Nitrogen Helium Leak Detection
Commissioning Leak Testing (CLT) is to confirm integrity of system where water may not be used and has been improved and refined continuously. CLT is achieved by pressurizing process system or component to be tested to their design pressure with a test medium comprising of 99% Nitrogen and 1% Helium.
To obtain 1% Helium in Nitrogen gas mixture, the liquid Nitrogen is pumped from the Nitrogen storage tanks at the rate of say 1000 scf/min. And then mixed with the Helium which is pumped by the Helium boost pump at the rate of 10 scf/min supplied from a quad of Helium cylinders.
To carry out the leak testing, all flanges are taped so that any gas leaking past the gaskets or seals is collected in the space between the outer edge of the gasket and the tape. Leak detection is performed by puncturing the tape with the remote probe. This in turn is connected to the portable Helium mass spectrometer. Hence, any Helium gas that has collected beneath the tape is sampled, detected and quantified.
Nitrogen/Helium leak testing offers the advantages of reducing the oxygen content of a process plant; systems are tested close to their operating pressure; all leaks are detected and repair before usage; and an inert nitrogen blanket can be left in the system prior to kick off.