Precise Flow · Calibration · Test Equipment

Capillary calibration and test leaks – series KL

Calibration and test leaks are used for the simulation of leakages during the adjustment or monitoring of leak testers or flow measuring devices. Capillary leaks are connected instead of a test sample or in parallel to a tight test sample for the measuring process.


Calibration and test leaks of the series KL consist of a stainless steel tube into which a glass capillary is inserted. A filter protects the glass capillary against contamination. Depending on the inlet pressure and the type of gas the capillary sets a defined flow, which increases in proportion to the differential pressure above the capillary. Due to the high manufacturing tolerance they are only delivered with calibration certificate.

Product features include:

  • Calibration and test leaks with capillaries
  • Leakage rates of 0.01 Nml/min up to 1.5 Nl/min
  • Inlet pressures of 0.01 up to 40 bar relative
  • Manufacturing tolerance ±5% up to ±10% of the nominal value
  • Media compatibility: Air and inert gases
  • Factory or DAkkS-DKD calibration certificate
  • Calibration accuracy: ±0.65% up to ±1.5% of reading

Special features:

  • Flow: Correction and conversion equations are indicated.
  • Filter: Standard: Inlet filter 80 µm, 4μm filter for small flows optional.
  • Operational safety: Lower susceptibility for contamination compared with sinter leaks.


In most cases the capillaries are operated laminar due to their small diameters. In this case the volume flow correlates very linear with the differential pressure between inlet and outlet and the mass flow increases approximately in proportion to the applied inlet density of the medium.

In rare cases of turbulent operation (Re > 2000) the very linear laminar flow is superimposed by the mass flow of an orifice. Thus a flow portion is added, which is in proportion to the square root of the product of differential pressure between inlet and outlet and the inlet density of the medium.

Capillary calibration leaks
series KL

For the simulation of leakages in leak tests

More information and technical details can be
found in the data sheet

Additional information
on this subject:


Testing tool calibration

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