Eight Great Things Engineers Must Know About Leak Testing Equipment

Medical equipment manufacturers report testing throughput increases of 50% to 200%.

Must quality engineers and product managers always be at odds? The former seeks perfection while the latter pushes for greater throughput. With the latest improvements in leak detection devices, both agendas can be served as the best examples of this testing equipment help speed the quality control process without sacrificing accuracy.

Especially within the field of manufacturing critical medical components, every single product must be tested. Random destructive testing has no place here, as the consequences for component failure can come back to haunt the manufacturer in the form of multi-million dollar liability claims. Yet, armed with some advanced knowledge about what to look for in leak detection devices, test engineers can increase the odds that their products will roll off the production line with absolute quality assurance, without acting as an anchor to production schedules.

"Before we got our automated leak detection equipment, it took 4.5 minutes to cycle through a test, but now we have it down to just 1.5 minutes—improving throughput by 200%," says Richard Ray, a testing engineer at Terumo Medical Corporation's Elkton, MD plant.

Such impressive gains come from a refocused emphasis on the process of selecting test equipment that recognizes the salient differences between devices. What follows are several important pointers that can help any engineer determine which leak testing equipment can quickly recast the quality control department into a strong ally of the production schedule, while still upholding the highest quality standards.

1) Insist on application specificity
This universal axiom especially applies to the medical equipment industry, partly because of its staggering range of products that include pumps, coagulators, diagnostic kits, drip chambers, drug delivery systems, implantable devices, irrigation and suction tools, syringes and valves, etc. A one-size-fits all approach barely works for consumer products, but invites disaster when applied to medical products.

Leak testing equipment—whether checking pressure decay, differential pressure, burst pressure or vacuum—demands especially exacting attention to detail, since even very small leaks can mean the difference between life and death in critical medical components. Any test equipment must be designed so that it can be adapted to accurately meet the needs of the quality check at hand.

"My product line is used for blood handling during cardiac bypass surgery, and involves the bonding of polycarbonate parts so we must do pressure-decay tests to make sure that we don't have any leaks or voids," explains Margaret Kleinhenz, Senior Manufacturing Engineering at Medtronic Profusion Systems. Headquarted in Minneapolis, Minnesota, Medtronic is a global leader in medical technology, providing a wide range of products and therapies.

"The testing equipment from Uson is the best choice for us because we could configure it to meet our particular needs," continues Kleinhenz.

From its Houston, TX headquarters, Uson L.P. has been at the forefront of leak detection and non-destructive testing for 40 years, pioneering the development of a broad range of testers designed specifically to address medical device test applications.

For particularly challenging applications, the experience of the test equipment vendor accounts for the bulk of successfully channeling a leak tester's capabilities for the benefit of a specific product. The vendor should consider each unique case, and then maximize the potential of the test equipment to fit that need through a redesign of the tester or by reconfiguring it¾with custom designed pneumatic circuits, for example¾to integrate within the medical device manufacturer's production system.

2) Look for equipment that automates the testing process as much as possible
As medical device manufacturers seek to improve productivity, the quality control process increasingly finds itself subject to the drive toward automation. Ideally, test equipment must feature semi-automatic or fully automated leak detection systems that streamline product delivery, sealing, clamping, testing, and marking.

Timesaving features such as "infills"—which reduce volumes and allow for varying container sizes to be tested in the same chamber with minimum changeover time and expense—PLC connectivity and remote-start input, can greatly speed the testing process. However, one of the biggest time-savers is the development of multi-channel testers.

"We have a particular part which requires 12 different leak and flow tests. This used to require the operators to manually select, via push buttons, the various tests and whatnot," recalls Terumo's Ray. Terumo Medical Corporation is a high quality manufacturer of medical products, with sister factories and sales branches throughout the world.

"But with our Uson Vector units, you load the part, you press start, and it will automatically cycle through all the tests for you," continues Ray. "With the Vectors we can go all the way up to 10 channels, so you could run two or more parts simultaneously to increase throughput."

3) Examine ease of operation
A leak tester, no matter how capable its performance, is nothing if the human/machine interface lacks ready comprehension. Programming should be simplified by software with pre-formatted test configurations easily modified to each application.

"Without a good HMI, testing can get confusing, so you must have something that's intuitive," Kleinhenz advises. "Part of our set up is to check a known leak before every shift to make sure the tester is working and calibrated accurately, so rapid set up is important. I use the Uson Sprint model because it is easy to set up new test parameters. The programming is right on the screen of the tester itself, and the programming process is straightforward."

Leak testers that work within the WindowsÒ environment also lend themselves toward instant, intuitive operation. Added features to look for include touch screen input, large graphical displays, selectable engineering units, built-in diagnostics and remote troubleshooting.

4) Check for fixturing that fits your product
Partly a product of application specificity, the physical process of affixing the product to the leak tester is extremely important, as failures here can quickly undue all other attempts at accuracy and expediency.

At a minimum, leak detection testers should have attributes like automatic clamping, sealing, and interlocking guards that perfectly match the dimension orifices of the part under test. When speed counts, "quick connect" or "auto coupling" pneumatic self-sealing devices can be specified.

Some leak testers have the potential—by way of custom volume filling inserts¾to accommodate medical components ranging from tiny Swan-Ganz catheters whose lumens are measured in millimeters, all the way up to 4.5" diameter specimen containers.

On the other hand, when complicated products, such as those with unusual geometry or multiple orifices, require testing, then a vendor who manufactures custom couplings must be located. Find one who will arrange custom CNC work to create fixtures to handle square and other odd-shaped orifices.

5) Hold out for options in output
When it comes to raising defenses in a court of law, there's nothing like a good paper trail. A complete leak detection system must provide documentation.

"In the medical industry you have to keep track of many pieces of information, including test results, so all of our product is serialized," affirms Kleinhenz. "The Uson Sprint tester we use talks to a PLC and downloads the leak rate right to our AccessÒ data base which stores our device history record. This saves us time because we are actually pulling test results from the tester right into the database."

"If an operator had to manually enter that data into, let's say an Excel file in order to process it, then I'd say the automated data collection feature cuts that time by 50%," concurs Ray. "This speed and accuracy is ideal in the FDA-regulated environment that medical manufacturers must operate in because it eliminates any possible error that an operator can introduce into the system."

Other industry options for data downloading include RJ-45 Ethernet connectors, RS-232 serial ports, PCMCIA card slots, digital I/O cards and 24-volt reference outputs. Also helpful are screens that display results at the control unit, for interrogation by a supervisor as required. Marking capabilities, whether by ink, percussion or laser, also speed and reinforce the documentation process.

"We will be implementing the bar code feature soon, where an operator can automatically pass text through to a printer or an SPC program, so there is a lot of versatility of what you can do with these results," adds Ray.

6) Consider repeatability
As any quality control person will tell you, a test has no meaning unless it can be repeated with the same results.

Unlike reliance on the memory of an operator to initiate a sequence of tests, the automation of leak-detection actually improves repeatability because the testing process becomes non-subjective. Innate to some leak detection equipment, the ability to automatically compensate for temperature and humidity changes also helps assure consistent product quality.

"We run our Uson testers through 1200 cycles per day with very few issues," comments Kleinhenz. "We have about 15 testers throughout the room, and we rarely experience any problems with any of them."

7) Demand good support from the supplier
Like most any other sophisticated piece of equipment, a leak tester is only as good as the support it gets after it leaves the factory. Here again, the number of years a supplier has been in business counts for a lot, as this adds to its knowledge base in following up on challenging applications.

Look for a supplier that offers custom system design, installation and commissioning services. As well, some suppliers provide online tools to help test engineers dial in their testing parameters. As an example, Uson provides online tables that offer quick calculations for: hole diameter to flow rate calculation; leak correlation for one gas relative to another; leak rate to pressure drop relationship; flow rate conversion; conversion for volume; conversion for pressure; and hole/size/flow rate approximation.

8) Seek system flexibility for future upgrades
Nothing is constant. Product variations, specification changes and the introduction of new products all mandate changes in testing parameters. A quality leak tester can accommodate such changes, saving the expense of having to buy a totally new piece of equipment.

A modular design suits future needs especially well, as users can choose only the features that may be needed for initial requirements, but later expand the same unit to add capabilities for more complicated applications easily and economically.

"A lot of the other test equipment manufacturers that we looked at required sending the leak-testing unit back so they could build you another unit if we wanted to increase throughput by increasing the number of channels," notes Ray. "Whereas with the Vector unit, you just buy a channel card from Uson, pop the case off, plug it in, boot it up, and you're good to go. Each channel can be for another test on the same product, or to handle another product simultaneously."

For more information, contact Uson L.P. at 8640 North Eldridge Parkway; Houston, TX 77041; Tel 1-281-671-2000; Fax 1-281-671-2001; info@uson.com or visit www.uson.com.

SOURCE: Uson L.P.