The MultiDog is a new Norwegian subsea deployment and recovery tool designed to bring substantial time and money savings to the lifting and mooring equipment industry. The patented tool was developed by Knut Ove Steinhovden, manager of Ejecto, and is being marketed under an exclusive licensing agreement by Balmoral Group, which also worked with the inventor on the development.
Steinhovden realized the need for a dedicated deployment and recovery tool when working as a subsea engineer. It was apparent that the tools used subsea were simply versions of equipment designed for onshore use, he says. He therefore set out to design a tool specifically applicable to ROVs.
Ejecto/Balmoral's MultiDog tool is designed to bring substantial time and money savings in subsea deployment and recovery operations.
The result is the MultiDog, a cylindrical tool 82 cm in length and 15 cm in diameter, which weighs 60 kg in air. It is deployed by the ROV's grabber arm, giving the pilot full operational control from a single-point connection.
When joined with a female connector on the item of equipment to be moved, three radial cam-dogs engage with hook grooves inside the connector. The locking mechanism is simple, with few moving parts, and the tool contains no seals or hydraulic mechanisms, says Steinhovden. For emergency back-up release, there are two bolts inside the locking ring, which can easily be removed by an ROV. The locking mechanism then falls to the bottom of the tool, releasing the connection. The cam-dogs are made of titanium. The remainder of the tool and the female ring are of high-grade stainless steel.
The tool can be used for lifting all kinds of objects, from frameworks to submersible buoyancy units. The head screws onto the main unit, thus making it easy to fit heads with different attachments, such as wire sockets and shackles. The tool can also be assembled as a guide post connector for easy ROV access.
The tool will be redeveloped in accordance with project requests, Steinhovden says. Probably the greatest time and money savings can be achieved if its use is incorporated at the engineering phase of a project as a multi-functional lifting and handling tool.
The tool has been qualified and certified by Det Norske Veritas, which also participated in its development. Testing has included failure modes and effect analysis, a wet test carried out in Bergen, and an ultimate break-test carried out at Balmoral's test-bed in Aberdeen. Here the destruction equipment had to be redesigned after the shackle to which the tool was attached failed.
Eventually the tool failed when subjected to a load of 428.6 tons. It will likely be upgraded to a safe working load of 85 tons, says Steinhovden.
The tool compares favorably in other ways with existing equipment, according to Petter Nilsen, Balmoral Norge's sales and marketing manager. No particular alignment is required between tool and receptor for stabbing. This can take place through the whole 360°. Nor does it require any particular alignment between the ROV manipulator and the tool. There are no snag parts on the tool, as is the case with standard shackles. As there are few parts, maintenance requirements are low. After operation, the tool needs only to be flushed with fresh water. The low weight facilitates deck rigging and storage.