| 1. | Loading pump device intended for rapid performance of the entire sequence of filling the tank on a tank vehicle (1) with liquid, such as water containing varying levels of contamination, the said tank vehicle being drawn by a tractor vehicle (2), which also drives a centrifugal pump (3) whose inlet (3a) is connected to the tank (la), characterised inthat the outlet (3b) of the centrifugal pump is connected to the drive inlet of a jet pump (4) whose outlet (4a) is connected back into the tank, and in that the suction port (4b) of the jet pump is connected to the liquid (5) to be loaded by means of one or more pipe/hose systems (4c). |
| 2. | Device in accordance with claim 1, characterised in that the said pipe/hose system (4c) is, at a point above the liquid surface, provided with a centrifugal pump (6, Fig. 2), which pump and its suction part are evacuated of air by the pipe/hose system when starting with the aid of the jet pump. |
| 3. | Device in accordance with claim 1, characterised in that the inlet end of the said pipe/hose system (4c) is connected to a submersible centrifugal pump which operates in series with the jet pump. |
fit a non-return valve at the suction line inlet. Further disadvantages, in addition to the priming problem, are limited capacity and disturbances in operation caused by the fact that the resistance to flow in the suction line easily causes cavitation, which interrupts the loading operation. A very advantageous solution to this problem is found in patent application EP-97944235.7, in which an upper centrifugal pump operates in combination with a submersible centrifugal pump connected to the lower end of the line. Although an arrangement of this type can obviously also be applied to a tank vehicle, it should be noted that loading applications differ greatly in terms of lift and liquid viscosity. Despite the fact that the solution described in the aforementioned patent application greatly increases the pumping capacity and reduces the risk of cavitation, problems of this nature can obviously occur with the pump on the tank vehicle when the capacity requirement is further increased, the pump speed is increased, and pumping conditions are difficult in terms of lift and liquid viscosity. Since the loading time usually represents pure waiting time for the tank vehicle driver, the capacity requirement is often the maximum possible. Another problem is that the extraction opening on many liquid containing vessels is so small that only a simple suction pipe/hose without a pump can be inserted for the purpose of positioning its inlet end below the surface of the liquid. This creates a priming problem which is solved in the case in which a submersible pump can be installed to prime the suction line when starting.
The main purpose of the present invention is to provide a means of loading a tank vehicle, as illustrated in the figures, with the aid of a centrifugal pump/centrifugal pumps of high capacity, without the aforementioned problems relating to priming and/or the operating conditions of the upper centrifugal pump on the tank vehicle.
The solution in accordance with the invention is described in the characteristic part of claim 1.
A number of embodiments of the invention, using an agricultural tractor as tractor vehicle, has been tested in practice and found to function satisfactorily.
The application in which a submersible pump is not connected to the inlet of the line (4c) assumes that the tank contains a small quantity of liquid, either stored
or added for the purpose, to accomplish the starting phase. This liquid, which may suitably be of the same type as the liquid to be loaded, is then circulated by the centrifugal pump (3), through the jet pump (4), establishing a stable and permanent vacuum in port (4b), which vacuum can be used to evacuate the air in the suction line (4c) and/or to pump liquid continuously. One embodiment of the invention is that in which, as shown in Fig. 2, the jet pump suction line (4c) immersed in the liquid is equipped with a hydraulically powered centrifugal pump (6), the drive fluid for which is supplied by a hydraulic pump driven by the tractor engine. In this case, the jet pump initially extracts the air from the suction line and raises liquid to the pump (6), which is already operating in series with the jet pump. Another embodiment covered by the claims is that in which the sole or most important function of the jet pump is to evacuate the air in the suction line to the pump (6), and the latter is primed in series with the centrifugal pump (3). After starting, the lower directional valve (Fig. 2) is closed to the tank and opened to (4c), while the upper directional valve is simultaneously closed to the jet pump and a flap valve (not shown) is closed to the discharge pipe (8), and an outlet (not shown) in the tank is opened, while the port (4b) is closed by a cock (not shown).
A further embodiment of the invention is that in which the pump (6), Fig. 2, can be submerged in the liquid (the line between the liquid and pump thus being eliminated), whereby the said pump expels the air from the line (4c) during the starting phase and then operates in series with the jet pump via (4b). Many loading applications can occur in practice, with major variations in lift, liquid <BR> <BR> viscosity etc. , while the feasibility of adapting the centrifugal pumps in terms of design and suction capacity is limited. Neither can the area of the line (4c) be modified.
Given the background to these problems, the aforementioned series connection affords high capacity. If the cavitation limit is exceeded in the jet pump, which may occur in practice, the unit will maintain full suction in a better manner than a centrifugal pump, which cannot pump a gas. The jet pump has a better tolerance to cavitation than, for example, the centrifugal pump (3), since it is completely free of moving parts, such as an impeller, shafts, bearings, seals etc.,
and is also very simple and inexpensive to repair or replace if and when required. In addition, the centrifugal pump (3) will operate in a smooth, vibration-free manner at the correct operating point, since the suction head will remain relatively constant, irrespective of level variations in the tank, the pump's operating conditions being very similar to those which prevail when it is used in pumping-out or spreading applications.