Leak tester

Spec it by what you need to detect. Example would be: Heliium, at a leak rate of 5.6 X10^-7

You cannot expect to have no leaks, but you will acheive it. The idea is to have a leak spec you can live with, such as "No leak to exceed .01 oz. with total leaks not to exceed 1.0 oz per year"

Hope that helps

What class medical device? For most class 1 devices, a calibrated instrument capable of accurately measuring the leakage rate may do. For class II and class III devices, you're under design controls, or you should be.

Read up on CFR 21, section 820.30, amongst others. The guidance the FDA gives on this sort of goes as follows:

'Doesn't leak' is a documented design input

Using documented engineering judgement, you arrive at 'air leakage rate of < .5 liter/min @ 76 mm Hg (.1 bar)'

You do an experiment with a prototype to verify this satisfies the design input of 'doesn't leak'.

You do validation on first articles, and probably spot / 100 % checking that validates production pieces meet your spec. of '<.5 l/min @ 76 mm Hg'

Whatever device you use to detect these leaks should be capable of accurately making the measurement and verfiably in calibration

Have a look at the "Uson" web site.

When spec'ing the test you will require info such as: -

- leak rate

- test pressure

- test time

- product volume

- cycle time required - larger the product volume the longer the fill and stabilization time

- Machine interface requirements

- Statistical control

- Calibration requirement - They can manufacure a calibrated leak with the same value as the fail value for your product. This is a necessary periodic check for the device. Check medical device standards for this.

If unsure talk to a Uson rep. They will be more that happy to help with the spec.

Regards

I suggest you decide what leak rate of what gas or liquid you require, and at what pressure differential. Plastic devices can be designed to be leak tight to liquids, however helium atoms ar very small. If you construct a plastic device free of conventional gas leaks, helium will still likely diffuse through the plastic material. Metals, ceramic, and glass are more effective barriers for helium.

There are two types of leak tests that i am aware of. Helium leak tests and pressure decay leak tests. The former consists of pulling a vaccuum on your part and spraying helium over it. The vaccuum leads to a mass spectrometer which will tell you if any helium enters the vessel. you could pressurize the vessel with helium and use a sniffer probe, but this method is less precise, and you have to "sniff" the whole outside surface area to be sure. Check out Varian or Pfeiffer for helium leak testers. This is probably the route you want to go but very expensive. Pfeiffer will charge you 22,000 US dollars for the leak tester, then you need some fixture to mount your part. Automated testing is preffered.

The latter test (pressure decay) is where you pressurize with air, and measure how much of that pressure bleeds off due to a leak. This method of leak test is much less precise than the helium leak test because you will have pressure decay due to heat transfer and elastic expansion of the vessel being tested. Check out Uson or TM Electronics for pressure decay leak testers.

Another source is Cincinnati Test Systems (CTS). I have had a good experience with their Sentinel Pressure Decay units utilizing Plant Air and Nitrogen. For helium testing, I looked into specifying CTS's Falcon system for an upcoming project. It looked solid for the application I had due to the mulitple sensors (my application was testing a valve stack), but I recently left that job, so I do not know the final decision. CTS is also capable of designing and fabricating up to a fully automated solution.

No, I do not work for CTS, I was just a satisfied customer.