Gas Blending - Oxygen Precautions

Oxygen Precautions

In the presence of large volumes of high-pressure oxygen, one corner of Fire Triangle exists in good measure. It is vital the other two corners are not allowed to exist.

Internally, the blending equipment and diving cylinders must be oxygen clean; all fuels and particles which could be sources of ignition must be removed. The materials chosen for use in the valves, joints and compressors must be oxygen compatible: they must not burn or degrade readily in high oxygen environments.

In gas blending, high temperatures are easily produced, by adiabatic heating, simply by decanting high-pressure gas into lower pressure pipes or cylinders. The pressure falls as the gas leaves the opened valve but then increases when the gas encounters obstructions such as a cylinder or a bend, constriction or particle in the pipe-work.

One simple way to reduce the heat of decanting is to open valves slowly. With sensitive valves, such as needle valves, the gas can slowly be allowed through the valve so that the pressure increase is slow on the low pressure side. The pipe-work, joints and valves in the blending system should be designed to minimize sharp bends and sudden constrictions. Sometimes 360 degree loops are present in the pipe-work to reduce vibration.

Spaces where gas is blended or oxygen is stored should be well ventilated to avoid high concentrations of oxygen and the risk of fire.