Gas Supplies
In the United Kingdom and South Africa, oxygen and helium is bought from commercial industrial and medical gas suppliers and typically delivered in 50 litre "J" cylinders at a maximum of 200 bar. In addition to the cost of the gas, charges may be made for cylinder rental and delivery.
The "cascade system" is used to decant economically from banks of storage cylinders so that the maximum possible gas is removed from the bank. This involves filling a diving cylinder by decanting from the bank cylinder with the lowest pressure that is higher than the diving cylinder's pressure and then from the next higher pressure bank cylinder in succession until the diving cylinder is full. The system maximises the use of low pressure bank gas and minimises the use of high pressure bank gas.
Booster pumps, such as the Haskel pump, can be used to scavenge the remnants of expensive gases in nearly empty cylinders allowing low pressure gases to be pumped safely into cylinders already containing gas at higher pressure.
Read more about this topic: Gas Blending
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