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American Petroleum Institute
The tensioner system should be designed to permit one unit to be out of service for maintenance or repair without jeopardizing the ability of the remaining tensioner units to provide the required tension to the marine drilling riser. A unit may be either a single tensioner or a pair of tensioners, depending on specific design.
- Maximum Tension Setting. The maximum tension setting should not exceed 90% of DTL so that the maximum tension, including dynamic variations, will be less than the DTL.
- Velocity Limiting Device. Some type of flow control device is normally located in the line between the fluid port on each tensioner and its respective air/oil interface bottle. This device should offer minimal resistance to fluid flow during all anticipated heave velocities. However, if a tensioner wireline should break or other failure occur which would allow the tensioner to stroke out at an uncontrolled rate, this flow control valve should sense the abnormally high fluid flowrate and immediately stop or greatly reduce the fluid flow into the tensioner.
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