Development of an Leak Detection System for Online Testing of Filled pMDI Devices

Dr Paul Miller, Thomas Hunter, William Lau, Stephen Waldron, Dr Iain Howieson

This paper describes an online leak detection system that provides real time instantaneous response to detected leaks at the specified leak rate, allowing for early detection of process failures or component faults, thereby minimising production losses and obsolescing the quarantine period as a means of leak detection in pMDI manufacture.
The sensitivity required to carry out the leak detection in real time is a result of the mid infrared spectroscopic technique pioneered by Cascade Technologies. This technique utilises a Quantum Cascade Laser (QCL) tuned to match the primary optical absorption band of r134a that is utilised as a propellant within the pMDI devices. Any loss of seal integrity in the pMDI device results in an escape of the r134a into the environment around the can. By containing the air around the can for a period of a few seconds, sufficient propellant is accumulated to allow for detection of leaks as low as 0.5 mg/day at a rate of up to 180 canisters per minute.
This is the first time that a device has been capable of detecting leaks at a high enough rate and with enough sensitivity to allow for 100% online leak detection testing of pMDI devices in a manufacturing environment.

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