A pump buyer selects his water pump on the basis of maximum reliability, durability and economy of operation. His decision is easy: Grundfos pumps. Grundfos deep well turbine pumps have earned themselves a reputation for reliability and low operation costs. Reliability is of utmost importance. A regular supply of water is a basic requirement, vital for domestic, industrial and agricultural purposes. To repair a pump, which involves pulling out, servicing and re-installation is both time consuming and costly. For these reasons the most durable material are used in Grundfos pump construction to give maximum trouble-free working life. Applications: Multistage deep well turbine pump with external motor for installation in boreholes of inner diameters of 6" to 10". Normally this pump is generally used in areas without electricity or where there is frequently voltage fluctuation. Typical applications are municipal and domestic water supply, irrigation, horticulture etc. Construction: Bowl assembly: The main components of bowl assembly namely, impellers, intermediate chambers, shaft, straps, discharge chamber are made in stainless steel. The impellers, intermediate chambers including guide wanes are manufactured from stainless steel plate which enable theoretically correct, double-curved blades to be employed for maximum operating efficiency. Column assembly: The column assembly connects the bowl assembly to the pump head. It consists of column pipes, column bearings and column pipe shafts. Column pipe shafts are threaded at each end and the couplings are designed to allow two adjoining shafts to butt perfectly. This ensures quiet vibration free operation. The column bearings have a large flow area to reduce friction losses to a minimum and are insulated from the column pipes by a rubber ring, thus avoiding any galvanic corrosion. The column bearing linings are manufactured from rubber, which enables these pumps to handle water containing sand in suspension and simplifies overhauls as these can be replaced easily and cheaply without the use of expensive special tools or equipment and without further machining. Column pipes are flanged. They are manufactured from high-grade steel and protected by a thick bitumen. This ensures high resistance to corrosion. Pump head: The pump head transmits pumped water from column assembly to rising main. It also supports the pump driver and ensures perfect alignment of driver shaft and top column pipe shaft. A cast iron base is supplied for the pump head. This enables the pump to be properly aligned and also ensures that it is correctly re-installed after overhaul and inspection. It also enables the well to be sealed against pollution. The shaft sealing is achieved by using a mechanical seal with tungsten carbide seal faces. This is maintenance free and does not wear the drive shaft. Prime-mover: Grundfos deep well turbine pumps can be driven by vertical motors in VI design or diesel engines via flat belt pulley or right angle gear-head. The flat belt pulley drive is available for pumps up to 22kW (30 HP) and for pump speed up to 3450 R.P.M.. The right angle gears are available from 22KW (30HP) to max. 92KW (125HP) nominal power at a ratio of 1:2 and a max. pump speed of 3500 R.P.M.. Facts concerning pump speed: For decades Grundfos deep well turbine pumps are being manufactured with a pump speed of 2900RPM/50Hz due to following reasons: The lift per stage is proportional to the square of the pump speed. The pump capacity is proportional to pump speed. With the same power consumption the shaft diameter is inversely proportional to pump speed. Therefore, when doubling the speed, the impeller diameter can be reduced by 50% while maintaining the same lift per stage. In consequence, more expensive and more corrosion resistant material i.e. stainless steel can be used in the manufacture of impellers because of their small dimensions, will still be able to compete with normal cast iron or bronze impellers of other make. A reduction in the impeller diameter made it possible to manufacture the pump chambers from stainless steel plate, thereby reducing the weight of the pump to approximately one tenth of cast iron or bronze pumps of other makes. The fabrication of impeller from stainless steel plate removes any chance of unbalanced mass in the impellers and eliminates the problem of vibrations in the pump. The high pump speed made it possible to reduce the shaft diameter and consequently to use a high quality material namely stainless steel. The strength of cold drawn stainless steel is twice as high as that of mild steel, which makes a further reduction in the shaft diameter possible and consequently made the prices more competitive. The development in the pump construction goes in the direction of high pump speeds. The pump of the future will be running at pump speeds of about 6000 rpm and more. All that prevents the manufacture of pump with these speeds today is the frequency of the electric network. Although they are still very expensive, static frequency converters are available in the market, so it is only a question of time when super speed pumps will be commonly available, as savings in the costs of materials by way of rational production methods make the only possible way of reducing pump prices.