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Leak and Flow Test for Drug Delivery Devices

In this post we are going to look at the challenges of testing drug delivery devices.

There are many different types of drug delivery device, but they all have things in common – an inlet port and an outlet port, a flow restrictor (regulator) and a bypass valve. These components are vital to the safe and efficient operation of the device and therefore must be tested.

To test this sort of device it will be necessary to measure low-flow, high flow, valve reseating, valve leakage and body leaks in the product. That’s a significant amount of measurement and requires a lot of equipment.

The resulting assembly will require a computer or programmable logic controller. It will probably be bulky difficult to operate, hard to calibrate and require a high degree of maintenance.

Sounds daunting, right?

Not so.

Uson’s versatile leak testers like OptimavT and SprintmD are highly configurable and can make this complicated test sequence seem easy. They work like this:

The product is attached to two test ports and the test is started by the operator or automated equipment.

Air is routed to both Port 1 and Port 2 to conduct a leak test on the product body. (Figure 1). During leak test time, air is sent to test ports 1 and 2 filling all passages in the device being tested. Leak testing verifies the absence of body leaks in the product.

Leak Max is the largest flow allowed during the leak test. When the flow drops below this value, the leak test ends and the First Flow test starts by sending air to Port 1 and opening Port 2 to atmosphere throughV2. This allows air flow through the restrictor in the device being tested. Flow is measured with the tester’s low-flow transducer. [F1}

Flow Max and Flow Min are the pass and fail limits established by the operator. If the flow is within this window, the first low-flow test passes and the high-flow test starts. If flow is outside the Min/Max window, the test fails and the message 1ST FLOW is displayed in the status box on the tester’s display.  

The product’s flush valve [FF] is activated by the operatoror automated fixturing. The resulting high flow is measured with a high-range flow transducer [F2]. At the start of this test, FLUSH is displayed to prompt the operator to activate the fast flush valve. Or the leak tester can send a signal to activate automated fixturing. The resulting high-flow rate is measured with a high-flow transducer. The leak tester displays the high flow rate. The operator or automated fixturing releases the flush valve. If the flow does not reach the established minimum flow rate, the test fails and FLUSH is displayed in the status box on the tester’s run display.

A second low-flow test is performed using the same parameters of the first low-flow test.

The first low-flow is compared to the second low-flow to make sure the flush valve [FF[ has properly re-seated in the device being tested.

Lastly, a percent deviation of the measurement made at the first low-flow compared to the second low-flow. A percent deviation limit is programmed by the operator to set the boundary for acceptance. If the comparison is beyond the set deviation, the product fails. The tester’s reject lamp will be illuminated. The deviation parameter ensures the bypass valve in the product properly re-seats after the high-flow (flush) operation.


• Completely self-contained.

• All components in one small enclosure

• Fully calibrated and simple to maintain

• Perfect for bench or automation

• Small footprint of 8.5 by 15 inches

• Resolution of 1/100 sccm at 200 full scale

• Resolution of 1 sccm at 5000 full scale

• Easy to program and calibrate

• Interface for statistical process control

For more information about OptimavT, SprintmD or any of our leak testers please call 281-671-2000 or email me at

Joe Pustka

Director Applications Engineering

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