Different Styles of Calibrated Reference Leak and HTP’s Patented Stainless Steel Vacuum Sinter

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.

Quartz Permeation Reference Leaks

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.

✔ Tiny flow rate available - 5x10^-8mbl/s to 5x10^-7mbl/s

✔ Established Variation with Temperature (2.9% per ºC)

✖ Extremely Fragile

✖ Expensive to Manufacture and Repai

✖ Available for Helium at a single flow rate only

Crimped Capillary Reference Leaks

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.

✔ Range of flow rates and gases available - Approx. 1x10^-6mbl/s to 5x10^-4mbl/s

✔ Some flexibility and control over gas and flow rate.

✖ Susceptible to Blockage and Contamination (Lab Applications Only)

✖ Expensive to Manufacture and Repair

Membrane / Silicon Permeation Reference Leaks

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

✔ Range of flow rates and gases available - Approx. 1x10^-5mbl/s to 5x10^-2mbl/s

✔ Some flexibility and control over gas and flow rate.

✖ Difficult and costly to incorporate into different formats.

✖ Wide variation through batch production

Stainless Steel Vacuum Sinter Reference Leaks

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.

✔ Any flow rate available - 1x10^-9mbl/s to 5x10^-2mbl/s for virtually any gas.

✔ Excellent performance at a range of temperatures with minimal variation

✔ Can be fabricated and welded into bespoke fittings and bodies.

✔ Operated effectively at any very high pressure differentials (Vacuum - 200 bar).

✔ Durable and Robust.

✔ Very low internal volume for extremely fast response.

✔ DTI Smart Award Winning Technology.