James Cropper is a specialist paper group comprised of three divisions, which include the manufacture of high quality papers and bespoke laminar materials. Lee Finch works at their plant in Cumbria and wrote this piece on using an Ultraprobe to find a tiny leak.

"I attended the Level 1 Ultrasound Course in 2010, and have since had many hours of successful use with the Ultraprobe on steam traps and compressed air leaks, but I must tell you about my biggest triumph yet."

"We run a rotary screw gas compressor (320 psi) to feed our gas turbine. We keep a spare of this in case of breakdown charged with nitrogen in storage (in a quiet area); however the nitrogen was always leaking out. I was tasked with finding the leak using the Ultraprobe 2000, and I spent a couple of hours going over every millimetre, closely following the flanges, seals, etc, with no joy."

"I charged the unit up to 100 psi with nitrogen and quickly found a small leak coming from a bolt head. Chuffed, I sealed the leak and went about my business. A day or two later, though, it was reported to me that the gas compressor had lost pressure again."

"Frustrated, I went back and did another check. The original leak was still OK, so the unit obviously had another one that I had missed. Now that the unit was charged to 150 psi, surely I would be able to hear this amount of pressure escaping from even the smallest of holes? Well, after a few hours of trying different things, I was getting nowhere. Even bubble solution wasn't showing anything - that's how small this leak was!"

"In the end, I threw caution to the wind and put the Ultraprobe into 'fixed band' mode, attached the Close Focus Module, set the sensitivity to 10 and scanned every millimetre of the compressor again. Eventually, I found the faintest leak I have ever heard - so faint that you really had to strain to hear it. Normally these settings would have blown my ears away in any other environment! I sealed the leak (a thread on a drain valve on a flange) and it is still holding to this day."