API RP16Q pdf free download

API RP16Q pdf free download.Design, Selection, Operation, and Maintenance of Marine Drilling Riser Systems.
4.4.3 Selection Criteria
Some important considerations for specifying a tensioner system are as follows.
a) Maximum tension setting (Tm)—The highest permissible tension setting with the vessel on location that provides sufficient margin so that anticipated conditions (such as wave-induced vessel motions, rig excursion, and/or tide change) do not cause any tensioner system relief valves to open, cause the tension experienced in the tensioners to exceed the limits of the design, or cause the pressure in the tensioners to exceed the limits of the design. With these considerations in mind, tension on any individual tensioner should not exceed this limit and the maximum tension setting for the riser, Tpj, should not exceed this limit multiplied by the number of active tensioners. Other considerations (e.g. riser and wellhead loading, recoil, etc.) may impose additional restrictions on tension setting.
b) Stroke—Each tensioner should provide enough stroke to accommodate wave-induced vessel motions, offset-induced changes in stroke, tidal variations, pup joint increment, changes in riser length due to changes in tension setting, etc. (see 6.4.2 for more details).
c) Number of tensioners—On some vessels, the tensioner system is configured to permit one tensioner or tensioner pair to be out of service for maintenance or repair without jeopardizing the ability of the remaining tensioners to provide the required tension to the marine drilling riser.
d) End cushioning—many riser tensioner cylinders include some form of end cushioning to limit forces when the tensioner rods reach their stroke limit. The configurations vary from one tensioner system to another. Some forms of end cushioning can interfere with efficient movement of the tensioner rods in the portion of the stroke range in which they are active.
e) “Fleet angle”—The angle from vertical at which the riser tension is applied to the riser.
f) Wire rope considerations—Wire rope life is a function of many parameters, including wire rope construction, sheave diameter, applied tension, operating circumstances related to travel, etc. (see API
9B).
g) Accumulators and pressure vessels—For tensioners that have an air-oil interface on the working side of the tensioner, an accumulator should be provided that has sufficient accumulator volume to store a volume of hydraulic fluid greater than the cylinder volume of the tensioner unit. The volume of air pressure vessels (or nitrogen pressure vessels) has a direct influence on the stiffness of the tensioners.
h) Fluid and air flow requirements-Pipe size, length, and fittings that connect riser tensioner components should be such to keep hydraulic friction losses within acceptable limits for the maximum anticipated flow rates.
i) Friction and inertia losses-Mechanical friction in the tensioner cylinders and sheaves and inertia of sheaves, wire rope, tensioner rods, and pistons all contribute to tension variations. The design of the tensioner system should strive to minimize the effects as much as is practical.
j) Velocity-limiting device-Many riser tensioner systems include a feature in each tensioner to limit tensioner rod speed in the event of a sudden loss of load in the tensioner (such as a parted wire rope or parted tensioner shackle). The design and location of these devices varies.
k) Recoil control systems-Many riser tensioner systems include a recoil control system that is intended to limit riser and tensioner speeds in events such as an emergency disconnect. Recoil analysis is discussed in 5.7.
API RP16Q pdf download.