Centrifugal pump for fire fighting - has controller which reduces speed before priming pump is engaged to avoid water hammer

摘要

The fire fighting pump (1) and its priming pump (2) are driven by a common variable speed motor (4) through a gear box (3). A controller (5) disengages the priming pump by opening a clutch (6) and closing a valve (7) when the main pump discharge pressure (10) reaches a preset value. The speed control lever (11) of the motor is moved by a positioning motor (12) which is activated by the controller. When the discharge pressure falls below the preset value the motor speed is reduced before the priming pump is engaged. This ensures that the priming pump starts gradually without causing water hammer in the main pump.