Acid pipeline (Polypropylene lined) leak detection

[soken2006]

In our steel pickling line, there are always little leaks which caused us lots of downtime. Leaky flanges, nipples, pipes, gaskets, and pipe connections. Is there a technology or suggestions to better detect them or predict them ahead of time so we can schedule for repair? Thanks

 

[BigInch]

Internal inspection pig. See my web page on pigging.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[soken2006]

Thank you very much for your input. Would you mind to elaborate or may I actually contact yourself to further discuss what Internal inspection pig is? Thanks.


My number: 1-800-263-9305 ext. 3167 (CANADA)

 

[Gator]

Here's a good start:

http://en.wikipedia.org/wiki/Pipeline_inspection_gauge

http://www.ppsa-online.com/about-pigs.php

Paul

 

[BigInch]

Sure.

Internal "pig" inspection is accomplished by a device "pig" that is introduced into the pipeline where it is pushed along by the fluid as it takes magnetic field readings of the pipeline circumference. The readings are correlated to remaining pipeline wall thickness. It is very convenient for long pipelines, but the pipeline must have fittings for introduction and removal of the instrument. Those fittings could be installed temporarily.

Ultrasonic inspection may also work, but is generally limited to inspecting specific problem areas, rather than the total length of a line.

If the line is above ground, there may be some other options, such as infrared, but I know far too little about that.

No phone numbers or e-mail addresses can be posted on this site, hence you can find my contact info in the Contact section of my pages.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[pvcman]

Are you having leak problems only at threaded and flange areas?
What kind of pressure and temperature are you running at?
Anytime you put threads on Polypro you derate pressure almost 50%. Flange gasket materials can be an easy fix .Send me the applications and I will try to help.Detecting the leak is not the way you solve this problem.Finding out why the system is leaking is the cure.
TAMP Temp Application Media Pressure Size

 

[moltenmetal]

Lined piping suffers from one major disadvantage: every fitting is flanged. Every elbow, tee etc.- that all adds up to a lot of joints needing periodic re-torquing and representing a potential future leakage point.

Periodic re-torquing of the flanged joints is key. The liners "creep" over time and re-torquing is essential to keep the joints tight.

I don't know what you're talking about with respect to "nipples etc." If you have any solid polypropylene components on your pickling system, eliminate them in favour of flanged connections whereever possible. I'm presuming your pickle liquor is hot! Polypropylene is a great material and can function as a pressure-bearing piping material to temperatures as high as 105 C at VERY MODEST pressures, but that all breaks down if you use NPT threaded joints. Creep tends to take over and makes these a leaky mess in short order. Substituting PVDF or PFA will give you modestly better performance at greatly higher cost.

You can also take particularly troublesome smaller assemblies with multiple fittings (valve manifold stations etc.) and have a welded component system rotationally lined with Tefzel or the like, to eliminate a large number of flanged joints. See Crane Resistoflex's website for examples.

 

[awol]

As suggested, in-line inspection is a good approach for proactive measures. For the instances where ILI and repair are both needed, suggest you contact a full-service pipeline company. Companies like TD Williamson can provide both services and help predict future leaks.

 

[dcasto]

pigs won't find the things you are having trouble with, flanges, threaded fittings, ect. In the words of the quality guru's, do not depend on inspections, if you can design it right up front you are better off.

I'd look into dfferent coupling systems or even double pipe systems. Seams to me a a graylock or sanatary coupling system would be better in your system.

 

[weeeds]

We perform Helium Leak Testing which will locate areas of "developing" leaks. Since Helium is such a small molecule it will find its way through very small leak paths and can show where a leak path is developing.
This is very effective, does not require shutting down the complete system, and leaves no residue or mess to clean up.
If you are interested I can contact you and provide more details of the process.

 

[STYMIEDPIPER]

widla
I 'googled' helium leak testing and found the web sites interesting. I have attached a site which explains about the 'over-pressure' and the 'vacuum spray' tests.

Have you tried both types of tests and which one do you currently use to test your acid piping??

http://www.ndt.net/article/ecndt98/offshore/268/268.htm

 

[BigInch]

Is there a limit to the scale at which He testing can be accomplished? In other words, can I get for instance, 1,000,000 std cu meters for a pipeline test?

http://virtualpipeline.spaces.msn.com

 

[weeeds]

STYMIEDPIPER:
We actually do the testing as part of our services, both in the shop and in the field.
We use both Vacuum and Pressure type testing, depending on the application. Each application has its positive and negative sides.
For existing acid piping we would most likely use the pressure method. Based on the parameters of the system we would pressurize with either pure Helium or a Helium/Nitrogen mixture (to control costs for larger volumes). The test pressure needs to be only a few PSI, but the higher you can go the easier and quicker it is to get the results. Also, using the pressure method you do not need to clean out the piping system in order to do the test. The Helium will find its way through thin films of residue and then through the leak path. It really is a powerful tool. The testing can be performed without dismantling the system which saves a great deal of time and money. All you need to do to be able to test is isolate the piping and have a port to supply the tracer gas. Most systems have these requirements in place already.

BigInch:
There is no practical physical limit for the equipment being tested, but an engineering evaluation needs to be performed prior to the start of any testing to ensure the equipment is able to withstand the test process. For high volumes like you describe we would mix the Helium with another inert gas such as Nitrogen to about 5% Helium and still be able to get meaningful results. If your pipeline in new or in clean service, it may be more advantageous to examine the vacuum process where the amount of Helium used is very small. The trick with this method is to ensure that the system can handle the vacuum condition without collapsing. An evaluation of the project at the outset will determine the best approach.