MTS Multi-Pump Control Manager Remote Human-Machine Interface - Manual (Page 28)

Remote Human Machine Interface 26
Run On Demand Detailed Example
Operation
An example is shown below. In the example Module Flow is set at 30 gpm,
Minimum Flow is set at 10 gpm, Buffer Flow is set at 4 gpm (which means the
total actual buffer is 10 gpm), Δt
on
represents the on delay and Δt
off
represents off
delay. The HPU starts out with one module running to create 30 gpm of available
flow. This satisfies both the Minimum Flow requirement (10 gpm) and the Buffer
Flow requirement (10 gpm). The demand rises and eventually hits 20 gpm, at this
point the on delay is started because the 20 gpm of actual flow and 10 gpm of
Buffer Flow meet or exceed the available 30 gpm. Because the flow stays above
20 gpm for the length of time Δt
on
, another pump module is started and available
flow goes to 60 gpm. Then a spike occurs which exceeds the available flow but
because the duration of the spike is less than Δt
on
, another pump module is not
started. Flow then continues to increase but never exceeding the next trigger
point of 50 gpm for a duration of Δt
on
. Then flow drops off below 20 gpm.
Because the flow does not stay below 20 gpm for the period of time Δt
off
, no
pump modules are turned off. Finally the flow tapers off and flow is below 20
gpm for the time Δt
off
and the second pump module is turned off.
Minimum flow is a variable that can be set on the ROD or AUTO (whichever
there is) page. This is what ROD will use to determine how much flow should be
available when the system is turned on. If the demanded flow value (which could
be just the value on the main screen or the sum of values on a multi-HPU system)
exceeds the minimum flow it replaces the minimum flow value in operation.
Once the demanded flow is less than minimum flow the minimum flow value is
again used for operation. In other words:
if demand ≥ minimum then minimum = demand
if demand ≤ minimum then minimum = minimum
Minimum
Minimum Minimum