UNDERWATER WATER PUMPS
The purpose of each drilling is to exploit the local water supply. A drilling is complete when it has successfully completed its final stage, which is the test pumping.
Choosing the right pumping unit, in order to achieve the best and longest lasting results, is a function of many factors.
Submersible drainage sump pump is the most advanced equipment for operating a productive well.
In the past, the drilling of wells was mainly done with vertical axis shafts. Nowadays they have been replaced by electric submersible pumps, in which the rotation of the pump (turbines, stages) is done with an electric motor built into the bottom of the pump. The movement of the electric motor is done with an electric current, which is transported using a special waterproofed submarine cable, from the ground surface.
The submersible pumping unit consists of:
- the submersible pump
- the submarine electric motor
- the submarine cable
- the discharge column or commonly pump hoses
- the level electrodes with wires
- the electrical panel for safe operation of the pump
The submersible drilling pump is characterized both by its technical characteristics (horsepower, flow, manometric, etc.), and by the quality of its construction materials.
The correct choice of the pump, according to the special characteristics of the drilling, results in the longer “life” of the pump, the better and more economical use and finally the longer “life” of the well.
In order to select the appropriate pump, in terms of its technical characteristics, it must be preceded by a test pump with proper programming and scientific application. The test pumping should be done with all the required phases: Pre-pumping, step pumping, pumping with constant flow and reset. Level and flow measurements are performed in all phases. We record the measurements in tables and record them in diagrams proportionally and semi-logarithmically. With the correct interpretation of the diagrams we calculate the hydraulic characteristics of the aquifer and the drilling. Following the above procedure we can select the submersible pump with the most suitable pumping curve.
The pump to be selected should run in the middle of the operating curve and the engine at its highest efficiency. The pump can be made entirely of stainless steel or have elastomeric parts (impellers, washers, ..). The final choice is made taking into account the water quality and the purchase cost.
The choice of the discharge column is very important to be suitable for the weight of the pumping unit. It must also be resistant to corrosion and electrolysis. The pipes used are divided into two main categories, steel or plastic UPVC.
For drillings with a depth of more than 200m we choose steel pipes, while in smaller UPVC pipes. We also choose plastic pipes, in those cases where oxidation problems are expected, for example in water with a high content of iron or with a high conductivity.
Steel pipes are produced by seam (Tubo) or by invisible seam (ERW / HF). The invisible seam (ERW) pipes have been heat treated – annealed. All pipes are coated with a special varnish for maximum protection against corrosion.
The plastic pipes used in drilling are of the PVC-U type (rigid PVC), which are more durable than plain PVC, with greater tensile and compressive strengths but also greater hydraulic conductivity. They have strong resistance to chemicals, sunlight and oxidation by water. They are also non-toxic and suitable for drinking water. They are distinguished in heavy (heavy) and super heavy (super heavy) type, with resistance of 26 and 35 atm respectively.
The connection between the parts of the pipes is made with connectors (sockets), made of the same quality material as the pipes. The sockets have fire for greater safety and plastic flanges for better sealing. The length of the pipes and filter pipes in the trade is 3 meters, while their diameter is from 1 ” to 5΄΄.
The power cord of the electric motor is a special submarine cable and can be NYY or HO7RN-F type. Its cross section is related to the engine horsepower, cable length, start type (D.O.L or Y-D) and the use of soft starter or inverter.
Each submersible pumping unit is accompanied by an electrical control panel – automation, which is necessary for the proper operation and protection of the submersible pump motor. In areas that have a large and frequent voltage drop, an asymmetry monitoring mechanism is also necessary.
For the best operation of the submersible pumping unit, a Soft-Starter can be installed, so that we have a smooth start-stop of the pump, avoiding the hydraulic shock, which is very large, especially at large pumps and depths. For the same reason we reduce the diameter of the cable.
For even better management of the submersible pump and the aquifer we can use an electronic Inverter device, with which we can have constant adjustment of the pump speeds and therefore of the water supply that we want to exploit. In this case we have an even smoother start and stop of the submersible pumping unit.
Wrong choice of pumping unit can lead to poor aquifer management, resulting in usually pumping excessive amounts but with poor water quality. A pump with excessive engine horsepower results in successive starts and consequently the frequent presence of failures. In these cases, the pump must be removed to repair, replace or clean the well, which poses a serious risk of causing general damage to the well.
Therefore, we conclude that the selection of the appropriate pump, results in the economic operation and the long operating time of the drilling, while at the same time ensuring the sustainability of the aquifer.