GB2113535A - Tank cleaning equipment - Google Patents

Abstract

Tank cleaning equipment comprises at least one vessel 2, 4 having a liquid outlet 22, 23, suction inlet 20, 21, and suction outlet 16, 17, the arrangement being such that, in use, cleaning liquid is sprayed into a tank from one of the vessels and the used liquid is recovered by suction and stored in the vessel. The cleaning liquid may be passed through a heat exchanger 12. The equipment may be mounted on a trailer, and may be used for cleaning rooms, roadways, or buildings. <IMAGE>

Description

SPECIFICATION Tank cleaning system The present invention is related to pressurized cleaning apparatus, particularly one which uses a vacuum line for the pickup of the cleaning liquid and dislodged contaminants.

Industrial tanks must often be cleaned, commonly after the tank is empty. To do so the interior of the tank or other container is usually sprayed with high pressure cleaning liquids to dislodge the contaminants, both liquid and solid, from the tank surfaces.

Because the impact of the high pressure spray is diffused if there is a liquid layer within the tank, it is desirable to keep the amount of cleaning liquid which gathers in the bottom of the tank to a minimum.

Removing cleaning liquid from the bottom of the tank is often accomplished by using positive displacement pumps. However, positive displacement pumps are often sensitive to solid contaminants in the liquid being pumped because of the small clearances necessary in their construction. Further, the valves commonly used are also sensitive to foreign solid material. These foreign solids can often lead to the early destruction of the pump. Centrifugal pumps are sometimes used; however, they generally do not work weil when air is mixed with the liquid.

Therefore, what has been missing in the prior art is a cleaning system insensitive to both drawing solid contaminants from the bottom of the tank and to drawing air in with the cleaning liquid.

Railroad tank cars are typically cleaned by trans- porting them to special cleaning facilities. Just getting the tank car to the cleaning facility is expensive and time-consuming. However, highly mobile tank car cleaning units, which could be driven to the railroad tank car, are not generally available.

In accordance with this invention therefore we provide a cleaning system comprising, a first sub stantiallysealed pressure vessel having a liquid outlet, a vacuum outlet and a suction inlet in fluid communication with the interior of said vessel, said vacuum outlet and said suction inlet communicating with an upper region of said vessel and said liquid outlet communicating with a lower region of said vessel; means, fluidly connected to said liquid outlet, for pumping a liquid cleaner from said vessel through a first line, said liquid partially filling said pressure vessel so that said vacuum outlet and suction inlet are above the free surface of said liquid cleaner; and means, fluidly connected to said vacuum outlet, for drawing a partial vacuum within said pressure vessel.

In a tank cleaning system disclosed herein as a preferred embodiment of the invention wherein a cleaning liquid is sprayed into the tank and simultaneously sucked out of the tank the cleaning liquid is stored in a pressure vessel and incompletely fills the vessel so that a space is left above the free surface of the liquid. A pressure pump draws the liquid from the lower regions of the vessel and forces the liquid through a pressure line to a gas fired heat exchanger. As the cleaning liquid passes through the heat exchanger it is heated and then passes through a line where the high pressure, high temperature liquid is used to clean inside of the tank.

Simultaneously with the spraying of high pressure, high temperature cleaning liquid in the tank, a vacuum line draws the sprayed cleaning liquid and dislodged contaminants from the bottom of the tank.

The vacuum line terminates at the pressure vessel where the cleaning liquid and contaminants are discharged into the cleaning liquid therein. A vacuum is created within the space above the free surface of the liquid within the pressure vessel by a vacuum pump. In this way, cleaning liquid and contaminants withdrawn from the tank never pass through the vacuum pump.

In the preferred embodiment, a pair of pressure vessels are mounted to a trailer for mobility. One of the vessels typically is used for the cleaning operation and the other is used for the rinse. Both are connected through valves to a common pressure pump for the application of high pressure liquid to the interior of the tank to be cleaned. It should be noted that the present invention will be described with regard to cleaning a tank. However, the invention can be used for cleaning various surfaces, even a room or a roadway, wherein the cleaning liquid collects at a low point for return to the pressure vessel.

A four-way valve is connected to the vacuum pump so that it either pulls a vacuum on one of the pressure vessels or pressurizes the pressure vessel.

The latter allows one of the pressure vessels to clean the other. To do so, one vessel is pressurized, the vessels are connected through their liquid outlets and the high pressure from one tank causes the liquid within that tank to clean out the other, non-pressurized, tank.

A container for holding concentrated cleaning agents is also mounted to the trailer, typically between the two tanks. Metering apparatus allows the controlled introduction of the concentrated cleaning agent into the cleaning liquid priorto passing through the pressure pump. This allows the concentration of the cleaning agent to be varied according to circumstances.

A primary advantage resulting from the present invention accrues through the use of an isolated vacuum pump for sucking up the cleaning liquid and contaminants from the bottom of the tanks. The vacuum pump, being isolated from any flow of liquids or solids, operates relatively independently of the amount or size of dirt and abrasives and also the amount of air which may be sucked in along with the liquids and solids. Therefore, a relatively high suction force can be maintained to insure that the bottom of the tank being cleaned is substantially free from having the cleaning liquid form puddles.

Therefore, pump life and cleaning efficiency are both increased. Also, because the vacuum pump operates effectively vvhen a substantial amount of air is sucked through the vacuum line along with the cleaning liquid and contaminants, the tank being cleaned is prevented from emitting gases and vapors. This is a distinct advantage when the emissions are noxious or toxic to the personnel who must operate the spraying equipment at the opening in the tank. If needed, scrubbers can be added to remove any particular compound from the cleaning liquid and gasses passing through the vacuum line.

Another significant advantage of the preferred embodiment of the present invention described herein is its mobility. By mounting the apparatus to a trailer the cleaning system can be moved to the tanks to be cleaned. Railroad tank cars can be cleaned almost anywhere while tanks on ships can be cleaned while docked along a wharf or pier.

The system may also provide for heating the pressurized cleaning liquid prior to being sprayed into the tank, thus greatly increasing its cleaning effectiveness. Provision of the separate container for holding concentrated cleaning agents and the associated metering apparatus allows greater flexibility in the concentrations used for different jobs and also at different times in the same job. More effective and more efficient use of the cleaning agent is thus insured.

In the accompanying drawings: Fig. is a side elevational view of a preferred embodiment of a system in accordance with the present invention, including two pressure vessels mounted to a trailer.

Fig. 2 is a schematic flow diagram of the system of Fig. 1.

Turning now to the figures, the tank cleaning system in accordance with the present invention broadly includes a pair of pressure vessels 2,4 mounted to a trailer 6. A vacuum pump 8, a pressure pump 10, and a heatexcahnger 12 are also mounted to the trailer and are interconnected to the pressure vessels via various pipes and valves as described in more detaii bellow.

The two pressure vessels, typically holding 3,500 gallons each, each have a fill hatch 14, 15 and a vacuum hatch 16, 17. These hatches extend from the top of the cylindrical wall of the vessels. Each has a removable cover plate 18 for access into the interior of the vessels. The vessels also have suction inlets 20, 21 communicating with the interiors of the vessels at the end of the tank opposite respective vacuum hatches 16, 17. Liquid outlets 22,23 are located along the lowermost portion of the vessels.

Pipes 26, 27 fluidly connect outlets 22, 23 to the inlet 28 of pressure pump 10 through coupling pipe 29 and valves 30,31 respectively. The outlet of pump 10 communicates through a pipe 32 with the inlet 34 of heat exchanger 12. Pump 10 thus can pump liquid from either pressure vessels 2 or 4 through the selective operation of valves 30, 31 into the heat exchanger. Liquid flows through the heat exchanger and exits through an outlet 36. A suitable high pressure line 38, shown only in Fig. 2, can be connected to outlet 36 to direct the pressurized and heated liquid to the appropriate area. The outer end of line 38 can have a variety of spray nozzles 40 connected thereto depending upon the particular configuration of the surface being cleaned.

The vessels are cylindrical with convex ends and are mounted end to end on trailer 6. The space between the opposed convex ends of the two vessels forms a cleaning agent container 24, typically holding 500 gallons, for the storage of concentrated cleaning agents.

The cleaning agent within container 24 can be added to the liquid pumped from either vessel 2 or vessel 4through metering apparatus 66. Container 24 is filled with an appropriate cleaning agent by a pump 68. A standpipe 70 within container 24 is connected to a valve 72 to allow the escape of trapped gas when filling the container.

The inlet 42 of vacuum pump 8 is normally connected to vacuum outlets 44,45 through respective pipes 46,47. Vacuum outlets 44,45 are located on the side walls of vacuum hatches 16, 17, respectively. Valves 48,49 are positioned along pipes 46,47 to control which pressure vessel will be in fluid communication with vacuum pump 8. A common line 50 connects pipes 46, 47 to inlet 42 through a four-way valve 52. The outlet of vacuum pump 8 is connected to a muffler 54 through four-way valve 52.

The four-way valve alternatively allows the vacuum pump to be used to pressurize vessels 2, 4 as more fully described below.

In normal operation, the vacuum pump draws a vacuum in a space 53 above the free surface 55 of the liquid 51 within one of the pressure vessels.

Suction inlets 20, 21 are located in vessels 2,4 above free surface 55. Shut-off valves 56,57 prevent liquid within the vessels from passing through vacuum outlets 44,45 to prevent damage to pump 8. Pipes 58, 59 are connected to suction inlets 20, 21 and are joined at a common vacuum return fitting 60. A pair of valves 62, 63 are used to control passage along pipes 58, 59. One end of a common vacuum line 64, shown only in Fig. 2, is connected to fitting 60. The outer end 65 of vacuum line 64 is used to siphon off cleaning fluid and dislodged contaminates from the surface being cleaned. Tanks often have a drain outlet so that the outer end of the vacuum line can be attached to the outlet with a suitable fitting.Other tanks may not have such an outlet, so that a suitable suction head may be used and placed on, and preferably anchored to, the bottom of the tank.

Heat exchanger 12 is mounted to trailer 6 adjacent to and parallel to vessel 4. A burner 74 is mounted at one end and is used to heat the liquid flowing through the heat exchanger. Gases are exhausted through a flue 76.

The operation of the tank cleaning system proceeds essentially as follows. For the sake of the following discussion, vessel 2 will be used as the supply of cleaning liquid. Valve 30 is opened and valve 31 is closed so that upon activation of pressure pump 10, liquid within vessel 2 is pumped from vessel 2 to the heat exchanger, through high pressure line 38, and into the tank to be cleaned. The pump develops relatively high pressures, for example, 200 psi, to enhance the cleaning efficiency of the system. If the cleaning liquid is to be a water-based product, a cleaning agent such as trisodium phosphate, is usually metered through metering apparatus 66 into the liquid being pumped from vessel 2, typically water. If the cleaning liquid is a solvent such as diesel fuel or jet fuel, a concentrated cleaning agent may not necessarily be added to the liquid.

Simultaneously while spraying the cleaning liquid into the tank, the vacuum pump operates to a draw vacuum on vessel 2 through vacuum outlet 44. This causes a suction force on vacuum line 64, valve 63 being closed and valve 62 being open. The outer end of the vacuum line, being piaced at a low point in the tank, therefore sucks up the cleaning liquid and dislodged contaminants from the bottom of the tank.

These contaminants may be liquids or solids. The cleaning liquid and contaminants sucked up by the vacuum line pass through pipe 58 and enter vessel 2 through suction inlet 20.

Since vacuum pump 8 operates only to draw gas from the space 53, it operates relatively indepen dentlyofwhatis being sucked up by vacuum line 64.

Therefore, a high suction level can be maintained, one which is insensitive to sucking air and to the type of contaminants, both solids and liquids, being drawn into the vacuum line. By maintaining a high degree of suction, the tank being cleaned can be kept relatively free from pools of cleaning liquid so that the effectiveness of the sprayed cleaning liquid is insured. Gaseous emissions from the tank being cleaned can be eliminated by insuring that a sufficient quantity of gas is sucked in with the liquids and contaminants.

It should be noted that the normal flow directions along the pipes and lines are shown by solid arrows.

However, by placing four-way valve 52 in an alternative configuration shown by dashed lines in Fig. 2, the vacuum pump can be used to pressurize either of the pressure vessels through outlets 44,45. This feature is usefui when cleaning the pressure vessels.

For example, if it is desired to clean pressure vessel 2, four-way valve 52 is shifted to pressurize vessel 4.

Valve 49 will be open while valve 48 will be closed.

This allows the user to energetically force the liquid out of pressure vessel 4 and through vessel 2, thus cleaning vessel 2.

The present invention is particularly suited for cleaning containers such as tanks. However, it can also be used for cleaning areas where a liquid is sprayed onto a surface and can be collected at a low point. For example, certain rooms or buildings may be amendable for cleaning by the apparatus of the present invention. Although the preferred embodiment has two pressure vessels, typically one used during cleaning and the other during rinsing, the invention can be practiced using only a single vessel.

Claims (15)

1. Acleaning system comprising: a first substantially sealed pressure vessel having a liquid outlet, a vacuum outlet and a suction inlet in fluid communication with the interior of said vessel, said vacuum outlet and said suction inlet communicating with an upper region of said vessel and said liquid outlet communicating with a lower region of said vessel; means, fluidly connected to said liquid outlet, for pumping a liquid cleaner from said vessel through a first line, said liquid partially filling said pressure vessel so that said vacuum outlet and suction inlet are above the free surface of said liquid cleaner; and means, fluidly connected to said vacuum outlet, for drawing a partial vacuum within said pressure vessel.

2. The cleaning system of Claim 1 further comprising a second line fluidly connected to said suction inlet at one end to provide a source of suction at the other end of said second line.

3. The cleaning system of Claim 2 further comprising means fluidly connected to said first line for directing said liquid cleanerto said object to be cleaned to dislodge contaminants from said object.

4. The cleaning system of Claim 3 wherein said other end of said second line is adapted to draw liquid cleaner and dislodged contaminants into said vessel.

5. The cleaning system of any one Claims 1 to 4 further comprising a liquid heater positioned along said first line to heat said liquid cleaner passing through said first line.

6. The cleaning system of Claim 5 wherein said heater is a gas-fired heat exchanger.

7. The cleaning system of any one of Claims 1 to 6 further comprising a second, substantially sealed pressure vessel having a second liquid outlet, a second vacuum outlet and a second suction outlet in fluid communication with the interior of said vessel.

8. The cleaning system of Claim 7 wherein said first and second vessels are mounted on a common frame.

9. The cleaning system of Claim 5 further comprising a vehicle for mounting said first vessel, said pumping means, said vacuum drawing means, said first and second lines, and said liquid heater thereon.

10. The cleaning system of any one of Claims 1 to 9 further comprising: a tank adapted to contain a cleaning agent; and means for controllably adding said cleaning agent into said liquid cleaner flowing through said first line.

11. The cleaning system of any one of Claims 1 to 10 further comprising a suction inlet shut-off valve means for preventing said liquid cleaner from being drawn into said vacuum drawing means.

12. Acleaning system comprising: a vessel adapted to hold a cleaning liquid, said liquid having a free surface in said vessel; means for pumping said liquid from said first vessel through a first line; means, connected to the outer end of said first line, for directing said cleaning liquid onto a surface to be cleaned; means for heating said cleaning liquid priorto passing from said directing means; means communicating with a space in said vessel above said free surface of said cleaning liquid for creating a partial vacuum in said space; a second line in fluid communication with said space at one end and having a suction head at the other end to draw said cleaning liquid and dislodged contaminants therewith into said first vessel.

13. The cleaning system of Claim 12further comprising: a containerforstonng a cleaning agent; and means forcontrollably adding a desired amount of said cleaning agent to said cleaning liquid passing through said first line.

14. A portable container cleaning system comprising: a vehicle; first and second vessels mounted on said vehicle and adapted to hold liquids therein, said liquids having free surfaces in said vessels; means for selectively pumping said liquids from said vessels through a first line; means, connected to the outer end of said first line, for directing said cleaning liquid onto a surface to dislodge contaminants from said surface; means for heating said cleaning liquid prior to passing from said directing means; means, selectively communicating with the space above said free surfaces of said liquids in one or both of said vessels, for creating a partial vacuum in said space; and a second line in fluid communication with said selected space at one end and having a suction head at the other end to draw said discharged liquid and dislodged contaminants therewith into said first vessel.

15. A cleaning system substantially as described herein with reference to the accompanying drawings.