Pack and draft is the ability to store natural gas in the pipe and is a key factor in control of a pipeline system.
Packing refers to adding more gas into a pipe than is being withdrawn. This raises the pressure of the gas within the pipe and allows more gas to be stored for later use.
Alternatively, the system can be drafted, which means allowing more gas to be withdrawn than is being injected. This reduces pressure.
The two actions are used to maintain an acceptable pressure in any specific section of pipe. They are also used to prepare for forecast conditions. If cold weather or other conditions causing high demand are expected, operators will pack a pipe to prepare for the coming large draw of gas supply. On the other hand, if pressures in a pipe are getting close to the Maximum Allowable Operating Pressure, operators will often draft the pipe to reduce the pressure.
