METHOD AND SYSTEM FOR RECEIVING AND HANDLING POLLUTED LIQUIDS, ESPECIALLY STRATIFIED OIL PRODUCTS IN PETROL AND OIL TANKS

Abstract: It is customary that a sewage truck be called when finding or expecting pollution of the contents of a petrol or an oil tank to suck up the entire tank contents and take it to destruction. The invention presumes that the tank contents normally separates in horizontal layers of useless, polluted liquid and fully usable liquid, respectively, and by the invention it is intended to produce a selective sucking up of these fractions to a sewer tank (4) and an extra tank (2), respectively, so that the extra tank (2) receives an immediately reusable product, which may possibly be returned to the tank from where it was sucked. The selective filling of the sewer tank (4) and the extra tank (2) is obtained through establishing a possibility for inspecting the sucked up liquid at its entering the sewer tank and a valve device for facilitating the switch-over referred to.

Description: Method and system for receiving and handling polluted liquids, especially stratified oil products in petrol and oil tanks. The present invention relates to a method for collecting and handling polluted oil products in petrol and oil tanks. In several cases it happens that the contents of such a tank accidentally or otherwise becomes polluted, and according to normal practice care must be taken that the tank be emptied by a sewage truck which can take the tank contents to a destructing plant, where it is, of course, possible to a certain extent to separate the impurities and hereby obtain a useful recovery of the pure oil product. For this achievement, however, a large amount of work has already been carried out with respect to transportation of the entire tank contents to the actual specialized plant. The invention is based on the consideration that in most cases it will be possible to decide in situ whether the sucked up liquid from the tank be immediately reusable or not, as most pollutions e.g. by water intruded into the oil product, reveal themselves by a stratification of the tank contents, whereby during the suction it is possible to ascertian whether: the sucked up product consists of a useful liquid or polluted liquid. Rather than uncritically gathering all the liquid in a sewage tank, it is thus pos¬ sible during the actual suction to watch the nature of the sucked up product and thereby lead this selectively to a tank for polluted liquid and a tank for non-polluted liquid, respectively; upon pumping up all liquid from the tank, the usable liquid part can immediately be returned to the tank and it then suffices to transport the polluted part of the liquid to a destrucing plant. Often the latter part will be of a very modest quantity, so that the total transport capacity concerning the polluted liquid will be reduced drastically, e.g. by postponing the transportation to a far away destructing plant until decidedly polluted liquid has been accumulated from a number of pollution incidents in a given regional area. On the other hand the user of a tank system, the contents of which is being exposed to pollution, will experience the great advantage that the tank contents is not removed completely because the reusable part thereof can be returned to the tank immediately upon isolation of the amount of polluted liquid in a sewage tank. The purpose of the invention is thus to provide for a method whereby it is possible already at the sucking up of the tank contents to distinguish between pure and polluted liquid and thus procuring that the pure part of the liquid may be reused immediately, whereas only the actually pol¬ luted liquid part needs, to be accumulated for transportation to a regional-destructing plant. For achieving this purpose, according to the invention, use is made of a mobile sewage unit, which is fitted with a sewage tank as well as a working tank, and during the suction operation the sucked up product is examined and led to the sewage tank, as long as the product is polluted and to the working tank when the product is pure, where¬ upon the pure product is returned from the working tank to the emptied tank and the separated part of the product in the sewage tank is transported to the destructing plant. Reclaiming the usable part of the product can thus be carried out far more economical than in the past. The invention, as further defined in the claims, also com¬ prises a mobile system for carrying out the method, viz. a sewage truck which is provided with an extra working tank and preferably one or more transportation tanks for pure products. A variety of jobs such as tank flushing can be taken care of more conveniently than before, cf. below comments, when applying such a system complete with suction and transfer pumping gear. In the following the invention is further described with reference to the drawing, which schematically shows a system according to the invention. Four tanks are shown in the drawing, viz. a working tank 2, a sludge tank 4 and two transportation tanks 6 and 8. The tanks, like the other equipment, are placed on a truck chassis, i.e. the system appears as a specialized tank truck. Besides the valves and pipe connections shown, which will be described below, the equipment also comprises a motor 10, a vacuum pump 12 a gear pump or so-called transfer pump , two flow gauges, a filter 18 and a liquid indicator 20. The latter is placed in a suction pipe 22, terminating in a suction pipe stub 24, and the truck is provided with the necessary hose equipment (not shown) , so that the suction tasks required can be carried out from the pipe stub. This equipment can com¬ prise various hose pieces and preferably also a long roller hose 26 behind the driver's cab. The tanks 2 and 4 are pre¬ ferably provided with gauge glasses 5 of a type easily cleaned. For carrying out a quite ordinary sewage suction, where it is known in advance that all liquid is sludge, the vacuum pump 12 is set to suck the tank 4, and thereby to suck in the liquid to this tank from the pipe stub 24 through a valve 28, whereby the liquid only passes the liquid indicator 20. Upon removal the sludge is emptied through a bottom valve 30, by pressurizing the tank 4. If it may be required to inspect the sludge further in situ, at least part of the suction can be carried out through a valve 32, whereby the sludge passes the filter 18. This filter is easily dismantled, and thus after a certain amount of time a solid-state specimen can be taken out, which for various reasons could prove interesting in certain circum¬ stances. If the task to collect a quantity or a tank-full of entirely pure liquid, e.g. from an earth tank, the liquid can at great capacity be sucked into the working tank 2 through a valve 34, by producing a vacuum in this tank. When the working tank is completely or almost full, the suction is stopped and the liquid be transferred to one of the trans¬ portation tanks, 6,8 by means of the transfer pump 14, through the valves 34 and 36, whereby the transportation tank is filled through its flow gauge 16, i.e. the quantity collected can be measured and optionally charged on the spot. There can or could perfectly well be effected a suction by means of the pump 14 alone, i.e. through a feeding valve 38 from the pipe stub 24, but towards finalizing the suction, air is inevitably entering the suction hose, causing the pumping effect to decrease drastically. Therefore at least the final phase of the suction must be effected to the tank 2 applying the vacuum cleaning-like effect of the vacuum pump 12. It is unattainable and absolutely impossible to guarantee the vital point that a sucked liquid with a possible content of air, which from the pump 14 be pressurized along to the tank 6 or 8, can show a precise flow meter reading, as this, of course, must apply to the liquid and not its content of air. This problem is totally overcome by using the working tank as a temporary collecting container. If polluted liquid has to be sucked up or in from a tank that is known or suspected to contain stratified liquid of pure and polluted liquid, respectively, then the invention facili¬ tates a practical possibility for suction of the sludge tank 4 and the pure liquid, or most of it to the working tank 2 and from there, if desired, further on to the transportation tanks 6,8 or return it to a tank on the spot. Depending on how the suction is effected i.e. whether suction is perma¬ nently effected from the bottom of the tank through the sinking surface layer, intermediary phases of sludge and pure liquid or vice versa, may occur, and already when watching the liquid indicator such intermediary phases can normally be ascertained. When sludge is concerned, the liquid is sucked straight into the sludge tank. When commencing suction or in connection with such an intermediary phase pure liquid is expected, a close control of this is carried out, viz. by applying a pipe or hose connection between a discharge valve 42 for liquid from the transfer pump 14 and the top inlet 44 on the sludge tank 4, whereby the use of the pump 14 allows inspection of the product at its falling into the sludge tank, and. if necessary the taking out a test for quick examination. Often just a simple inspection suffices to ascertain whether the liquid is pure or not, e.g. whether an oil product con¬ tains no water nor other relevant impurities, and perhaps it needs further pumping for a certain period of time till the liquid is pure. Until, the liquid reaches complete purity, o at least a degree of purity sufficient for its purpose of application, it is still led to the sludge tank. When the product can be approved, suction is changed to being applied from the working tank 2 as described above. If suspic¬ ion exists that a fraction of polluted liquid may appear, the liquid indicator can be watched and if necessary the liquid may be closer inspected at certain intervals or even contin¬ uously by leading it through the hose 40 to the top inlet 46 of the working tank. At the first sign of pollution the suc¬ tion is switched over to the sludge tank. If the working tank be filled, its contents can be transferred to a transportation tank 6 or 8, whereupon the operation can continue. After suction of a polluted tank contents, which merely ac¬ cording to the invention immediately can be separated into a sludge fraction and a reusable fraction, it can be relevant to carry out a flushing of the emptied tank. This can be effected by leading clean liquid through a pressure hose from one of the transportation tanks 6 or 8 down to an inlet pipe stub on the tank, optionally to a special cleaning ball in¬ stalled in this, whereafter the tank is flushed while flushing liquid is sucked from the bottom to the sludge tank 4. The applied pure liquid can be taken from the previously sucked up pure liquid fraction in one of the tanks 6 or 8, or from a volume of clean liquid carried by the service truck or optionally a special cleaning liquid from the other one of the tanks 6, 8. Having completed the cleaning and the renewed emptying of the tank, the sucked up clean liquid fraction can be returned to the tank from the working tank 2 or from one or the other of the tanks 6, -8, which were in fact used for the temporary collection. The truck is thus applicable for a variety of specialized jobs within a rather extensive geographical area. Further examples comprise exchanging wrong deliveries, where the truck can deliver correct goods and carry out the exchange all in one visit to the customer in question. By exchanging o£ tanks the truck can assist by sucking up the remaining contents of the old tank, even in carrying out a pertaining separate suction of its residue sludge, upon which it can wait while the old tank be removed and the new one be instal¬ led, and thereafter the usable part of the old tank contents can be transferred to the new tank. The truck can also take loose liquid-drums for delivery. Instead of using the pump 14 for pressing up test liquid through the hose 40 to an inspection area at the top of the sludge tank 4 or the working tank 2, respectively, a sampling device installed in the suction inlet of the tank in question can be used. Such a device may allow reentry of the sample into the suction inlet, thereby enabling the taking out of test samples without polluting the surroundings. It has been mentioned that when pressing liquid into the transportation tanks 6, 8 it must be ensured that the liquid is free from air, as the flow gauge 16 may otherwise show an incorrect reading. However, as long as the service truck is only delivering to a single user, where the collected pure liquid is to be returned, it will of course be without signi¬ ficance whether the measuring in is correct, if only the measuring out is correct, and in such cases it is without importance if there is air in the liquid pressed into the tank. On the other hand, during normal working days the truck will have to visit several customers and carry out a variety of jobs, and thereby it becomes important that the quantity of clean liquid, which at the individual site be led into the transportation or storage tank 6,8, be correctly measured. These tanks moreover, have a usual pumping equipment driven by the truck motor.

Claims: C L I M S : 1. A method for receiving and handling polluted liquids, especially oil products in petrol and oil tanks, where the pollution manifests itself in strata of pure and polluted liquid, characterized in that at the suction of liquid into a sludge tank the sucked up product be inspected and redirected to another collector container, as long as the product originates from a fraction of clean liquid, use hereby being made of a mobile sewage truck having an extra suction tank and prefer¬ ably an extra transportation or storage tank as well as a liquid pumping equipment, which allows a delivery of the sucked up liquid from the extra suction tank, the working tank, to the transportation tank or the storage tank through an inspection Or sampling zone. 2. A method according to claim 1, characterized in that by means of the pumping equipment the sucked up liquid is temporarily led to delivery in an inspection area above the top Inlet of the sludg& tank. 3. A method according to claim 1 , characterized in that the suction be carried out through a filter, which can be dis¬ mantled. 4. A method according to claim 1, characterized- in the suction being carried out through a liquid glass. 5. A system for carrying out the method according to claim 1 , characterized in that it is constituted by a sewage truck of the kind having a suction connection to a sludge tank and a vacuum source connected to the latter, and that the truck furthermore is provided with a working tank, which through valve equipment is connected to the same suction connection and vacuum source, €he truck preferably also being provided with a transportation or storage tank, which through a pumping equipment is connected to the working tank, the inlet connection to the sludge tank being adapted so as to enable the liquid supplied to the tank to be sampled or in¬ spected. 6. A system according to claim 5, characterized in that in the suction connection there is provided a liquid indicator and preferably also a filter which can be dismantled.

Inventors: ANDERSEN ARNE, ANDERSEN, ARNE
Applicants: ANDERSEN ARNE, ANDERSEN, ARNE
Application year: 1987
Main classification: B67D5
IPC codes: B67D5