After the initial refining process is complete, many of the resulting products are then utilised as feedstocks in order to further manufacture petrochemicals. Often the driving forces to these processes are compressors. Large turbo-compressors are used for most high flow processes, whilst smaller rotary and reciprocating machines are used for side-streams.
With many complicated and potentially dangerous reactions and processes running simultaneously, it is necessary for safety reasons to have a system in place, that will take away any quantities of gas that can be suddenly produced or emitted when a reaction goes slightly out of control. These gases are typically flared at a single central facility. As above these gases can also be recompressed and either re-injected into another process stream, or used as fuel gas.