Salalah tests put MoorMaster through its paces

01 May 2007

Patrick Rosenwald, technical director of Cavotec Specimas, believes that the benefits of the MoorMaster automated mooring system are best illustrated by the results of testing done at the Port of Salalah in Oman in the summer of 2005. 

He explains: "During the monsoon season (or Khareef as it is called in Oman), the Port of Salalah is subjected to 'infra-gravity' waves that penetrate the harbour defences and stimulate undesirable ship movements. The resulting stresses caused by these movements frequently stretch and snap mooring lines,wreaking havoc on container loading and unloading processes."

Cavotec and the authorities at the Port of Salalah put MoorMaster to the test by installing and operating a pair of units at the height of this 'long wave' activity. The results were excellent - container ship movement was reduced by a factor of 10.

The tests at Salalah, which resulted from a contract between SPS, AP Møller Terminals and Cavotec Group Holdings, evaluated the reduction in vessel motion achieved by holding vessels with two MoorMaster 400 units in Khareef waves during August and September 2005.After the test, in 2006 the Salalah Port Services confirmed to Cavotec Holdings an order for four new MoorMaster 600 (MM600), this being an evolution of the MM400 design that was developed by MSL following a technical review of the results of the previous testing in Oman. The Khareef or gravity waves have periods ranging from 30 seconds to several minutes and tend to 'surge' around breakwaters like a quickly incoming tide.

They affect many ports around the world. Larger vessels are generally more stable in wave  conditions but at Salalah,Khareef waves move the whole vessel in the fore/aft direction. This means that cranes have  to be frequently repositioned in the long travel direction and spotting containers on the ship is much more difficult and time consuming.

The MM400 units were tested with a number of ships including a Maersk super post-panamax ship with length overall of 347m and a breadth of 42.8m. "The procedure for attaching the units worked very well and the radio controller was successfully tested from the bridge and up to 1km away.

Waveinduced ship motions averaged 400mm in both the fore and aft direction. With the hydraulics active vessel motion could be dampened to 50mm-100mm," Cavotec Moormaster spokesperson Michael Scheepers tells Port Strategy. Overall, the tests demonstrated that the technology can effectively reduce movements in long wave conditions.

Ships were held in a much narrower fore/aft band with the hydraulics active and cranes did not need to reposition over bays while the ships were being held. Other observations made during testing were that ropes actually tended to make fore/aft vessel movement worse and that the movement of smaller feeder ships at berth tends to increase with cargo operations.

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