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Case Studies - Variable Frequency Drives

Drives and motors from ABB are helping the Royal National Lifeboat Institution (RNLI) to launch its fast inshore lifeboats quickly and safely.

The small dockside cranes used to launch the boats, known as davits, are traditionally operated by a shore support crew winching the boats off a trolley and into the water.

Following a rescue operation, the boat is recovered and winched back on shore in preparation for the next call-out.

The davits will now be fitted with an 11kW motor for the hoist and a 0.37kW motor and drive, together with a control panel, providing power and precise control for turning the davits and bringing the boat safely back.

“Retrieval of the boats can be slow, potentially dangerous, and can cause damage to the boat”, explains Andrew Tate, Principal Engineer of RNLI.
“Lowering the boat into the water with the winch is helped by the weight of the boat, but when it is returned to the winch after operations, the retreating tide can mean the boat is now much lower than the quayside.

Winding the winch down to retrieve it is also time-consuming and tedious for the recovery crew”. The RNLI instructed Hunter Gears of Tyneside to upgrade two of its lifeboat stations’ davits to all electric operation.

The drive solution was provided by local ABB Drives Alliance partner, Slater Drive Systems (SDS) in Northumberland.

The first of the electrically operated davits is to be installed at RNLI’s facility in Harwich. Jonathon Marks, Managing Director, Hunter Gears, says: “We needed a system that could start smoothly without jerking the boats and risking damage to them and the ABB drive provided this. The new system allows the boats to be moved more quickly and efficiently”.

As well as the Harwich installation, the system will also be installed at the RNLI station at Gorleston Lifeboat Station, near Great Yarmouth and potentially other RNLI facilities round the country. The inflatable lifeboats of the Atlantic class weigh around 1.5t.

Equipped with two 70hp outboard motors, they carry a crew of three and can reach a speed of 32 knots.

The Royal National Lifeboat Institution is a registered charity.

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