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JUNE 27 TUESDAY MORNING
WS-18-TuM-OR.8 CURRENT TRENDS IN LEAK TESTING TECHNOLOGY
A. P. Fonseca, H. P. Marques, A. M. C. Moutinho and O. M. N. D. Teodoro. METROVAC – Laboratório
de Tecnologia e Metrologia de Vácuo. CEFITEC, Departamento de Física, Faculdade de
Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 CAPARICA, Portugal
Leak detection techniques are not of exclusive use of the vacuum scientist but are increasingly taking
their place in the demanding industrial environment. Accordingly, the definition of what is a leak
must also evolve to accommodate the points of view of the industry. A leak always involves a flow
of mass though the walls of a vessel. It usually results in an escape of liquids, vacuum or gases from
sealed components or systems.
Due to the demands of the electronics industry and increased activities in space exploration, the need
to develop new equipments and devices that had to be free of significant leakage appeared.
The maximum acceptable leak rate for a given product depends upon the nature of the product. In a
compact electronic device, like a photon multiplier, with a size of 2 cm 3 even a leak rate of 10 -
10 mbar l s -1 will be too high, producing a lifetime of only about 7 hours!
Leak detectors range in complexity from a tank of water, in which bubbles from a leak can be seen,
to highly sophisticated systems using radioactive tracer gases, depending on the leak detection technique
– e.g. acoustics, hydrostatic test, tracer fluids or gases, high voltage discharge. However, is the
application that defines the most appropriated method.
Commercial helium mass spectrometer leak detectors can commonly detect leaks down to 10 -10
mbar.l.s -1 range. Lower rates can appear from molecular permeation and not from orifices and therefore
are difficult to distinguish.
High sensitivity in commercial leak detectors is longer the most demanded requirement. Most developments
are being made in order to miniaturize the detectors as well as to fully automate its operation.
It has been developed a miniature mass spectrometer [ref MKS] with dimensions of
30x30x15 cm and weight less than 8 kg. With this kind of portable detectors it’s less time-consuming
to detect leaks in large vacuum systems that often require access to a great number of test points.
The latest published papers favour developments in acoustics detection technology for example Holland
et al describes a method for in-orbit identification and location of a leak in the International
Space Station using structure-borne ultra-sonic noise.
In this paper is work we summarize the most suitable leak detection methods according to the application
and the maximum admissible leak rate.
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