Of UPS and HPUs
The hydraulic power unit (HPU) used with a davit system can feature separate or integrated power packs, while electric motors can be mounted as standard on top of the tank, or ‘submerged’ inside. In either case, the preferred solution represents a straight choice and the market is split roughly but firmly 50/50 between the options.
User preference and experience influence the market share each solution commands, but it is always worth asking how the benefits of any ship’s equipment are shared between the vessel’s operator and its shipbuilder. One owner will prefer a submerged electric motor, for example, due to the superior protection it offers the HPU against weather and corrosion. Another might conclude that, since electric motors fail without warning, a top-mounted motor offers better access for maintenance.
Decision Making
These decisions are clearly for owners, irrespective of yard of build. However, a third decision facing specifiers is closer to first principles: choosing a dedicated power unit or drawing power off the ship’s hydraulics involves a clear divergence in approach. Shipbuilders far prefer the latter but, in what is no longer a suppliers’ market, perhaps it is time for shipowners to ask themselves whether yard preferences should continue to hold sway.
Vestdavit recommends separate HPUs
In most cases, Vestdavit supplies separate HPUs to work with our davit systems and, while we don’t say it’s definitively the superior option, what we can say is that those choosing this option show a very strong preference. A standalone unit is configured to supply hydraulic power to the specific davit, and is more likely to be up and running if there’s a man overboard or if there’s a problem with the main ship, they point out.
More significantly, any ship’s hydraulic system is likely to feature sizeable pumps and, while that means plenty of power to work the system, there are several “users” fighting for the same hydraulic power from time to time. Also, there may be issues with high pressures and the risk of overload. Our recommendation is for davits to be fitted with HPUs working at pressures of around 250 bar.
Also, working in the standalone solution’s favour is that some launch operations require stealth; some of our customers need to ensure that noise levels are no more than 80 dB in the engine room, let alone anywhere else. Our customers may be keeping quiet on the benefits of the separate HPU; but as experts in safe boat handling for life, there’s no reason we should.