Did a search on here, didn't see it as a topic.

Does a double wall pipe thickness tester exist? Any details please.

Not in ultrasonic form (that I'm aware of anyway).  No matter how tight the liner-to-shell fit, ultrasound will bounce off between the layers & only measure the thickness of the shell (as long as you are placing the probe on the outside surface).

I do have some customers that use their ultrasonic tester from the inside diameter which will give you a reading on the liner.  The question is how accurate is that actual measurement because of the concave surface that you would be placing the probe on?  This also then makes you have to open the pipeline up anyway so you can visually inspect that liner.

The other way that an ultrasonic tester would work is to remove a portion of the shell & then measure from the OD of the liner material.  Now, where do we put those 'windows' in the shell of the tubes or elbows for this to work?  Will it have a negative affect on the working pressure (or burst pressure) of the pipe or elbow? Most likely anyway.

I also have some customers that use a good ole fashioned caliper to measure.  Again, you have to open up the pipeline, visually inspect, & measure any areas that may be suspect upon inspection.

If anyone knows of an ultrasonic thickness tester that works on double walled tubing without addressing the above, I'd question how accurate it would be anyway.

Tom Johnston

BTW - Ultrasonic testers are not accurate on cast manganese elbows either.  No two readings will come out the same due to the metallic composition.

Thank you for the reply, guess I'll stick to breaking it apart and visually inspecting it.