Jul 9 2015
New hydrogen-based leak-detection technology is helping automakers and their suppliers reduce costs and improve quality.
More than 1,000 leak tests are performed on the average car and its components before a vehicle rolls off a final assembly line and into a new-car showroom. Fuel, brake and other critical safety systems are tested multiple times for leaks, as well as driveline components, fluid containers and wheels.
More and more of these tests are conducted with hydrogen-based leak detectors, less expensive than helium-based systems and significantly better than more traditional water and pressure-decay methods.
The early detection of even the smallest leak with a hydrogen sensor can play a key role in reducing costs and improving customer satisfaction, according to Thomas Parker, the North American automotive sales manager for INFICON, a leading global supplier of leak-detection systems.
The sooner a leak can be identified the quicker it can be fixed or eliminated through improvements to the manufacturing process, Parker says.
"An automaker or its suppliers may know that an individual engine or transmission has a leak, but finding that proverbial needle in a system's haystack is the real challenge," notes Parker. "Our Sensistor Sentrac is one solution for quickly pinpointing a leak. It uses a maintenance-free microelectronic sensor that can focus 100 percent on detecting a safe hydrogen mixture that is injected into a component. "
Most manufacturers use basic air testing, also known as a pressure-decay test, to leak check engines and transmissions on a pass-fail basis. A more sophisticated helium or hydrogen "tracer" gas must then be used to pinpoint actual leak locations, although some manufacturers still use out-of-date water tests.
Engines, for example, often are pressure-tested on a pass-fail basis. Each subsystem -- oil, coolant and emissions -- is pressurized simultaneously at a test station. (Permissible leak rates may vary from 0.05-10.00 SCCM at pressures from 100-500 kPa depending on the test circuit.) In case of failure, each component then will need to be retested with tracer gas to identify exact leak locations.
Parker estimates that leaks requiring fixes or repairs are found on more than 25 percent of the engines and transmissions annually produced for cars, light trucks and commercial vehicles sold in North America.
Based in Redford, Mich., TrigTec is a company that recently introduced INFICON technology to improve engine and transmission testing. TrigTec provides test products on a global basis for powertrain and vehicle-assembly operations.
"In an effort to eliminate water testing and replace a less effective performing hydrogen leak tester, we decided to utilize INFICON's hydrogen-based technology last year," said Steve Kravis, TrigTec's owner and president. "Our Sensistor Sentrac leak detector provides much more accurate test results. Leaks can be detected more quickly and sniffer recovery times after pinpointing a leak are much shorter as well."
Wet testing also could be used to pinpoint leaks, but is considered out-of-date. The time required to visually locate "leak bubbles" created by a specialized soap and water mix, for example, would be excessive in today's rapid production environment.
There are a variety of other downsides to wet testing. Using a soap-and-water solution to coat an engine, then waiting for bubbles to form might take hours. It also requires line-of-sight visual verification. Large leaks also can blow away bubbles and cause a leak to be overlooked.
In addition, Parker points out that there is no way to reliably quantify leaks using soap bubbles. And water-soap solutions can lead to unsafe work conditions that can result in slip-and-fall accidents. Submerging a transmission or engine in a soap-and-water solution also can damage electrical sensors and cause rusting that might affect warranty costs.
Parker adds that many manufacturers are moving to a "no liquid policy" to prevent rusting as well as liquid damage to electrical parts. A hydrogen tracer-gas mixture is a much safer, dry method for detecting leaks.
Source: http://www.inficonautomotive.com/