Pneumatic Test 1

[mcm1209]

Guys
I am working for a pipeline construction company.
I have been in the process and pipeline services since 1999.

I joined this company to start a hydrotest division.
We are being asked by our customer to conduct a pneumatic test of 7 miles of 20" pipeline.
Test pressure is somewhere in the neighborhood of 1300 psi.

I am very opposed to this but my company wants to push forward. The customer has given us the green light.

Oh yeah
We are doing this test within the week.

I need hard facts to stop my company from doing this. I have been looking for info on the net but have not been able to find something concrete.Or facts so i feel better about this.

I did find
"437.4.3 Only allowed for piping systems operated at 20% or less of SMYS"

Need help

 

[LittleInch]

what does your design code and more importantly your regulator allow? If the person who has to "accept" the pipeline isn't happy then there's not much point in it. Which design code and ocuntry is this.? Canada seems to have allowed quite a few, but most other safety authorities are more conservative and you need a very good reason whay you can'y hydrotest it.

Key questions are:
Are there any people in the potential "blast" zone?
Do you cross any public roads?
Can you keep everyone out of a zone about 15m either side of the pipeline for the duration of the test?
Has every weld been NDT'd?
Have you run an ILI pig?

Depends on the answers to those questions. If you're in the middle on no where and can keep every one out of the way, the real issue is the initial burst damge if the pipeline fails. The whole energy quaotient thing is probably a bit of a dead dog as very soon after a rupture, the pipeline will develop a pressure profile and blowdown over a period of time.

This has been discussed a number of times - Look at a few on this site and also linked in as below.

http://www.eng-tips.com/viewthread.cfm?qid=346492

http://www.linkedin.com/groupItem?v...p_search_item_list-0-b-ttl&goback=.gna_106074

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[mcm1209]

Key questions are:
Are there any people in the potential "blast" zone? Yes, line is close to residences
Do you cross any public roads? Yes, at least 10 road crossings
Can you keep everyone out of a zone about 15m either side of the pipeline for the duration of the test? in all honesty, unless i formed a 7 mile human chain i cannot keep people out of blast zone
Has every weld been NDT'd? Yes, this is a new pipline
Have you run an ILI pig? not yet, caliper tool will be run wednesday or so.

SMYS is 2437.5 psi
20% of that is 487 psi

I am for sure this line will not operate at less than that pressure.
The company PM is working out numbers.

Im sure the 1300 psi will not be test pressure after all the number are ran.
More along the lines of 535 psi for test pressure.

 

[mcm1209]

My main concern is the time to "engineer" this pneumatic test.
I am no way an engineer but I know my profession and from being involved in them before, i know its something you just don't decide to do overnight.

Reason for Pneumatic test is lack of space for 32 frac tanks.
Of course cost plays a big roll

Gas Company we are doing this for is who asked for the Pneumatic test.

 

[zdas04]

Take a look at Static Safety Manual When we started that document 4 of the 6 guys on the team were ADAMANT that they would never approve a pneumatic test. The other two of us had done a couple of dozen each and see no problem. By the time we published the document in the link we were all on board.

Pneumatic tests without proper Engineering represent unreasonable risk/reward mix. With proper Engineering, they are quite safe. Issues addressed in proper Engineering are:
[ul]
[li]Minimum ambient temperature to begin pressurization[/li]
[li]Minimum gas temperature (if you are using nitrogen from a liquid nitrogen truck then you can easily end up with ultra cold gas and a real brittle failure risk, fix this by specifying a minimum injection temperature, make sure the operator knows that value and that he adheres to it)[/li]
[li]Soak periods of 15-30 minutes about every 10% increase in hoop stress. [/li]
[li]Rate of pressurization/depressurization[/li]
[/ul]

The "blast radius" fairytale comes from some of the worst work that NASA ever did. They built a computer model with a very large volume of gas a a very high pressure and calculated the total energy in the volume. Then the assumed that that energy was concentrated in a single explosive decompression event. What utter nonsense. You have a 20 mile long pipe. If you have a guillotine fracture in the dead center of the line, then you will develop about a dozen standing waves from zero to 200 ft from the failure and the rest of the line would see flow rates to the failure on the order of 0.1 Mach. Something like 98% of the stored energy will dissipate as flow. No harm no foul.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[LittleInch]

When I said "blast zone" what I meant was the size of the crater which could be formed plus a little for collateral damage - for a 20" line probably about 5-8 m radius if it went bang at over 1000 psig. PRCI have done some excellent work showing crater size for different line size, presusre and soil types.

Your pressures confuse me though, - 535 psig test for a pipeline operating above 487psi?? - but really it's the number of crossings and proximity of the public which is the real issue to me.

You still haven't said whether the "regulator" approves of it or not or whther your insurance company konws about it. Whose responsibility is this?? The client / customer will vanish faster than the air you're pressurising if it all goes horribly wrong and will point to your companies expertise and profesisonal judgmeent and their "green light" will count for nought.

David is perfectly correct when he says that this is not something you decide to do a whim, but carefully write up and get approval / review well before you actually do it. Frankly 7 miles of 20" pipeline shouldn't be that much volume you can't find it if theres that many people about??

ALthough 20% may be quoted, that's probably because below 30% SMYS it is difficult for a single hole to cause a rupture (20% x 1.5 test presusre). Above that then it is a risk based judgement. From what you describe at present it looks like far too much risk for too little benefit.

We could do with design pressure, wall thickmess and SMYS of the pipe to help you a bit more.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[BigInch]

IN THE USA, ASME CODES ARE ONLY AN ADDITIONAL REFERENCE.

CFRs ARE THE LAW![/color red]

Do it only if you like the interior of a jail cell.
OUTLAWED! FEDERAL REGULATIONS CFR 49 PART 195.306

http://www.law.cornell.edu/cfr/text/49/195.306

Independent events are seldomly independent.

 

[mcm1209]

As far as approval!
Only approval we have is from our client telling us "proceed" this morning.

No engineering has been conducted.
Project manager is running numbers right now is what I'm being told.

7 miles 20"
X65 .375

I agree that the number of crossings and proximity to homes etc... is the real issue.

 

[zdas04]

BigInch,
The link to Cornell's copy of an extract of 49 CFR 195 is pretty consistent with what you will find in ASME B31.8. If hoop stress under test is less than 50% of SMYS then you can use various non-fuel gases and don't have to evacuate anything. If you are over 50% of SMYS then you have to evacuate buildings within 300 ft of the pipe while the pipe is above 50% of SMYS. You use the full pipe wall thickness for this calculation (since the corrosion allowance has not yet been consumed).

The regulation does not have a maximum hoop stress for pneumatic tests. ASME B31.8 wants you to stay below 70% of SMYS for a pneumatic test and below 20% of SMYS for a pneumatic test using hydrocarbon gases. Not a big issue in most tests.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[BigInch]

I totally agree zdas, but some people don't let codes stop them from doing stupid things. Likewise the law, but at least they may think twice before stepping across that line.

Independent events are seldomly independent.

 

[BigInch]

Since the only OP's reference to code was 437, I assume s/he has a liquid line meaning B31.4 and CFR 49 Part 195. ASMEs and the CFRs agree for the most part, but it's the CFRs that profoundly settle any incompatibility issues.

Independent events are seldomly independent.

 

[BigInch]

The "gas company" s/he's doing this for may subject it to CFR 49 Part 192

Independent events are seldomly independent.

 

[zdas04]

I missed the 437 reference, but the "gas company" seems to trump the reference to B31.4. I also skipped over the "SMYS is 2437.5" so I guess the pipe is X65 silly putty. Then the jumping between stress numbers and pressure numbers. I'd say this guy needs to find an Engineer to help him define terms before his "hydrotest group" gets into full swing.

The rule of thumb for water requirements for a test is the volume/1000 ft (in barrels) = ID^2 (with ID in inches). For the water to fit in 32 frac tanks would require that each frac tank held 462 bbl. Biggest frac tank I ever worked with was 300 bbl.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[BigInch]

and maybe a lawyer.

Independent events are seldomly independent.

 

[mcm1209]

Because of the time I was given to do this test. I told my superiors (VP of the company) that I will have no part in this test. They have a third party company that will be doing the test.

Frac tanks I work with are 20,000 gallons. 500 BBL's

 

[BigInch]

Since you only mentioned the lack of time, you should also advise them to check the legality and validity of proceeding with their plan. If not, since you now actually know it is illegal, technically you may also be found somewhat liable, should worse comes to worse. PS "somewhat liable" is like being "somewhat pregnant". Good luck. I know you mean well.

Independent events are seldomly independent.

 

[zdas04]

BigInch,
What in the preceding discussion would lead you to believe that the pneumatic test is illegal?

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[cloa]

This line in
FEDERAL REGULATIONS CFR 49 PART 195.306
(d) Air or inert gas may be used as the test medium in low-stress pipelines.

Depending on what is low stress- it think it means illegal.

http://www.eng-tips.com/threadminder.cfm?pid=1529

Use translation assistance for Engineers forum

Note the rules include No Student posting

 

[zdas04]

Reading other parts of the code I get a "low stress" number of anything less than SMYS.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[BigInch]

Low stress is a pipeline operating at a pressure that gives a stress LESS THAN OR EQUAL TO <= 20% OF SMYS. Not exactly economic use of the material, but if it keeps you out of jail, it might be worth it.

Independent events are seldomly independent.