Automatic cleaning equipment and method for slop tank

Abstract

Cleaning a tanker's slop tanks requires manual, careful outside work such as opening and closing various valves installed in various places on the deck and starting and stopping pumps, so it takes a long time and is dangerous, especially when done at night or in bad weather. [Solution] To provide equipment and a method for reliably performing the coordinated operations required for tank cleaning and drainage even on a rocking ship in offshore waters by installing means for remotely controlling equipment such as tanks, valves, pumps, and sensors for detecting the status of each piece of equipment and consolidating them in a cabin.

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] Since the work of cleaning slop tanks and discharging tank wash water on tankers requires personnel other than those on watch and involves long working hours, there has been a demand for automating 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 attitude is unstable, so they still rely heavily on the manual labor of experienced 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 be discharged in offshore waters more than 12 nautical miles from the baseline of territorial waters. Since this work requires offshore outside work, it can be dangerous in bad weather or at night. Therefore, there has been a demand for equipment and methods to 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 drainage is performed manually by opening and closing various valves installed in various places on the deck, starting and stopping pumps, etc. Carrying out spacecraft operations in offshore waters at night or in bad weather conditions in a timely manner is a long and dangerous task even for experienced workers. [Means for solving the problem]

[0006] The present invention provides equipment and a method for automatically performing all of the above-mentioned extravehicular work in a safe, reliable manner while the user checks information displayed on a monitor screen installed inside the cabin. Specifically, the goal is 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 control means and sensor information indicating the status of each piece of equipment in the cabin to ensure that the necessary coordinated work can be carried out even on a rough, rocking ship in offshore waters, and a method for displaying and confirming information essential for the work on a monitor. The system will also monitor the ship's position during operation to ensure it does not deviate from legally designated sea areas due to factors such as tides, and will provide a method to halt the discharge operation if necessary. Effect of the Invention

[0007] The advantage of this system is that the draining of slop tanks and cleaning of the slop tanks after drainage, which previously took a long time outside the ship, can now be done fully automatically in a short time inside the ship's cabin in legally designated sea areas, while safety is monitored and confirmed. In addition, during the operation, the ship's position will be monitored to ensure that it does not deviate from the legally designated sea area due to tides, etc., and the discharge operation can be stopped if necessary. [Brief description of the drawings]

[0008] [Figure 1] Figure 1 is a diagram of the automatic slop tank cleaning equipment. [Diagram 2] Figure 2 is a schematic diagram of the operation of the automatic slop tank cleaning equipment. [Diagram 3] FIG. 3 is a flow chart 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 territorial baselines while performing operations. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLES

[0009] Figure 1 is a diagram of the automatic slop tank cleaning equipment. The automatic slop tank cleaning equipment consists of a control device 1, a cleaning 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 cleaning 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 equipment status, 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 showing the direction of water flow and the functional relationship of each device. The inflow path of the wash water from the cargo tank to the slop tank 31 is not shown.

[0011] The drainage operation of 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 valves and pumps of the cleaning water device 2 and drainage device 3 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 with the procedures and conditions from slop tank cleaning to draining, and is set to operate under appropriate procedures and conditions using information from the above-mentioned control lines and sensors that indicate the status of the equipment. Therefore, the only operation required for the control console 6 is to press an automatic cleaning start button (not shown) to instruct the control device 1 to start the automatic cleaning operation, and thereafter, it is sufficient to check on the image monitor 5 the progress of the operation as it 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 drainage of washing water and washing operation 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 by the wash nozzle 24 into the slop tank 1 via the Butterworth line valve 23 to wash the inside of the tank. Through 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 washing 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 a so-called air-sucking 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 drainage 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 tanks is carried out in offshore waters more than 12 nautical miles from the territorial baseline, where the ship is rocking due to waves, and the angle of inclination of the slop tanks fluctuates due to the rocking of the ship due to waves. Therefore, the above-mentioned draining cannot be interpreted as the water in the tank being depleted.

[0014] A method for completing drainage in response to the rolling of a ship according to the present invention will be described with reference to the flow chart of FIG. The control device 1 takes in the water level of the slop tank 31 in step 101 in Fig. 3, and judges in decision step 102 whether it has reached a low water level at which it can be determined that the tank is almost empty. If the water level has reached the low water level, in step 103 the Butterworth pump 22 is stopped, and the Butterworth line valve 23 is closed to stop 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 this 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 decided that the slop tank 31 has become empty, and drainage completion processing is performed in step 106. According to the literature listed below, the period of waves on the ocean near Japan is a maximum of 20 seconds or less, so it is safe to set the prescribed time T at several times that, or about one minute to several minutes, to be on the safe side. <Article>Joint Probability Distribution of Ocean Wave Height and Period (Proceedings of the Coastal Engineering Conference, Vol. 25, 1978, p. 75-79, Authors: Tadao Honda, Tsune Mitsuyasu)

[0015] Incidentally, empirically, it is extremely rare for dry suction to occur several times during the actual drainage process of a 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 several minutes after the first dry suction occurs.

[0016] Next, the link between the GPS receiver and the drainage of slop tanks according to the present invention will be explained using the flow chart 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 must 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 tides or the like during the course of work for several hours. In the present invention, in step 201, the control device 1 constantly obtains position information from the GPS receiver 4, and in step 202, 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 margin of time is displayed on the image monitor 5 and an alarm is sounded by an audio device (not shown). Furthermore, if the margin of time becomes 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 overboard. [Industrial Applicability]

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

[0019] 1 Control device 2. Cleaning water equipment 3 Discharge device 4 GPS receiver 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 Wash water transfer line valve 35 Wash water overboard discharge valve

Claims

1. An automatic slop tank cleaning facility comprising a slop tank and a slop pump which draws in and discharges liquid from said slop tank, said slop pump repeatedly sucking in air together with the liquid that is generated when the remaining liquid in said slop tank is low, a phenomenon known as air entrainment, and continuing to operate for at least 30 seconds or more after the occurrence of the first air entrainment described above, before stopping the operation of said slop pump and completing the drainage work.

2. 2. The automatic cleaning equipment for a slop tank according to claim 1, wherein the operating power of the slop pump is reduced after the occurrence of the air entrainment.

3. An automatic cleaning method for a slop tank using automatic cleaning equipment for said slop tank, which is provided with a slop tank and a slop pump which draws in and discharges liquid from said slop tank, said slop pump repeats a so-called air intake multiple times, in which said slop pump draws in air together with the liquid that is generated when the remaining liquid in said slop tank is low, and continues to operate for at least 30 seconds or more after the occurrence of the first air intake as described above, and then stops the operation of said slop pump to complete the drainage work.

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