Vacuum Engineering Services Ltd,
St. Modwen Road, Stretford,
Manchester, M32 0ZE
Other Offices:
& training standard parts
& accessories protecting
the environment
Leak Test Information
How leak tight is leak tight?
Ensuring parts are leak tight often is an essential feature for both the function and safety of the part. Defining the parameters necessary can have a great effect on the manufacturing and testing techniques chosen. So how leak tight is leak tight?
Of course nothing will ever be completely leak tight and to be able to define the required specification it's necessary to define a measure for leak tightness and then define what leak tightness is required for the part to complete its function within its operating parameters.
Examples are:
- the part does not leak droplets of liquid (radiators)
- does not lose pressure so ceases to function (stored pressure fire extinguishers)
- does not leak away required media so it no longer operates (refrigeration parts)
- does not leak away gas which would damage the environment (nuclear waste)
- does not emit harmful gases (SF6 switchgear).
Types of Leak
- Connections or joints
- Weld leaks
- Apparent or virtual leaks (trapped volume)
- Permeation leaks
- Thermal leaks
Helium Leak Testing is the only method possible for tighter leak rate requirements
- Refrigeration lndustry 2 grams/year (10-5 mbar.l/sec)
- Fuel Systems 10-5 mbar.l/sec
- Fire Extinguishers EN standard 10-5 to 10-7 mbar.l/sec
- SF6 typical 10-6 mbar.l/sec
1Vessel is evacuated with a vacuum pump as the component is simultaneously charged with nitrogen for strength / pressure test
2Component is isolated and pressure monitored. A drop in pressure signals a large 'Gross' leak and so fails.
3Component passes gross test and pressure is vented
4To ensure good helium concentration the component is evacuated with a vacuum pump
5Vessel vacuum levels are good so leak detector opens onto vessel. Any helium escaping into the vessel (from the component) will be quantified by the helium leak detector
6Once the leak detector is ready, helium is charged into the component
7Helium is sampled by the leak detector and the levels must remain below 'X' for a pass. If the levels are above 'X' the component is a fail
8Helium is vented from the component (can also be recovered for re-use)
9Component is evacuated (reduce contamination and for safety), then component and vessel are vented to atmosphere. End of cycle.
Other Leak Test Applications
Multi-gas helium & hydrogen leak testing for twin-volume applications
- Two volumes connected together, leak testing required between the two volumes as well as externally.
Hydrogen Leak Testing
- Hydrogen leak testing – yes we can do this too!
Butane Leak Testing
- These days portable equipment is very common, from the likes of hair - straightening products, to gas solder - irons, to camping - gas stoves. Direct leak testing of butane can be made in a production environment
Calibrated Helium / Hydrogen Leaks
- Each helium mass spectrometer comes with it's own calibrated leak...
- In-line calibrated leaks can be fitted to machines for automatic leak verification...
- Calibrated leaks can be connected in place of components for automatic leak verification...
