JPS5918808A - Auxiliary device for supporting load of jack-up type offshore working platform - Google Patents

Abstract

PURPOSE:To strongly hold the piers of a jack-up type offshore working platform against external forces by a method in which one of two oil chambers partitioned by a piston is connected to the oil chamber of a cylinder with a pin coupled with a rack and the other is connected to the oil chamber of a plug-type gas accumulator. CONSTITUTION:To use an auxiliary device 9 for a jack-up type offshore working platform 14, an air cylinder 17 is extended, a pin 14 is allowed to come near a rack 3, an oil pressure is applied to a cylinder 10 through a stop valve 34 and a tube 29, and the pin 14 is coupled with the rack 3. During no-load operation, the piston 23 positioned at the upper end of the oil chamber 26 is lowered by the pressure of the oil chamber 28, oil flows from the oil chamber 24 to the oil chamber 21, and loads on the oil chamber 28 and the plug 20 are equilibrated. Since the variation in the load of the oil-pressure cylinder 10 results in the variation of the pressures of the plug 20, high compression spring constant of working oil is eased by low spring constant of the plug, and during the storm period, no separation of the pin 14 from the rack 14 occurs and also no breakage takes place even during peak-load operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pedestal supporting auxiliary device for firmly holding the pedestal of a jack-up type offshore working platform against external forces such as intense wave force and wind force.

As shown in Fig. 1, the above-mentioned offshore work platform is usually equipped with a polygonal hull 1 and two pillars of 5 to 4 truss structures that can be raised and lowered, and a rack 3 provided on the pillars 2 is used to raise and lower the jacks. By meshing the pinion 5 of the device 4 and driving the pinion 5 with a motor 6 via a reduction gear train, the entire pedestal 2 is raised and lowered relative to the hull 1.

Therefore, when jacking up the hull 1 with the pedestal 2 landing on the seabed and holding the hull 1 above the water surface (Fig. 1a), the hull 1
External forces such as the weight of cargo and loading equipment, wind, currents, waves, etc. are applied as loads to the pinion 5, and when the pedestal 2 is raised to be towed (Fig. 1b), the weight of the pedestal 2 is The inertia force due to the oscillation is applied to the pinion 5 as a load.

Figure 2 shows the load state of the pinion 5 when jacked up, where FBti is the load when jacked up without the external force, F is the load when the external force is applied, that is, in a storm state, and reaches the maximum value FP. Sometimes. Since such storm conditions occur very rarely, it is very uneconomical to increase the number of pinions to withstand the maximum value FP. For this reason, conventionally the maximum value F
There was an idea to compensate for the part exceeding the load holding capacity Fhtf when P is jacked up, that is, tsF = Fp - FM k with an inexpensive auxiliary device (storm chock).

FIG. 6 shows the load state of the pinion 5 during towing.

A load -FL due to the weight of the column is normally applied to the pinion 5, and when the column 2 moves due to waves or the like, the load of the inertial force is added to the load -FLK, resulting in a maximum value of -FF or +FP2k. However, the direction of the load is as shown in Figure 4a,
As shown in b, when the torque that the pinion 5 receives from the rack 6 is in a counterclockwise direction, it is positive, and when it is clockwise, it is negative.

The sign of the torque reverses after a backlash period t'l corresponding to the gap g between the teeth of the pinion 5 and the rack 6. Even during towing, the maximum value -Fp.

may exceed the load holding capacity FMk of the pinion 5, and it is economical to compensate for the shortfall N=Fpl-FM with an auxiliary device.

Usually, the jack-up device 4 has a gear train with a large reduction ratio interposed between the pinion 5 and its drive motor 6, and applies a brake to the end of the motor shaft to maintain the pedestal 2 in a jack-up state or a towed state.

Therefore, the power transmission system from the brake to the pinion is distorted with a spring constant specific to the load. The relationship between the relative displacement δ of the pillar 2 with respect to the hull 1 due to this distortion and the pinion load F is shown in Figure 5 (when jacked up) and Figure 6 (
In Figure 5, point A and B are respectively F in Figure 2.
If the point corresponds to B, FM, and the 0 point corresponds to the peak load FP in the storm state, then the auxiliary device has an operating characteristic D- that gives a load difference between B and 0 at strain δB at point B. E? It is desirable to have one. Also the 6th
In the figure, if the points corresponding to 1FL+'B1'M9-FPI and +FF in FIG. Operating characteristic S-R'fr that gives a load difference:
0 As the above-mentioned auxiliary device, a method of simply interposing a hydraulic cylinder vertically between the hull 1 and the pedestal 2 is such that the amount of oil in the hydraulic cylinder is within one pitch of the teeth of the rack B. Due to changes over time and the small compressibility of oil, the compression spring constant of the hydraulic cylinder changes,
It is difficult to secure the desired generated force at point E in FIG.

Auxiliary devices other than hydraulic cylinders have also been proposed, but since their spring constants are much higher than that of the jack-up device 4, there is a risk that excessive loads will be concentrated on the auxiliary devices and damage them. The current situation is that it cannot be used.

The purpose of the present invention is to hold an auxiliary device in which the overall spring constant is reduced by using a hydraulic cylinder and an accumulator in an oblique position between the teeth of a rack and the longitudinal wall of the hull in the vicinity thereof, so that the auxiliary device is in a stretched state. J:v1 An object of the present invention is to provide an auxiliary device for supporting a pedestal that improves the current state of the art.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 7, a bottle holder 8 is fixed to a vertical wall 7 of the hull near the rack 6, and a base end clevis 11 of a hydraulic cylinder 10 of an auxiliary device 9 is pivoted thereon with a pin 12 for vertical rotation. The bottle 14 attached to the tip clevis 16 of the cylinder 10 is brought into pressure contact with the tooth flanks 15 on both sides of the tooth groove of the rack 6, and the air cylinder 17 is connected to the bracket 16 fixed to the vertical wall 7 and the clevis 16 at both ends. It is held in place by meshing with the rack filter.

The vertical angle α of the hydraulic cylinder 10 is determined to be 60 degrees or more with respect to the horizontal angle β (approximately 25 degrees) of the lower tooth surface 15 that the bottle 14 presses against.
0 and t't are at right angles. Both cylinders 10.1 above
7 is attached as shown in solid lines in FIG. 7 when jacking up, and as shown in chain lines when being towed. In order to switch between these two states, 12 bottles are removable and there is a platinum on the top) 1
6a'. The air cylinder 17 may be replaced with other well-known suppressing means such as a lever for engaging and disengaging the bin 14 and the rack 6, a hydraulic cylinder, an electric cylinder, etc., and a constant pressing force is maintained during the operation of the hydraulic cylinder 10. It will be done.

An accumulator device 18 shown in FIG. 9 is attached to the hydraulic cylinder 10. In the figure, reference numeral 19 denotes a plug-type gas accumulator, which has a bladder 20 filled with nitrogen gas or other inert gas and an oil chamber 21 completely filled with oil around the bladder. 26 is connected to the oil chamber 24 on one side by a pipe 25, and the oil chamber 26 on the other side is connected to the oil chamber 28 on the side opposite to the rod of the piston 27 of the hydraulic cylinder 10.
Connect to with pipe 29. Check valve 30.51 on pipe 29
and a pressure regulating valve 52t, and the entire accumulator device is housed in a closed oil tank 65.

The bladder 20 has a predetermined initial pressure when the hydraulic cylinder 10 is unloaded, when the piston 25
It hits the upper end of the oil chamber 26 (FIG. 9) with a pressure of 0.

When the auxiliary device 9 is not in use, the air cylinder 17 is shortened to remove the bin 14 from the rack 3, but when it is used, the air cylinder 17 is first extended to bring the pin 14 close to the rack 3, and then Hydraulic pressure is applied to the hydraulic cylinder 10 from a portable hydraulic pump unit (not shown) through the stop valve 34 and the pipe 29, and in combination with the expansion of the air cylinder 17, the bottle 14 is brought into engagement with the rank B.

At this time, the load state is at point A in FIG. 5 if the ship is jacked up, and the hydraulic cylinder 10 is at point D, bearing a part of the hull load.

Therefore, the piston 23 separates from the upper end of the oil chamber 26, and oil flows into the oil chamber 21 from the oil chamber 24, compressing the Prada 20 and increasing its pressure. Therefore, the piston 2 stops at a position where the load on the hydraulic cylinder 10 and the pressure on the bladder 20 are balanced. When the load increases and reaches point B in FIG. 5, the load on the hydraulic cylinder 10 reaches two points, and the bladder 20 is further compressed.

During the above operation of the hydraulic cylinder 10, since the vertical angle α of the hydraulic cylinder 10 is larger than the horizontal angle β of the rack tooth surface as described above, the operating force of the hydraulic cylinder 100 is ? Rack 6
A horizontal component of force is generated that presses against the hull 1 during a storm.
However, even if the pillar 2 moves, the bin 14 will not come off the rack 6.

As mentioned above, load fluctuations in the hydraulic cylinder 10 always cause pressure fluctuations in the bladder 20, so eventually the hydraulic cylinder 10
The high compression spring constant of the hydraulic oil is relaxed by the low spring constant J:v due to the compression of the bladder 20, and the auxiliary device 9 operates with a low overall spring constant, even at peak loads during storms. Concentration of excessive loads can be avoided.

When the load on the hydraulic cylinder 10 decreases and reaches point G in FIG.
The oil in the oil tank 63 flows into the oil chamber 28, and the load on the hydraulic cylinder 10 rapidly decreases from point G to zero. Further, when the load on the hydraulic cylinder 10 exceeds point E in FIG. 5, the oil in the oil chamber 28 flows out from the pressure regulating valve 62 into the oil tank 66, thereby preventing the hydraulic cylinder 10 from being overloaded.

Even if the oil in the oil chamber 28 leaks from the sliding surface of the piston 27, the inflow from the check valve 31 prevents the hydraulic cylinder 10 from deteriorating in function, and maintains good functionality over a long period of time. be able to.

It will be easily understood that the auxiliary device 9 operates in the same manner as described above even during towing.

The present invention has the above configuration, and one hydraulic cylinder equipped with a plug-type gas accumulator can be used for jacking up and towing, and its mounting structure is simple, so it can be manufactured at low cost. The spring constant of the hydraulic cylinder during operation is lowered by the accumulator, so that it is not subjected to concentrated overload at the maximum load during a storm, and there is no deterioration in function due to oil leakage of the hydraulic cylinder. There is.

[Brief explanation of drawings]

Figures 1a and b are partial elevation views of the jack-up type offshore work platform during jack-up and towing, respectively.Figure 2 is a diagram of the load state of the jack-up device during jack-up.Figure 6 is the load on the jack-up device during towing. State diagram, 4th
The figure is an explanatory diagram of the pinion load of the jack-up device, Figure 5 is a load characteristic diagram of the jack-up device during jack-up, and Figure 6 is the load characteristic diagram of the jack-up device during towing.
FIG. 7 is an elevational view of one embodiment of the present invention, FIG. 8 is a side view of a hydraulic cylinder, and FIG. 9 is a structural explanatory diagram of an accumulator device. 1... Hull, 2... Pillar, 6... Rack, 4...
・Judge-up device, 10... Hydraulic cylinder, 14
... Pin, 17... Pressing device, 18... Accumulator device, 19... Bladder type gas accumulator,
20... Bladder, 21... Oil chamber, 22... Piston type accumulator, 26... Piston, 24.26
...Two oil chambers, 28...Hydraulic cylinder oil chamber, 3
1...Check valve, 32...Pressure adjustment valve, 3
6...Oil tank. Agent: Patent attorney Yugawa Satoshi - 1 other person Figure 1 Figure 4. b 4 Figure 2

Claims (1)

[Claims] A hydraulic cylinder that supports a load that exceeds the load holding capacity of a jack-up device that raises and lowers the pedestal of a jack-up type offshore work platform relative to the ship's hull, with one end pivoted to the ship's hull for vertical movement and a hydraulic cylinder provided at the other end. A hydraulic cylinder whose pin engages with a pedestal lifting rack at an appropriate vertical angle of the hydraulic cylinder; a pressing means provided between the hull and the hydraulic cylinder for engaging or disengaging the hydraulic cylinder; and an accumulator device attached to the hydraulic cylinder. The accumulator device has:
Inside the oil tank fixed to the hydraulic cylinder, there is a bladder-type gas accumulator with an oil chamber filled with oil around the Prada, and one of the two oil chambers separated by a piston is filled with the oil of the Prada-type gas accumulator. A piston-type accumulator that is connected to one end of the chamber and the other end connected to the oil chamber of the hydraulic cylinder, a check valve that allows oil to flow from the oil tank to the oil chamber of the hydraulic cylinder, and a check valve that allows oil to flow into the oil chamber of the hydraulic cylinder when the hydraulic cylinder exceeds a predetermined maximum load. A load supporting auxiliary device for a jack-up offshore work platform, characterized by housing a pressure regulating valve that drains oil from a cylinder into a hydraulic tank.