What would be a suggested method to do Non Destructive Testing on a system with Alloy 20 1/2"OD x 0.035"Wall bent tubing and compression fittings. The system is transferring 50% sulfuric acid @ 68-74F @ <40PSI. The current Alloy 20 system replaced a poorly designed and poorly installed polypropylene system that experienced leaks at fragile flange connections and valve stems. Although Alloy 20 will withstand the SA for a period of time it will eventually erode away. I want to be sure that the preventative maintenance will catch problem areas prior to tubing failure. The system is designed such that the tubing, not the fittings, can be replaced easily. Tubing should be the weakest link, particularly where it has been bent.

Dan Alloy 20 tubes with such a small bore (12 mm bore) and 0.9 mm wall thickness. Eddy current technique cannot detect and will not prove to be an effective NDT tool for such thin walled tubing. ET will not be possible for such thin walled tubing. Even to set a calibration standard for such thin walled tubing by ET will not give accurate results as machining to high precision of such thin walled tubing for calibration reqires electro-etching to high degree of precision. You have to live with erosion - corrosion at the bends of such thin walled ltubing at the bends if velocity increases due to temperature being higher than design. You may have to think of a higher wall thickness tubing with a higher OD tubing to use ET. C.V.Srinivasan Nishi Engineers Pvt Ltd Chennai 20 India July 01, 2004 E-mail: nishi@vsnl.com >Dan: > >You might look into eddy current inspection if someone has >probes that will go in 1/2" diameter tubes. > >Hope this helps! > > > >David Hendrix >The Hendrix Group Inc.