How to Replace Mechanical Seals in Centrifugal Pumps

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Mechanical seals are used in centrifugal pumps to keep water or any liquid from making contact with the delicate parts of the machine. They are situated on the shaft of the motor. Regular maintenance of these seals is needed to ensure there are no leaks. This article teaches you how to replace the mechanical seal. You will need to purchase a new seal to be able to follow these instructions.

Steps

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     If the centrifugal motor is in motion, turn it off. Shut off the main power supply. Ensure that there is no possibility of the machine starting up, once you get to work.
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     Cut the plumbing tubes connected to the centrifugal pump. You can use a saw to perform this action. Once disconnected, you are free to set the pump on a table or the floor, wherever you are comfortable.
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     Using a wrench, unscrew the bolts holding the pump housing in place. Carefully disconnect and detach the pump located beyond the housing. Keep these bolts safe. You will need it later to reattach this setup. [1]
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     The seal is located on the shaft behind the impeller. To detach the shaft, first hold the shaft in place using a wrench. Then unscrew the impeller by rotating it.
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     Part of the seal will be attached to the impeller, while the other part will be attached to the motor shaft. Slide the seal off from both these places.
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     Slide a mechanical seal along the shaft of the motor. Note that the front face of the shaft is extremely sensitive, even to the oils secreted by the fingers. Make sure that you don’t touch the face. [2]
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     With the help of a wrench, hold the motor shaft. Screw on the impeller. [3]
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     Using a wrench and the bolts from Step 3, reattach the pump and the motor.
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     Place the reconnected system back into the plumbing. Reconnect the plumbing tubes with the help of industrial strength PVC glue and primer.
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     After reattaching the plumbing to the centrifugal pump, the PVC glue and primer takes a minimum of one day to dry off completely. Start the machine after a day.
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Community Q&A

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  • Question
    What clearance should there be between the impeller and the backing plate?
    Community Answer
    Look on the pump shaft, you usually can see the mark where the set screw was previously. Use the same mark.
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  • Question
    Why is it important to ensure mechanical seals are correctly tensioned?
    Community Answer
    If the tension is too tight, the new seal will not last as long due to more heat from increased friction. Too loose will result in the seal leaking prematurely.
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  • Question
    Where can I find a step by step diagram for replacing a seal?
    Community Answer
    If you are referring to a mechanical seal, then I usually find that if you phone the pump manufacturers and ask nicely, they will usually send out some information to help. You can also search for Vulcan seals on the internet and ask for one of their seal books to be posted to you (they are free).
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      Warnings

      • Ensure that there is no power supply to the machine when dismantling it.
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      • Be sure to wear the right safety gear including industrial grade shoes, hard hats, protective gloves, safety glasses, etc.
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      References

      1. ↑ https://www.youtube.com/watch?v=06KZ3gZcedk
      2. ↑ https://www.youtube.com/watch?v=YXxFKnjsytE
      3. ↑ https://youtu.be/GTmeV_UkU0I?t=270

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