The following procedure describes a typical impeller clearance adjustment for a slurry pump.
The flexibility inherent in centrifugal slurry pump design does allow other settings as may be desired to optimize specific operating conditions. Slurry Pumps with recessed impellers do not rely on close running clearances with the liner. In such cases the impeller is normally adjusted back to keep shaft seal pressure at a minimum.
1. Loosen CLAMP BOLTS (012) on Side 'B' only, except on 8/6 AH or larger pumps, when such are fitted with mechanical seals. In this case loosen only the clamp bolt furthest from the slurry pump shaft end. This will ensure the bearing assembly will not lift up on one end, resulting in possible damage to the mechanical seal faces. A maximum .010" rise at the bearing assembly drive end is allowed.
2. Rotate the shaft clockwise by hand and move the bearing assembly forward (toward cover plate) by tightening the rear nut on ADJUSTING SCREW (001) until the impeller starts to rub on the front liner.
3. Release the nut just tightened by 1/3 turn (2 flats), then move the bearing assembly back by means of the front nut until the housing lug is secure against the rear nut.
4. Tighten CLAMP BOLTS (012) on side ‘B’ . Bolts on side ‘A’ were tightened earlier.
5. Tighten both adjustment screw nuts against housing lug.
6. Rotate the shaft and, if rubbing occurs, adjust the impeller back in the casing until the rubbing stops. NOTE If the process fluid could cause expansion due to heat or swelling (in the case of a rubber lined pump), provide for additional clearance in the adjustment procedure to allow for these conditions. On pumps fitted with a centrifugal shaft seal, forward impeller adjustment may increase seal area pressure. Thus on some applications it may be necessary to operate the slurry pump with a slightly greater impeller clearance to ensure proper shaft sealing is achieved.
Operation of a slurry pump with the impeller rubbing against the liner may cause severe damage to the pump. Proper operating clearance must be checked prior to operating the slurry pump.