JP2011036738A - Method of washing underground tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of washing an underground tank comparatively inexpensively and highly safely, particularly as combustible vapor measures prior to removal operation of an underground tank. <P>SOLUTION: With a washing nozzle 20 mounted on the tip end of a high pressure hose 10, and with a high pressure washing machine 30 connected to the rear end, high pressure water is supplied. The high pressure hose 10 is inserted into the underground tank T through an air duct-oil gauge opening L. In the suction opening S, there is inserted a suction pipe 40 whose tip end extends near the bottom of the underground tank T, while the other end of the suction pipe 40 is connected with an air-driven diaphragm pump 60 through a hose 50 and is further connected to a vacuum vehicle 80 through a hose 70. When the high pressure water is supplied from the high pressure washing machine 30 to the high pressure hose 10, high pressure water H jets out from the washing nozzle 20, washing away deposits such as gasoline remaining on the inner face of the underground tank T. Simultaneously, washing wastewater W collected in the underground tank T is recovered from the suction pipe 40. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for cleaning an underground tank that mainly cleans an inner surface of an underground tank buried underground for storing petroleum products, and more particularly to a method suitable for a cleaning process performed before the underground tank is removed.

  Underground tanks buried underground are mainly used to store petroleum products such as gasoline, kerosene, light oil and heavy oil. When such an underground tank is to be removed for reasons such as aging, it is required to give due consideration to the environment and safety. In particular, countermeasures against flammable steam inside underground tanks must be taken sufficiently to prevent combustion and explosion. Conventionally, as a countermeasure against combustible steam, two methods of water filling method and nitrogen replacement method have been implemented. The water filling method includes a process of collecting residual oil in the underground tank as much as possible, then pouring water to fill it up, digging out the underground tank and piping connection, drawing out the water, removing and removing the underground tank. . In the nitrogen replacement method, after the residual oil is recovered, the neutralizing agent and water are injected and left to stand, the neutralizing agent and water are recovered, all the piping of the underground tank is covered, and nitrogen is injected into the underground tank. Then, it includes a step of digging out the underground tank and the pipe connection portion and removing and removing the underground tank. The water filling method is highly safe because the tank is full when the underground tank is dug, but the drained water is expensive to dispose of as industrial waste. The nitrogen replacement method can be implemented relatively inexpensively, but there is a possibility that combustion or explosion may occur if flammable vapor remains in the underground tank and the oxygen concentration in the underground tank increases due to removal of the lid during construction. is there.

  Japanese Patent Laid-Open No. 2006-231153 discloses a cleaning method for an existing steel oil storage buried tank. Cleaning is done by foaming detergent diluted with water, spraying it on the surface of the buried tank until the foam turns white, pumping out the water from the oil in the tank with a submersible pump, and washing the neutralizer diluted with water with high pressure. The oil and volatile gases are removed by spraying inside the buried tank steel plate using a machine, and rust, sludge and washing sewage are pumped using a vacuum pump. This method is proposed as a pretreatment for lining the inside of the tank with FRP in particular, so it is costly and troublesome, and is not suitable as a countermeasure against flammable steam before the underground tank removal work.

JP 2006-231153 A

  Accordingly, an object of the present invention is to provide a relatively inexpensive and highly safe cleaning method for an underground tank, particularly as a countermeasure against flammable vapor before the operation of removing the underground tank.

  In order to achieve the above object, the present invention provides a high-pressure liquid that is ejected from a washing nozzle while a washing nozzle is attached to the tip and a high-pressure hose to which high-pressure liquid is supplied is inserted into the underground tank to collect washing waste liquid. An underground tank cleaning method was configured including a cleaning process for cleaning the inside of the underground tank.

  In the underground tank cleaning method according to the present invention, a high-pressure hose having a cleaning nozzle attached to the tip is inserted into the underground tank. When high-pressure liquid is supplied to the high-pressure hose, high-pressure liquid is ejected from the washing nozzle, and the residue on the inner surface of the underground tank and sludge and other deposits are washed away. By performing this while recovering the cleaning waste liquid accumulated in the underground tank, the inner surface of the underground tank can be cleaned.

  The liquid that can be used in the method for cleaning an underground tank according to the present invention is water (which may contain a cleaning agent such as a surfactant or a neutralizing agent), kerosene / light oil, or an organic solvent, and generates static electricity. Low volatility is suitable for suppressing the above. When it is performed before the underground tank is removed, industrial water or clean water can be used advantageously from the viewpoint of cost. When an underground tank is used for storage again after washing, it is desirable to use a liquid suitable for the object to be stored. For example, in the case of a tank for heavy oil, kerosene / light oil is used as the washing liquid. The

  The cleaning nozzle is preferably of a type that ejects high-pressure liquid toward the rear, which is the direction opposite to the tip direction, and desirably is a type that ejects the trajectory of the high-pressure liquid so as to form a conical shape extending rearward from the cleaning nozzle. . The washing nozzle naturally moves forward in the underground tank with the force of jetting high-pressure liquid backward. If a conical shape is formed at the rear, the inside of the underground tank can be washed thoroughly, and the force to be ejected becomes uniform in the radial direction, and the forward force as the resultant force is supported by the high pressure hose. , The cleaning nozzle is not prone to rampage.

The high-pressure liquid is supplied from a high-pressure washing machine, and when the high-pressure liquid is water, the pressure is, for example, 30 to 70 kg / cm ² , and the amount of water is 50 to 100 L / min. If the liquid stored in the underground tank or the high-pressure liquid is flammable, the washing waste liquid is preferably collected by a pump that does not generate sparks, such as an air-driven diaphragm pump. For example, the cleaning waste liquid is sucked up by an air-driven diaphragm pump through a suction pipe inserted into an underground tank, and further sent to a vacuum vehicle.

  Inserting a high-pressure hose fitted with a cleaning nozzle at the tip and collecting cleaning waste liquid can be done through a pipe connection that is connected in advance to the underground tank, and operations such as drilling holes in the underground tank are not essential. . For example, a vent pipe / oil level gauge can be used as a pipe connection part for inserting a high-pressure hose, and a suction pipe can be used for collecting cleaning waste liquid.

  The method for cleaning an underground tank according to the present invention may further include a gas-free process of inserting a ventilation air hose into the underground tank and feeding air after the cleaning process is completed to perform forced ventilation in the underground tank. Good.

  This is a process suitable for cleaning before the removal of flammable liquid underground tanks such as petroleum products. This reduces the concentration of flammable gases and prevents accidents such as explosions in subsequent removal operations. Occurrence can be prevented. This gas-free process is preferably continued until the gas concentration in the underground tank is measured by a gas concentration measuring instrument and the gas concentration is reduced to 1/5 (20% LEL) or less of the lower explosion limit at most. Air is supplied by, for example, a compressor.

  The underground tank cleaning method according to the present invention may be configured such that at least a portion of the cleaning nozzle in contact with the inner surface of the underground tank is covered with an explosion-proof metal.

  In particular, when the high-pressure liquid or the liquid to be stored in the underground tank is flammable, the cleaning nozzle that blows out the high-pressure liquid may be violent, collide with the inner surface of the underground tank, generate a spark, and ignite. In order to avoid this, at least the portion of the cleaning nozzle that contacts the inner surface of the underground tank is covered with explosion-proof metal. Examples of explosion-proof metals include brass and beryllium copper alloys. For example, all cleaning nozzles are made of brass.

  As described above, the underground tank cleaning method according to the present invention is particularly suitable as a countermeasure against flammable steam before the removal of the underground tank, and is relatively inexpensive and highly safe.

FIG. 1 is a schematic view showing a state in which a cleaning process is performed in one embodiment of a method for cleaning an underground tank according to the present invention. FIG. 2 is a schematic diagram showing a state in which the gas-free process in the embodiment of FIG. 1 is being performed.

  Hereinafter, an embodiment of a method for cleaning an underground tank according to the present invention will be described with reference to the accompanying drawings. In addition, the following description is for understanding the invention more deeply, and does not limit the scope of the present invention.

  FIG. 1 shows a state in which a cleaning process in one embodiment of a method for cleaning an underground tank according to the present invention is being performed. In FIG. 1, a cleaning nozzle 20 is attached to the front end of the high-pressure hose 10, and a high-pressure cleaning machine 30 is connected to the rear end to supply high-pressure water. The high-pressure hose 10 is inserted into the underground tank T through the vent pipe / oil level gauge L. A suction pipe 40 whose tip extends to the bottom of the underground tank T is inserted into the suction port S, and an air-driven diaphragm pump 60 is connected to the other end of the suction pipe 40 via a hose 50. Further, it is connected to a vacuum wheel 80 via a hose 70. The underground tank T is a gasoline storage tank provided in a gas station, and in addition, a pipe connection portion such as a vent V is provided.

  This embodiment is performed as a countermeasure against combustible steam accompanying the removal of the gasoline storage tank. Before the cleaning operation, the manhole, cap, flange, etc. necessary for the operation are opened, the suction pipe 40 is inserted, and the air is driven. The ground wire is installed in the diaphragm pump 60 and the vacuum vehicle 80, and the air-driven diaphragm pump 60 is operated first, and the gasoline remaining in the underground tank T is vacuumed as much as possible through the suction pipe 40. Collect in 80. After this operation, a neutralizing agent may be appropriately injected into the underground tank T by the end of the cleaning process.

  When the remaining gasoline is recovered, a washing step is subsequently performed. When the high-pressure hose 10 having the cleaning nozzle 20 attached to the tip is inserted into the underground tank T through the vent pipe / oil level gauge L, and the high-pressure water is supplied from the high-pressure washer 30 to the high-pressure hose 10, the cleaning is performed. High-pressure water H is ejected from the nozzle 20 and the deposits such as gasoline remaining on the inner surface of the underground tank T are washed away. At the same time, the cleaning waste liquid W accumulated in the underground tank T is collected from the suction pipe 40.

  Cleaning nozzle 20 in the present embodiment is configured to eject high-pressure water H toward the rear, which is the direction opposite to the tip direction. The trajectory of the high-pressure water H is ejected from the cleaning nozzle 20 so as to form a conical shape that spreads backward. Since the washing nozzle 20 naturally moves forward in the underground tank T by the force of spouting the high-pressure water H toward the rear, the worker P gradually feeds the high-pressure hose 10 so that the inner surface of the underground tank T is cleaned. Move. Further, since the direction in which the high-pressure water H is ejected is conical, the force from which the high-pressure water H is ejected is uniform in the radial direction, and the forward force as a resultant force is supported by the high-pressure hose 10, so that the washing nozzle is not easily violated. . In actual work, the worker P slowly advances the cleaning nozzle 20, passes near the tip of the suction pipe 40 in FIG. 1, and hits the front end of the underground tank T. The operation of moving the cleaning nozzle 20 back and forth so as to move back to the position just below the surface metering port L is repeated, and the inner surface of the underground tank T is cleaned evenly.

The pressure of the high-pressure water H supplied from the high-pressure washing machine 30 is 30 to 70 kg / cm ² , and the amount of water is 50 to 100 L / min. The high-pressure water H is industrial water, and is not particularly mixed with a cleaning agent or a neutralizing agent. The cleaning nozzle 20 is all made of brass, which is an explosion-proof metal, so that it does not violately contact the inner surface of the underground tank T to generate a spark.

  The cleaning process is performed continuously without interruption or intermittently in a plurality of times, and ends when it is determined that the cleaning has been sufficiently performed. For example, when the gasoline contained in the collected cleaning wastewater W becomes almost invisible, the process is terminated. After the completion, a neutralizing agent may be injected into the underground tank T.

  After completion of the cleaning process, a gas-free process as shown in FIG. 2 is performed. In the underground tank T, two air hoses 90 for ventilation are inserted from the vent pipe / oil level gauge L and the suction port S. A compressor 100 is connected to each air hose 90.

  The compressor 100 is operated to blow air E from each air hose 90 to perform forced ventilation in the underground tank T. In the gas-free process, the gas concentration in the underground tank T is measured every hour with a gas concentration measuring device (not shown) until the gas concentration drops to 1/5 (20% LEL) or less of the lower explosion limit at most. Continued.

  When the gas-free process is completed, the underground tank T and the pipe connection portion are excavated, the underground tank T and the pipe connection portion are disconnected, the underground tank is removed and carried out, and the underground tank removal work is completed.

  As described above, the method for cleaning an underground tank according to the present embodiment can remove combustible vapor while securing relatively low cost and high safety as a countermeasure against combustible vapor before the removal work of the underground tank. it can.

10 High Pressure Hose 20 Cleaning Nozzle 30 High Pressure Washing Machine 40 Suction Pipe 50, 70 Hose 60 Air Driven Diaphragm Pump 80 Vacuum Wheel 90 Air Hose 100 Compressor T Underground Tank L Vent Pipe / Oil Level Gauge S Suction Port V Vent V H High Pressure Water W Wash wastewater E Air P Worker

Claims (4)

A cleaning nozzle is attached to the tip, and a high-pressure hose to which high-pressure liquid is supplied is inserted into the underground tank, and a cleaning process is included for cleaning the underground tank with the high-pressure liquid ejected from the cleaning nozzle while collecting the cleaning waste liquid. A method for cleaning underground tanks. The method for cleaning an underground tank according to claim 1, further comprising a gas-free process of inserting a ventilation air hose into the underground tank to send air after the cleaning process and performing forced ventilation in the underground tank. The gas-free process is continued until the gas concentration is reduced to at most 1/5 (20% LEL) of the lower explosion limit by measuring the gas concentration in the underground tank with a gas concentration measuring device. How to clean underground tanks. The method for cleaning an underground tank according to any one of claims 1 to 3, wherein at least a portion of the cleaning nozzle in contact with the inner surface of the underground tank is covered with an explosion-proof metal.

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