Hydrotest of Pipe During Winter 3

[SeanB]

We have to hydrotest a new ULSD shipping line. The pipe is approximately 10,000 ft in length. The pipe is to be hydrotested in April, 2006. As we are located on the eastern coast of Canada there are concerns about hydrotesting with water. Thus we are considering other mediums for hydrotest fluid. One idea floating around is to use ethylene glycol. However, this would require a significant amount of EG and then there are disposal concerns. I would like to know if anyone out there has expeience with hydrotesting in cold months and if you have any suggestions.

Thanks.

 

[vzeos]

I have done hydrotests using antifreeze mixed with water. The environmental people suggest using propylene glycol since it is more environmentally friendly than ethylene glycol. The use of a water glycol mix does not present any major problems other than spillage and disposal. Your strategy could minimize these problems. If you are going to test 10,000 feet, you might think about splitting the pipeline into test sections, say 10 sections of 1000 feet each, then after you finish testing the first section the glycol could be pumped into the next section to be tested, etc. Thus, you could purchase and dispose of one-tenth the volume of glycol than if you were to test the entire pipeline at once. In addition, I would suggest doing a pretest with high-pressure air to eliminate as many leaks as possible prior to introducing the glycol. Also, you may experience some problems with freezing in your gage lines and taps. This occurs because glycol does not prevent the formation of ice crystals in the glycol/water mix and the ice crystals may clog smaller lines. This problem can be minimized by priming your gage lines with pure glycol.

 

[zdas04]

A lot of people in Eng-tips.com will disagree, but ASME B31.8 allows static tests with air up to 70% of SMYS. I've tested lines longer than your 10,000 ft with air with excellent results. You didn't say the diameter of your line or the test pressure, but as long as you keep the hoop stress below 70% of SMYS and your area classifications are consistent with ASME B31.8 air tests you can save yourself a lot of pain and suffering by just doing the test with gas (either air or an inert gas). All of the calculations are in ASME B31.8 or you can look at my web page for a document that pulls the issues into one package.

There are people in these fora that will tell you that I'm giving you irresponsible advice, and that the total stored energy in an air test is just too great to be risked. ASME disagrees with that assertion, and I've done dozens of big static tests with air with great success by following all of the rules.

Regardless of your final choice of test media, be very careful of the temperature that you put into your calculations. Eastern Canada in April can be pretty chilly and cold temperatures shift the brittle-failure curve dramatically.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

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[MJCronin]

Sean....

I agree with the above two options.

Furthermore, I believe that they are your ONLY two reasonable options. However, the use of PG will be fairly expensive and there is the cost of disposal.

I agree with zdas04 aboth the use of gas/air for pressure testing.

If there ever was an application where the dangers of air testing could be justified, I believe that this is it !!

I suggest that the best plan is a "segmented" air test of the system with a properly sized compressor system (consider and calculate the "pump-up time" required)

By the way, for carbon steels, I recollect that the minimum temperature where NDT is not a concern is -20F (ASME B31.1)

Will you be above this temperature in Canada in April ?

My opinion only

-MJC

 

[SeanB]

Thank you so far for the information. I thought I had put the diameter in my original query but I guess I didn't, it is a 24", 150# rated pipe. I have thrown around the idea of using air, but as mentioned by zdas04 there are concerns about the stored energy. I wonder if anyone has any experience with using a methanol/water mix?

 

[zdas04]

SeanB,
Before you get too far looking at methanol, look at its MSDS sheet. That is some hazardous stuff and you really have to be careful to keep it off the ground.

David

 

[jte]

Sean-

"... eastern coast of Canada..." Would that perchance be "King of Cats" territory?

Would it be horribly unreasonable to use diesel as a test medium for an ULSD job? Seems to me that it would be a reasonable candidate. See thread378-112650

jt

 

[SeanB]

I don't think you can actually use diesel as a test medium. It would be great if you could. If you have a leak you are then leaking diesel all over the ground rather than water.

 

[zdas04]

SeanB,
You might want to read the link that jte provided. Tests with relatively non-volitile hydrocarbon liquids are frequently done and are often a better alternative than adding anti-freeze to water.

Davud

 

[SeanB]

Just a follow up to the proposal of hydrotesting with Diesel. I checked out ASME B31.4 - here is what it states:

"The hydrostatic test shall be conducted with water, except liquid petroleum that does not vaporize rapidly may be used provided:

(1)the pipeline section under test is not offshore and is outside of cities and other populated area..."

My pipeline is within city boundaries, thus is not an option.

 

[adrianviorel]

Just a crazy idea. What if you put some resistances , at a certain distance from each other, to warm the water? Fluid will not go under 5 deg Celsius, and you may use the normal nozzles of the pipeline.