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TIP OF THE MONTH 10 : Lifetime of a calibrated leak

My Helium leak detector is equipped with an internal calibrated leak. What is the lifetime of this leak?

TIP OF THE MONTH 10 : Lifetime of a calibrated leak

A calibrated leak can last for many years. However, the implementation into a quality system is as important as the technical suitability of the leak.

BACKGROUND: Calibrated leaks can be categorized as several types of leaks. The leaks that are integrated in a Helium leak detector are equipped with an internal gas reservoir which is filled with pure Helium. The reservoir volume is roughly 200 ml. The internal pressure is ambient pressure. Let us assume that the loss rate of the leak is constant over the life time of the leak (this is facilitation). Then the life time of a calibrated leak with a nominal value of 1.2 x 10-7 mbar l/s is roughly 53 years!

Calibrated leaks with higher depletion rates in the range of 10-5 or 10-4 mbar l/s are delivered in bigger containers with higher internal pressures in order to achieve long life times. These leaks are designed to be conveniently refilled by the supplier or the end user.

Leaks with gas reservoir have a defined depletion rate. In addition there is the danger that the permeation leak element may be damaged. For these reasons a calibrated leak should be checked and re-calibrated regularly. There is no European regulation that indicates the time span for calibration. In practice a re-calibration should be done annually or bi-annually. In case that more than one Helium leak detector is used it may be advantageous to purchase an additional reference leak. This leak acts as an external reference for all Helium leak detectors and is used for comparison and calibration of the integrated leak of the respective leak detector. Regular re-calibration and implementation into a quality system is then restricted to one single factory-internal calibrated leak standard.

In addition to the above-mentioned calibrated leaks with a gas reservoir there are also “open-style” or “in-line” gas leaks without any reservoir. They can easily be used with any tracer gas type. However, these leaks can clog easily and should be checked or re-calibrated regularly within fairly short cycles.

Adixen provides both types of calibrated leaks. You can download a full overview right here (PDF).

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