Helium Leak Testing

You’ve probably already heard about tightness, for instance water-tightness or else seal tightness. Thousands of products manufactured for and by any industry have this common feature : tightness to a fluid, e.g. gas or water. An injection pump couldn’t serve its purpose if not tight to fuel, an oxygen tank wouldn’t be safe if not gas-proof. What about a leaking air-con hose?

Now, what about “leak testing” or “tightness validation”? How is the “leak rate” quantified? Which products can be tested? What type of equipment do I need? These are most certainly some of the questions you are asking yourself if you’re here.

Alliance Concept leak testing is perfect for challenging industries such as Automotive, Energy, Refrigeration, Electronics, Aviation , Connectors, Medical and others.

Parts suitable for testing include injection pumps, injectors, fuel tanks, aircraft brake pistons, compressors, connectors, gas meters, electrical equipment such as switch gears, battery packs, ultracapacitors, HP valves.

Alliance Concept of France is an internationally renowned manufacturer of vacuum systems and equipment, certified ISO 9001-2015, thanks to its high level of expertise in the application of different vacuum techniques.

System Set-up

A reliable leak testing system consists of :

A tracer gas, helium : helium has some of the smallest particles, after hydrogen. It can flow through the smallest defects to be detected and quantified by a detector,
A frame : depending on your needs, a frame can consist of a cast-iron welded frame, polycarbonate cover panels and/or aluminium structures. The frame supports the vacuum test chambers in which your parts will be tested (if global method is used). Compact vacuum pumps can be set up directly onto it.
A leak detector : one of the key-parts of the system, this mass spectrometer works under vacuum. Its “heart”, the analyser cell is calibrated to detect specifically helium molecules (well, ionised ions) which escape from your part, if there is a leak.
Optimal operating system : touch screen to control the machine functions, additional flat screen or industrial screen for extra monitoring (Excel diagram in real time or generated at the end of the test cycle for traceability purpose), LED light column for production means, integrated traceability (printer, bar code scanning, datamatrix…).
Your specifications : your system will be assembled to match what you really need, not what we want you to need.

Test Methods Available

Global Leak Test

The global test is the method that provides the highest sensitivity up to 10-10 atm.cm3/s. The working principle is as follows :

The part is loaded into a test chamber,
The part is then pressurised using helium gas,
Helium escapes through potential defects and is quantified by the mass spectrometer cell.
Semi-automated test : manual loading and unloading,
Fully automated : the equipment is integrated directly into the production main flow. Un/loading is achieved using rotary tables, conveyors, lifts, arms etc.
Single or multiple stations : depending on your production rate.

Helium Sniffing Leak Test
The sniffing method helps to localise the leak(s) location. Here is how it works :

The part is pressurised with helium,
The sniffer probe is connected to the leak detector,
The operator passes the probe searching for the leaks.
The helium sniffing can be performed after the global test, prior to rework to pinpoint the location of the defect.
To avoid pollution or influence such as unwelcome drafts from the production area, a containment zone can be used. The operator will perform the leak detection inside the zone

Pressure Decay Leak Test
This helium-free method is based on pressure decay measurement using pressurised air. This is suitable for gross leak detection or parts with no particular tightness requirements.

The part to be tested and the sample part are simultaneously pressurised with air,
A differential manometer monitors the pressure decay during a given time frame. The pressure decay between both parts mirrors the actual leak in the tested part.
The sensitivity of the measurement is a function of the volume and is expressed by the following expression : VdP/dt avec dP/dt = 1Pa.s-1