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Pneumatic Leak Test

10/18/2014 8:30 AM

Hi folks,

I am looking for as many justifications against pneumatic leak test of process vessels and pipework as possible. How would you risk rank (from 0 to 10) pneumatic leak testing vs inservice leak test with process medium. thanks in advance for your detailled replies.

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#1

Re: pneumatic leak test

10/18/2014 8:35 AM

7

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#2

Re: pneumatic leak test

10/18/2014 9:16 AM

Regarding safety, a lot depends on the actual test pressure and the volume contained.

Several companies limit pneumatic testing to 75 - 100 psig and put a volume limitation on the test. Engineering experience also plays a role here.

This seems reasonable, but both factors must be considered together. (eg. a 100 psig pressure test on a short 12" Sch 40 piping system is OK, but a 5 psig test on a large, thinwalled storage tank may not be OK)

http://www.engineering.com/DesignerEdge/DesignerEdgeArticles/ArticleID/8180/Pneumatic-Testing-of-Pipelines-as-an-Alternative-to-Hydrostatic-Testing.aspx

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#3

Re: pneumatic leak test

10/18/2014 10:17 AM

Your not going to find any justifications. Sound like your trying to cut corners. Well go ahead. You ever try welding on a leaking tank. It can be a problem with just water. You have indicated process medium which is an unknown. What if the medium is flammable? Even if it's not flammable the heated medium may off gas and contaminate the weld.

Also the air molecule is small it will find leaks that most fluids will take time to develop. So your not sending men back to the job to correct leaks that would have been found with air quickly.

The process that's in place to test systems saves time. Also reduces hazards.

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#4

Re: pneumatic leak test

10/18/2014 10:33 AM

Thanks for your comments. I am not looking of cutting corners at all (as it wasunderstood by one of the responders), I am looking for justifications that conducting the leak test is not very much safe comparing with service test(even with some hydrocarbons), considering that the leak test is conducted at relatively higher pressures comparing with service test. There must be a bit more room for use of common sence about when to conduct and on which systems leak and service test.

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#6
In reply to #4

Re: pneumatic leak test

10/18/2014 11:46 PM

"There must be a bit more room for use of common sence (sic) about when to conduct and on which systems leak and service test."

Common sense tells me to test everything before it is put in service. It is much simpler to repair a leak before it has been contaminated by working fluid than after.

"I am looking for justifications that conducting the leak test is not very much safe comparing with service test(even with some hydrocarbons), considering that the leak test is conducted at relatively higher pressures comparing with service test."

It is a whole lot safer to test with excess pressure and a non-flammable medium (like air or nitrogen), than any pressure whatsoever with a flammable or otherwise dangerous medium. It SHOULD be obvious that this testing MUST be done at a time when no personnel are in the vicinity of the vessel being tested.

If you are not looking to "cut corners", then what the heck are you looking for?

There is NO justification for NOT testing!

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#9
In reply to #6

Re: pneumatic leak test

10/19/2014 3:49 AM

"Common sense tells me to test everything before it is put in service" - this is how the guys thought when they launched a vessel in Durango as a result of incorrectly conducted leak test. - I am just telling that under certain circumstancess it is safer to conduct a service test rather than leak test (spec breaks etc)

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#17
In reply to #4

Re: pneumatic leak test

10/20/2014 7:36 AM

"There must be a bit more room for use of common sence about when to conduct and on which systems leak and service test."

So you question the procedure for testing. You feel that in some cases the testing procedure is over done. That parts of the procedure could be eliminated if you use common sense. I hope you realize that some people have more common sense then others. That's why they spell out the procedure for testing. So there is nothing to cause injury to others.

It also puts everyone on an even playing field. You don't have someone under bidding and foregoing testing.

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#5

Re: pneumatic leak test

10/18/2014 1:01 PM

If you want to stack the deck, it works better to stack it according to reality rather than non-reality.

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#7

Re: pneumatic leak test

10/19/2014 12:19 AM

You said..

How would you risk rank (from 0 to 10) pneumatic leak testing vs inservice leak test with process medium...

wow, you are dangerous!

You EVER heard of Health and Safety? EVER heard of construction procedures? EVER heard of test procedures? EVER heard of a snagging list? EVER heard of final acceptance and hand over?

Please let everyone know where you are building your plant, so we can say the hell away from you and it.

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#8
In reply to #7

Re: pneumatic leak test

10/19/2014 3:42 AM

I was really hoping to see open minded thinking here, where people can analyse and firstly understand what is the question about.

Often missunderstanding leads to missinterpretation and giving of wrong advice.

I said how would you risk rank one against another... you got it wrong.

when questionning somebody's competence with regard to healt and safety you need to know the person first (his experience, documented competencies etc) instead of jumping into conclusions. If you guys do the business in this manner than I have nothing to do at this web.

Quite often people do not see anything outside the fence, this is how I saw approach of few guys here. Often people do not have the b...lls to question correctness of existing procedures - this is why we have so many incidents in the industry. None of the ETPs / GDPs or other practices is "100% bullet proof" and these documents are regularly updated when gaps are identified, the learnings mainly come from incident analysis (unluckily).

The facility I work for and I am in charge of has an outstanding safety record since day one and for the last 11 years (touch wood). We have proven competency, hold the licence and quite a few international audit teams identified my facility as one of the safest, best maintainned and most rigidly controlled site.

Again, try to see what is outside the fence, especially if you are an engineer, otherwise you will never create a history.

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#12
In reply to #8

Re: pneumatic leak test

10/19/2014 9:05 AM

You started with the question. I would think you would consider yourself responsible for any misunderstandings..

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#18
In reply to #12

Re: pneumatic leak test

10/20/2014 7:40 AM

Exactly.. the question was, blah, blah, blah....... and the answer was (well my answer IMHO was) in line with that question!

I don't see a problem.. does anyone else? (OP excluded)

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#19
In reply to #8

Re: pneumatic leak test

10/20/2014 7:54 AM

you said...

pneumatic leak testing vs inservice leak test

"In service leak test".. surely that is just a LEAK? Therefore it should not be considered a leak test, but a potentiality dangerous occurance that should set off alarms bells, people running for safety and the fire teams running towards that leak!!

I did not get it wrong! I got it RIGHT! Let me audit your site, and see how safe you are!

when questioning somebody's competence with regard to health and safety you need to know the person first (his experience, documented competencies etc) instead of jumping into conclusions. If you guys do the business in this manner than I have nothing to do at this web.

Well.. that might be the case, but all we had to go on is your question. If I had a "in service leak" as you put it on my offshore rig.... Damn it man everyone runs to muster, gathered at the lifeboats, roll calls and safety teams running about for hours with un measurable loss of production.

It is a fact of life that while we are ALL clever on this site, we are NOT mind readers, so we cannot sense your cleverness or competencies.... all we got to go on is your question.

You got the answer you deserved for the question you posed, and if it don't like it.. well you only have yourself to blame as you wrote it.

ps quick question.. what is outside the fence? Just in case we wanna get off!!

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#10

Re: pneumatic leak test

10/19/2014 5:45 AM

http://www.engineering.com/DesignerEdge/DesignerEdgeArticles/ArticleID/8180/Pneumatic-Testing-of-Pipelines-as-an-Alternative-to-Hydrostatic-Testing.aspx

API B31.3 2012

345.5 Pneumatic Leak Test

345.5.1 Precautions. Pneumatic testing involves

the hazard of released energy stored in compressed gas.

Particular care must therefore be taken to minimize the

chance of brittle failure during a pneumatic leak test.

Test temperature is important in this regard and must

be considered when the designer chooses the material

of construction. See para. 345.2.2(c) and Appendix F,

para. F323.4.

Appendixx F

F300 GENERAL

This Appendix provides guidance in the form of pre-

cautionary considerations relating to particular fluid

services and piping applications. These are not Code

requirements but should be taken into account as appli

cable in the engineering design. Further information on

these subjects can be found in the literature.

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#16
In reply to #10

Re: pneumatic leak test

10/20/2014 1:24 AM
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#11

Re: pneumatic leak test

10/19/2014 6:50 AM

Somewhere between 4.999 and 5.001 I think. The view from the fence is intriguing.

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#13

Re: pneumatic leak test

10/19/2014 11:26 AM

Pneumatic test ranks very low on the I want to do this scale.

Testing with the process fluids unless it is water seems rather a no-no.

So we are going to "risk rank" two evils.

What else do you have in your testging box. Me seems the justification you are seeking does not come easy.

How about hydraulic testing with all the assorted problems?

We dont even know whats in your tanks.

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#14

Re: pneumatic leak test

10/19/2014 11:52 AM

See what I found there in addition to really valuable information - "My personal practice for an air test is to be at least one zip-code away from the site" (copied) Finally at least one user posted normal and informative answer. Most of others remind me the engineers that work at office and rarely come to site to smell the reality. Seems like you read lots of books but never gonna write one if you keep like this. I bet very few of you have hands on experience with leak testing (against my 18 years of field work and lots of leak tests without a single injury). I was hoping to see polite, friendly conversation here... Dissapointment... The requirements for leak testing became so tight I have a feeling people will start making shortcuts... Posted here to get as many opinions as it was possible, wanted to take it to my subordinates and to frontline... Not much value here except few guys- thanks to them. Admin, please close the topic. Thanks

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#15
In reply to #14

Re: pneumatic leak test

10/20/2014 12:09 AM

GIGO

Your request was poorly phrased and lacked pertinent information.

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#20

Re: Pneumatic Leak Test

10/20/2014 8:10 AM

Mishaps and failures during pressure testing may result in injuries, fatalities, and property damage. Thegreatest potential hazard is an uncontrolled release of the large amount of energy that can be stored incompressed air, gas or other fluid, either in a pneumatic test or in a hydrostatic test, where gas may betrapped in such places as unvented high points, horizontal lines, and valve bodies. Other hazards areassociated with the handling of chemical additives, entering confined spaces, brittle fracture of materials,and disposal of test mediums.Uncontrolled releases of stored energy from compressed air or other gas can take the form of explosions.High velocity streams of fluid can be created or piping and equipment can move. The degrees of thesehazards are determined primarily by the test pressure and the volume of air, gas or other fluid involved.Avoid the following typical examples of poor practices which may result in incidents:- Striking or working on equipment, while it is under pressure, to stop leaks- Improper or missing test equipment, such as testing without a relief valve, having an inadequately sizedrelief valve, or having no pressure gauge(s)- Omitting or changing steps in the test sequence such as failing to conduct a low pressure tightness testto check for leaks prior to strength pressure tests at higher pressures- Failure to vent air from the system prior to the test- Use of gas instead of water as a test medium- Metal temperature below that at which the impact requirements can be met by the material- System not adequately supported to withstand the weight of water during the test- Pressure gauge(s) and relief valve(s) not calibrated and tested- Pressure gauge located too far from pressurizing equipment for reading- Appurtenances not adequate for the test pressure or not isolated from the test- Pressure increased too rapidly to be controlled- Relief valve inoperative because of a closed block valve- Temporary test piping not designed for the test pressure- No bleed valve provided on test piping- Failure to pressure test the test equipment and piping prior to putting them in service.WP

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