The alignment of engines and propeller shafts is critical in shipbuilding and marine maintenance, where the stresses and vibrations created by rotating misaligned shafts will not only lead to breakdowns in the engines shaft assembly itself, but can also result in damage to struts and hulls, leading to leaking and possible sinking.
The W-configuration and 3-joint configuration may be seen in marine applications as shown opposite.
One important point to note in comparing readings obtained with any clock gauge system and a laser based system is that in virtually every case a laser system will show that the shafts are lower than they are thought to be.
When the Royal Dutch Navy realised that significant savings could be made by properly aligning its machines, the department in charge of the project decided to invest in the most modern laser-optical alignment systems. They purchased 14 Laser Shaft Aligment Kits for their complete fleet requirements.
To meet the Navy's needs, instruments had to be easy to install even in the confined spaces aboard ships, and designed to align both horizontally and vertically built machines (e.g. pumps). It was of the utmost importance that all data should be stored directly in PC's, enabling results to be printed out immediately and easily compiled in a database for future reference. The instruments had to be robust enough to withstand the ships’ tough environment, and the price/cost ratio had to be favourable. But perhaps the most important requirement of all was that the instruments should be easy to use even by inexperienced operators.
Unlike land-based driven shaft applications, boats and marine craft are not rigid structures, and are subject to twisting forces as a result of environment and load, all of which will affect the mounting of engine and propeller shaft. Boat engine drive systems do not indefinitely remain in alignment and need to be periodically checked and realigned to reduce wear to drive train units, components, and the craft itself.
When a driver like an electric motor or a turbine is coupled to a pump, a generator, or any other piece of equipment, it is essential that the shafts of the two pieces are aligned. Any misalignment between the two increases the stress on the shafts and will almost certainly result in premature breakdown of the equipment. This can be very costly. When the equipment is down, production might be down. Also bearings or mechanical seals may be damaged and need to be replaced. A proper shaft alignment can prevent this.