Patent Application
20150315856
The present invention relates to a device for use on an offshore vessel, more precisely the invention relates to a device for use in connection with an active wave- or heave compensator. Compensator systems like that are often arranged together with fixed passive compensators at the top of a derrick or at the bottom of the derrick near the hoisting dead end on a floating drilling installation.
An active heave compensator usually comprises a linear actuator, typically a hydraulic cylinder construction with three chambers. This construction has typically axial movement of about 8 meter. The actuator could also be of another form of linear actuator, such as electric powered. This active compensator actuator is generally related to a passive heave compensation machine, called drill string compensator or passive compensator. The passive compensator exploit the gas compressibility of air or nitrogen in large pressurized containers (APV's) which are hydraulically connected to one or more hydraulic cylinders via piston accumulator(s). The piston accumulator(s) is acting as a phase separator between the pressurized gas volume and the oil-filled hydraulic cylinders. The hydraulically cylinders balance thereof the load in this passive compensator and offsets most of the vessel heave motions using spring force from the pressurized gas volume. A typical drill string compensator manipulates the load in that the hydraulic cylinders in the passive compensator are mechanically connected to a movable crown block in the draw work system of the derrick. The actuator of the active compensator is also connected to and manipulates actively the movable crown block with a smaller force that helps to reduce the load fluctuation and deviation position from the passive compensator in that it outweights the friction in the passive compensator. A control system regulates the force- and position load based on real time measurements from an acceleration sensor (MRU) on the vessel. In this way the performance of the total heave compensator system are improving in that all heave induced influences are eliminated. This is important when delicate operations are carried out on the seabed or in the well.
In drilling rigs which are equipped with top-mounted active heave compensation actuator and passive heave compensator, the actuator of the active compensation is usually connected permanently to the movable part of the passive compensation machine.
The total amount of time the drilling rig is operational with active heave compensation is often limited compared with the time it is operational with passive heave compensation alone. The actuator of the active compensator is hence driven out and in by the spring force in the passive compensator in a greater portion of the time.
To minimize the abrasion and achieve optimal operation, it is advantageous to have an arrangement where the actuator of the active compensation can be connected and disconnected when it is needed. Such an arrangement will increase the lifetime of the active compensator actuator and increase the capacity of the passive compensator.
The invention provides a device for connecting and disconnecting an active heave compensator actuator or additional passive compensator actuators which is operatively connected with a fixed structure at its first end. The device is distinctive in that the heave compensator actuator comprises a connection device which are operatively connected to a crown block or other load carrying device, said connection device being adapted to selectively grip a second end of the heave compensator actuator, and that it further comprising a safety device being adapted to selectively grip the heave compensator actuator second end when it is not in engagement with the connection device.
Preferable embodiments of the device are defined in the dependent claims, to which reference is made
The purpose of the device according to the present invention is to permit connection and disconnection of the active heave compensator actuator or additional passive compensator actuators against the movable crown block or other load carrying device which is passively compensated by fixed passive compensator actuators. The arrangement protect also against collisions between the movable end of the active compensator actuator and the movable crown block attached to the passive compensator. Usually the active compensator actuator is flexibly supported using a gimbal-mounting towards the tower structure. This is to prevent transmission of lateral forces to the active compensator actuator when the movable crown-block is driven in and out, this may damage the seal assembly and the rod, because there always will occur lateral movement of the crown block. When the rod end on the active compensator actuator is disconnected from the crown block, the arrangement will need a support mechanism to prevent that the active compensator actuator tilt. In addition the support arrangement contribute to a possible subsequent connection, in that the active compensator actuator is aligned to obtain the right entry (in this case vertical) of the connection device at the end of the actuator rod against the connecting arrangement on the typically passively compensated crown block.
The arrangement has the capability to connect and disconnect the dynamically loaded load bearing device, both when the actuator is set in motion or it is in stationary state.
a) shown in open position,
b) shown in closed position.
a) shown in open position,
b) shown in closed position,
c) isometric view of the closed position.
a) shown in open position,
b) shown in closed position,
c) isometric view of the closed position.
Reference is made to
The supporting device 3, the safety device 6, the connection device 7 and the connection with the adaptor head is further described in the following
The actuated supporting device 2 is mounted at or around the active compensator actuator 1. The supporting device 2 is connected to the derrick structure 4 with a hinged connection.
The supporting device 2 comprises three adjustable contact supports 9 that are run or placed against the stationary end of the active compensator actuator 1 using an arm construction. The arm construction comprising one main arm 10 and two linked arms 11, 13, positioned at an angle relative to the main arm 10 The main arm 10 and the linked arm 11 are hingedly connected at an upper end of the supporting device 2. The link 13 is connected to link arm 10 and supported in the lower end of device 2. The contact supports 9 are activated by hydraulically or electrically adjustable actuators 12.
The function of the supporting device 2 is to align the actuator when connecting and disconnecting as well as being a lateral support to the active compensator actuator 1 when this is disconnected. This is shown in
b shows the safety arrangement in a closed position where the grapplers 14 engaging the flange of the adaptor head 18.
The safety device 6 is also attached to the derrick structure 4.
a shows the connection device 7 in an open position where the grapplers 19 are not in contact with the adaptor head 18.
b shows the safety connection device 7 in a closed position where the grapplers 19 engaging the flange of the adaptor head 18.
When the adaptor head 18s connected to the connection device 7 the rod end (not shown) of the active compensator actuator 1 may be hydraulically driven in and out. When the adaptor head 18 is connected to the safety device 6, the rod end (not shown) of the active compensator actuator 1 is held in a fixed position.
The present invention has been described with reference to some preferred embodiments and some drawings for the sake of understanding only and it should be clear to persons skilled in the art that the present invention includes all legitimate modifications within the ambit of what has been described hereinbefore and claimed in the appended claims. Henceforward this connection and disconnection device can also be used for passive compensator actuators in passive compensators comprising two or more passive compensator actuators. This to allow using only the number of compensator actuators needed to achieve the necessary compensation force.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20121501 | Dec 2012 | NO | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2013/076375 | 12/12/2013 | WO | 00 |
