The marine environment poses a number of challenges for those who design vessels and the equipment which is used on board. As equipment gets larger so the demands for more efficient systems increase as well; all the while having to contend with the inhospitable environment encountered at sea. To deliver a reliable and efficient product, while still achieving the requirements and specifications of the industry, demands an integrated and flexible approach from designers.
In today's world of rising costs and energy prices, the terms 'energy efficiency' and total cost of ownership (TCO) are dominating the list of requirements when it comes to specifying new equipment. Taking a long-term view when investing in a new project has become increasingly important. So, designers are looking to incorporate these characteristics, while still maintaining the required levels of reliability.
As part of the Altra Industrial Motion group, Bauer Gear Motor has many years experience in designing and manufacturing a wide range of geared motors for a variety of marine applications. While advances in electric motor efficiency have evolved to IE4, Bauer has also made significant advances in improving the mechanical efficiency of their drive systems.
The key to a successful design is ensuring that the individual components are carefully matched to the application and then integrated into the equipment, thereby reducing the number of areas susceptible to efficiency losses. This can be achieved by combining a series of modular components to achieve the required specification, or by designing a bespoke drivetrain in conjunction with the OEM. This allows the engineers to maximise the potential energy savings and delivers a fully integrated solution.
Bauer has used its engineering expertise and understanding of the marine sector to ensure its products will deliver reliable and efficient service while also meeting the international standards required. It has supplied a considerable number of BF Series geared motor drives for use on perforated screens which are used in the wastewater treatment plants on larger marine vessels.
The BF Series complies with many international standards which certify it as suitable for use in marine applications. It features a corrosion protected, high-tensile, cast iron housing which is available with up to IP66 protection thanks to its high quality seals. A hardened wear sleeve and spray ring at the rotor seals further reduce the risks of leaks while ensuring reliable lubrication. The design uses low noise gearing, which improves working environments while also increasing efficiency.
Providing engineering expertise to OEMs usually means offering existing products with suitable modifications for a particular application. However, in some cases it can mean ground breaking design for a completely bespoke solution. One such example has been completed by TB Wood’s, also part of the Altra Group, where it was approached to work on delivering the deepest sand dredging pump in the world.
An underwater sand mining company needed to extend an existing suction pump dredge in order to allow the mining operation to continue for a further 40 years. However, designing a drive system that was 65% longer than any other dredging unit would pose some considerable challenges for the designers.
TB Wood’s supplied a number of 6 metre long disc couplings which would bolt together to form the drive shaft. The Form-Flex couplings use a hollow tubular shaft - which reduced the overall weight of the solution - with specialised taper lock mounted hubs which allow for easy field service, including axial adjustment at the pump end.
For this application TB Wood’s customised the hubs with a unique flange disc pack and tapered bushing mounting to facilitate ease of installation and adjustment to the underwater pump impeller. The abrasive nature of the material being pumped, meant that axial adjustment of the impeller was necessary when it became worn down. The couplings are able to handle parallel offset and angular misalignment which is essential in an application that will be subjected to unavoidable external forces.
Improved materials technology
Designing durable and reliable equipment also requires expertise in materials technology and the ability to incorporate both innovative and proven materials into new designs.
When the application demands a braking system capable of generating 250 tonnes of tension, it is important to select the correct materials to ensure both excellent friction properties as well as heat dissipation characteristics. For this particular case, Wichita Clutch, the heavy-duty clutch and brake experts of the Altra group, was asked to design the braking arrangement for a winch system for a semi-submersible drilling platform.
The platforms are self-propelled and capable of drilling in depths of up to 2,400 metres. Once the platforms are in position they can use dynamic positioning to remain stationary, however if the platform is going to remain in the same place for an extended amount of time then a pattern of mooring anchors will be laid out. The winches are used to control the anchor cable payout and need to be able to withstand substantial heat build-up.
In any braking application it is important to consider the brakes heat dissipation capability, if the heat generated by the friction of the cable tensioning duty exceeds the convection capacity of the unit to dissipate it, the brakes operation may become compromised. During the payout of the mooring cables typical power levels of 1,600 kW of continuous heat energy can be produced due to the high torque slipping of the brake.
Wichita used copper cooling technology, which is the most efficient method of heat dissipation in the range. Copper discs are used for high heat transfer from the friction surface to the continuous flow of cooling water. The use of a patented Jacket Design, coupled with the copper wear plates, provides precise stopping / tensioning capabilities with very high heat dissipation characteristics.
Wichita is able design and manufacture each braking system specifically suited to each customer’s requirements and can include options such as saltwater corrosion protection and various friction materials depending on the application.
Achieving a client’s expectations while maintaining the required standards for the application requires expertise in a number of different areas. Combining an understanding of the application with leading edge engineering design can deliver the optimum solution in terms of reliability and efficiency.
The Altra Group encompasses a wide range of engineering expertise, supported by a world wide support network. A continuous programme of research and development combined with a wide range gear motors, couplings, clutches, brakes and actuators ensures that every customer receives the precise, technically advanced, cost effective, solution required.
Philip Crowe is with Bauer Gear Motor GmbH, Esslingen, Germany.