grundfos data booklet

SP A, SP2Bearings with sand channelsAll bearings are water-lubricated and have a squaredshape enabling sand particles, if any, to leave the pumptogether with the pumped liquid.Inlet strainerThe inlet strainer prevents particles over a certain sizefrom entering the pump.Fig. 3BearingTM00 7301 1096TM00 7302 1096Submersible pumpsFig. 4Inlet strainerNon-return valveAll pumps have a reliable non-return valve in the valvecasing preventing backflow in connection with pumpstoppage.Furthermore, the short closing time of the non-returnvalve means that the risk of destructive water hammer isreduced to a minimum.The valve casing is designed for optimum hydraulicproperties to minimise the pressure loss across the valveand thus to contribute to the high efficiency of the pump.Valve flapTM01 2499 1798Fig. 5Non-return valvePriming screwAll Grundfos pumps with radial impellers are fitted with apriming screw. Consequently, dry running is preventedbecause the priming screw will ensure that the pumpbearings are always lubricated.SP pumps with semi-axial impellers require no primingscrew. The pumps are primed automatically.It applies to all pump types, however, that neither pumpnor motor will be protected against dry running if thewater table is lowered to a level below the pump inlet.TM00 7304 1096Fig. 6Priming screwStop ringThe stop ring prevents damage to the pump duringtransport and in case of up-thrust in connection withstart-up.The stop ring, which is designed as a thrust bearing,limits axial movements of the pump shaft.The stationary part of the stop ring (A) is secured in theupper chamber.The rotating part (B) is fitted above the split cone (C).ABCTM01 3327 3898Fig. 7Stop ring (rotating and stationary parts) and splitcone7