The part has a leak, but where is the leak and how much is leaking? In many cases, just knowing that a part leaks is not enough, and in those cases manufacturers need quick answers.
"Manufacturers want to immediately identify the problems in their manufacturing process that cause reject parts so that they can take corrective action," says Gary Grebe, marketing manager for Cincinnati Test Systems (Cincinnati), a manufacturer of leak-test equipment. "By immediately correcting manufacturing problems, they can reduce the scrap rate and save money."
A new leak test system from Cincinnati Test has been designed to simultaneously identify the leak location and measure the leak rate for the part. The Falcon Leak Test System identifies leak location and displays on-screen graphics for visual recognition while at the same time calculating the leak rate. The system can store the data for leak-trend tracking or interface with factory communication systems in real time.
Grebe says that there is no other simple solution to identify the leak location and total leak rate at the same time. While he says that attempts have been made to do so, it took more than two years of trial and error for Cincinnati to develop the Falcon, and each attempt has been stymied because of the "rigors of everyday production."
"Typically it is difficult to isolate the test systems in the production environment from the background influences that affect the test's sensitivity and repeatability," he says. "The cost of some technologies is prohibitive for the applications. Usually the manufacturer will implement a manual testing method like dunk testing or sniffer systems to find a leak location, but he sacrifices the reliability of an automated test technique and the determination of the overall leak rate."
The Falcon Leak Test System interfaces with a matrix of strategically integrated sensors called Intelense sensors that were developed by the company. The Falcon Leak Test system bridges the gap between traditional pressure decay technology and helium vacuum mass spectrometry, providing detection sensitivity to 10-5 standard cubic centimeters per second (sccs).
According to Grebe, pressure decay testing can traditionally measure leak rates that are as small as 1.0 standard cubic centimeters (sccm) (6 x 10-2 sccs) depending on the part volume. Mass spectrometer systems can measure small leak rates down to 10-8 sccs up to larger leak rates of 10-2 sccs, but at a significantly higher price than pressure decay testing.
"There is always a gap in measurement requirements when the manufacturer does not want to invest in a mass spectrometer system and couldn't meet the requirements with pressure-decay technology," Grebe says. "The Falcon system's measurement leak rate range is 10-3 sccs and higher, which fills the measurement gap between the two technologies."
The Falcon cannot test all parts. Potential parts have to be analyzed to determine if they are good candidates for this test method. Factors such as reject leak rate, part geometry, part size, part sealability and part configuration influence whether the part can be successfully tested by the Falcon Leak Test System. This integrated solution involves designing a test chamber for the part and strategically placing the helium Intelense sensors at critical locations within the chamber. During the test cycle, the part is charged with a helium mixture.
The Intelense sensors continuously monitor the chamber for the presence of helium. The Falcon Leak Test System surveys the Intelense sensors connected to its network for responses caused by a leak. If a leak is found, its location is immediately displayed on the Falcon operator screen. After determining the location, the Falcon System analyzes all the outputs from the sensors to calculate the total part leak rate. That total leak rate is also displayed on the operator screen.
The fixtures for the test parts are integral to the system. The fixtures are supplied by Cincinnati Test Systems when designing and building the test stand. There is no defined part size limit, but the volume of the chamber that encloses the part, excluding the part volume, directly controls the sensitivity and cycle time of the test. The limitation on part size is a function of chamber volume, leak rate and test time.
The cost of a Falcon System depends on the complexity and size of the test part, production rate, interface to the production process and the customer's build specifications.
For more information on the Falcon Leak Test System, contact:
Cincinnati Test Systems
5555 Dry Fork Rd.
Village of Cleves, OH 45002
Fax: (513) 367-5426