How does a passive heave compensator work?
A passive heave compensation device acts as a spring device with a predefined, relatively low stiffness. It allows relative motion while keeping load variations in wires, suspending the load within acceptable limits. Passive heave compensation systems normally require no power supply for their operation.
Why do we have motion compensation on the rigs?
Designed to compensate for the vertical movement of offshore drilling rigs, motion compensation (MoCom) systems work to isolate the heaving motion of the vessel from the drill string, to apply a constant tension to prevent riser buckling, and to tension guidelines and pod lines.
How does active heave compensation work?
Active heave compensation (AHC) is a technique used on lifting equipment to reduce the influence of waves upon offshore operations. AHC differs from Passive Heave Compensation by having a control system that actively tries to compensate for any movement at a specific point, using power to gain accuracy.
How does a motion compensator work?
A motion compensator is a device that decreases the undesirable effects of the relative motion between two connected objects. Not only does the anchor prevent the ship from drifting, but the chain itself dampens the movement of the ship due to undulating motion of the waves.
How does drill string compensator work?
Crown-mounted and direct-line compensators work to isolate the heaving motion of the rig from the drill string, while wire rope tensioners apply a constant tension to tension guidelines and podlines to prevent riser buckling.
What is heave accuracy?
Accurate heave measurements are important in many applications to compensate for vessel wave motion, e.g. in hydrographic seabed mapping, dredging, and offshore crane heave compensation. The accuracy is often specified to be better than the larger of 5 cm and 5% relative.
What is standpipe in drilling rig?
A rig standpipe is a solid metal pipe attached to the side of a drilling rig’s derrick that is a part of its drilling mud system. It is used to conduct drilling fluid from the mud pumps to the kelly hose. Bull plugs, pressure transducers and valves are found on the rig standpipe.
What is heave data?
Heave data are records of the vertical motion of the platform. Echoview can read heave data (see note) and generate a heave line that is a time series of depths. In Echoview, a positive heave value (from the heave line) represents downward motion.
How does a motion reference unit work?
Motion reference units are employed in large vessels operating at sea. MRUs capture roll, pitch, yaw and heave measurements with high accuracy to monitor vessel performance. These measurements apply to observing the wave height or determining dynamic positioning.
What is Kelly in drilling?
1. n. [Drilling] A long square or hexagonal steel bar with a hole drilled through the middle for a fluid path. The kelly is used to transmit rotary motion from the rotary table or kelly bushing to the drillstring, while allowing the drillstring to be lowered or raised during rotation.
What is Rotary hose in drilling?
1. n. [Drilling] A large-diameter (3- to 5-in inside diameter), high-pressure flexible line used to connect the standpipe to the swivel. This flexible piping arrangement permits the kelly (and, in turn, the drillstring and bit) to be raised or lowered while drilling fluid is pumped through the drillstring.
What is heave response?
Heave response is the most critical response for the support of the risers, and for the operability of a drilling platform. Figure 7.3. Example heave RAOs of various floaters. Several semi-submersible designs are included to show the influence of optimisation on the heave response.
What is the purpose of a string compensator on a drilling rig?
This compensation motion has the effect of nullifying relative motion between the rig and earth generated by heave of the vessel. This eliminates the rig motion that would otherwise be superimposed by the data read by the logging sonde. This compensation device is not required when a drill string compensator (DSC) is installed.
What is the compensation rate of an actual-size heave compensator?
The compensation rate was 95%, based on which the dynamic behaviors of an actual-size heave compensator were presumed. Furthermore, the speed of each cylinder and the acceleration of heave can be determined and used to fabricate an actual-size heave compensator.
Is there any analysis model for a heave compensator oil pressure system?
build a reliable analysis model for a heave compensator oil pr essure system. in the drawings and the catalog of each part. They were confirmed using the design tool concept by improvement plans. model. Moreover, the attenuation rate of 95% obtained thr ough the analysis and test can be used as
Where is the heave compensator located on a boiler?
The heave compensator is located at the top of the derrick, and fixed to the bottom of the frame. The four DSC cylinders, which reduce th e heave motion at the lower part, are connected to the crown block and are slanted relative to the frame.