04:50 Oct-14-2008 Re: PE Coating defeats If the coating is external, a simple straight beam test with an ultrasonic flaw detector and a contact transducer can usually find bubbles larger than 0.5 mm or so. Transducer selection will depend on polyethylene thickness -- try 10 MHz up to about 5 mm thickness, and 5 MHz up to about 25 mm.
If the coating is internal and there is access only from the outside, the test is significantly more difficult because of the poor acoustic impedance match between steel and polyeythlene and the numerous multiple echoes that will occur within the steel. If the PE is less than half the thickness of the steel, then any bubble echoes will occur between the first and second backwall echoes from the steel, but if the ratio is larger there will be difficulties. Testing from the ID with special fixturing is a possibility.
07:06 Oct-14-2008 Re: PE Coating defeats ----------- Start Original Message ----------- : What is the best method/system to confirm Air entrapment in PE Coating of Pipes? ------------ End Original Message ------------
You can try Holiday Detectors to identify the areas of air bubbles. This will be easy and simple, if the test reqt is not so critical like coating of PE for corrosion protection on pipes etc.,
The FlexoFORM™ solution integrates flexible phased array probe
a scanner to solv
e the challenges that come with inspecting pipe
When combined with a water column, this solution can be used to
easy-to-interpret data on elbows with diameters ranging from 4.5
in. OD up
to flat and offers many benefits.