Re: concrete inspection : Can anyone advise me of methods to inspect concrete lined tanks and pipes. Visual is not a problem but defects which are not readily visible are. It has been suggested that I try low freq UT
03:00 Jan-27-2000 John O'Brien Consultant, - Chevron ETC , USA, Joined Jan 2000 278
Re: concrete inspection It depends upon what the specific application is and the defects you are considering.
Cement Lined Carbon Steel Piping as commonly used in Firewater systems is commonly a problem with internal cement lining failing at the welded field joints in particular. Many people have had success in finding gross defects by using Infrared Imaging where there is sufficient variation in the internal process fluid and the external temperature. Areas where the cement has broken away show up warmer. It is however a quick search technique, very difficult to quantify damage with and of course you need to pipe surface to be available for inspection.
The Lixi Scope imaging device mentioned by Joe Pascent will of course also do an excellent job and the new version will provide quantification information if calibrated for the application.
Conventional ultrasonic is also commonly used from the non concrete side to look for lack of interface. It can be slow and in some case unreliable. Also is most effective when substantial deterioration has taken place.
If you wnat a more sophisticated inspection for early damage such as disbondment then probably something like the Ultraspec Ultrasonic Spectroscopy System would be best. This uses swept frequencys which can be analysed in real time and provides very good indications of back surface properties at much higher sensitivities. This should clearly show breakdown in bond interface between the base pipe and the lining material. Concrete lined tanks depends on how much access you have to them and the extent of damage expected. If you can get to the lined side - Infrared Thermography either passive or Pulsed Wave may provide information on disbonding etc. Technique is used often in concrete decking.
If you can get access to the outside (I assume these are typically carbon steel tanks lined with cement for water slops, sewage, seawater etc. If this access is available you may be able to apply an AE test but you have to consider signal path travel , thickness of cement etc. Scanningthe surface with a Neutron Backsactter device might indicate areas of differentiation where water has seeped into structure etc.