Accuracy With 



Respect to Damage 



(%) 



Spacial 



Width, 



Aw (mm) 



Minimum 



Scan Time 



(min) 



Internal 



External 



0.01 

 0.02 

 0.03 



0.03 

 0.05 

 0.1 



6 



8 



12 



12.0 

 5.1 

 1.5 



A brief summary of the underwater CAT system requirements for inspection 

 of wood pilings follows. 



• Fan Beam Full Illumination Scanner 



• 78.3 Fan Angle 



• Center of Rotation (COR) - centered detector array configuration 



• Iridium Source 



• 200 Curie Intensity 



• 127 Detector Array 



INDIRECT ULTRASONIC TESTING 

 Commercial Demonstration 



A demonstration of commercial ultrasonic inspection capabilities by 

 Agi and Associates was completed in 1982. Timber piers known to suffer 

 from marine borer damage (San Diego, Calif., and Pearl Harbor, Hawaii) 

 were inspected. 



The basic components of the ultrasonic system used by Agi and Asso- 

 ciates are: two magnetostrictive transducers, a single trigger and 

 timing unit, a transducer drive, the received signal and amplification 

 system, and a meter presentation of the received signal. The transducers 

 operate at approximately 30 kHz and transmit over a fixed distance of 

 about 3 feet. A rigid framework maintains spacing between the trans- 

 ducers as they are moved along the length of the pile (Ref 12). 



The testing crew consists of two persons. One using scuba equip- 

 ment to scan the entire pile from the water surface to the mudline with 

 the sonic probe and a second on the surface to maintain a continuous 

 record of the sonic and visual data. 



The initial reading is taken at a known solid region of the pile 

 (usually above the waterline) and used as the standard reference. The 

 analog display in the surface unit provides a direct readout of the per- 

 centage of undamaged wood remaining in the pile cross section (compared 



15 



