Safe lifting for navigation skid modules enabled by Modulift
Modulift Spreader Beam Lifts Offshore Navigation Skids on to platforms with no power source available due for decommissioning. Photographs – Modulift
Date – 11 December 2018
If the answer to the problem is a Modulift 6t capacity spreader beam, what is the problem? Here, below are the details of the problem that delivered this answer.
After decommissioning and before complete removal of offshore oil and gas satellite platforms there is a period when the installation presents a hazard to navigation, without any hazard lights or other anti-collision equipment that need a power source for operation.
Jansen Marine & Offshore Trading BV, of the Netherlands, delivered the scope of work to U.S.-headquartered Tideland Signal. Consequently, the Dutch company now supplies several types of skids that include marine lanterns, aviation obstruction lights, and fog signals, fog detectors, remote monitoring via satellite, and more. Supplied with or without photovoltaic (PV) modules, both types are fitted with batteries, but only the one with PV modules is capable of charging them. Skids without PV modules are commonly used for periods up to half a year versus the year-round utilisation possible with the more advanced system.
Lifting the skid modules on to the abandoned platform presents several problems due to their relatively large wind surface compared to their mass and that they are not symmetrical. Specifically, the weight of the batteries moves the centre of gravity to the back of the skid, and in order to provide the strongest holding points, the lifting eyes are installed at the base of the skid. All these factors can result in an unstable load during lifting. The lift has to be made stable and as safe as possible by making sure the centre of gravity is directly beneath the crane hook.
The answer to this stability problem provided by Modulift was a MOD 6 spreader beam combined with chain slings, wire rope slings, and attachment points that can rotate 360 degrees under load, to lift two 1.6t (1,600kg) skids from supply vessels onto each of three platforms. The same configuration also has been used to lift skids onto five other platforms last year and one offshore wind jacket in 2018. The base of the skids measure (approximately) 2m (6.6 ft.) by 2m and they stand 3m (9.8 ft.) high. They were lifted by crane onto the main deck where batteries were installed before being raised to the helideck and welded into place at predetermined positions.