Proper maintenance and overhaul of industrial pumps are crucial for ensuring their longevity and optimal performance. This step-by-step guide outlines the essential procedures and safety measures to follow when dismantling, inspecting, and reassembling a centrifugal pump. By adhering to these instructions, technicians can prevent potential failures and maintain the efficiency of the pumping system, contributing to the smooth operation of industrial processes.
1). Switch off the breaker and remove the fuse, keeping it in a safe place. Place a “men at work” board.
2). Close the suction and discharge valve of the pump to be overhauled.
3). Remove the suction and discharge pressure gauge connection to check whether the valve is holding or not.
4). Disconnect the electrical connections of the motor and mark them appropriately.
5). The procedure we will be discussing is for the top cover type.
6). Mark the motor to the body, coupling, top cover, and body with a permanent marker.
7). Remove the coupling bolts between the pump and motor shaft.
8). Take out the motor and place it on the floor, securing it properly.
9). Remove all nuts from the top cover of the pump.
10). With the help of a chain block of the required SWL and wire sling, take the pump shaft out.
11). Take the pump to the workshop and cover the open pump cover with a cloth.
12). Unlock the locking plate and remove the impeller nut.
13). Take out the locking plate.
14). Remove the impeller with the help of a bearing puller, but first, check the direction of the impeller blades.
15). Take out the impeller key and the washer placed behind the impeller.
16). Push the shaft out from the other direction.
17). Clean the shaft and remove the mechanical seal. Before removing the seal, note its position on the shaft using a vernier caliper, so the new seal can be placed in the correct position.
18). Remove the gland cover.
19). Check the condition of the sleeve for grooves and markings where the mechanical seal is fixed.
20). If the sleeve has a lot of grooves, it needs to be replaced.
21). Clean the impeller, key, shaft, and top cover.
22). Check the impeller for corrosion, pitting, cavitation, and wear. Also, check the condition of the impeller blades for narrowing.
23). Check the key for cracks and also inspect the keyway.
24). Check the following clearances:
- Sleeve to shaft: 0.03-0.04 mm
- Impeller to shaft: Metal-to-metal fit to 0.13 mm
- Wear ring clearances:
- Stuffing box throat bushing and shaft
25). If the clearances are okay, start reassembling the pump in reverse order.
26). Clean and dry the shaft. Install the gland cover, place the new mechanical seal in the exact position, and ensure that the seal is evenly positioned in all screw locations.
27). Clean the stuffing box and check for a clear passage for water.
28). Place the shaft on the top cover.
29). Install the washer and key in place.
30). Reinstall the impeller and secure it with the locking plate.
31). Take the pump to its place and reassemble it.
32). Tighten the top cover nut and reinstall the motor.
33). Connect the couplings and rotate the pump to check for free movement.
34). Slightly open the suction valve and purge the pump.
35). Reconnect the pressure gauge connections.
36). Check for leakage in the mechanical seal.
37). Reconnect the motor.
38). Fully open the suction valve.
39). Start and stop the pump to check the pressure buildup and ensure the impeller is placed in the correct direction.
40). If everything is okay, start the pump and slowly open the discharge valve to put the pump into operation.