Pipe testing - Air vs water testing 4

[lfg2007]

I am being told that air testing is the same as water testing for pipie pressure testing. I do not believe that the air pressure required would be the same as water. Also theree is probably a saftey issue for high pressure test. Test would be 150 psi water max.

Any thoughts

 

[BigInch]

Then zdas you agree with my comment in thread378-240527. Bye.







**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[Berndt]

Hi BigInch,

I was not aware of required NDEs prior to pneumatic testing. You mentioned Section 945.1, 2 and 3. What code are you referring to as I would like to read up on it?

 

[zdas04]

BigInch,
I learned that in Middle School. A really hard lesson for a know-it-all 14 year old.

David

 

[BigInch]

B31.3 was the topic at the time. At least that's how it is in my 2002 edition 345.1, 2, &3.

I believe that B31.3 allows pneumatic testing, only as a method of last resort, see 345.1., the last stop on the testing flowchart and the Alternate leak test can be used only if "damage" would be caused by other methods.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[Ballbearing1]

Big Inch,
As I have a bit of spare time this morning this "pig" will respond.
Our server will not allow TGML so I will mark my responses with *


*The original response from zdas04 to the OP was totally inappropriate and I was attempting to defend the OP.

zdas04 "This topic has been beaten up, but you do add one bit of foolishness that I haven't seen before-that you would require higher pressure for air than water."
OP original statement "I do not believe that the air pressure required would be the same as water."
Where does the OP state anything about using higher pressure for air than water ?*


lfg2007,
Your 4 x less psi may have been misintepreted by yourself, pneumatic can be 40% less than hydrotest.
I'm not sure... and I don't feel like doint the math and responding. Sorry

*150% of design pressure (hydrostatic) minus 110% of design pressure (pneumatic) = 40% difference.*


Biginch,
"It is an excessive hazard that can only be used when hydros is not possible."
Incorrect - B31.3 states it can be done if a hydrostatic leak test is impracticable - not impossible.
I said "not possible", not "not impossible", The code uses "impractical" as you state, however, if you do attempt to avoid making air tests as I believe you MUST, and as you should in order to minimize risk of all kinds, impractical does in effect equal impossible, so I have no problem with the symantics that I used.

*There are numerous cases where it is definitely possible but not practical (my sulphuric acid lines for example)*
[/color]

"..must be 100% radiographed / Uted and structural welds examined via liquid penetrant, if an air test is done."
Please advise where in the code this requirement is stated ?
Please see Section 945.1, 2 & 3.

*There is no requirement for 100% NDT prior to pneumatic testing in ASME B31.3*


shmar
"If this is a fuel line you would not want to test it with water."
Fuel lines are hydrotested (with water) daily all over the world.
The only lines we do not hydrotest on site are sulphuric acid lines. (I am not a chemist but I think it is due to exothermic reaction)
[Being that you are in pipelines, I suspect you are quilty (as I often am) of thinking that the OP is talking about pipelines where water testing would be the norm, but the OP said "pipes". Perhaps Shmar thinks this pipe might be a fuel line on a A380 that needs to be tested in place. If so, who am I to argue? I know less about that than Shmar.
Why should zdas comment on that? I don't want to.[/color]

*Where did I mention anything about pipelines ?, I am actually working on a refinery hence the reference to B31.3*

lfg2007,
Dependant on your code and whether the pipe is buried you may not even have to hydrotest.
If the test was 150 psig then you would presume the design pressure was 100 psig ( 1.5 x) which would make it Cat D in B31.3 and an ISLT only is required.
But you assume, without justification, that the OP is testing to B31.3

*As far as I am aware you were the first one to mention B31.3. Other postings just followed your comments
"If the code is B31.3, see pp 345.1 to 345.9"*

My suggestion is that EVERYBODY, READ the OP and concentrate on making a constructive comment to that rather than making outrageous assumptions, mentioning some obvious exclusion as a contradiction to another's post and arguing in perpetuum about the last poster's text. At least if nothing else of true engineering interest arose.
Deal?

PS No offence noted... or taken.

*In my honest opinion there is far too much scaremongering regarding pneumatic testing.
If you use the correct procedures, correct material and comply with all safety requirements there is no reason why a pneumatic test cannot be performed as safely as a hydrostatic test.
We use them regularly in the LNG industry.
If you cross the road and look both ways before crossing there is a strong possibility you will cross the road safely everytime but if you only look one way there is a strong likelihood of an accident.
Then you have the unavoidable incident of a speeding driver that creates an accident even though you have looked both ways.
When accidents happen with pneumatic testing they are quite often very nasty but how much research has been done on the causes, how much is human error and how much is faulty material / machinery?
The European PED (Pressure Equipment Directive) requires all material to come from approved manufacturers / mills so the chances of faulty material exploding are greatly reduced.*
End of rant,
Regards,
BB


**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

Thank BigInch
for this valuable post!


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zdas04 (Mechanical)

 

[BigInch]

I said "If the code is B31.3, see pp 345.1 to 345.9." I assumed nothing.

I agree that it is 40% less in B31.3. I never said anything else.

I did not say impractical always means impossible.
My opinion is that pneumatic testing must be avoided whenever it is possible to avoid them. I do recognize that for those specific cases where the code allows, there is no other choice, except to radiograph 100% of all welds.

OK, I see I said "all" welds. The 100% radiograph requirement is for "golden" welds. It is not for all welds, as I mistakenly said above.

Speaking of LNG, you did see the latest results of a pneumatic test gone wrong in China, right? So scare mongering or not, bad things can still happen and those things usually are worse with air.

I realize things can be made as safe as you can make them, if you're willing to work at it. That's why I still fly ultralights, but not without a full (usually 1 hour) inspection beforehand. Hey, just like wrestling in the mud, you have to make inspection part of the fun.

Stay safe.




**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[Ballbearing1]

Big Inch,
I think we have all experienced some horror stories or near misses during out careers, be they hydrostatic or pneumatic.
I once worked on a Shale Oil project in Australia, similar to the oil shale sands in Canada but with shale rock.
Discovered 23 hydrostatic test acceptance certificates signed off by Operations before the piping had even been fabricated. Product was 500 degree C hot oil so could have been a very nasty accident.
Unfortunately it is quite often innocent parties that are injured / killed in some of these incidents,
Regards,
BB

 

[786392]

Dear BB
It's true though; but I did come across tempering of PG's employed with intentional positive errors(almost criminal I consider)

by sometimes 'contractor's people or even by the permanent staff while in haste or work closing hours;without PG zero error checking bleed/drain arrangements.

In all such situations,I as an operation or third party refused to witness until the provision was made and Nil zero error was ensured.

These do contribute in accidents;even catastrophe I believe if pass un-noticed.

Best Regards
Qalander(Chem)

 

[stanweld]

lfg2007,
Leak tests can be performed in a variety of ways depending on the Codes of Construction and other contractual and design requirements. Hydrostatic tests are often specified at a pressure > the design pressure, typically between 1.25 and 1.5 X design pressure. Pneumatic leak tests are performed at a pressure somewhat less than defined for a hydrostatic test because of safety concerns (typically 1.1 to 1.2 x the design pressure. Sensitive leak tests (bubble leak, Halogen and Helium leak tests)are pneumatic tests normally performed at pressures substantially less than the design pressure. Finally initial service leak tests can be performed where pressure is the operating pressure.

The vast majority of hydrostatic tests are not proof tests; that is, they do not stress the pipe near its specified minimum yield strength (SMYS). Think of a standard wall, 6" diameter, A-106 B pipe with test pressure of 150 psi - the hoop stress imposed is a tiny fraction of the material's specifed yield strength.

Cross country pipelines are often hydrotested at 90% to 105% of the material's SMYS - that ia a proof test! For a location factor of .80 the minimum induced hoop stress at the test pressure is 100% of the SMYS. In aerospace applications, hydrostatic tests often produce similar hoop stresses.

I hope this provides some enlightenment.