Brakes for powerful shipyard vessel lifts

In large-scale shipbuilding and repair, a principle challenge has always been that of moving ships from sea to land and vice versa, a vital part of the shipyard. Working under huge loads, for obvious reasons it is important that key safety-related assemblies such as brakes are up to the task. Most modern shipyards utilise immensely powerful shiplifts, which can raise and lower huge vessels in a controlled manner. A shiplift works by positioning a platform underneath the ship, which is then raised or lowered by multiple hoists in synchronicity. This allows horizontal or angled (if ballast is a factor) lifting of the ship, ideal for launching or dry-docking vessels. Consequently, the vessel can be released out to sea or moved to an onshore transfer system for maintenance work in a highly streamlined manner. This contributes to a reduced time for repair, which benefits both the shipyard and the operator.

Lifting a load as large as a ship requires a mix of precision, power and reliability. Any loss of synchronicity risks the ship tipping, so power transmission equipment must move the huge load in a highly controlled manner. Furthermore, in conditions such as a loss of power, the hoists must be able to brake effectively to hold the vessel in place. Added to this, are the inherent corrosion risks of a salty application environment, which can damage poorly specified equipment.

A leading Italian winch and gearbox manufacturer approached Stromag to provide a reliable and robust braking system to be incorporated into shiplift hoists it was designing. The shiplift systems were destined for a yard which was aiming to improve its launch and dry-docking efficiency. Stromag's 4BZFM Series electromagnetic, spring-applied, double-face brakes were specified, which are specifically designed for marine and offshore applications. Supplied in size 16/13, each provided a static braking torque of 130Nm. Installed on the winch's gearbox, the brakes provide stopping and parking functionality in the case of power loss, and each unit was modified to incorporate a special mounting flange and radial cable bespoke to the application.

The 4BZFM is stated to be seawater-proof thanks to an IP67 rating, and all steel components feature special nitrocarburated and postoxidated surfaces to provide a high level of durability and corrosion protection. The low inertia, high heat dissipation brakes are designed for easy motor mounting without the requirement to disassemble the brake itself. During braking, no axial or radial forces are generated, and Stromag says that the brakes are highly serviceable and can operate without a cover, further reducing costs and improving serviceability.

Learn more about the company at www.stromag.com.