Purifier Basic Principle and Working!


What do you understand by term Purifier?

As the term itself suggest Purifier is an instrument or equipment that purifies something. Now-a-days due to increase of pollutant in air; our air is becoming polluted and to counter the problem of air pollution, few cities are installing Air Purifier. Home are also buying small air purifier for domestic purpose. Thus it make it clear that purifier is any equipment with the sole purpose of purifying or cleaning the given media.

Purifier is also termed as Centrifuge, as on-board the vessel, purifier use centrifugal force to separate the two medium. A purifier consist of a electric motor which drive the various component, such as Bowl, Nodge(rotating counter), Tachometer, Gear-pump(via pinion gear)

To start the revolution of Bowl, it is necessary that Friction clutch(Friction coupling or Centrifugal coupling) get engage with the Drum.
Centrifugal coupling

Gear Box

1) Provided as a safeguard against the starting current, because if there is solid coupling, then due to starting the large current will flow through the winding of the motor to rotate the bowl, so friction coupling allow for some time, and after certain R.P.M is being achieved by the motor the coupling get engaged
2)Every 24 hours Purifier is stopped and cleaned up, so while boxing up if something goes wrong the extent of damage because of use of friction coupling will be of lesser extent while solid coupling damage extent will be more

Electric motor via friction coupling drive the horizontal shaft, which in turn drive vertical shaft on which bowl is mounted.

Working of Purifier

The dirty oil is supplied to the center from the settling tank. Then due to centrifugal force the separation between oil and water took place due to their different density. Water being heavier than oil is thrown out toward the wall of the bowl whereas the oil is positioned in center. Water is applied first, because if oil is supplied directly to the purifier, it will come out from the water side, so water is supplied first and it is checked that it is coming from the waterside, gradually the seal water is shut off.

If we supply seal water quickly, it may come to the oil side. An interference line is formed between Water and oil, this line is also known as E-line. The position of this interface within the purifier is very important for correct operation, this interface is achieved by gravity disk at the outlet.

A number of gravity disc is provided with the purifier. This Gravity disk (a.k.a Regulating Ring) that is used has different diameter for different density of oil to be purified, so if oil is beinged change the gravity disk has to be changed. As a thumb rule, large diameter gravity disk which does not break the seal should be used. Blind disc is at the top disc stack.

What is Clarification

Cleaning of dirty oil, which contain small amount of water or no water at all along with the ample amount of solid impurities, which collect at the bowl periphery. For clarifying process no gravity disk is needed, that is, a Clarifier has only one outlet at is subjected to maximum centrifugal force. Blind disc is at bottom.

Disc Stack

Purifier and clarifier bowls has conical disc stack, which maybe numbered from 150 to 200 and are separated from each other by a small gap. Small holes are provided on these disc stack where the interference line is formed and separation take place. The centrifugal force cause oil to move inward and water and solid particle to move outward.

Maintenance procedure :

follow the step given below
1) Particular care should be taken when moving the main bowl parts so to avoid damage to the sealing faces and prior opening it must be ensured that the purifier is at complete stop and not rotating.
2) All seals to be renewed.
3) Clutch drive to be checked and lining renewed if required.
4) Gear box to be checked for abnormal wear. Bearing to be within makers running period limit. Gear case lubricating oil to be renewed.
5) Prior to reassembly all sliding faces to be suitably lubricated. Bowl height to be measured and adjusted according to makers limits. Record to be taken.
6) Before closing top cover, turn the bowl by hand. To test if it’s free of obstruction.
7) After running up to normal speed the operation of the purifier shall be checked especially the separating efficiency of the purifier with regard to selection of the correct gravity disc or plug.
8) Correct torque should be employed as mentioned by the maker.
9) Necessary entries shall be made in the record.

Centrifuge is perfectly dynamically balanced piece of equipment with very high R.P.M, so the care should be taken while dismantling and boxing it up and also during maintenance.

***Always refer to maker manual before carrying out any maintenance***
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  1. Janib

    I need to know good purification principl. How can i understand that my purifier is woriking good conditio?

    1. admin

      The most common method used by us engineers is to take a note of sudden or gradual increase in change in oil filters. If there is a sudden increase in oil filter change overs, reduced oil quality and change in purifier running parameters; there is a clear indication that the purifier is not in good condition and need to be overhauled. But most of the time we stick to the planned maintenance schedule on purifiers which prevent from such sudden problems in purifiers.

  2. Aljun

    Why is it necessary to maintain the temperature of 98deg.cel when purifying heavy fuel oil?

    1. admin

      Increasing the temperature of the working medium in a purifier help with its purification. The higher the temperature the better and efficient will be the separation of sludge and suspended particles from clean oil. Furthermore, if the temperature is kept too low it may lead to poor flow rate or even wax formation.

  3. Arpit Singh

    Comment…How to adjust purifier bowl height

    1. admin

      The relative height of the bowl is adjusted by changing or replacing the bowl shim with of different thickness.


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