CLP Calibrated Helium Leaks




The CLP Helium Calibrated Leaks are high-precision Standards for use in critical calibrations of leak detectors and systems, in Ultra-High Vacuum systems, and as Transfer Standards for calibrating other Helium Leaks. They feature all-welded stainless steel construction, a premium all-metal shut-off valve, a glass-permeation leak element, and are bakeable for UHV applications. The CLP Leaks are part of a family of Helium Calibrators including the GPP, GPPT, and GPC Models offered by VTI.

Additional Information

These models cover leak rates from 10-12 up to 10-3 atm-cc/sec and larger, as detailed in other brochures. The CLP Model is available with leak rates of 10-6 to 10-12 and is the only model made for the very low rates of 10-10 to 10-12 atm-cc/sec. VTI’s experts are always eager to help you select the best model – technically and cost – for your application. Without obligation, of course.

The CLP Accu-Flow™ Calibrated Leaks are based on the principle that helium flows through certain materials at a measurable rate depending on the material thickness, driving pressure and temperature, and use Quartz or Pyrex as the permeation material for the leak element. These leaks are available with or without the leak shut-off valve, but the latter is rare, and with many types of attachment fittings such as QF (NW,KF), Conflat®, VCR® and others.

All CLP Leaks are provided with Certifications of the NIST-traceable calibrations performed in our A2LA-accredited Calibration Laboratory.

Why choose the CLP Calibrator?

  • WILL NOT CLOG – permeation leak element
  • LONG TERM STABILITY – Low depletion rate
  • WIDE LEAK-RATE CHOICE – 10-6 to 10-12 range
  • BAKEABLE FOR UHV USE – all metal valve
  • NEVER NEEDS REFILL – Lasts for years
  • SIMPLE TO OPERATE – minimal user training
  • MEETS ISO REQUIREMENTS – NIST-traceable, A2LA-accredited Calibration Certification

Ordering Information

The CLP Calibrators can be ordered for a specified Helium Leak Rate within a wide range of values. When ordering or requesting a quotation, please provide the Part Number, confirm the Fitting needed, and state the specific Leak Rate requested including your preferred leak-rate units. Also, please specify the Manufacturing Variance (“Tolerance”) that you can allow on that Leak Rate. The usual manufacturing variance is +/- 40% of the requested rate. An example specification is 2.0×10-8atm-cc/sec +/- 40%. Alternatively, the allowable values as manufactured can be specified as 1 to 3×10-x, 4 to 6×10-x, or 7 to 9×10-x in a Leak Rate Range listed below.

Also, a “Special Range” manufacturing variance is available of +/- 15% of the requested leak rate. For this special variance, an “-SR” is added to the end of the Part Number and there is an additional cost. In all cases, the leak rate provided will be within the selected manufacturing variance and will be as close as we can make it to your specified rate. The actual rate, as calibrated, will be recorded on the Calibration Tag and the Certifications.

Part Number Build Up

The CLP Series Part Numbers are constructed as follows:


where X = the code for the Leak Rate Range required

where YYYY = the fitting required

where ZZZ = the code for the reservoir size

The addition of a Fill Valve is required on all leaks in the mid 10-6 range and for all 10-11 and 10-12 leak rates. In these cases, -MFV is added to the part number for the premium all metal valve. For the large 10-6 leaks a Teflon-packed metal fill valve can be used for some non-UHV applications, and -WFV is added to the part number.

Example Fittings Available

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

Leak Rates Ranges Available and Example Part Numbers

Leak Rate Ranges Available for the CLP Code for Leak Rate Range (X) Code for Fitting (YYY) Sugg’ed Reservoir Size Code for Reservoir Size(YYY) Example Part Number
(Specify a value in the range)
1.0 to 9.9×10-6 atm-cc/sec   KF40  1000  1000DOT  CLP-6-HE-KF40-1000DOT-WFV 
1.0 to 3.0×10-6 atm-cc/sec   1/2T  1000  1000DOT  CLP-6-HE-1/2T-1000DOT-WFV 
1.0 to 9.9×10-7 atm-cc/sec   KF16  110  (Blank)  CLP-7-HE-KF16 
1.0 to 9.9×10-8 atm-cc/sec   2CFF  110  (Blank)  CLP-8-HE-2CFF 
1.0 to 9.9×10-9 atm-cc/sec   MCFF  110  (Blank)  CLP-9-HE-MCFF 
1.0 to 9.9×10-10 atm-cc/sec 10   4MVCR  110  (Blank)  CLP-10-HE-4MVCR  
1.0 to 9.9×10-11 atm-cc/sec 11   2CFF  110  (Blank)  CLP-11-HE-2CFF-MVF 
1.0 to 9.9×10-12 atm-cc/sec 12   MCFF  110  (Blank)  CLP-12-HE-MCFF-MVF

Additional information


1.0E-10 to 9.9E-10 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, 5.0E-11 atm-cc/sec, 5.0E-12 atm-cc/sec


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