Automated washing facility and automated washing method for slop tank

Abstract

To eliminate long amount of time required for manually and surely carrying out outboard work such as opening and closing of various valves installed in various places on a deck and starting and stopping operations of a pump, etc., in slop tank washing work of a tanker, which is dangerous especially at night and under stormy weather conditions.SOLUTION: A facility and a method are provided for surely carrying out linked work necessary for washing and draining of a tank even aboard a rolling vessel in offshore waters by installing and consolidating and integrating a means for remote controlling equipment such as the tank, a valve, and a pump, and a sensor for detecting the status of each equipment, into the cabin.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to equipment and a method for automatically performing a series of operations from cleaning a tanker's slop tank to discharging the tank wash water. [Background technology]

[0002] Because the work of cleaning tank slop tanks and discharging tank wash water requires personnel other than those on duty and involves long working hours, there has been a desire to automate this work. Cargo tank cleaning has become automated with the development of cleaning fluids and equipment, but the draining of slop tanks that store waste cleaning fluid and the cleaning work after draining are complex and must be carried out in offshore waters where the ship's position is unstable, so they still rely heavily on the manual labor of skilled workers.

[0003] The Act on the Prevention of Marine Pollution and Maritime Disasters stipulates that the treatment of wash water after slop tank cleaning can only be discharged in offshore waters 12 nautical miles or more from the baseline of territorial waters. As this work requires offshore work outside the ship, it can be dangerous in rough weather or at night. Therefore, there has been a demand for equipment and methods that can automate the offshore work required for draining and cleaning slop tanks, without having to go outside the ship, especially for coastal tankers that navigate coastal waters. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 62-149597 Summary of the Invention [Problem to be solved by the invention]

[0005] Work related to draining a ship's slop tank and cleaning it after draining is done manually by opening and closing various valves installed in various places on the deck and starting and stopping pumps. Even for experienced workers, carrying out extravehicular work in these offshore waters at night or in rough weather conditions in accordance with procedures is a long-term and dangerous task. [Means for solving the problem]

[0006] The present invention aims to provide equipment and a method for automatically performing all of the above-mentioned extravehicular work in a safe and reliable manner while checking information displayed on a monitor screen installed inside the cabin. Specifically, the system aims to provide a means for remotely controlling equipment such as tanks, valves, and pumps required for the work, a method for installing sensors that detect the status of each piece of remotely controlled equipment in real time, and a method for consolidating the sensor information indicating each control means and status in the cabin, thereby ensuring that the necessary linked work can be carried out even on a rough, rocking ship in offshore waters, and a method for displaying and checking information essential for the work on a monitor. The system also provides a method for monitoring the ship's position during operation to ensure it does not deviate from legally designated sea areas due to factors such as tidal currents, and for halting the discharge operation if necessary. [Effects of the Invention]

[0007] The advantage of this system is that the draining of slop tanks and the subsequent cleaning of the slop tanks, which previously took a long time to complete outside the ship, can now be done fully automatically and in a short time from within the ship's cabin in legally designated waters, while safety is monitored and confirmed. During the operation, the ship's position will be monitored to ensure it does not deviate from the legally designated sea area due to factors such as tidal currents, and the discharge operation can be stopped if necessary. [Brief explanation of the drawings]

[0008] [Figure 1] Figure 1 is a diagram of the automatic slop tank cleaning equipment. [Figure 2] Figure 2 is a schematic diagram of the operation of the automatic slop tank cleaning equipment. [Figure 3] FIG. 3 is a flowchart showing a processing method for dealing with the rocking of a ship caused by waves. [Figure 4]Figure 4 is a flow chart showing how a vessel can remain more than 12 nautical miles offshore from the territorial sea baseline during operations. DETAILED DESCRIPTION OF THE INVENTION [Example]

[0009] Figure 1 is a diagram of the automatic slop tank cleaning equipment. The automatic slop tank washing equipment consists of a control device 1, a washing water device 2, a drainage device 3, a GPS (Global Positioning System) receiver 4, an image monitor 5 that shows the control status of the equipment, and an operation console 6 for manual input. The washing water device 2 and drainage device 3 each consist of a water storage tank, valves and pumps that control the water flow, and the valves and pumps are equipped with control lines that enable remote operation and sensors that show the status of the equipment, and each is connected to the control device 1.

[0010] Figure 2 is a schematic diagram of the operation of the automatic slop tank washing equipment, with the upper half of the figure showing the water purification device 2 and the lower half showing the drainage device 3, and the arrows indicating the direction of water flow and the functional relationship of each device. The inflow path of washing water from the cargo tank to the slop tank 31 is not shown.

[0011] The operation of draining the wash water stored in the slop tank 1 will be explained below with reference to FIGS. 1 and 2. In Figure 1, the control device 1 automatically controls the opening and closing of the valves of the cleaning water device 2 and the drainage device 3 and the pumps in response to instructions given by an operator via an operation console 8, and remotely monitors the status of each device in real time using status sensors for the valves, water level gauges for the tanks, and status sensors for the pumps (not shown), and displays the status on an image monitor 5. The control device 1 is programmed in advance with the procedures and conditions from cleaning the slop tank to draining the water, and is set to operate under the appropriate procedures and conditions using information from the above-mentioned control lines and sensors that indicate the status of the device, so all that is required to operate the operation console 6 is to press an automatic cleaning start button (not shown) to instruct the control device 1 to start the automatic cleaning work, and then it is only necessary to check on the image monitor 5 how the work automatically progresses and is completed in accordance with the above-mentioned program. The control device 1 also detects the ship's position in real time using a GPS (Global Positioning System) receiver 4. The interaction between the GPS receiver 4 and the control device 1 will be described later.

[0012] The flushing water drainage and flushing operations will be described in detail below with reference to FIG. By opening the suction line valve 34, wash water stored in the slop tank 31 is supplied to the slop pump 33, pressurized, and discharged overboard via the wash water transfer line valve 34 and the wash water overboard discharge valve 35. In conjunction with the above operation, wash water stored in the water tank 21 is pressurized by the Butterworth pump 22 and sprayed into the slop tank 1 by the wash nozzle 24 via the Butterworth line valve 23, thereby cleaning the inside of the tank. By this operation, the wash water stored in the slop tank 31 is discharged while the slop tank 31 is cleaned at the same time. This flushing and draining operation continues until the control device 1 detects that the slop tank 31 is almost empty, based on measurements from a water level gauge (not shown) installed in the slop tank, and closes the Butterworth line valve 10 to stop the supply of wash water; however, at this point a small amount of water remains in the slop tank, and the slop pump 33 continues the draining operation.

[0013] The drainage operation is completed when the slop tank 31 becomes empty and the wash water supplied to the slop pump 3 runs out. Generally, when the liquid supplied to the pump runs out, both liquid and air flow into the pump, causing the pump to make an air intake noise due to dry suction, and immediately after that the load on the pump becomes lighter. Therefore, if the tank is installed on land, the draining operation can be completed by detecting the lightening of the pump load using the pump's drive current or a sensor. However, the draining of a tanker's slop tank is carried out in offshore waters more than 12 nautical miles from the baseline of territorial waters, where the ship is rocking due to waves, and the angle of inclination of the slop tank fluctuates due to the rocking of the ship due to waves, so the above-mentioned emptying cannot be interpreted as the tank's water storage being depleted.

[0014] The method for completing drainage in response to the rolling of a ship according to the present invention will be described with reference to the flowchart of FIG. The control device 1 takes in the water level of the slop tank 31 in step 101 in Figure 3, and determines whether it has reached a low water level at which it can be determined that the tank is almost empty in decision step 102. If the water level has reached the low water level, the Butterworth pump 22 is stopped in step 103, and the Butterworth line valve 23 is closed, thereby stopping the injection of wash water into the slop tank 31. Even after the injection of wash water has stopped, the slop pump 33 continues to discharge water, and when the amount of water stored in the slop tank 31 approaches zero, the pump enters a dry suction state, and the load on the slop pump suddenly changes and becomes lighter. As mentioned above, when the slop tank is installed on land, the load fluctuation due to dry suction occurs almost only once, so the drainage work can be completed at that point, but when the ship is rolling with waves, the inclination of the tank fluctuates with the wave period, so dry suction may occur multiple times. Therefore, in the present invention, the load fluctuation period Δt of the slop pump is measured in step 104, and if that period exceeds a specified time T in decision step 105, it is determined that the slop tank 31 has become empty, and drainage completion processing is performed in step 106. According to the following literature, the period of waves on the ocean near Japan is a maximum of 20 seconds or less, so it is safe to set the specified time T at several times that, about one minute to several minutes or more, to be on the safe side. <References>Joint Probability Distribution of Ocean Wave Height and Period (Proceedings of the 1978 Conference on Coastal Engineering, Vol. 25, pp. 75-79, Authors: Tadao Honda and Hisashi Mitsuyasu)

[0015] Furthermore, based on experience, it is extremely rare for dry suction to occur more than a few times during the drainage process of an actual slop tank, so rather than performing the drainage completion process according to the flowchart of FIG. 3 described above, it is also possible to simply perform the drainage completion process after several minutes have passed since the first dry suction occurred.

[0016] Next, the coordination between the GPS receiver and slop tank drainage according to the present invention will be explained using the flowchart in Figure 4. As mentioned above, the Act on the Prevention of Marine Pollution and Maritime Disasters stipulates that the treatment of wash water after slop tank cleaning can be discharged in offshore waters 12 nautical miles or more from the baseline of territorial waters, so in the past it was necessary to navigate the ship well beyond 12 nautical miles so that the conditions stipulated by law could be met even if the ship's position changed due to tidal currents or the like during the several hours of work. In the present invention, in step 201, the control device 1 constantly obtains position information from the GPS receiver 4, and in step 202, the control device 1 obtains the trajectory of the ship's position.

[0017] Meanwhile, the control device 1 predicts the completion time of the series of tasks shown in Fig. 2 in step 203, and calculates the margin of time until the time when the ship's position will no longer satisfy the conditions stipulated by law before the tasks are completed in step 204. If the margin of time is long, the procedure in Fig. 2 is continued in decision step 205, but if the margin of time becomes short, the image monitor 5 displays the margin of time and an alarm is sounded by an audio device (not shown). If the margin of time becomes even shorter and there is a risk that the ship's position may be within 12 nautical miles, the control device 1 closes the wash water overboard discharge valve 35 to prevent wash water from flowing out of the ship. [Industrial Applicability]

[0018] According to the present invention, all outside work such as cleaning and draining the slop tanks of a tanker, which has previously been done manually by opening and closing various valves installed in various places on the deck and starting and stopping pumps, can now be done automatically, safely and reliably while checking the information displayed on a monitor screen installed inside the ship, which is of great industrial utility. [Explanation of symbols]

[0019] 1. Control device 2 Cleaning water device 3 Discharge device 4 GPS receivers 5 Image monitor 6 Control console 21 Water Tank 22 Butterworth Pump 23 Butterworth line valve 24 Cleaning nozzle 31 Slop Tank 32 Suction line valve 33 Slop Pump 34 Cleaning water transfer line valve 35 Wash water overboard discharge valve

Claims

1. An automatic cleaning facility for a slop tank, comprising a slop tank and a slop pump that sucks and discharges liquid from the slop tank, and after the slop pump has repeated a number of cycles of sucking in air along with the liquid that is generated when the remaining liquid in the tank becomes low, the operation of the slop pump is stopped to complete the drainage work.

2. 2. The automatic cleaning equipment for a slop tank according to claim 1, wherein the slop pump continues to operate for at least 30 seconds or more after the occurrence of the first air entrainment described above, and then the operation of the slop pump is stopped.

3. 3. The automatic cleaning equipment for a slop tank according to claim 2, wherein the operating power of the slop pump is reduced after the occurrence of the air entrainment.

4. An automatic cleaning facility for slop tanks, comprising a slop tank mounted on a ship, a slop pump that sucks and discharges liquid from said slop tank, and a GPS (Global Positioning System) receiver, wherein said slop pump will not be operated to drain said slop tank unless said GPS receiver indicates that the position of said ship is beyond an offshore area 12 nautical miles or more from the baseline of Japanese territorial waters.

5. 5. The automatic cleaning equipment for slop tanks according to claim 4, wherein if the GPS receiver indicates during the automatic cleaning operation that the position of the vessel has approached a boundary distance of 12 nautical miles from an offshore sea area that is 12 nautical miles or more from the baseline of Japanese territorial waters, an alarm is issued on a monitor screen or by an acoustic device.

6. An automatic cleaning method for a slop tank comprising a slop tank and a slop pump that sucks and discharges liquid from the slop tank, wherein the slop pump repeats a number of cycles of sucking in air along with the liquid that is generated when the remaining liquid in the tank is low, and then stops operating the slop pump to complete the drainage work.

7. An automatic slop tank cleaning method comprising a slop tank mounted on a ship, a slop pump that sucks and discharges liquid from said slop tank, and a GPS (Global Positioning System) receiver, and wherein unless said GPS receiver indicates that the position of said ship is beyond an offshore area 12 nautical miles or more from the baseline of Japanese territorial waters, said slop pump is not operated to perform drainage work for said slop tank.

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