The Naval Architect January 2021
Considering that this year it celebrates 70 years of involvement with the maritime sector, it’s safe to say that Veth Propulsion by Twin Disc can claim to know a thing or two about marine propulsion. The Papendrecht, Netherlands-based firm has grown into a global player, but it prides itself on remaining true to its origins where meeting the customer’s (service) expectations and the personal touch are key elements.
“Besides developing new thrusters, we are doing repairs and overhauls. Nowadays it’s only a small part of our company,” explains Marco Huisman, Veth’s technical director. “We started developing products because customers were asking us. The man who founded our company (Mr. Jan Veth) was able to think in terms of solutions and developed certain types of bow thrusters, then in 1987 came our first rudder propeller. But we came from a service company, it’s in our DNA. We like to try on the shoes of the customer and see what he’s going through and offer him solutions he would like to use and solve issues quickly.”
Integrated L-drive
With that customer focus comes the ability to adapt to their changing requirements, not least of which is the demand for electrical propulsion solutions. In 2017, it launched its Integrated L-drive, an azimuth thruster solution available with power ranging from 265kW to 2,350kW. Described as the world’s most compact propulsion system, with extremely low mounting space requirements, it is attracting interest as a solution for inland barges, tugs and superyachts. Notably, it represented the first Veth system to use permanent magnet (PM) which is partly built inside the thruster, rather than asynchronous, motors, while the absence of gears inside the ship also means it generates less noise.
Huisman explains that the development process began a few years earlier, when it started exploring the feasibility of using the smaller, lighter PM motors. He says: “In the beginning there wasn’t much interest, nobody was asking for a super compact thruster. Our innovations are often based on (scientific) market analysis and the latent needs of our customers. Then we had a project where the client required a very compact unit and decided to take that opportunity.
“So we designed a slightly different L-drive thruster. We found increasing the diameter of the slew ring, which is for steering, gave space to mount the electric motor inside the inner diameter of this slew ring, which enabled us to make everything much lower than the existing L-drive in our portfolio. We also mounted the elastic coupling partly inside the motor, which allowed us to lower the motor so half of it was inside the thruster.”
PM motors offer excellent efficiency at full load, but Huisman says it is particularly at half load that a PM motor performs better than asynchronous motors. Nor is the price of PM motors such a deterrent; especially bigger motors (in excess of 1,000kW) are at the more specialised end of the market and will always come at a premium due to lower production volumes. The price of water-cooled asynchronous motors and PM motors are in the same magnitude. Up to 2,000kW, in particular superyachts and ferries desiring low noise production, there is also the option of including a contra-rotating propeller. In collaboration with Promarin, Veth’s contra-rotating solution features a patented asymmetric ‘shark tail’ design that’s said to ensure an optimal flow of water toward the second propeller.
According to Huisman, the Integrated L-drive is a “game changer” for the superyacht market. “Because our thrusters are extremely compact, it gives them design opportunities that they didn’t have before. Superyacht designers often want to include an infinity pool or beach bar, which requires some space that would normally be occupied by engine exhaust systems. It’s very beneficial to them that they can use our thruster with diesel electric propulsion, which can be positioned much more easily than conventional diesel propulsion with a long shaft line.”
The future
With Veth’s acquisition by power transmission manufacturer and distributor Twin Disc in 2018, Huisman believes there are now opportunities to expand the company’s reach. “However, what we are finding, from talking to our partners in the United States, is that outside of western Europe many shipyards don’t work with system integrators with knowledge of diesel electric propulsion. So, we need to be able to supply a complete package with generators, battery banks, power management, frequency drives and a monitoring system.
For the full article please see the January 2021 edition of The Naval Architect.
