A calibrated reference leak should provide a stable, accurate reference for a leak detector or be tested and adjusted to give a greater level of accuracy. There are several methods producing the flow rate required. Each application has it’s own demands and the production method for the reference leak should be considered when deciding on a specification.
HT Products Ltd. Is an expert manufacturer of calibrated reference leaks and our technicians have considerable expertise in the calibration and maintenance of reference leaks of all types.
The traditional style of reference leak takes advantage of the natural permeability of Quartz glass to helium. A Quartz glass element is immersed in a pressurised helium reservoir, this will deliver a fixed flow rate for helium which can be used to deliver the precision required to calibrate a mass spectrometer type vacuum leak detector.
A Crimped capillary reference leak uses a length of capillary tube to restrict the flow, the end of the capillary is then crushed to give a further restriction of the flow rate and reduce the output flow to the level required for the reference leak. An alternative manufacturing technique is to extrude a fine glass capillary to restrict the flow. This method offers some flexibility and can be used with different gases.
Membrane and silicon permeation reference leaks are generally used in coarse applications where precise, accurate flow rates are not required. The mebrane can have the effect of filtering or altering the characteristics of a gas so there are many design considerations in specifying a suitable part. There are also large set-up costs associated with these product though they can be cheap to produce once a specification has been established
HTP’s preferred style of reference leak for most industrial applications is produce from a micron stainless steel powder which is highly compressed and fixed in a vacuum furnace creating a porous leak element which restricts the gas flow. The process is highly controllable and a huge variety of flow rates and gases can be accommodated. The technology can also be welded with little or no change to the flow rate and pressed into specially machined end fittings giving the maximum flexibility for bespoke applications.