Product category:
Monitoring and sensor equipment and systems
News Release from: Sensistor Technologies | Subject: Hydrogen-based leak detectors
Edited by the Manufacturingtalk Editorial
Team on 14 October 2005
Hydrogen detects leaks in refrigeration
units
Hydrogen-based leak detectors have replaced air/water submersion tests to more effectively detect leaks in wire-on-tube evaporators used in refridgeration un its.
Hydrogen-based leak detectors from Sensistor Technologies are playing a key role in the production testing of refrigeration units manufactured at Kenmore International's UK operation at Crook, County Durham The Kenmore UK operation is one of Europe's leading manufacturers of wire-on-tube evaporators, which are exported all over the world and are used by many household names in the refrigeration industry
This article was originally published on Manufacturingtalk on 21 Oct 2004 at 8.00am (UK)
Related stories
Counter flow probe detects leaks in confined space
Counter flow probe, developed as an accessory to a hydrogen leak detector, locate leaks in enclosed spaces such as pneumatic cabinets, engine rooms, airplanes, or boats.
Hydrogen gas lightens leak testing
Hydrogen can be safely employed for leak testing, advises Dr Claes Nylander of Sensistor Technologies, and the gas penetrates leaks readily and vents away very easily.
Kenmore, a Norwegian-owned company with other manufacturing plants in Germany, Italy, China, India, the USA and Turkey, supplies products for a wide range of applications from domestic fridge/freezers up to large industrial bottle coolers.
The wire-on-tube evaporators are produced under tightly controlled conditions in accordance with DIN8964 and ASTM B117-200h.
The evaporators are made from refrigeration-quality steel tube, and range in size from one to eight shelves, with a maximum overall evaporator length of about 1.2m.
Further reading
A hat-trick of benefits in data recording
Metallic pigment and coatings manufacturer Wolstenholme International Ltd has scored a hat-trick of benefits with the installation of an ABB InformIT SM3000 multipoint recorder.
State of the art car dealer uses Abac compressors
The latest low noise ABAC compressors are being used to provide a high quality supply of compressed air for powering various air tools and workshop equipment at a new Hamer Toyota dealership
Weekend fan parts search saved chipboard output
Tens of thousands of pounds worth of lost production at chipboard manufacturer Sonae Industria, Merseyside, has been saved by ABB Drives Alliance Partner Central Electrical.
The tubes themselves often take convoluted shapes, and can be round, square or a combination of both, which inevitably leads to joints being introduced to achieve the final shape.
The number of joints per unit ranges from two to eleven, and can involve steel-to-steel or steel-to-copper welds.
Even with the utmost care being taken during the manufacturing process, these joints are a potential source of leaks, and so it is necessary to introduce some form of leak detection to provide quality control at the end of the production line.
Traditionally, leak testing has been carried out by immersing the units in water, filling them with pressurised nitrogen, and looking out for bubbles.
While generally effective, this method is relatively cumbersome and messy, and is not always 100% effective because bubbles from the smallest leaks (which are invisible to the naked eye) are relatively infrequent - perhaps one every ten seconds - and can occasionally be missed.
Kenmore engineers were aware that other techniques for 'sniff' testing were available, and looked at a number of alternatives including a chamber test system using helium as the tracer gas.
They were eventually led to the Sensistor units by a customer who was using them, and initially started out with three of the company's earlier 8505 instruments.
However, the biggest step forward in productivity came when Kenmore invested in the latest Sensistor H2000 leak testers, which have built-in digital electronics to make the logging and display of results much easier.
The Sensistor units are mounted on a control station in conjunction with simple controllers that allow each operator to log on and specify the unit being tested, as well as storing the test results and 'pass/fail' details.
Once the operator has logged on and specified the test, the operator has only to pass the 'sniffer' probe over the joints and everything else proceeds automatically.
Hydrogen is the ideal tracer gas for leak testing in production environments such as Kenmore's plant.
It is the lightest element, with higher molecular speed and lower viscosity than any other gas.
As a result, it can easily be introduced into the system to be tested, mixes more quickly with air and other gases, and is easily evacuated.
More importantly, it has the highest leakage rate of any gas.
Moreover, the normal background concentration of hydrogen is just 0.5 parts in 10power6, in contrast to helium, which at 5 parts in 10power6 is ten times more common.
Background concentration in air is a limiting factor for any detector.
The Sensistor H2000 is sensitive enough to detect background concentration levels of hydrogen.
This allows it to identify even the smallest leaks, with a sensitivity of just 5 ( 10-7mbarl/s (millibar-litres per second).
The detector uses a semiconductor sensor head mounted on a convenient handle.
The sensor is specifically designed for hydrogen, and the presence of other gases does not affect the results.
The device does not contain any moving parts, making it completely maintenance free.
Les Shaw, Quality Engineer at the Kenmore plant, is very pleased with the Sensistor units.
"The instruments are easy to use, and the operators like them because the test process is clean and dry." He says: "In addition, because they are more effective at finding the smaller leaks, we believe the overall attention to detail in our manufacturing process has improved.".
• Sensistor Technologies: contact details and other news
• Email this article to a colleague
• Register for the free Manufacturingtalk email newsletter
• Manufacturingtalk Home Page
Search the Pro-Talk network of sites
