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issue: December 2002 APPLIANCE Magazine

Quality and Testing
Detecting a Better Method


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by Lisa Bonnema, Managing Editor

As the demands for quality performance and energy efficiency in the HVAC industry continue to increase, OEMs are starting to upgrade their testing methods in order to meet the needs of both the industry and the consumer.

That's the reason Outokumpu Heatcraft, a manufacturer of evaporator/heat exchanger coils for HVAC equipment, decided to move from air under water leak testing (the "water bath/water bubble" method) to helium leak detection. "We continue to see our customers demanding heat exchangers with lower leak levels," says Gerald Gant, project engineer for Outokumpu Heatcraft (Grenada, MS, U.S.). "We believe that helium leak testing provides a greater level of sensitivity for detecting smaller leaks, which will enable Outokumpu Heatcraft to provide a better quality coil to our customers."

After deciding on a helium pressurization and leak test approach, Heatcraft consulted with several vendors and decided to work with Serv-I-Quip, Inc., a Downingtown, PA, U.S -based supplier of testing equipment, and Inficon, a Syracuse, NY, U.S.-based supplier of leak detectors. Together, the companies developed a complete testing system that reduced cost and improved productivity.

The Upgrade

Mr. Gant says there were several reasons Heatcraft decided to change to helium leak detection. "Because the helium leak test systems are able to find smaller leaks, our customers will be getting coils that they can use with confidence, thereby increasing customer satisfaction, reducing warranty costs, and reducing field related leak problems," he explains.

Mike Ryan, sales manager of Leak Detector Products at Inficon, adds that helium leak detection has many advantages over water bubble system methods. "Helium leak detection eliminates the coil moisture/water bake-out required after the water bubble test. The elimination of this bake-out process added another reduction to the production cycle time and reduced associated material movement and expense," Mr. Ryan explains. "Moisture left in the coils is detrimental to product quality, as moisture reacts with the refrigerant to create an acidic by-product. This by-product reduces system life, as it corrodes the coil, valves, seals, etc., and this corrosive effect eventually leads to premature system leakage/failure in the field."

He adds: "Removal of the water bubble bath test and evaporative baking ovens reduced the consumption of floor space in the factory and has allowed Heatcraft to increase their production capacity without incurring major capital expenditures for facility expansion."

In addition, the previous testing method was an off-line process that created a bottleneck between manufacturing and shipping, adds Mike Richey, president of Serv-I-Quip. "Leak testing is now integrated into the manufacturing process. Product goes directly to boxing and shipping after manufacture," he explains.

Specifically, the integrated process eliminated material movement from the production environment over to the water bath area and the subsequent evaporative baking ovens to dry the product.

The Solution

The installed system consists of a Helium and Air Gas Mixing and Recovery System and DataTest NH100 Test Stations from Serv-I-Quip and Protec Helium Sniffers from Inficon. The Mixing and Recovery System generates a pre-set mixture of helium and air at a pressure and volume that meets Heatcraft's production requirements. After the gas is used to leak test units, the gas is vented to a recovery line and brought back to the system to be processed for reuse.

The DataTest 100 utilizes a bar code scanner to automatically set up the appropriate test cycle. A normal test cycle includes a UL pressure test, a pressure decay test, the helium leak test, test gas vent to recovery, and a final rough evacuation. According to Mr. Richey, typical cycle time is less than 30 sec. The network-connected PC in the test station sends all test and production data to a centralized server, providing easy access to data.

For the actual detection, Heatcraft chose to use the sniffer method of inside-out pressurized leak detection. The helium leak testing is performed by an operator using an Inficon Protec Helium Leak Detector, which is said to provide 10-6 cc/yr leak rate sensitivity and <1 sec response time.

Choosing the equipment took careful consideration, says Mr. Gant. "Testing heat exchangers is not a simple, straightforward process," he explains. "Heat exchangers come in a large range of sizes, they have to be tested fairly quickly, and some of them have a lot of brazed copper connections. All of these items have to be taken into account when you are trying to pressure decay/helium test coils."

When developing the complete system, Mr. Gant says that both Serv-I-Quip and Inficon worked very closely with Heatcraft engineers to develop a system optimized for its specific needs. "During the early stages of the Inficon startup, we realized that it confused our operators to show leaks in the 10-7 atm cc/sec range. The graph was constantly going up and down. Inficon changed the system so that the graph would start sniffing in the 10-6 atm cc/sec range. Since our rejection point was 1.8 x 10-5 atm cc/sec, this worked out fine," he explains.

Heatcraft's initial goal was to find a better quality leak testing method that could be incorporated into production without inhibiting throughput. All three companies believe this goal was achieved, as well as some additional benefits.

"Helium Leak Detection improved their leak detection capabilities by a factor of 1,000," says Mr. Ryan of Inficon. "[This] enables Heatcraft to find quality critical leaks, which were undetectable using the water bath/water bubble method."

Another benefit that Outokumpu Heatcraft can now provide to their customers is improved Work-in-Process information, adds Mr. Richey of Serv-I-Quip. "By tracking manufacturing data at the leak test station, Heatcraft can advise their customers on the status of their order and a delivery schedule. This is valuable information for a manufacturer scheduling production and inventory receipts. Heatcraft can also now provide unit test data to satisfy customer quality requirements or ISO procedures," Mr. Richey explains.

Mr. Gant of Outokumpu Heatcraft says that while the results thus far have been positive, the system upgrade is far from finished. "The integration of helium testing into our production process continues," he says. "Helium testing is a part of an overall plan to make coils flow through our plant. The benefits of helium testing are in the fact that you are using a high-quality test method that does not require the coil to be put under water or to be oven dried."

Suppliers mentioned in this article:
Serv-I-Quip Inc.
Inficon Inc.
 

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