It happens at every plant: during start-up after a turnaround, the system components expand due to the increase in temperature. This can cause leaks, which can be tricky to detect. What added value can the latest infrared and ultrasonic cameras offer?
The source of a leak is difficult to locate
André Reinaerdts (Production Manager Ammonia at OCI Nitrogen) acknowledges the problem. “After a turnaround, we check the spots that have been open. Then we add slightly pressurized nitrogen to the system and check suspected weak points by soaping them. Where the soap bubbles up, there is a leak. It's a reasonably reliable method, but it very much depends on the human eye. And of course, there are some parts of the plant that you can't reach without a scaffold,” says André. “Another common technique is to listen for or try to smell the gas,” adds Rob de Heus (Champion World Class Maintenance at Sitech). “But it’s difficult to determine where a noise or a smell is coming from when a plant is up and running. You can also use a Dräger tube to show that there is in fact a leak, but not where it is.”
“Infrared cameras produce thermal images, which show very clearly what hazardous substances are escaping and where the source of the leak is located”
Rob de Heus, Champion World Class Maintenance at Sitech
Infrared camera proves effective
Sander Schepers (Asset Engineer Mechanical at Sitech) found himself faced with this problem last year. “After we started up AFA2, our gas detection sensors told us that we potentially had a leak somewhere around the gas turbine. Since we were unable to find the source ourselves, we brought in a specialist company to locate the cause via ‘optical gas imaging’ using infrared cameras,” says Sander. “Infrared cameras produce thermal images, which show very clearly what hazardous substances are escaping and where the source of the leak is located,” adds Rob. Using the infrared cameras, several small leaks were discovered which had evaded detection using conventional methods.
Searching remotely using ultrasonic waves
“Some time ago, we heard a high whistling sound in the vicinity of a turbine, which could indicate a leak or resonance vibrations in the machine,” Rob continues. “We were unable to track down the source of the noise ourselves, but the company with the infrared cameras helped us to find the leak then too – this time by using an ultrasonic camera for ‘acoustic leak imaging’. That camera also proved effective. In addition to the source of the noise, we also discovered several other small leaks.” André explains: “They searched for the source of the noise using a directional microphone. The advantage of this technique is that you can search from quite a distance, including at a height. You don’t have to physically be there yourself, which makes it quite safe. It allows you to locate all kinds of leaks, large and small. The only thing you have to determine yourself is what medium is leaking. In this particular case, we also detected a signal up high, which we would otherwise never have been able to see.”
Accurate, reliable and safe
“We see lots of opportunities for using infrared and ultrasonic cameras to detect small leaks,” Rob concludes. “The measurements are accurate, reliable and, since they can be carried out at a distance, it’s safe. We are very curious to see whether other organizations on the Chemelot site are interested in this, so that we can pool our resources.”