Leak Testing
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Leaks may develop in any part of a gas system but particularly at joints. As a matter of routine, always check for leaks when cylinders are assembled with equipment for use.
It is important to ensure that leak-detection fluids are compatible with the materials used in equipment construction. Incompatible fluids can lead to stress corrosion cracking of the cylinder valve. Solutions that contain fatty acids or that have an oil base can ignite if they come into contact with oxygen. For this reason, soapy water or washing-up liquid must not be used.
BOC Industrial recommends:
- Using approved leak-detection fluids such as:
- BOC part no 3731
- A solution of 1% Teepol in demineralised water
- Checking with the manufacturer to ensure the leak-detection fluid is compatible with any material it may come in contact with
- Checking all equipment that is part of a gas system is cheaks after assembly and taking corrective action before use
- Using the smallest quantity and most dilute solution possible for effective leak-detection
- Applying the leak-test solution to ALL joints
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The following steps describe how to perform a leak test, using an oxy-acetylene assembly as an example:
- Ensure that all joints are tightened in accordance with the equipment assembly instructions
- Check that torch valves are closed
- Check that the pressure-adjusting screw or knob on the acetylene regulator is fully out or backed off
- Repeat with the oxygen regulator
- Using the correct spindle key, open the acetylene cylinder valve slowly
Always open the valve slowly so that the sudden in-rush of gas does not damage the regulator
- Pressurise the gas by adjusting the pressure-adjusting screw on the acetylene regulator until a pressure of 0.5 bar is reached
- Close the acetylene cylinder valve
- Repeat the procedure on the oxygen cylinder
- Apply the leak detection solution to joints and any potential leakage points, such as the cylinder valve at the point of connection with the regulator
- You should never apply leak test solution into a cylinder valve outlet
- A leaking joint is indicated by frothing as shown in the photograph
- If there is any frothing, the system should be immediately depressurised and the leak corrected
- Depressurise the system by opening the torch valve; tighten the affected joint with an appropriate spanner; re-pressurise the system; and check the affected joint or joints again
- Do not use the equipment until the leak has been rectified. If in any doubt, contact BOC Industrial for further advice
- After testing, ensure the area is dry by wiping each joint with a clean lint-free cloth
- Remember that greasy cloths in contact with high-pressure oxygen pose a safety hazard
- Ensure that the oxygen and acetylene lines have been purged of air before using the system
- Once the leak test has been completed, use the lighting-up procedure as demonstrated within the ‘Safe Under Pressure’ video and CD
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