30Te winch upgrade for subsea operations

A vessel owner was looking to upgrade a number of electrical winches on board its PLSVs operating offshore Brazil - originally designed and manufactured by MDL for onboard tugger operations - to enable them for subsea use. Among these, the 30Te winch presented an opportunity to support subsea lifting activities. This required confirmation that the equipment could sustain the proposed loads while remaining compliant with the Lloyd’s Register Code for Lifting Appliances in a Marine Environment, including the increased hoisting factor applied to subsea operations.

MDL carried out an engineering assessment to determine the winches’ suitability and maximum rated capacity for subsea lifting. This included defining the relevant load cases, completing mechanical engineering calculations and reviewing the components and wire rope against the latest code and operational requirements. The calculations confirmed that the winch structure could sustain the required load without exceeding allowable stresses in its primary structural elements. MDL subsequently developed a mechanical upgrade incorporating load cell pins within the winch mounting assemblies. The corresponding electrical and controls design routed the load cell signals to the PLC, supported by updates to the PLC and HMI software. MDL also produced a new deck eye drawing, allowing the vessel owner to adapt the existing deck eyes for secure sea fastening.

The assessment confirmed that the existing 30Te winch could be adapted for subsea lifting without modification to their primary structural elements, enabling the client to extend the capability of equipment already installed across on the vessel. The design calculations were reassessed for the new operating case, with Lloyd’s Register reviewing the structural design. MDL also updated the Operation and Maintenance Manual and provided a revised Design Appraisal covering the subsea lifting application. Together, the mechanical, electrical and controls upgrades provided the load monitoring and system integration required to support the winch’s expanded operating scope.