FlowCERT

Page 100
Pump Duty
Description
5= Duty backup and assist First pump comes on, if it cannot cope,
it goes off and next pump comes on
(duty backup). This continues until the
last pump comes on and if it cannot cope
the first pump comes back on to assist
the last pump (duty assist) if the level
continues to rise all other pumps will
come on (assist) in turn until the level
decreases to the pump off points. Each
pump has its own setpoints, (P213, 223,
233, 243, 253 & P214, 224, 234, 243,
253).
6= Service ratio duty assist All pumps are used to assist each other
(run at the same time) and each pump
has its own setpoints (P213, 223, 233,
243, 253 & P214, 224, 234, 244, 254).
And a service ratio setting. The third
setpoint (P215, 225, 235, 245, 255) is
used to set the service ratio. Each time a
pump is required to start then the pump
with the least running hours (with
respect to the service ratio) is started
(i.e. the setpoints are re-assigned
accordingly). For example, if
two pumps A and B have the service
ratio set to 2 and 1 respectively, then
pump A will operate for twice as many
hours as pump B.
7= Service ratio duty backup If a pump fails to meet the demand (due
to malfunction, intake blockage and so
on), then it is stopped and another pump
shall take over. Each time a pump is
required to start then the pump with the
least running hours (with respect to the
service ratio) is started (i.e. the setpoints
are re-assigned accordingly). Each pump
has its own setpoints (P213, 223, 233,
243, 253 & P214, 224, 234, 244, 254).
The third setpoint (P215, 225, 235, 245,
255) is used to set the service ratio. For
example, if two pumps A and B have the
service ratio set to 2 and 1 respectively,
then pump A will operate for twice as
many hours as pump B.