Marine Centrifugal pump are mostly use onboard ship, for transferring liquid from one point to another.

Both Engine and deck department need to know how to use and overhaul this equipment.

This article will give you basic knowledge about how you can smoothly operate centrifugal pump and as well how to overhaul it.

Someone may ask, why did I mention deck department above?. Deck department operators require this knowledge because when you are operating an equipment, there is need for you to have basic knowledge (if not professional) about the equipment you use.

Knowing this will not only gird you on proper way of operations, but also give you confident to dictate or understand the behaviour of the equipment.

Most of the time, the engine department do have clash with the deck crew only because of Improper use of machineries. This clash normally happen either between the top four, or the junior officers (3rd class).

Therefore always try to understand basically the equipment you operate, operate with care and have it serve you.

Main objective

The main objective of this article being to bring to your knowledge the mode of operations of centrifugal pump and how to overhaul it, first we are going to learn proper way of starting and stopping this pump.

• Open the suction valve ( mostly located at sea chest or tank area)
• Make sure the discharge valve are on close position
• Keep the power off
• Manually turn the pump shaft ( shaft between the pump and motor, to check how free the pump is, maybe how any obstructions). Note in case of large pumps, you need to start and stop (some seconds) to observe the behaviour.
• If free, crack/fully open the discharge valve ( incase of high pressure) and start the motor.
• Open the discharge gradually till it gets full open.
• Check the pressure and regulate with the bypass ( incase you have more than required pressure)

The above listed local mode of starting centrifugal pump has been adjusted with automatic air release system. Therefore always check the pump golden book(manual) before using it.

How to overhaul centrifugal pump

• Check and close suction and discharge valves
• Switch off the power from the distribution panel or main switch.
• Disconnect the electrical wire, note the rotation direction terminals(incase of three face connection), and connect the same way after overhaul.
• Check the coupling bolt ( if bellow,beam,etc coupling ) and remove them.

For types of coupling and pumps to use them check here

• If your pump is on vertical position, connect chain block and pull the motor up, check for locked water pressure,then open the pump.
• If the pump is on horizontal position, loose the pump motor base bolt and remove the motor to create space for you,then follow same safety procedure mentioned above.
• Loose the pump flanges or pump impeller joint( as recommended by your pump type), then bring out the pump.

How to dismantle pump mechanisms

• Dismantle the pump starting from the impeller side. Loose the guide nut and washer.
• Use pulley to screw out the impeller, then remove mechanical seal.
• Remove the bearing guide pin/lock ring behind.
• Tap carefully on the shaft( recommended with wood or robber hammer) from behind to remove the bearings together with the shaft.
• Check and inspect bearings. If necessary change them.
• To change, clean the shaft, lubricate with oil and tap carefully from behind the bearing groove.
• To install new bearing,clean the groove very well and lubricate then install from the small end as removed.
• Clean the bearing housing, grease properly, and install the shaft from the impeller side. Don’t forget the difference between the two ends.
• Install new mechanical seal carefully.
• Install any washers as removed.
• Place the impeller to the end side ( most be straight and hand free) then tap around it, to seat proper(lock pin should be available).
• Put the washers and nut as removed, and tight.
• Check and rotate the shaft for free movement.
• Box up and check alignment. Mount the electric motor and connect the pump.
• Before starting the pump, check again for free movement.
• You are done.

Note: the above instructions may be different depend on the pump purpose. The above instructions are mostly for water centrifugal pumps.

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