City of London: Pump Station Assessment

Location: City of London, Canada
Population: 405,000
Purpose: Transient Mitigation

The operation of pumping stations can significantly impact the
asset life of distribution systems and the amount of leakage in a
system. Distribution systems are best maintained at consistent
water pressures with minimal pressure spikes. Large and rapid
swings in pressures are known to damage water systems and over
time cause failure of watermains. Even before a watermain fails
from these large swings in pressure, leakage at joints begins to
increase as the transient events start to loosen the joints.
One of the most common causes of pressure swings is the
operation of pumps either on startup or shutdown or during a
power failure. If the pumps are not programmed to slowly start
up and slowly shut down, or if there are not appropriate transient
control devices in place, sudden changes in pump status will cause
transient events in the distribution system. Transient events in a
distribution system without a relief to the atmosphere such as an
elevated tank can attenuate longer and may have larger pressure
swings as the pressure spike cannot escape the water system.

The Experience

Four hydrant.AI Devices were installed in the City of London water
distribution system to monitor pressures and listen for leaks as
part of a model calibration and system performance review. Fire
flow field testing was conducted to stress the system to better
understand the system hydraulics. During the fire flow testing
additional pumps were turned on to supply the higher system
demands. During field testing the hydrant.AI Devices noted large
swings in pressures as the pumps struggled to find the appropriate
setpoint to provide the higher flows as shown below.

The Results

Based on the system pressures noted by the hydrant.AI Devices,
and SCADA data including pump speeds and discharge pressure,
the study has recommended modifying the pump control
operation to slow the pump startup speeds, adjust setpoints of
the pumps so multiple pumps could operate without exceeding
the high pressure threshold and install a transient relief valve that
would react quickly to relieve transient pressures and protect the
distribution system.