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"
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.
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.
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.
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:
Minimum ambient temperature to begin pressurization
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)
Soak periods of 15-30 minutes about every 10% increase in hoop stress.
Rate of pressurization/depressurization
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.
"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"
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,
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.
"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"
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.
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.
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.
"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"
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
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.
"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"
"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"
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.
Turn on CNN 15 years from now when corrosion finally completes its job.
Latest Pipeline Incident data shows
Most common cause of an incident: Corrosion
Highest Loss Potential: Third Party Damage from excavation
The Surprise Dark Horse: Failure from Instrument Malfunction, failure to operate or operates incorrectly
Of all Valves & Hardware caused incidents: Relief Valves Failures are the most common
The last two are especially worrying from a safety in design perspective.
Overpressure (Operating pressure > MAOP at the time of the incident) hardly appears on the list at all.
MJCronin,
I keep seeing those same incidents. Fatalities are a big thing and need to be studied and understood. It bothers me that so many people use these examples to indict pneumatic testing.
The first link was REALLY short on details, but I've only seen brittle failure of pipe at seriously depressed temperatures. I've seen several incidents over the years where nitrogen was introduced to CS piping at temperatures significantly below 0F. That doesn't often end well, and the failure is always described as "brittle fracture" like in the link. Most of these that I see I assign a root cause of either bad procedures, no procedures, or not following procedures.
The second link requires a subscription that I don't have. I can't comment on those incidents.
The third link above is titled "Fatal accident during pressure testing". A PSV on the nitrogen supply was not properly captured. The valve lifted and the tailpipe pinwheeled. I've seen the same thing happen on pressure vessels and compressors. Most of the time it just ends up breaking the elbow off. Attributing this fatality to "pressure testing" feels quite disingenuous.
Thank you for the fourth one. I use one of those pictures in my Engineering Course. The details I had were really vague about how that much pressure built up in the tank. Now I know. A really crappy isolation plan (terrible Engineering) allowed testing of the pipe against some number of closed valves with inadequate protection of the downstream systems. Clearly not an indictment of pneumatic testing, but an example of an Engineer who shouldn't be in responsible charge of a can opener.
"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"
I think the key point from those incidents is that the failure doesn't have to be the pipe being tested, but other associated equipment which because of the stored energy leads to large movement of pipes (and vessels!) or items being ejected like a bullet or artillery shell.
Of course procedures, isolation, weld testing, temperature control can prevent such incidents, but you wouldn't have seen the level of destruction in these pictures. Not sure about the brittle failure in the Chinese weld, looked too neat for that and more like weld failure, but I'm no metallurgist.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
I live in the Rocky Mountains. More lines have failed from elevation changes (test point at the top, pressure at the bottom of the hill twice test pressure) than have ever failed from pneumatic tests. It is all about responsible risk mitigation.
There are many systems on the flat that were designed for dry gas that have no earthly way to get all the test water out after the test. We never are able to kill all the microbes in any test water that we use. Ever. So that bit of water that you just can't get out grows into a septic environment that can have accelerated pitting and rapid failure. Do that in a Cyanide plant an you can go to bed every night saying "if I had only refrained from introducing that water into the system because of my irrational fear of pneumatic tests ...".
Good Engineering is all about managing the risks you cannot avoid. To demonize pneumatic tests is the exact opposite of that goal.
"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"
With the greatest of respect, failure during a test due to lack of consideration of hydrostatic head is simply truly terrible engineering.
The real issue, IMO, is that not enough people give real thought and discussion about the potential impact of a failure of a system under test. There is a thought process which just regards testing as a necessary evil to get the certification, not what is safest or the best in the long term.
Corrosion due to microbial action in the test water can be very serious, especially when significant quantities are left in hot locations. Removal of test water is again something often overlooked and can lead to problems with drying the pipe and preventing corrosion.
As BI says, it's all about balancing and controlling risks as to what the"best" solution is in any one place and set of circumstances.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
Risk avoidance is a means of risk mitigation. But if we avoid all risks then we just sit in a basement and quiver. There are other means of minimizing the mix of risks that always exist.
"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"
The real problem is that risks are not evaluated properly.
Many parameters are not understood and wide generalizations are drawn. Many variables simply are not considered and many others are considered independent when they are not. If one valve fails, do you really think that the valve next to it has the same failure probability. The facts are that it is almost always assumed to be equal to some standard number for that type of component, however if one valve fails it could just as easily be a symptom of improper maintenance that is applicable to everything in the whole plant, dramatically increasing the probability of failure of each and every item. In other words, the events are not independent and there is a much higher probability of cascade events. This is evident in just about every major incident. The probability of the several events that come together to produce an "incident" if evaluated independently, would give you a zillion years of trouble free operation, yet people get killed and damage is done.
When you do an air test, have you considered that marijuana has recently been legalized in Colorado... for example. Texting while walking has dramatically increased the risk of accidents of pedestrians crossing the street. The numbers in the book are not correct, are not evaluated correctly and do not consider the ever changing environments. Calculate the probability of a nuclear plant problem, and a tsunami that floods the pumps, because somebody thought that the probability of a tsunami big enough to wash over the dike and shut down the cooling pumps was too small. It would never happen in a zillion years, but it did. Please explain how that was possible. Do HIPPS systems have the same probability of failure in Iraq as they have in the North Sea? Probably not because there is no concept of maintenance in Iraq. Complex systems, by definition are hard to understand, so therefore very difficult to analyze at all. Some risks are better left avoided when there are other means available to accomplish the same objective at less of a risk, even they might cost more. Theoretically you could figure the costs x risk balance of losses and make a mathematically justifiable decision, but nobody has any real numbers to do so. They usually work in the imaginary matrix of probabilities, most drawn from the perfect world of NASA or nuclear plant data, and of independent events. The present method of risk evaluation is complete nonsense.
There are people who do a poor job of risk assessment and that is a bad thing. There are people who do a competent job of risk assessment and that is good thing. To say "risks are not evaluated properly" is painting with a pretty broad brush. I do a lot of pneumatic tests and feel that I understand the risks, understand the alternatives and their risks, and believe that the procedures I put in place and personally supervise limit those risks to appropriate levels.
My big problem is that the growing hysteria in the Engineering community against pneumatic tests makes it harder every year to get a test protocol approved. Last year I had a job with a 2200 ft elevation change (952 psig pressure difference between the top and the bottom when full of water) over 18 miles. We wanted to do a 900 psig test. The alternatives were (1) put the gauge on the bottom and accept that the top 120 ft would be "tested" at atmospheric pressure; (2) put the gauge at the top and accept that we were testing the bottom to 130% of SMYS; or (3) design a pneumatic test. I couldn't find a fourth alternative. Making up drag sections and testing in 60 segments left us with too many untested welds and too much pipe that was moved after test (really high risk). There wasn't an accessible location in the middle of the line to isolate and do two (or more) tests--this was really rugged country. I presented my evaluation and my client said "Yes, but a pneumatic test is just too dangerous". The contractor supported my plan and said that it addressed all of the potential for failure and he would much rather use my plan that try to do a hydrostatic test. I finally had to get the company's Engineering Manager to override the local Engineer. That created a lot of hard feelings and that company hasn't called me back, but we did the right test, safely, and with appropriate risk avoidance/mitigation. It chaps my butt that I lose a good client for trying to do the safest possible evolution. The reason for the problems was NOT that pneumatic tests cannot be done safely, it was the hysteria that is being created by comments like this thread is full of.
"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"
It's that clients have finally realized that it's harder to do business than before with the vast liabilities they face on a day to day basis. They have realized, like the company I work for now, that one wrong move can finish a $6B company and, fortunately, they prefer not to take that risk. If you have no choice, then everybody has to do it that way, or not do it at all. If there's a choice, then you have to choose the safest way, or .. not do it at all.
We just moved 500 people to Abu Dhabi, because it's too dangerous to have them on the road for an hour&half each way trying to make the commute from Sharjah.
The 1400 miles of BTC pipeline pipe in Turkey was transported around the country at a maximum of 50 KilometersPH 30 mph!
Our clients not only want to do it the safest way, they INSIST ON IT.
If the client want's to pay for it, what problem do you have, more work???
Our biggest problem is our guys that think they know better.
I don't think low stress level test has been established. There is no point using that pipe for a such a low op pressure.
Quote:
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.
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
Wall thickness is 0.375
SMYS is 65,000 (X65)
Diameter is 20"
If DF is 0.5 (residences nearby), then Pmax = 1218
Just a test pressure factor of 1.1 would be a 1340 psig test pressure.
I don't believe for a second that this pipeline will run at 20%.
Answer a question with a question:
Why isn't the pipe designed for 535?
Or maybe he's confused.
At this point I have more confidence in my calculations.
There was one report of at least one death occurring during a hydrotest involving connecting hoses being disconnected with trapped air inside. I'd not forget to mention that hydrotesting can be a dangerous enough operation on its own.
I'm looking for that report now. If I find it I will post the link.
my two cents, we had an engineer sold on the no pneumatic test religion. so he tested the plant with water. It was a cryogenic plant. He lost 2 weeks production because he froze the plant up upon start up. He almost lost the 35 week delivery platefin exchanger to.
I've got a dozen cryo plant N2 test under my belt, no incidents, no freeze ups.
Had a high pressure 30" X-60 gas line installed through populated areas and under a main Blvd of L.A. once. One pipe failure in the long seam during hydrotest at pressures exerting < 60% of SMYS. If pneumatic testing was performed, the event would definitely had made the nightly news.
We routinely pneumatic test 12" seamless fuel gas piping at 660+ psi at new powerplant installations but tests are thoroughly evaluated, specific procedures written with safety issues paramount. Fill lines must be tested, pressure relief valves installed, etc. Have not had any safety related, catastrophic incident in the 17 years of my review/involvement.
Additional pneumatic test considerations are:
1. Pipe manufacture -seamless, sub arc welded or ERW
2. Pipe manufacturer (China??)
3. Pipe testing by manufacturer witnessed by Purchaser
4. Other inspections made by Purchaser
5. Mode of transportation
I'm glad things have worked out well for you.
Under well controlled access, probably behind locked fences and manned guard post entry permits much of the risk can be at least limited to company facilities and personnel.
Pipeline layouts are somewhat different.
And... Pneumatic tests are not allowed at all under B31.4
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RE: Pneumatic Test
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?view=&gid=10...
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Pneumatic Test
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.
RE: 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.
RE: Pneumatic Test
Pneumatic tests without proper Engineering represent unreasonable risk/reward mix. With proper Engineering, they are quite safe. Issues addressed in proper Engineering are:
- Minimum ambient temperature to begin pressurization
- 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)
- Soak periods of 15-30 minutes about every 10% increase in hoop stress.
- Rate of pressurization/depressurization
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"
RE: Pneumatic Test
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
RE: Pneumatic Test
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.
[color red]OUTLAWED! FEDERAL REGULATIONS CFR 49 PART 195.306
http://www.law.cornell.edu/cfr/text/49/195.306
Independent events are seldomly independent.
RE: Pneumatic Test
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.
RE: Pneumatic Test
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"
RE: Pneumatic Test
Independent events are seldomly independent.
RE: Pneumatic Test
Independent events are seldomly independent.
RE: Pneumatic Test
Independent events are seldomly independent.
RE: Pneumatic Test
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"
RE: Pneumatic Test
Independent events are seldomly independent.
RE: Pneumatic Test
Frac tanks I work with are 20,000 gallons. 500 BBL's
RE: Pneumatic Test
Independent events are seldomly independent.
RE: Pneumatic Test
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"
RE: Pneumatic Test
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
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RE: Pneumatic Test
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"
RE: Pneumatic Test
Independent events are seldomly independent.
RE: Pneumatic Test
RE: Pneumatic Test
RE: Pneumatic Test
Latest Pipeline Incident data shows
Most common cause of an incident: Corrosion
Highest Loss Potential: Third Party Damage from excavation
The Surprise Dark Horse: Failure from Instrument Malfunction, failure to operate or operates incorrectly
Of all Valves & Hardware caused incidents: Relief Valves Failures are the most common
The last two are especially worrying from a safety in design perspective.
Overpressure (Operating pressure > MAOP at the time of the incident) hardly appears on the list at all.
Independent events are seldomly independent.
RE: Pneumatic Test
RE: Pneumatic Test
Some of my favorites.....
http://www.tedpelling.com/news/Pneumatic%20Shangha...
http://webwormcpt.blogspot.com/2009/07/pneumatic-t...
http://www.stepchangeinsafety.net/incidentsdiscuss...
http://www.safteng.net/index.php?option=com_conten...
Some good pressure testing information:
http://www.hse.gov.uk/pubns/gs4.pdf
RE: Pneumatic Test
I keep seeing those same incidents. Fatalities are a big thing and need to be studied and understood. It bothers me that so many people use these examples to indict pneumatic testing.
The first link was REALLY short on details, but I've only seen brittle failure of pipe at seriously depressed temperatures. I've seen several incidents over the years where nitrogen was introduced to CS piping at temperatures significantly below 0F. That doesn't often end well, and the failure is always described as "brittle fracture" like in the link. Most of these that I see I assign a root cause of either bad procedures, no procedures, or not following procedures.
The second link requires a subscription that I don't have. I can't comment on those incidents.
The third link above is titled "Fatal accident during pressure testing". A PSV on the nitrogen supply was not properly captured. The valve lifted and the tailpipe pinwheeled. I've seen the same thing happen on pressure vessels and compressors. Most of the time it just ends up breaking the elbow off. Attributing this fatality to "pressure testing" feels quite disingenuous.
Thank you for the fourth one. I use one of those pictures in my Engineering Course. The details I had were really vague about how that much pressure built up in the tank. Now I know. A really crappy isolation plan (terrible Engineering) allowed testing of the pipe against some number of closed valves with inadequate protection of the downstream systems. Clearly not an indictment of pneumatic testing, but an example of an Engineer who shouldn't be in responsible charge of a can opener.
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"
RE: Pneumatic Test
Of course procedures, isolation, weld testing, temperature control can prevent such incidents, but you wouldn't have seen the level of destruction in these pictures. Not sure about the brittle failure in the Chinese weld, looked too neat for that and more like weld failure, but I'm no metallurgist.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Pneumatic Test
When there is a less dangerous way to do something, that is the best way.
If only I'd been hydrotesting at the time...
Do you really want to say that every night before you go to sleep.
Independent events are seldomly independent.
RE: Pneumatic Test
There are many systems on the flat that were designed for dry gas that have no earthly way to get all the test water out after the test. We never are able to kill all the microbes in any test water that we use. Ever. So that bit of water that you just can't get out grows into a septic environment that can have accelerated pitting and rapid failure. Do that in a Cyanide plant an you can go to bed every night saying "if I had only refrained from introducing that water into the system because of my irrational fear of pneumatic tests ...".
Good Engineering is all about managing the risks you cannot avoid. To demonize pneumatic tests is the exact opposite of that goal.
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"
RE: Pneumatic Test
Independent events are seldomly independent.
RE: Pneumatic Test
With the greatest of respect, failure during a test due to lack of consideration of hydrostatic head is simply truly terrible engineering.
The real issue, IMO, is that not enough people give real thought and discussion about the potential impact of a failure of a system under test. There is a thought process which just regards testing as a necessary evil to get the certification, not what is safest or the best in the long term.
Corrosion due to microbial action in the test water can be very serious, especially when significant quantities are left in hot locations. Removal of test water is again something often overlooked and can lead to problems with drying the pipe and preventing corrosion.
As BI says, it's all about balancing and controlling risks as to what the"best" solution is in any one place and set of circumstances.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Pneumatic Test
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"
RE: Pneumatic Test
Many parameters are not understood and wide generalizations are drawn. Many variables simply are not considered and many others are considered independent when they are not. If one valve fails, do you really think that the valve next to it has the same failure probability. The facts are that it is almost always assumed to be equal to some standard number for that type of component, however if one valve fails it could just as easily be a symptom of improper maintenance that is applicable to everything in the whole plant, dramatically increasing the probability of failure of each and every item. In other words, the events are not independent and there is a much higher probability of cascade events. This is evident in just about every major incident. The probability of the several events that come together to produce an "incident" if evaluated independently, would give you a zillion years of trouble free operation, yet people get killed and damage is done.
When you do an air test, have you considered that marijuana has recently been legalized in Colorado... for example. Texting while walking has dramatically increased the risk of accidents of pedestrians crossing the street. The numbers in the book are not correct, are not evaluated correctly and do not consider the ever changing environments. Calculate the probability of a nuclear plant problem, and a tsunami that floods the pumps, because somebody thought that the probability of a tsunami big enough to wash over the dike and shut down the cooling pumps was too small. It would never happen in a zillion years, but it did. Please explain how that was possible. Do HIPPS systems have the same probability of failure in Iraq as they have in the North Sea? Probably not because there is no concept of maintenance in Iraq. Complex systems, by definition are hard to understand, so therefore very difficult to analyze at all. Some risks are better left avoided when there are other means available to accomplish the same objective at less of a risk, even they might cost more. Theoretically you could figure the costs x risk balance of losses and make a mathematically justifiable decision, but nobody has any real numbers to do so. They usually work in the imaginary matrix of probabilities, most drawn from the perfect world of NASA or nuclear plant data, and of independent events. The present method of risk evaluation is complete nonsense.
Independent events are seldomly independent.
RE: Pneumatic Test
My big problem is that the growing hysteria in the Engineering community against pneumatic tests makes it harder every year to get a test protocol approved. Last year I had a job with a 2200 ft elevation change (952 psig pressure difference between the top and the bottom when full of water) over 18 miles. We wanted to do a 900 psig test. The alternatives were (1) put the gauge on the bottom and accept that the top 120 ft would be "tested" at atmospheric pressure; (2) put the gauge at the top and accept that we were testing the bottom to 130% of SMYS; or (3) design a pneumatic test. I couldn't find a fourth alternative. Making up drag sections and testing in 60 segments left us with too many untested welds and too much pipe that was moved after test (really high risk). There wasn't an accessible location in the middle of the line to isolate and do two (or more) tests--this was really rugged country. I presented my evaluation and my client said "Yes, but a pneumatic test is just too dangerous". The contractor supported my plan and said that it addressed all of the potential for failure and he would much rather use my plan that try to do a hydrostatic test. I finally had to get the company's Engineering Manager to override the local Engineer. That created a lot of hard feelings and that company hasn't called me back, but we did the right test, safely, and with appropriate risk avoidance/mitigation. It chaps my butt that I lose a good client for trying to do the safest possible evolution. The reason for the problems was NOT that pneumatic tests cannot be done safely, it was the hysteria that is being created by comments like this thread is full of.
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"
RE: Pneumatic Test
We just moved 500 people to Abu Dhabi, because it's too dangerous to have them on the road for an hour&half each way trying to make the commute from Sharjah.
The 1400 miles of BTC pipeline pipe in Turkey was transported around the country at a maximum of 50 KilometersPH 30 mph!
Our clients not only want to do it the safest way, they INSIST ON IT.
If the client want's to pay for it, what problem do you have, more work???
Our biggest problem is our guys that think they know better.
Independent events are seldomly independent.
RE: Pneumatic Test
RE: Pneumatic Test
Wall thickness is 0.375
SMYS is 65,000 (X65)
Diameter is 20"
If DF is 0.5 (residences nearby), then Pmax = 1218
Just a test pressure factor of 1.1 would be a 1340 psig test pressure.
I don't believe for a second that this pipeline will run at 20%.
Independent events are seldomly independent.
RE: Pneumatic Test
RE: Pneumatic Test
Why isn't the pipe designed for 535?
Or maybe he's confused.
At this point I have more confidence in my calculations.
Independent events are seldomly independent.
RE: Pneumatic Test
I'm looking for that report now. If I find it I will post the link.
Independent events are seldomly independent.
RE: Pneumatic Test
I've got a dozen cryo plant N2 test under my belt, no incidents, no freeze ups.
RE: Pneumatic Test
We routinely pneumatic test 12" seamless fuel gas piping at 660+ psi at new powerplant installations but tests are thoroughly evaluated, specific procedures written with safety issues paramount. Fill lines must be tested, pressure relief valves installed, etc. Have not had any safety related, catastrophic incident in the 17 years of my review/involvement.
Additional pneumatic test considerations are:
1. Pipe manufacture -seamless, sub arc welded or ERW
2. Pipe manufacturer (China??)
3. Pipe testing by manufacturer witnessed by Purchaser
4. Other inspections made by Purchaser
5. Mode of transportation
RE: Pneumatic Test
Under well controlled access, probably behind locked fences and manned guard post entry permits much of the risk can be at least limited to company facilities and personnel.
Pipeline layouts are somewhat different.
And... Pneumatic tests are not allowed at all under B31.4
Independent events are seldomly independent.
RE: Pneumatic Test
And done on a weekend with only the defined test personnel permitted on the site.
RE: Pneumatic Test
Independent events are seldomly independent.