CL Calibrated Leaks




VTI’s CL Model Calibrated Gas Leaks have a stainless steel capillary that has been precision crimped to provide an accurate flow-rate restriction for any gas. The gas, under pressure in the reservoir, flows through the capillary restriction and into the system to which it is attached using one of the many fittings available. This yields a precise, known flow rate.

Additional Information

The CL models have an all-welded construction and use an all-metal shut-off valve making them unbreakable and bakeable for UHV applications. They also have a low temperature coefficient, approximately 0.2% / °C and are available in a wide range of leak rates. Caution should be taken when considering capillary leaks for flow rates smaller than 10-6 atm-cc/sec, however, due to potential plugging of the leak. VTI takes care in the proper construction and processing during manufacture to insure a clean and stable flow of high-purity gas or gas mixtures.

Why choose the CL Calibrator?

UNBREAKABLE – all stainless steel, all welded
WIDE LEAK-RATE CHOICE – typically 10-7 to 10-3 range
STABLE – low temperature coefficient of 0.2% / °C
BAKEABLE FOR UHV USE – using all metal fittings
MEETS ISO REQUIREMENTS – NIST-traceable, A2LA-accredited Calibration Certification

Ordering Information

For an order or quotation for a CL Leak, please provide the Part Number and confirm the Outlet Fitting for connection to your system or part. It is also necessary to specify the Gas and specific Leak Rate with your preferred leak-rate units. In addition, the Manufacturing Variance (“Tolerance”) that you can allow on that Leak Rate should be specified as +/- 40% (the normal allowance), or as +/- 15% (the “Special-Range Variance”), for which there is an additional cost and an “-SR” added to the part number. An example specification is 2.0 x 10-5 atm-cc/sec +/- 40%. In all cases, the leak rate provided will be as close as we can make it to your specified rate, and the actual rate, as calibrated, will be recorded on the Calibration Tag and the Certifications.

Part Number Build-Up

The CL Series Part Numbers are constructed as follows:


where X = the code for the Leak Rate Range required

where BB = gas to be used

where YYYY = the fitting required*

where ZZZZ = the Reservoir required

and FVO = the Fill Valve Option

A fill valve is required for many gases other than Helium, Argon, Nitrogen, Carbon Dioxide, and Air. Due to the high gas depletion rates for leak rates of 10-4 and 10-3 atm-cc/sec, these leaks must also have a fill valve for all gases.  Additionally, leaks in the 10-3 range, and often in the 10-4 range, have an integral pressure gauge installed to monitor the residual pressure and indicate when filling is necessary.

* Except for Helium leaks, the fitting for 10-7 atm-cc/sec and smaller leaks must be a VCR or Conflat flange.  If you require a different fitting, an adapter can be purchased.

Example Gases Available

Helium (HE), Argon (AR), Nitrogen (N2), Hydrogen (H2), Carbon Dioxide (CO2), Oxygen (O2), Air (AIR), Methane (CH4), Sulphur Hexafluoride (SF6), Refrigerants (“R”#), Xenon (XE), Deuterium (D2), Mixed gases (MIX)

Example Fittings Available

Please contact us for other fitting requirements.

Code: Description:
118T 1-1/8″ OD Port Tube
4FVCR ¼” Female VCR
4MVCR ¼” Male VCR
MCFF 1.33″ OD Mini Conflat Flange
2CFF 2.75″ OD Conflat Flange
½T ½” OD Tube
KF16 ¾” OD ISO Flange
KF25 1″ OD ISO Flange
KF40 1.5″ OD ISO Flange
118T/34T 1-1/8″ OD Tube with step to ¾” Tube
4MPT ¼” Male Normal Pipe Thread

Additional information


1.0E-10 to 9.9E-10 atm-cc/sec, 1.0E-2 to 9.9E-2 atm-cc/sec, 1.0E-3 to 9.9E-3 atm-cc/sec, 1.0E-4 to 9.9E-4 atm-cc/sec, 1.0E-5 to 9.9E-5 atm-cc/sec, 1.0E-6 to 9.9E-6 atm-cc/sec, 1.0E-7 to 9.9E-7 atm-cc/sec, 1.0E-8 to 9.9E-8 atm-cc/sec, 1.0E-9 to 9.9E-9 atm-cc/sec, Unknown


1.33" OD Conflat Flange, 1/4" Female VCR, 1/4" Male VCR, 1/4" Swagelok Compression Fitting, 2.75" OD Conflat Flange


+/-10% of Target Leak Rate, +/-15% of Target Leak Rate, +/-20% of Target Leak Rate, +/-40% of Target Leak Rate – Standard, +/-5% of Target Leak Rate