Print this pageFlywheels
Flywheels used to be a common method of surge suppression. They operate by slowing down the rate at which flow decays when a pump trips and are especially beneficial during a power failure, or blackout, because they do not need any power or controls. They used to be common on foul water systems because they do not intrude on the flow and so are less-prone to ragging and blocking.
The magnitude of surge pressures (Waterhammer) is generally proportional to the speed at which the flow is changed and so slowing that change can reduce the surge pressures.
In recent years flywheels have been installed less frequently and some of the modern pumps cannot be fitted with flywheels.
Extra care must be taken when existing systems are fitted with flywheels. If the system is being maintained then designers and operators must be aware that they cannot change the pumps for ones without flywheels without also replacing the flywheels or undertaking surge studies to investigate how the surge pressure will change.
Changes to the duty flow (or even replacing pipes with a different type) need similar caution. The design of flywheels is strongly linked with the original design flow and the overall construction of the system.
So we strongly recommend that a surge study (or review) is undertaken whenever a system that is currently fitted with flywheels is being modified or repaired.
