PSVs Undergo Rapid Shipdock Antiroll Retrofit

For its recent retrofit of two antiroll tanks onto GulfMark UK’s Highland Defender and Highland Guardian, Shipdock Amsterdam said it is most proud of its rapid response and production speed, along with the ratio of 150 metric tons of steel deployed and processed relative to the contract’s limited total lead-time. In consideration of the fact that all work, from scratch, was carried out within one single location as a complete turnkey package by two Damen Shipyards subsidiaries, is a close second on the shipyard’s satisfaction scale.

Whereas Niron Staal manufactured the actual antiroll tank and hull sections, the onboard installation was done by Shipdock, part of the Damen Shiprepair & Conversion division.

The entire operation required simultaneous action, from the initial steel cutting to the final installation and commissioning, with the two PSV’s docked together in Shipdock’s 250-meter Panamax drydock.

Both Damen companies involved, are located within the same shipyard premises in Amsterdam.

“The contract was completed within a six week lead-time only, from the initial steel cutting to the vessels’ delivery. The lead-in time was practically zero,” Flip van der Waal, managing director Shipdock Amsterdam noted. “Niron and Shipdock started almost upon receipt of GulfMark’s steel cutting-drawings. The prefabrication part took three weeks to construct the two 75-metric-ton sections, painting included.”

The production schedule shown below, required the vessels to dock within the yard for a period of four weeks. Overall they encountered a total of six weeks downtime before reentering service.

• Order placed at Damen Shiprepair & Conversion: May 12, 2014
• Drawings received by Shipdock Amsterdam : May 22, 2014
• Started cutting steel: May 23, 2014
• Vessels docked: June18, 2014
• Vessels undocked: July 17, 2014
• Vessels departed for sea trials: July 22, 2014
• Sea trials completed: July 23, 2014
• Vessels arrived in Aberdeen: July 25, 2014

The Highland Defender and Highland Guardian main characteristics are 87 meters LOA, 3,900 GT and 5,100 DWT. The sister ships were built in 2013.

The antiroll tank units retrofitted to improve the vessels’ roll characteristics, benefit not only the marine crew, but further enhances the operational capability of the vessels in adverse weather. Antiroll tanks are installed onto ships in order to reduce the roll motion and roll angle during adverse weather conditions. They are placed abeam so that their internal baffles slow the rate of water transfer from the port side to the starboard side. As a large amount of water is restricted on one side of the vessel, this creates an asymmetrical force that opposes the natural but significant rolling motion imparted by a heavy sea swell.

The antiroll sections were installed directly against the aft face of the vessels’ accommodation. Constructed as a complete single section, extending across the entire weather deck from port to starboard side, they extend upward from B deck to the Bridge deck. The Antiroll tanks are now a seamless and fully integrated part of the ships’ structure.

According to Damen, there’s no shortage of challenges to pick from when describing this assignment, short as its duration may have been.

Being familiar with Shipdock Amsterdam’s performance level from several previous assignments, GulfMark UK Ltd, also commissioned the shiprepair and conversion specialist yard to complete additional work on the Highland Defender and Highland Guardian to further enhance the operational characteristics of two significant vessels.

“Our vessels are now even better equipped to face the harsh environments they will encounter within the operational arenas that they were designed for,” said Jim Bradford, GulfMark’s General Manager Operations comments.

“The antiroll retrofit and the general upgrade put together, we’d like to dub this contract a retro-upgrade,” Shipdock’s Flip van der Waal concluded.

damen.com