forepumps

Forepumps are small auxiliary pumps used to create initial suction or pressure to start a larger pump or hydraulic system. They are typically installed on the suction line ahead of a main pump, or connected in parallel to provide priming flow. The forepump's primary function is to remove entrapped air and to deliver enough fluid to overcome static head and system losses so that the main pump can develop continuous flow. Forepumps are often hand-operated or mechanically driven by belts or electric motors, and may be designed to operate with the same fluid as the main pump.

In boiler feed and steam plant applications, a forepump can provide initial feed water when the main feed pump is not yet available or cannot prime the boiler. In marine and industrial settings, they are used during starting, maintenance, or in pumps that are frequently restarted to maintain prime. In fire-fighting equipment, forepumps historically served to establish a water supply quickly before the primary firefighting pump takes over.

Design considerations include compatibility with the pumped fluid, suction head, priming capability, reliability, and ease of priming. Forepumps are sometimes integrated with priming lines or tanks to ensure rapid re-priming after shutdown.

The term is more common in older or historical engineering literature; modern systems more often use booster, priming, or transfer pumps that serve similar roles. Forepumps remain a reference point for understanding the sequence of priming and starting a larger pump in many mechanical and fluid-handling contexts.