DNV approval for easily assembled slings

April 1, 2000
A new chain coupler has been introduced by lifting component manufacturer Gunnebo Industrier to provide more flexibility in meeting the offshore industry's needs.
Gunnebo's new Berglok connector.
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A new chain coupler has been introduced by lifting component manufacturer Gunnebo Industrier to provide more flexibility in meeting the offshore industry's needs. When it becomes available later in the year, the Berglok chain coupler will ensure that container-chain slings supplied by Gunnebo continue to meet DNV 2.7-1 requirements yet do not require long delivery periods, due to the possibility of local assembly.

Gunnebo was a leading proponent of the Det Norske Veritas type approval introduced to standardize the quality of lifting equipment used by offshore companies. Before DNV 2.7-1 standards were applied individual oil companies had imposed their own requirements but this had proved impractical and costly. The unified quality assurance has been a major benefit for manufacturers and users of container chain slings and other equipment. However, the high standards demanded have required companies such as Gunnebo to take a fresh look at their products in order to meet market needs.

Non-welded slings

Chain sling configurations using the Berglok connector.
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This has resulted in Gunnebo working to receive a DNV type approval for non-welded chain slings that use the Berglok chain coupler after the complete container has gained final DNV certification. The Berglok chain coupler now makes it possible for a sling to be tailor-made by a local certified dealer to meet both the DNV's and the customer's requirements. Previously, the different sizes of offshore container slings had required each one to be produced individually at the manufacturer's factory. The slings were all welded and local assay was not possible, which resulted in long delivery times. The Berglok unit was subsequently introduced to serve as the connector at the master link and as the end link that joins the chain sling to the shackle and container's padeye lifting point.

The type approval of the offshore chain slings and the Berglok chain connector system began five years ago and the concept received DNV approval last September. The connector consists of a horseshoe shaped unit with a load pin. Stainless steel rivets are used to lock the load pin in place and create a connection as durable as that found on a welded sling. All of the parts are marked with a size code to ensure that different size parts are not assembled together. All parts also carry a forging number for traceability. This arrangement will soon enable certified slings to be quickly manufactured by the Gunnebo certified dealer using stock materials. These can be assembled to meet a customer's precise requirements by, for example, taking into account the exact measurement of the chain legs required for a special container.

When the Berglok chain connectors for offshore use enter the market later this year, they will be available in four different chain sizes; 10 mm, 13 mm, 16 mm and 19 mm, which will cover almost 100% of the chain slings needed offshore. Their arrival will place Gunnebo Industrier in a unique position in an industry in which other manu facturers are only able to supply all welded slings.

The standards imposed on suppliers of lifting equipment for the offshore industry are the highest in the world. For normal onshore applications a load safety factor of 4:1 is considered adequate. The extreme climatic and environmental conditions in which slings can be used offshore, coupled with the risk of corrosion, makes it necessary for safety factors from 5:1 up to 8:1 to be applied. In addition to meeting the direct load requirements, each new Gunnebo lifting set will be capable of withstanding an impact of 42 joules at -20°C (27J in the weld). It will be supplied with its own certificate confirming that it meets DNV 2.7-1 requirements.

For more information contact Morgan Lindblom, Gunnebo Industrier, Tel: +46 220 221 00, Fax: +46 220 359 61, E-mail: morgan.lindblom @ind.gunnebo.se