon a minute - you're making statement here not backed up by the OP.

Who said there weren't any chart recordings? (I agree if there weren't any then you don't have a pressure test, but I can't see anywhere where the OP said that?)

Who said there weren't any records kept?

Who said that the inspector didn't actually check the piping whilst it was under the proof test pressure?

We don't know because Engineer 4143 hasn't told us, but from the information available to us, IMO, this is a valid test so long as the pressure didn't drop below the minimum test pressure AND the inspector visually inspected the manifold during this test period.

The judgment is in adapting the particular circumstances to the intentionally vague requirements of the CODE. Ultimately this piece of pipe was (as far as we can tell) subjected to a proof test of the required pressure for the required amount of time. Why is this not acceptable?

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

 

[BigInch]

Who said there was. If there was, then you've got no real test with ... records. I really want to see the volume in - volume out charts. Not buying.

Richard Feynman's Problem Solving Algorithm
1. Write down the problem.
2. Think very hard.
3. Write down the answer.

 

[Engineer4143]

BI and LI

We are only required to have the pressure and temperature(pipe and ambient) charts for the duration of the test.
I dont have a volume chart, however we know how much volume was bled during the 3 hours of continuous bleed, we do not know what rate it was bled at.(Rate at which the test pressure remained fairly constant). However we know how much volume was pumped in to reach test pressure.

Pressure remained with in the specified target pressure, and all the piping was visually inspected to be free of leaks..

I am not going to entertain any of these magic tricks by inspectors to show a pressure chart free of fluctuations in the future, even for an above ground test. Somehow this procedure as BI said violates the basic principle of a test.

Always be a Student

 

[LittleInch]

Well that's up to you and your test procedure.

We clearly don't fully agree, but be careful about no water being bled off. If your system gets a lot of solar gain you can exceed SMYS if you're not careful, especially for a low pressure manifold.

Some inspectors get a bit obsessed with a precise test pressure instead of just inspecting and making sure you keep it inside a band.

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

 

[BigInch]

I can imagine this could be a perfect fit to something my dad always told me. You could be very cooperative, try to make this look like a real test, write it all down, stand on your head, do the calculations and prove there was no leak. Do all the work and submit it. And then they don't approve it. Maybe they get upset because the system just isn't right without a proper test, like I said. Anyway, what my dad always told me was, "No good deed goes unpunished."

Richard Feynman's Problem Solving Algorithm
1. Write down the problem.
2. Think very hard.
3. Write down the answer.