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- since 1996 -
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Technical Discussions
Guru
Guru
00:56 Oct-14-2008
PE Coating defeats

What is the best method/system to confirm Air entrapment in PE Coating of Pipes?


    
 
 Reply 
 
Tom Nelligan
Engineering,
retired, USA, Joined Nov 1998, 390

Tom Nelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
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.


    
 
 Reply 
 
Simon Amallraja
Simon Amallraja
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.,

Simon


    
 
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faheem anjum
faheem anjum
09:22 Oct-23-2008
Re: PE Coating defeats

plz send me the coating defect book


    
 
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