Belgian underwater repair specialist, Hydrex, has developed a new method of maintaining ship propellers to help achieve maximum propulsion efficiency.
The traditional approach is to let the propeller foul and build up a calcareous growth and polish the propellers once or twice a year underwater or in drydock. Usually, a grinding disk is used which can potentially damage the propeller blades, removing a substantial amount of metal.
Hydrex founding chairman Boud Van Rompay, said: “This can alter the shape and efficiency of the propeller, cause roughness and increase, rather than reduce, friction. It is also a major source of marine pollution which is a problem in many ports.”
Dave Bleyenberg, Hydrex Production Executive, added: “We discovered that more frequent, lighter buffing of the propeller is the optimum approach to propeller maintenance. This is done using a different tool to a grinding disk to buff the propeller before any calcareous layers build up and cavitation erosion impacts efficiency. If done correctly and regularly we can achieve 5% or more in fuel consumption, which more than offsets the cost of this propeller maintenance process.
“Because the propeller is being buffed regularly, the cleaning is light and quick. No material is ground away, which is excellent for the propeller and the environment. The propeller is kept in an ultra-smooth condition and this is where the fuel savings are achieved.
“Many of our customers who have used this service have noticed a remarkable difference in their fuel efficiency after each cleaning. One Chief Engineer told me: ‘you can clearly tell the difference in a ships’ performance after Hydrex has done its thing’,” said Bleyenberg.
Van Rompay said that a recent experiment carried out on a 134 m cruise ship, where the propellers were maintained using this technique, it was found that the fouling was not very heavy since the propellers were regularly cleaned but fuel saving calculations showed that on a 30-hour trip from Aruba to Barbados, the cruise ship saved $2,100 in fuel, compared to the same trip operating with rough propellers. A fuel saving of more than 5% was a direct result of the more effective propeller maintenance procedure, he claimed.
