How to measure or test for small leaks and bypasses in a pleated paper filter.

I work for a company that manufactures and assembles cartridge filters that consist of a top, and bottom cap that interlock in the middle and are glued to the opposing ends of a pleated paper filter. The glued filter holds the assembly together. To test the filter, we pass 5 psi of air at 3cfm through ports at the cap's bottom. The air passes through the paper and out the top cap to atmosphere. If we use a higher pressure/flow, we risk blowing the partially cured glue into places it should not go, essentially creating the defect we are trying to capture.
The purpose of this particular test is to make sure there are no pinholes in the paper or bypasses in the glue that bonds the paper filter to the caps. We use a pressure transducer to measure the pressure in the chamber that supplies air to the bottom cap. Basically, we measure the backpressure to be in a specific range to qualify as "good." A good filter measures from .250-1psi. The test takes about three seconds.

We also test offline once per hour on a TSI Model 8130A Automated Filter Tester. This tester measures particles through the filter and is the standard test. Unfortunately, the test is slow and expensive and can't be used as part of the production process.

Recently I discovered we are throwing away good filters that fail the 3-second test on the machine but pass on the TSI 8130A.

To that end, I was tasked with finding or developing a new 3-second test that is more accurate than the current method. There's no expectation to match the TSI test, but we think we can do a lot better than we are doing presently.

Note: The end-use for the filter is liquid in the food & beverage industry. The air for testing purposes only.

Does anyone have advice or know of a company that could help? I really appreciate any help you can provide.
Andrew
 
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