Motion Conventional equipment includes a variety of products that are designed to compensate for the vertical movement of offshore drilling rigs due to heave. Crown Mounted and Direct Line Compensators work to isolate the heaving motion of the rig from the drill string. Wire rope tensioners are used to apply a constant tension to prevent riser buckling and to tension guidelines and pod lines. National Oilwell Varco's motion conventional products lead the industry and are backed by the company's known history of customer service and dependability. These products maintain the standard set by National Oilwell Varco and provide the highest quality to ensure safety and reliability in use.