New pump control systems boost efficiency

The system developed by the German pump manufacturer Allweiler uses frequency converters to control the power supplied to pumps on board, enabling them to meet exactly the required output at any moment in time. Previously, components ran at constant loads and excess cooling water that wasn’t required, for example, was discarded as waste. This meant that components were running at heavier loads and faster speeds than required, resulting in wasted energy, excessive component wear, high bearing temperatures, extra pressure on shaft seals and reduced mean time between failures (MTBF). Allweiler says its new approach to power management yields savings that typically lie in the 30-40% range, but the company says that, in some cases, these can reach 60-70%, depending on the application.

The greatest benefits are likely to be achieved by ship operators whose components have varying load requirements, for example cruise ship air-conditioning systems in tropical regions as compared with northern seas. But standard vessels such as tankers and bulk carriers can also realise significant energy savings and seawater cooling pumps are a good example. In tropical conditions, where seawater temperatures are high, such systems typically function at full load. In contrast, when a vessel sails into the colder waters of northern Europe, much less cooling water is required and any surplus has typically been pumped overboard.

On ships like the Stena Hollandica, which operate in constant temperature conditions, speed control of seawater cooling pumps makes good sense as well. Typically about 20% of such a vessel’s operating time is manoeuvring, when the requirement for cooling water is typically just one third of the requirement when operating at cruising speed.

Using Allweiler’s frequency converter control system, however, optionally combined with external information, e.g. from a condition monitoring system and/or the bridge, the pump can operate using significantly less power, typically 30-40% less but perhaps as little as 20% of its maximum. Related benefits include less component wear and longer maintenance intervals. The

Stena Hollandica

and the

Stena Britannica

both have Allweiler seawater cooling pump control systems to provide more effective power management for varying loads at sea and in port.