Drive-based system offers diesel generator energy savings

03 April 2012

At the Felixstowe container port, in the UK, the search for greater energy efficiency has led to investment in Control Techniques’ RIS.GA. system for diesel saving on 12 rubber tyre gantry cranes (RTGs).

RIS.GA. is a drive-based system that manages the diesel generator, allowing its speed to be reduced during stand-by, while maintaining essential power for auxiliary and safety equipment.

With a recent assessment of diesel usage confirming savings of up to 25% per crane, this investment is expected to give a return on investment (ROI) of under three years. Diesel generators onboard RTGs and mobile harbour cranes (MHCs) usually run at constant speed to provide the drive system and auxiliaries with a constant supply voltage, regardless of whether the crane is in operation or stand-by.

The dedicated container terminal at the Port of Felixstowe handles over 3 million TEUs (20ft equivalent units) per year and over 40% of the UK’s import and export trade passes through the port. The container storage area is served by a fleet of 74 RTGs and is currently undergoing further development, hence the need for the new cranes.

The 12 RTGs fitted with the drive-based system are rated at 40 tonnes under the spreader, have a hoist speed of 50 m/min, a trolley speed of 70 m/min, a gantry speed of 140 m/min and each is fitted with a 670 kVA diesel generator. Each RTG will complete around 100,000 moves per year.

Analysis of the RTG oil samples indicates that periods of idling have not been a problem and that savings have been very substantial, varying with duty up to around 30%, though generally averaging at about 25%. The RIS.GA. software, pre-loaded onto a 37kVA Unidrive SP AC drive, is set to allow the diesel generators to run on for a minute before initiating run down to tick-over speed. At tick-over, the diesel generators produce 300V, which is boosted by the drive with RIS.GA. up to the 415V required for operation of the auxiliary equipment. When required, the diesel generator will run up to operational speed in 5 seconds.

The RIS.GA. system is very compact, and all 12 were supplied fully wired and assembled, and ready to connect in an IP65 protected stainless steel cubicle. Each is fitted above the electrical house of its crane.

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