UK SBS Discovery ROV Powered Diverter Sheave

Tender description

National Marine Facilities (NMF) are seeking to procure a dedicated portable Powered Diverter Sheave and tugger assembly to enable the Marine Autonomous and Robotics Systems (MARS) Remotely Operated Vehicle (ROV) ISIS to be operated on board RRS Discovery to meet future Scientific demands. The docking is to be positioned between the ROV Traction Unit and Storage drum (components currently held within the National Marine Equipment Pool) and the ship fitted overboard bullhorn gantry. The Purpose of the powered sheave and tugger assembly is to ensure tension remains on the cable during the deployment and recovery phases of ROV operations. The addition of a powered diverter sheave and tugger assembly at the inboard end of the deployment boom is required to maintain a constant tension on the umbilical from the sheave to winch system. This will be required for use when the boom is being deployed and recovered. This assembly is to be energised from the existing control console, whereby once the jockey wheel has engaged the umbilical, the outboard sheave starts to rotate in the veer direction maintaining a tension between the winch and the diverter sheave. Typically the tugger assembly consists of a tugger idler wheel on a truck assembly that applies pressure on the umbilical against the sheave groove by use of a hydraulic cylinder. A tugger motor rotates the over boarding sheave via a chain drive providing tractive effort through the sheave groove against the umbilical. The tugger control is biased to reduce the tension when hauling in the umbilical and pre-set cable tension when paying out the umbilical. The motor rotation is sequenced to ensure that the sheave will not rotate unless the pinch wheels are at pre-set pinch pressure setting. The powered diverter sheave and tugger assembly will be required to be installed as part of the mobilisation for an ROV cruise and to be removed at the end of the cruise, and is not to be a permanent part of the deployment boom.