air test HDPE 1

[brnt]

We are presently installing twin 16inch HDPE Dr17 forcemains --total length is 2 miles. They run from a lift station to a water treatment plant. The water treatment plant wont be up and running for at least another year.There is not a water supply near the site and if we were to pressure test with water the contractor would have to truck the water in.This would be onerous on the contractor and he wants to test the lines using air. Another problem associated with testing with water is until a road is built later this year the pipe won't have enough cover to protect it from freezing ( I am in Canada)

The procedure for testing with air is described in ASTM F2786-10.The formula it provides for determining the test pressure to use results in 150psi. Everything else I read tells me this is ver dangerous--yet ASTM gives us the industry standards--and I want to protect myself by following the industry standards.

Any thoughts on this dilemma?

 

[BigInch]

Yes you're right cvg. a Basically if you can do a hydro, you should do a hydro. Many codes won't allow it. Stanier AS code apparently won't allow it. B31.4 will allow gas testing if it is to be operated at < 20% of SMYS. Who designs their pipeline for 20% SMYS! Gas code B31.8 will allow higher gas tests under some circumstances.

My point is that he needs to get the right code, covering the design, constuction and testing of his water line and then he can do an air test if it is allowed and if he can do that safely. I don't think he's got it. A mill fabricationb test is not a constructed pipeline test procedure.

From "BigInch's Extremely simple theory of everything."

 

[BigInch]

sorry I mean, Many codes won't allow gas tests. Stanier's AS code apparently won't allow gas tests.

From "BigInch's Extremely simple theory of everything."

 

[brnt]

In the area I work, construction specs are written by the jurisdiction covering the area where the construction is taking place. This is a peice of infrastructure which will eventually be turned over to a town. Each city and town has their own construction specs. The city I live in has a detailed construction spec manual for all pipelines. This particular pipeline will be turned over to a small remote town which doesnt have there own engineering department. As is generally the practise they have hired an engineering firm (not ours) to oversee their interests. This engineering firm doesn't have a construction spec manual.The standards for construction fall under a general guideline of following industry standards and doing due diligence.The standards for construction also come down to our company's *ss is on the line if anything goes wrong.

 

[BigInch]

You've gotta find out which one applies to water pipeline construction. Surely there must be one. Contact the Alberta Gov and ask them. If not, I'd suggest an AWWA. All my specs are for petroleum & gas pipelines.

From "BigInch's Extremely simple theory of everything."

 

[BigInch]

look around here. Maybe there's something you can use.

http://www.sandiego.gov/water/cip/guidelines.shtml

From "BigInch's Extremely simple theory of everything."

 

[BigInch]

But don't bury it at San Diego depth. Know where your frost line is.

From "BigInch's Extremely simple theory of everything."

 

[stanier]

zds04 et al,

The standards committee that produce the ASME, AS etc standards designed for metal pipe materials generally do not thoroughly address the design of thermoplastic pipe materials.

There is no mention of creep properties, properties being dependent upon strain rate and temperature in the standards.

If you want to check this out review ASME B31.3 appendices on thermoplastic materials.

AWWA, PPI and thermoplastic resin manufacturers have a much better handle on designing in these materials. they have had to get involved because the legacy standard committees did not weant to completely re write their standards. The Europeans are far in front of the uS standards when it comes to thermoplastics.

As for a pipe manufactuer saying you can pneumatically test their product is ignoring all the requirements of statutories. The last time I checked pipe material manufactuers do not carry professional indemnity insurance and are not design engineers. authorities.

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

http://waterhammer.hopout.com.au/

 

[zdas04]

Stainer,
We simply work in totally different environments. From your posts I get the feeling that most of your work is utilities distribution in reasonably flat areas (elevation changes don't seem to be a major factor in your work). References to ASME B31.3 usually indicate work in a reasonably compact area.

My work is on upstream Oil & Gas in hilly country. It is not unusual for a gas line in this place to change elevation 2,000 ft from end to end--fill that up with water and the low points are 880 psig higher pressure than the high points. Hydrotest simply doesn't meet the actual needs of the piping system very often in this environment. Because of that I've done a lot of work to develop processes and procedures to allow the pneumatic tests that I design to be safe. Not "kind of safe", not "safe enough", but "safe". Yes, I include some analysis (like soak times) that I don't have to considered in hydrostatic tests, but so what? The purpose of a procedure is to accomplish a set of goals within the boundaries of acceptable risk.

I don't think that the industry we support is really germane to what kind of test the OP does. He thinks that the risks that he has control over can be better mitigated with a pneumatic test. I don't care if he's taking about an industrial cooling-water system or a supply lateral off a residential main, he's done the HazOp and the risks of a pneumatic test satisfy his risk tolerance. That should be the end of the story. He shouldn't get a lot of grief about being a cowboy or lazy or whatever the in

If a pneumatic test is safe, then why would someone consider it an inappropriate procedure? The only answer that comes to mind is fear and superstition.

David

 

[waterpipe]

Dear David,

May I ask what is the "normal" and "maximum" test pressures you've done so far for pneumatic tests and if you've done it for steel pipe as well? I work within water sector and haven't done pneumatic tests myself but thinking about the compressor size (power, flow rate) I would need for normal pressures and test section sizes I'm dealing with ... (well, I've put the safety concern aside for the sake of my thinking at this moment!).

 

[BigInch]

zdas Please, generalizing what you can get away with in the wild west as applying to what most everyone else must do by law is getting a bit reckless. If it wern't for the fact that none of your pipe is regulated by anybody, you too wouldn't be able to freely test anything you wanted to with air. B31.8 ss 341.3 allows gas tests in some circumstances, but has almost a whole page of conditions that go with it. Many of those conditions simply making it virtually impossible for a pipeline to be air tested and still result in a reasonable operating pressure or an economic wall thickness. B31.4 Liquid hydrocarbon pipelines does not allow air tests. Oil and gas transmission pipelines crossing 10,000 foot mountain ranges are routinely tested with water. You have to break up the line into short length test sections where the extra elevation pressure difference added to the minimum test pressure does not overpressure the pipe.


From "BigInch's Extremely simple theory of everything."

 

[zdas04]

BigInch,
Wild-west jokes aside, ASME B31.8 is the code that I am most familiar with, and it doesn't have the page of exclusions that you are talking about. It has a table (841.3.3-1) to lay out maximum hoop stress during an air or flammable-gas test. This table says that if I'm using air or a non-flammable gas then in Location Class 2 I can go to 75% of SMYS, in Class 3 I can go to 50% of SMYS and in Class 4 (i.e., under a high-rise apartment building) I can go to 40% of SMYS. If I want to test with a flammable gas I'm limited to 30% of SMYS. None of these restrictions have ever been much of a problem since most of my clients have a maximum hoop stress at MAWP of 20-30% allowed in their company standards

Pneumatic testing is not reckless. It does require more engineering expertise than is usually applied to hydrostatic testing (not necessarily more than should be applied, but certainly more than is typically applied), but so what? The tone of this thread is really starting to bother me. The implication in many of the posts is that only an irresponsible cowboy would ever do pneumatic testing.

Your comment that all oil pipelines are always tested with water really bothers me. It may be true, but if so our profession has become quite stupid. The 10,000 ft elevation example you talk about has to involve drag sections. I've done that evolution and I'll tell you that a properly designed pneumatic test has a small fraction of the total risks encountered while installing a long drag section of big inch pipe in difficult terrain, to say nothing about the number of untested welds.

Waterpipe,
I calculate an MAWP for my pipeline then determine a test pressure (based on location factors, codes, and company standards). Once I've determined the required test pressure, I evaluate the pipe to determine the hoop stress during the test. Based on this information (along with terrain features, the availability of water, and expected difficulties in dewatering) I design a test. I saw the end of a water test last year where the operator opened the end of the pipe into the bar ditch and drained the water. The test was with river water, but they added a few hundred gallons of biocide--I wonder what the impact of that biocide on the river was in the short term. Dumping hydrotest water on the ground has been illegal for at least 30 years, but the local regulator didn't know it was illegal and didn't care. Yeah, hydrostatic tests are always better and lower risk.

Most of the work I do calls for ANSI 300 kinds of pressure (call it nominal 600 psig MAWP), and most company standards call for 1.5 times (even when Table 841.3.2-1 calls for at least 125%), so it is common to test to 900 psig.

Of course this is not for HDPE. For HDPE I calculate an MAWP, but ASME B31.8 caps HDPE MAWP at 100 psig, so I've never done an HDPE test above 150 psig.

In Oil & Gas we regularly do evolutions on wells that require high pressure air injection so high pressure rental air compressors are readily available. You can test to around 60 psig with a single stage compressor. A two stage gets you to 225 psig. Typically, we use a 2-stage compressor discharging into a single-stage "booster" compressor (I know, calling an after-compressor a "booster" is backwards as it can be, but if you don't use the [irrational] terminology of your industry you get inconsistent results) which can get you to nearly 1,000 psig. If I have to go higher than that, I find it is less expensive to go to nearly 1,000 psig with air and top off with nitrogen than either doing the whole job with nitrogen or getting a fourth stage of compression.

Using nitrogen REALLY scares me. Nitrogen in this quantity is only available as a liquid. This liquid is kind of cold. If the operator is not paying really close attention you can find yourself applying gas at high pressures and sub-zero (Fahrenheit) temperatures which is a really good way to observe brittle failure.

Bottom line on static testing is that any sort of test demands competent engineering design. The risks, costs, and regulations must be considered and the test designed to optimize the risk mitigation and follow the intent (in addition to the letter) of the law.

David

 

[BigInch]

The reckless part is not that you do air testing, it's that you give the idea that its all right for everyone else to do it too. You have a very specific situation.

"Most of the work I do calls for ANSI 300 kinds of pressure (call it nominal 600 psig MAWP), and most company standards call for 1.5 times (even when Table 841.3.2-1 calls for at least 125%), so it is common to test to 900 psig. "

When you can do air tests, test press limit is 1.10 operating pressure in class 1 Div 2 areas, and 1.25 in class 2. Not 1.5

From "BigInch's Extremely simple theory of everything."

 

[BigInch]

Water pipeline construction spec. With hydrotest Ch 33.

http://www.carkw.com/engineering/std_specs.pdf?bcsi_scan_DF3614DB9E09526D=1

From "BigInch's Extremely simple theory of everything."

 

[waterpipe]

Thank you both BigInch and zdas04. I find it always interesting to see different (historical or proven) approaches in different sectors for relatively a same purpose.

Regarding the field pressure test, I personally try to stick with the standard/specification that rules the projects. Different codes allow different percentage of SMYS for the MAWP and pressure test and they have their own sets of permissions/constrains regarding using miters, bends, fittings, etc. (read it stress concentration points). You apply the 100% SMYS during the field pressure test to a pipeline that allows 45 degree miter and you don’t wana be around the bends during the hydro test.

Zdas04, you are so competent that could see all these sort of issues and manage the risks but this is not the case in many other projects (at least in water sector). I stick to the code/specification that I have in hand when the pipeline is designed by others and I stick to the code/specification when I design the pipeline myself to have a clear cut of liabilities. Well, at least this is how I do it until I’m working as the consultant or owner’s Engineer. From the Contractor’s point, longer sections (higher test pressures), more cost-effective alternative (perhaps air instead of water) or whatever other options are favorable. I don’t have any problem with this provided that the Contractor could make a “justifiable” technical proposal, is “allowed” under the project agreement for such a deviation from the code and has the full “liability” over the pressure test.

 

[BigInch]

What contractor is going to take on the liability for proposing not to follow code.

What operator is going to take on the liability for proposing not to follow code.



From "BigInch's Extremely simple theory of everything."

 

[rconner]

It sounds like you may be interested in all the twists, turns and legal arguments of the perhaps not entirely dissimilar case of Juno Industries, Inc. vs Heery International mentioned at

http://fl.findacase.com/research/wfrmDocViewer.aspx/xq/fac.19941209_0054094.FL.htm/qx

. While I guess some will continue to argue that high pressure air testing as opposed to water testing can been done safely, Mr. Lawrence E. "Buddy" Hefner will be just as dead, Mr. William Bielawski, III just as injured, and I suspect the anguish on the part of the families and effort of all involved from all the parties standing around that decision will not be relieved.

 

[zdas04]

That is a sad story. I've read hundreds of similar suits and they are all sad. Something else they all have in common, in every single one of them there is clear evidence that either the procedure was incompetent or the procedure was not followed or both.

In this case, the procedure was not part of the brief, but there were some indications. The hydrotest procedure called for backfilling for a very specific reason (and in this case a water test not backfilled would have whipped the 24-inch pipe like a water hose, just like the air did). The reason still existed during the air test and it was irresponsible to skip that step either in the procedure or its execution or both.

The injuries and fatality are very sad, but don't blame them on the air, blame it on the process. There is an excellent chance that a water test not backfilled would have resulted in Mr. William Bielawski III drowning after he was injured instead of "just" being injured. No way to know.

David

 

[BigInch]

The process engineers have figured it out. If there are two processes that can make a chemical compound, and one involves dangerous procedures or toxic components, even if it is cheaper to manufacture, and the other one doesn't, which do you suppose they chose. I don't say that air testing cannot be safe. I just favor safe alternatives, where they exist.

As an example, how can you say this whole air testing thing, practice and procedure, is safe, if you yourself can't even get the procedure right all the time and, just once, maybe, just once, happen to think you can air test to 1.5? That is exactly the kind of things going wrong that cause these and almost every accident. When too many things ALL must go right to make something safe and just one going wrong can kill, the risk is high. When there are a large number of steps in a procedure, even risk management theories fail, A x B [&ne;] B x A. When you have a safe alternative, you need to consider using that alternative, even if it is a RPIA. Just because you can write a safe procedure to do something, doesn't necessarily mean that performing that procedure will be safe.

From "BigInch's Extremely simple theory of everything."

 

[brnt]

Workers are killed and injured all the time laying pipe. Trenches collapse, cables break lowering pipe into the trench, workers are run over by equipment, workers are overcome with toxic gas.It doesn't stop the industry from using the same metheods. In my province there is a governing body--Occupational Health and Saftey--that has codes and rules to mitigate the danger.

There are no satey codes on pressure testing pipe.

I am not being flippant but bringing up one incident from 20 years ago is dramatic but not fair.

This pipe is buried at least 2 meters. The pipe can't move. The pipe is exposed once where the air is injected and once where the guages are installed.Can the contractor manage the danger? Just like lowering a section of concrete box culvert into a trench there are procedures to limit the danger.

 

[BigInch]

There are safety codes on pressure testing pipe, buried or not, even for water pipe. If you don't want to use them, or they don't officially apply in Canada, that's between you and your lawyer.

From "BigInch's Extremely simple theory of everything."