A marine riser tensioner is a device used on an offshore
drilling vessel which provides a near constant upward force on the
drilling riser independent of the movement of the floating drill vessel.
The
marine riser
Marine is an adjective meaning of or pertaining to the sea or ocean.
Marine or marines may refer to:
Ocean
* Maritime (disambiguation)
* Marine art
* Marine biology
* Marine debris
* Marine habitats
* Marine life
* Marine pollution
Military
...
is connected to the
wellhead
A wellhead is the component at the surface of an oil or gas well that provides the structural and pressure-containing interface for the drilling and production equipment.
The primary purpose of a wellhead is to provide the suspension point and ...
on the sea bed and therefore the tensioner must manage the differential movements between the riser and the rig. If there were no tensioner and the rig moves downward, the riser would buckle; if the rig rises then high forces would be transmitted to the riser and it would stretch and be damaged.
Tensioners have historically been composed of hydraulic actuated cylinders with wire sheaves. More recently, active electrical motors have been used for compensation purposes.
Hydraulic Tensioner
A hydraulic riser tensioner consists of a
hydraulic cylinder
A hydraulic cylinder (also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in construction equipment (engineering vehicles ...
with
sheave
A sheave () or pulley wheel is a grooved wheel often used for holding a belt, wire rope, or rope and incorporated into a pulley. The sheave spins on an axle or bearing inside the frame of the pulley. This allows the wire or rope to move fre ...
s at both sides. The cylinder is connected to a number of high-pressure gas bottles via a medium separator. A
wire rope
Steel wire rope (right hand lang lay)
Wire rope is several strands of metal wire twisted into a helix forming a composite
''rope'', in a pattern known as ''laid rope''. Larger diameter wire rope consists of multiple strands of such laid rope in a ...
is rigged in the cylinder; one end is connected to the fixed part of the tensioner, the other end is connected to the riser.
[Fundamentals of Marine Riser Mechanics: Basic Principles and Simplified Analysis, Charles P. Sparks, ]
On board a drill rig tensioners are usually required for
drill string compensator
A drill string compensator decreases the influence of the heave of a drilling vessel on the drill bit. Drill string compensators are also known under the more general name: heave compensator. Drill string compensators are used onboard drill ships ...
,
riser tensioner
Riser may refer to: Engineering
* Stair riser, the vertical elements in a set of stairs
* Riser, another name for a theatre platform
* Riser, a length of vertically oriented piping used to deliver fluid, gas, or electrical signals or power upward
...
, and
guideline tensioner A guideline tensioner is a hydropneumatic device used on an offshore drilling rig that keeps a positive pulling force on the guidelines from the platform to a template on the seabed.
The guidelines act as a guidance for equipment and tools that mus ...
.
See also
*
Hydraulic jigger
A hydraulic jigger is a hydraulically-powered mechanical winch.
From the mid-19th century, hydraulic power became available throughout the increasingly modern dockyards and warehouses. This was generated centrally and distributed by pipework, eit ...
References
{{DEFAULTSORT:Marine Riser Tensioner
Petroleum production
Drilling technology