Contributed by: Rob Plumridge
When you’re in the market for a new leak test system, it’s a purchase decision that could be worth hundreds of thousands/millions of dollars to your plant.
That means your job could rest on the choice you and or your team makes.The best approach is to pit your top vendors against each other in a head-to-head trial.
Preparing for your leak test trial
But first, you need to step back and evaluate your own needs and objectives. Are you looking for shorter cycle times on the test, improved repeatability, greater performance to meet more stringent leak limits, better data management and analytics, or maintenance support? Maybe it’s a combination of several of the above.
Next, decide if your trial will focus just on Gage R (repeatability), or Gage R&R (repeatability and reproducibility). The former focuses just on the equipment – testing the tape measure. The latter takes into account your entire process, including the human element – how your test operators do their jobs.
When we take part in a trial, we focus only on Gage R – how our equipment performs versus the competition under controlled conditions, for a true apples-to-apples comparison. The manufacturer’s process is their concern.
After that, the devil is in the details, to eliminate or control the variables as much as possible.
What are these leak test control variables?
For best results, you want the units/parts tested to be identical, but the more complex the part, the greater the likelihood of some variance that could skew test accuracy. The best option is for the same individual parts to be tested by each competing system in the trial.
Check connection points and plugs
Look for damage, leaks or any other flaws. The actual connection to the leak test system is often the greatest variable. Sometimes, it’s a matter of design – different leak test systems use different sized ports, which impacts the fill and empty cycles for the test and can give one system a leg up over another.
Variances between the temperature of the ambient air and the part can have a drastic impact on Gage R. Larger parts made of thick materials can even have significant differences in temperature between their interior and exterior surfaces. Swings in temperature due to cold parts coming off a truck, parts coming out of a wash and even A/C units cycling on and off can throw off results.
Understand what’s inside the part
Are there internal check valves or other restrictions that may impact how the part reacts to being filled? Does the part have to be mounted in a jig to prevent the pressure of the test from changing its internal volume? If so, the jig must be regularly checked to ensure there has been no deviation.
Ensure a consistent air supply
You need clean air delivered at a constant pressure. If you are sharing an air supply with other stations, this could cause fluctuations.
And lastly—raw data
Require the vendors to submit their raw data. This is the only way to ensure the results you get don’t consist of “interpreted” data that could have been massaged. The end goal is to have accurate and objective data you can trust and bring to the boardroom table without any doubts.
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