ABSTRACT This paper summarizes the design of the production, pipeline, and drilling riser tensioners for a TLP application. The riser tensioners are similar in concept and were designed to be comp act, se1f -contained units. The production, pipeline, and drilling riser tensioners provide 200, 400, and 1,000 kips nominal tension, respectively. Tension variations do not exceed ± 20% for the production and pipeline riser tensioners and ±10% for the drilling riser tensioners. Tension variations include the cumulative effects of 100 year storm wave cycle fluctuations, maintenance requirements, and variations resulting from any single component failure. The physical size of each tensioner does not exceed the space available per the Phase II TLP Structure Design. All tensioners provide a 49-½ diameter clear center opening and have a 30 year design 1ife. Several design alternatives were evaluated during the initial design phase of the tensioners. Alternates considered were as follows: the applicability of a single ram failure mode and its inherent bending moment as opposed to a dual ram f ai1ure mode; number and arrangement of rams; the use of rams or cylinders; the use of bladder or piston type accumulators; the use of mechanical ball/spherical joints or elastomeric joints to allow omni-directional rotation of the upper support ring; and a selection between types of hydraulic fluids and pneumatic system gasses. The initial configuration per original specification for the production and pipeline riser tensioners is illustrated in Figure 1, while the drilling riser tensioner is shown in Figure 2. A revised specification allows a 6 ram production and pipeline riser tensioner illustrated in Figure 3. The following items are identified in Figures 1, 2 and 3: a support structure that transmits the tension loads to the platform, ram-accumulator assemb1ies that generate the required forces needed for tens ioning the riser, an upper support ring that acts as an interface between the hydraulic rams and the riser string, retractable latches that provide a suitable landing shoulder for the riser tension sub, and guide rails that transmit horizontal and torsional riser loads into the platform. The initial study defined an area in which additional work was undertaken. That is, the discussion of the number of rams required suggests specification changes that would permit reducing the number of rams required for the tensioner. Specification changes which include an automatic control scheme lead to a 6 ram system versus a 12 ram system for the production riser tensioner and a similar component reduction in the other tensioners. INTRODUCTION The purpose of the study was to demonstrate the ability of the riser tensioner to properly maintain the required riser tension under all operational conditions. The principal problems encountered in the design were in packaging a unit that would fit within the allowable deck space and in selecting components that would provide the maximum service 1ife.