Higher rating reduces energy consumption
15 Jan 2000
At Plymouth's Devonport Royal Dockyard, DML is a refitting contractor for warships and nuclear submarines. When at sea, the main utilities on board vessels are cooled with pumped sea water but in dry dock this is not possible. Instead chilled water is pumped around the vessel from a nearby tank. The water is artificially chilled using a heat exchanger to around 7 degrees C.
ALSTOM Drives and Controls has supplied ALSPA variable speed drives for pumping water to vessels while in dry dock. Previously chiller pumps were driven at maximum speed, resulting in high energy consumption. Furthermore, associated vibration caused the failure of hoses. DML realised that by running more powerful pumps at slower speed - just sufficient to achieve required flow rate - energy consumption would be minimised.
Pressure signals from external transducers are sent to an ALSPA GD3000E, which in turn uses its built-in PID software to provide tight control of the pump speed. Advanced algorithms provide accurate speed holding and high torque over a wide speed range, ensuring smooth breakaway from standstill without tripping.
Energy savings realised a pay back period for the drives of between nine and 18 months.
