Expansion joint spark testing

[jistre]

I know that when dealing with things like lined pipe or lined valves, spark testing for holidays is a good idea.

However, I'm looking at some PTFE bellows expansion joints and some elastomeric expansion joints. Is there any reason why you would spark test these?

It seems to me that any holes in these types of joints would make themselves evident during the pressure test since there's no external steel or iron casing to hold the pressure in. Further, there's not steel or iron casing to be corroded from the inside out.

I'm not an expert on these things, so if anyone can think of any reason to spark test these things, even one unrelated to what I'm thinking of, feel free to pile on because it's good information to have.

Thanks!

 

[vesselfab]

SPARK TEST...or Holiday check....is to check the lining of a steel part to make sure there are on discontinuities or "holidays" in the lining that woul exposes the steel parts to service fluids or gas.

since these are solid ptfe or elastomer, that particular test would be not only unjustified but impossible to do without the steel to conduct the signal.

 

[jistre]

Well, it could still be done for holiday checking. The test doesn't care if the metal used for ground is actually part of the joint or not and you could wrap the bellows with sheet metal to provide the ground. With this kind of part, though, pressure testing is a far better way to test for holes.

I guess I'm really asking if anyone knows of any reason OTHER than holiday testing to do any kind of spark test.

 

[rmw]

I assume that these are piping EJ's and not ductwork EJ's, and if so how about a hydrotest? If ductwork, them you could build a jig and pressurize them with air and soap bubble test the outsides.

rmw

 

[corrosionman]

Jistre,
No matter how the joint has been made you can ensure there are no defects in the material very easily before it is installed so giving time to carry out repairs if necessary. The spark tester will "jump" about 1.5 inches so either hold a piece of steel on one side and test from the other, or paint one side with graphite dust which will then act as the earth conductor instead of the steel.
cheers CM

 

[jistre]

Yep, piping EJ. I'm trying to get a solid argument AGAINST the spark test on these things because the mfg. standard is to pressure test to at least 100 psig, which should show any holes in the material.

It's my feeling that there is no reason to incur the added costs of spark testing since it would not show us anything that the pressure test wouldn't. I know that the mfg. will do it for an additional cost, so I'm not worried at all about whether or not it can be done. I just wanted to make sure there was no reason to do one that I hadn't thought of, and I'm pretty confident that there isn't and my bases are covered when the client asks about it.