Kenmore International (Oslo, Norway) is one of Europe's leading manufacturers of wire-on-tube evaporators. These evaporators are exported around the world for use in domestic refrigerators and industrial bottle coolers.
At its UK facility in County Durham, England, the company produces the evaporators from refrigeration-quality steel tube in a range of sizes and configurations, with a maximum overall evaporator length of about 1.2 meters.
The tubes themselves often take convoluted shapes, and can be round, square or a combination of both. This inevitably leads to the use of joints to achieve the necessary final shapes. The number of joints per unit ranges from two to 11 and can involve steel-to-steel or steel-to-copper welds.
Even under the best conditions, these joints represent a potential source of leaks, so the company has incorporated leak detection as part of its production process.
Traditionally, leak testing has been carried out by immersing the units in water, filling them with pressurized nitrogen and looking for bubbles. But while this method is generally effective, it is cumbersome and messy, and not always reliable. Bubbles from the smallest leaks can be relatively infrequent-perhaps only one bubble every 10 seconds-which means they are easily missed.
To improve the process, Kenmore invested in a number of H2000 "sniff" testers from Sensistor Technologies (North Billerica, MA), which detect leaks using hydrogen as a tracer gas.
The testers, which are equipped with built-in digital electronics, are mounted on a controller that allows operators to both specify the unit being tested, and store test results and pass-fail details. Once an operator has logged on and specified the test, all he has to do is pass the sniffer probe over the joints. Everything else proceeds automatically.
The detector uses a semiconductor sensor head, does not have any moving parts and has a sensitivity of 5 x 10-7 millibar-liters per second. The sensor is specifically designed for hydrogen, so the presence of other gases does not affect the results.
"The instruments are easy to use, and the operators like them because the test process is clean and dry," says Kenmore quality engineer Les Shaw. "Because they are more effective at finding the smaller leaks, we believe the overall attention to detail in our manufacturing process has improved."
For more on industrial leak testing, call 978-439-9200, visit www.sensistor.se or eInquiry 4.