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Up Topic Welding Industry / Inspection & Qualification / Dye Penetrant Testing on PVC Pipe
- - By swsweld (****) Date 08-08-2008 01:49
I've got an 8" pvc pipe that has been "scuffed up" with a track hoe bucket. No obvious crack or tear to the eye. It's very brittle and susceptible to cracking upon impacts. The insulation took the brunt of the impact. We are out of this size pipe for the job. I can put a repair coupling and eliminate the potential danger OR I can PT the spot.

Anybody have experience or opinions on the value of a PT on pvc pipe?
I know that it can be done but I'm concerned about the affects of the penetrant and cleaner might have on the material.

The pipe manufacturer said not to, but they have never been asked this question before and of course do not want to assume liability if they said it was OK. Err on the side of caution.

A coupling will not be available until next week.
It will get a hydrostatic test but really need to know before we fill the line.

Thanks in advance for any input.
Parent - By 803056 (*****) Date 08-08-2008 05:07
I had a cheap "welder's" watch once with a plastic case. I sprayed it with some solvent/remover to clean off some penetrant overspray. POW! The plastic literally blew apart. The springs in the retainer pins on the strap popped the case into several pieces when the solvent reacted with the plastic.

There are many types of plastic in use today. One never knows how it will react with different chemicals. I think you did right by asking the manufacturer, but you have to remember they are risk averse, so they most likely will say no if they don't have all the details.

Best regards - Al
Parent - - By Mikeqc1 (****) Date 08-08-2008 14:00
i found this please read the general description it may sway your desision of PT testing

http://www.magnaflux.com/files/library/pds/material_product_data_sheets/Spotcheck~reg_SKL-WP_Water_Washable_Penetrant.pdf
Parent - By NDTIII (***) Date 08-08-2008 21:00
Why dont you just do a pressure test on it?
Parent - By swsweld (****) Date 08-09-2008 02:22
Mikeqc1,that will do it.
Between Al's watch and this product data sheet I DEFINITELY will not PT the PVC pipe.
I spoke to the manufacturers CWI and he called the engineer and they had no info or experience with this but suggested that I not do it.
I checked Dynaflux (that is the brand that I have) web site but did not uncover anything close to the warning in Magnaflux site.

NDTIII, I will do a hydrostatic test as stated it the original post. This line is approx. 700' long and very flat. No pitch for draining. We also will put at least one lift(12-18 inches) of soil on top of the pipes so that when we test it the PVC pipe will not move. Better to find out before we fill the lines if possible. Air test is prohibited and dangerous.
I will leave the backfill off of that spot and then hydro the line and observe. 150 psi.

Thanks for the replies.
Parent - By CWI555 (*****) Date 08-11-2008 11:51
Try water washable. Nothing says you "have" to use the Solvent removable. You will only have to worry about the penetrant itself then.
Parent - - By Joseph P. Kane (****) Date 08-11-2008 13:03
Tim

I had to find a leak in two miles of back filled water pipe one year.  I used Freon.  It will go through cracks, where air will not pass.  I used an ordinary battery powered leak detector, and walked along the line.  I was amused to find that the leak was back one joint up from the starting point, where I injected the Freon.  The Contractor who had already back filled and tamped  the trench per contract spec.,  was very very very  happy.  He dug up the first joint where I detected the leak, found a wet spot and replaced the rubber seal.  The second hydo test (24 Hour Test) passed.  He gave me a $1000.00 totally unexpected cash bonus for a $700.00 job that had no guarantees.   
Parent - - By swsweld (****) Date 08-14-2008 02:02
Gerald, you are correct. This is just for info only. I only have the solvent removable on hand.

Joe, I hope I never have to resort to using Freon but that is good to know. I commonly backfill and compact before testing. The steel pipe doesn't worry me but the PVC SDR-21 gasketed pipe does. Was the line you found the leak on a PVC pipe or ductile pipe? We have used dye to detect leaks but didn't have enough circulation to work.

I've got about 4000' of 8" PVC and 4000' of 6" steel pipe to hydro test in a week or two 100% compacted with lots of offsets/thrust blocks. Couldn't leave it open to the summer downpours for too long so we had to backfill it. Hoping for the best but if drops pressure I may be in touch.

I bet he was happy.

Thanks for the help.
Parent - By 803056 (*****) Date 08-14-2008 02:07
There are too many types of plastic to list, each with its own properties. Many of them are resistant to oils, but there are others that can be degraded by oil based materials. Dye penetrants of all kinds are oil based and can interact with certain plastics.

Best regards - Al
Parent - By Joseph P. Kane (****) Date 08-15-2008 00:31 Edited 08-15-2008 00:35
Tim

The pipe was Ductile Iron.  The leak was reportedly in a gasket.  When I got toward the end where we were putting the freon in, I thought that the leak I detected came from leakage in the filling operation, which I picked up because I was downwind.   I figured that the method failed. However, when I passed the second joint coupling, the alarm went silent.  The contractor called up the back hoe, and a few operating engineers, and dug up the second joint area.  They didn't even get the whole joint uncovered when they saw the wet sand.  Everyone was extremely happy.

By the way, I believe that the freon method is probably illegal now.  However, If I were faced with 8000 feet of back filled and tamped pipe to dig up along a busy road, I would probably ignore that law.
Up Topic Welding Industry / Inspection & Qualification / Dye Penetrant Testing on PVC Pipe

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