What are the advantages of helium recovery in industrial leak testing

April 25, 2022

4 MIN READ

What is leak testing?

Leak testing or performing a leak test is a form of non-destructive quality control in a production process. During a leak test, a single component or assembly is tested to determine if it falls within a specified leak limit.

Leak testing can be achieved using various detection methods, all depending on the required specification or product requirements. There is a global consciousness of the importance of the environment and a concerted effort to reduce our impact on future generations. As a result, this has led to many manufactured products needing to meet more stringent specifications and international standards. For example, the escape of hazardous gasses or liquids from a system or containers.

To meet the more stringent specifications, or to just speed up the leak test cycle itself to meet production demands, many industries have now implemented testing methods using helium as the tracer gas. However, when all's said and done this means that for every cycle, there is an accompanying helium usage cost!

Although it will require an initial investment, in the long run, integrating a helium recovery system into the leak test process can reduce costs. Especially with how volatile the helium supply market has been over the past years.

How much helium is used per cycle?

The amount of helium required per test cycle is influenced by two aspects:

The physical internal test volume of the test part
The required test pressure

The bottom line is that the larger the internal volume and the higher the test pressure, the more helium is required per leak test cycle and consequently the higher the overall usage cost.

So, how much helium can be recovered?

Traditionally, at the end of the test cycle, the helium gas is vented to the atmosphere and is lost. However, the helium cost can now be significantly reduced by implementing a helium recovery system. In this case, at the end of a leak test cycle, the helium gas mixture inside the test part is captured and can be re-used for additional cycles. The amount of helium that can be recovered will depend on the leak test process settings, namely:

The vacuum level that can be achieved before injecting the helium tracer gas. It is important to note that the vacuum level determines the attainable helium concentration during the test. This in turn impacts the set-point of the pass/fail leak limit level of the leak test system.
The vacuum level that can be achieved after the test. Any helium gas mixture left in the test part is lost and must be replenished with new helium in the helium recovery system to maintain the required helium concentration levels.

In due course, the right balance between the helium recovery efficiency and the overall cycle time must be determined.

Additional benefits of helium recovery

When looking at the benefits of helium recovery, it’s important to distinguish between adding helium recovery to an existing leak test system or a new leak test system.

Adding a helium recovery system to an already existing system can lead to operating cost savings. How much will depend solely upon the overall cost of the recovery system and helium usage versus the helium usage cost without a recovery option.
For both an existing and a new system, in many applications less than 100% helium concentration may suffice to accurately complete the test. This of course already is a way to achieve cost savings. However, using a higher helium concentration allows the user to set the pass/fail setpoint at a lower sensitivity level. In this case, the leak test process can be sped up, as the right test conditions can be met in a shorter time frame.
When less than 100% concentration is required in conjunction with a new system, a singular unified system design approach can be taken, allowing for supplementary collective cost efficiencies to be achieved.

How is a recovery system sized?

A recovery system can be used to operate with a single or with multiple leak testing systems.

Just like with compressed air systems, it requires the proper interconnecting pipe sizes (and of course proper tightness). When sizing the recovery system, the complete design must be considered; recovery system, leak test system(s) and interconnecting piping, etc.

Also, a worst-case load scenario must be assumed (i.e., all leak test systems requiring tracer gas at the same time while testing the parts with the largest internal volumes).

Conclusion

A properly sized helium recovery system can:

Enhance the system test capabilities,
Diminish the risk of helium background within the facility,
And most importantly reduce overall helium tracer gas costs.

With the volatility of helium supply on the market, it will also be important for companies to secure their future helium needs to guarantee their production capabilities and maintain product quality standards.

If you have an application that requires leak testing, we are happy to help!