Troubleshooting tips for oxygen leaks
Effectivity: Global Express, Global 5000, Global 5500, Global 6000, Global 6500
ATA 35
The following article provides helpful guidelines on what to look for when troubleshooting oxygen leaks. It is recommended to perform these troubleshooting instructions before opting for the use of a Helium or Nitrogen/ Hydrogen mixture as tracer gas (Reference Information Letters Ref GX-0084 and GX-0089). The instructions listed below are simple and can be accomplished rapidly. They are based on in-service findings.
With all four (4) bottle regulators open, using leak detection compound, perform the following:
1- Saturate the vent hole on the oxygen bottle regulators one at a time and make sure there are no bubbles. A mirror is required to see these holes. We recommend applying a thin flow of detection fluid over the hole while watching it with a mirror.
2- Per AMM, disconnect the eight (8) overboard discharge lines from the regulators (one (1) high pressure relief and one (1) low pressure relief per bottle). These are AN fittings with 9/16 nut. Using a clear type flexible tube over the fitting on the regulator, saturate the openings one at a time with leak detection compound and make sure there is no bubbling.
3- Verify the capillary lines very carefully at each bottle regulator. Pay close attention to the vent hole on large nut at the regulator. Leakage through this vent hole is an indication that the o’ring has been compromised.
4- Verify each capillary line connection at the unions and tee fittings all the way to the pressure indicator. Capillary lines are very fragile and are can easily be damaged during maintenance.
5- Verify the lines on the low pressure side of the regulator. Inspect the lines at the unions, tee fitting and check valves from the bottle all the way to the pilot and co-pilot quick donning masks. Pay particular attention to tee fittings which have been found to leak through micro cracks. These cracks are usually the result of over-torquing.
6- Verify the pressure switches (4) for any leaks at the connections. Also verify that the switch housing and the vent hole are not leaking (bubbling). Cover the vent hole and verify again that the switch housing is not leaking.
NOTE: Occasionally, Oxygen Pressure Switches are replaced due to leakage when performing Aircraft Maintenance Manual (AMM) task 35-12-17-790-801 - Leak Test of the Oxygen Pressure Switch.
An investigation on a few returned units has revealed that in some cases the unit may be declared as leaking when in fact it isn’t. Once leak check fluid is applied and the unit is initially pressurized, a small bubble at the weep hole located on the cylindrical housing of the pressure switch may be present. This is not always indicative of a leak. A diaphragm located inside the cylindrical housing will inflate upon initial pressurization and may force a small amount of air out of the cylinder. This bubble should be wiped away from weep hole. If a new bubble forms after wiping, then a leak in the unit is present.
If all of the above has been performed without finding the source of the leak, Reference Information Letters (RIL) GX-0084 or GX-0089 can be used as an alternate procedure of detecting leaks using tracer-gas mixtures. (RIL) GX-0517 may also be used as instructions for the use of new GSE 35X-00-04 leak test kit. These RILs can be found on the Bombardier Customer Portal.