Variable-volume pump
Pump flow can be controlled by various means such as manual, electric motor, hydraulic, or mechanical. How closely flow output actually matches command depends, in part, on slip, which increases with load. With a pressure-compensated, variable-volume pump, output flow decreases with the increasing pressure. This type of pump can be used for traverse and clamp operations. An external relief valve is usually unnecessary when a pressure-compensated pump is used. For details on the different types of pumps, their operation, and how they vary flow, refer to the pumps section of this Handbook.