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back pressure

1. n. [Well Completions]
The pressure within a system caused by fluid friction or an induced resistance to flow through the system. Most process facilities require a minimum system pressure to operate efficiently. The necessary back-pressure is often created and controlled by a valve that is set to operate under the desired range of conditions.
Alternate Form: back-pressure
2. n. [Production]

Pressure opposing the desired flow of a fluid in a pipe. Usually results from obstructions and tight bends in confinement vessels.