[SBE] Ultrasonic Leak Detection

[Edwin Bukont]

J. Fred Reily always said 'its not the tube' and the leak is not always on the tower.
 
Several engineers and tower folks had spent the better part of 15-20 years dealing with a leak on 600' of 3-1/8 rigid line.  By the time I got there, the place was being pressurized with a dewar...the equivalent of I think 8 typical N2 tanks.  I did replace that with a dehydrator, which had to be serviced after about a year.  New station owners said to have the tower crew inspect the line again (mind you, it was always the same tower crew) when doing the due diligence.
 
In the process of their inspection, for whatever reason, I stepped up on the base pier of the tower and wrapped my arm around the transmission line, which was now about ear level....and thought I heard something rushing in the line.   A return visit with stethoscope indicated there was indeed some sort of noise in the line.  Working back along the  line, it got louder as I went towards the building.  Since the level got louder, it was unlikely to be air rushing in the line, but maybe something vibrating the line.
 
It turned out to be where the line entered the building, and some knuckle head had mounted the coax switch almost flat to the outside wall (straight thru, not with elbows and into the switch, right above the dummy load, with just barely enough room for the downward transition to the dummy load.  They used a short peice of solder flange line to get from the switch to outside, such that the flanges were inside the block wall.  The wall was sealed, of course.  The rigid line seal was damaged, probably from wrestling with the too tight fit.  The noise of the gas was not noticed inside the building because the building is noisy and the gas was venting into the wall.  All that wasted time and cost to inspect a leak that could have been avoided by proper, rather than cute, engineering.  The building was big enough and had enough ceiling clearance to properly mount the switch and bring a proper run of line inside the room.  
 
The point being,,,has the system been fully disassembled  at the easiest to access end and fully inspected rather than assuming the leak is further along.  Have you tried listening for any noise in the line?
Edwin Bukont CSRE, DRB, CBNT Comm-Struction and Services LLC P.O. Box 629;  Bel Air, MD 21014 USA V- 410.879.5567 F- 240.368.1265 C- 240.417.2475 ebukont at msn.com Member: IEEE, SBE, AES, PMI Digital Media and Power Systems Integrators. A Harris Broadcast Channel Partner