A Lighter Touch Aids Propulsion

BY IAN CAMERON

When it comes to maximizing the propulsion efficiency of vessels it is easy to overlook the critical part played by propellers.

However, Hydrex Underwater Technology (Hydrex) headquartered in Antwerp, Belgium, said it has developed a new way of maintaining ship propellers to achieve maximum propulsion efficiency.

Established in 1974 Hydrex specializes in underwater repair and replacement services in various sectors including commercial shipping, naval and offshore.

The company said that a traditional approach by operators is to let a 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 said.

“This can alter the shape and efficiency of the propeller, cause roughness and increase, rather than reduce, friction,” said Hydrex founding Chairman Mr. Boud Van Rompay. “t 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.”

Van Rompay cited a recent experiment carried out on a 134 m cruise ship where the propellers were maintained using this technique. 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 US$2100 in fuel compared to the same trip operating rough propellers. A fuel saving of more than 5% was a direct result of the more effective propeller maintenance procedure, the company said.