Centrifugal multistage horizontal high pressure pumps, according to their construction peculiarities and sphere of application, are classified into several groups:
The type CNS pumps are designed for pumping neutral cold water with temperatures of 1°C to 45°C and the contents of solid impurities within 0,2% by mass, not more than 0,2 mm in size and the hardness of no more than 1,46 gPa. They are used for water drainage in coalmines, in water-supply systems and for increasing pressure in cold water circuits.
The type CNSg pumps are designed for pumping neutral hot water with temperatures of 45°C to 105°C and the contents of solid impurities within 0,1 % by mass, not more than 0,1 mm in size and the hardness of no more than 1,46 gPa. The additional pressure of the in-coming water should not be less than 10 m of water column.
CNSk pumps - are designed for pumping acidic waters with pH less than 6,5, with temperatures of 1°C to 40°C, the contents of solid impurities not more than 0,2% by mass and not more than 0,2mm in size and the hardness not higher than 1,47 gPa.
CNSn pumps are designed for pumping water-containing gas-saturated, as well as commercial, petroleum in the course of in-field collection, preparation and transportation, the oil being free of hydrogen sulfide, its density within 900-1050 kg/m3, paraffin-content not more than 20% and pressure within 500 mm mercury.
CNSm - are designed for operating in turbo-generator oiling systems to supply oil to the sealing bearings at starting, stopping and working of the generator. Oil temperature should be up to 60°C for CNSm of 38- and 60- series and up to 55°C for CNSm of 180- and 300- series, at viscosity of 20-25 cSt and density of 0,88 g/cm3.
In multi-stage pumps water is transferred successively with the help of several impellers mounted on one shaft within one body.
The pump's body consists of separate sections (chambers), their number being equal to the number of impellers minus one, as one impeller is situated in the front cover. The chamber structure of the pump's body allows increasing or decreasing the head without change in the capacity. The head is equal to the sum of the heads created by every impeller.
Cast iron CNS pumps ensure stable and lasting work with backwater of 2-6 m. Without backwater, cavitation destroys these high-speed pumps. If the water temperature is higher than 45°C, it is necessary to increase backwater.
For pumping highly mineralized waters from coalmines, CNSk pumps are produced. The peculiarity of the pumps is that the flow-passage details are made of chromium-nickel steel.