Leak checking a tube bore for to check for imperfections

Leak checking a tube bore for to check for imperfections

Ensuring fast and accurate leak checking can be a bit tricky, as even the smallest leaks must be detected. One company came to Alicat for a way to test for imperfections in tube bores with a diameter of only 0.001″.

Their test setup was simple:

  1. Use a high accuracy, precision motor to pass a ported hollow rod between two O-rings, allowing for the rod to pressurize the annulus in the bore.
  2. Check for leaks created by the annulus passing by imperfections in the bore walls.

Problem: Finding a leak checking device

The company required a device to check for very small system leaks (<1 mL per minute at 30 PSIG).

Alicat engineers determined this system would require two Alicat devices to check for these very small leaks – one PC3-100PSIG-D to maintain constant pressure and an M-1 SCCM-D to detect the small leaks.

Solution: Remote sensing pressure controller and mass flow meter

Historically, our solution for leak checking setups has been a two unit leak checking system. This setup consists of a remote sensing pressure controller for maintaining pressure at the device under test and a mass flow meter to measure the leak rate.

This company’s system ended up using a 100 PSIG remote sensing pressure controller to maintain system pressure and a 1 SCCM mass flow meter to detect the small leaks.

Test setup

Assuming temperature remains constant, continuous bleed though the needle valve enables the pressure controller to hold pressure at the device under test. When the bypass valve is closed, any flow through the meter is due to leakage.

Alicat M-Series Mass Flow Meters are available with full scale ranges as small 0.5 SCCM with a flow measurement range of 0.01-100% of full scale, allowing for resolution of flows as low as 0.00005 SCCM.