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In perfect alignment

The importance of mounting and chocking

Improper shaft alignment is still one of the main causes of machinery breakdowns at sea. All too often, it comes down to the equipment mount itself. But it can be avoided.

Mounting a ship’s rotating equipment to foundations can be very labor-intensive. This task needs to be carried out with utmost precision—especially in critical systems such as the main engine or generator. Mounts must be strong and well-designed or all the effort that goes into shaft alignment can quickly be undone. So how do shipyards reliably secure large, heavy machinery like diesel engines?

Alignment and chocking challenges

Shaft misalignment is a common cause of machinery failure. It generally occurs as a result of inadequate measurement techniques or an improper or worn foundation. Deformations in a vessel’s engine room and hull can also influence the alignment of a propulsion unit. These are typically caused by changes in operating conditions, such as whether the vessel is carrying cargo and whether the engine is running slow or at full throttle. Weather and sea conditions also play a part.

Optimal shaft alignment increases the life of bearings, seals, and couplings, while reducing energy consumption, noise, vibrations, and excessive wear. This decreases the risk of costly downtime.

Chock-full of difficulties

“Conventional approaches to chock installation are usually labor-intensive and require considerable skill,” says Paul Vermunt, Product Manager at SKF. “A popular chocking method is to use epoxy resin, but the curing time involved can be 24 hours or even longer. Plus, if you need to realign, you basically have to start from scratch.”

Time to adjust

Adjustable chocks, such as the SKF Vibracon, address these issues. The chocks feature self-leveling top plates that swivel to accommodate for angular differences, thereby compensating angles and maximizing surface contact between foundation, chock, and machine foot. “Height adjustment is hugely beneficial for mounting,” says Vermunt. “It enables quick and easy installation, eliminates soft foot, and supports accurate mounting and alignment.”

Different causes of soft foot.

Different causes of soft foot.

The new “kit” in town

At the SMM 2016 trade fair in Hamburg, SKF launched the brand-new SKF Vibracon mounting kit. This comprehensive one-box solution is a complete package for chocking a resilient mount. It includes SKF Vibracon chocks, bolts, washers, an adapter plate, and an adjustment tool. The kit makes it easy to comply with manufacturers’ installation requirements and saves time in the chocking process. This solution requires no resin or welding, so chemicals and welding fumes are eliminated.

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Bad resilient mount chocking.

Good resilient mount chocking.

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