PURIFIERS

Some useful links for purifier construction and working:

http://www.marineinsight.com/marine/marine-news/headline/10-things-must-check-starting-fo-purifier/

http://www.marineinsight.com/tech/auxiliary-machinery/high-speed-centrifuge-on-ship-construction-and-w/

Purifier is a centrifuge,  arranged to separate water and solid impurities from oil.

   Clarifier is a centrifuge,  arranged to separate finer solid impurities from the oil.

To understand just follow the below diagram

Actual on board purifier working diagram

Purifier

•        Remove water & suspended Solids particles from oils
•        Two outlets - water , clean oil
•        Gravity disc on top
•        Blind disc on the top of disc stack
•        Sealing water required

Clarifier 

•  Remove finer and lighter solid particles from oil  
•  one outlet for clean oil
•  No gravity disc .only sealing ring
•  Blind disc at bottom.
•  Sealing water not required

To run a  purifier as clarifier

• Open up the purifier and set the blind disc at the bottom of the disc stack.                                                                                            
• The water outlet is blocked by a seal on the gravity disc.                                                                              
• Blank off the sealing water inlet line

(Pure D.O purifier cannot change to H.O, it has no heater.Pure clarifier cannot change to purifier, it has no water outlet)

Changing over purifier from H.O to D.O 

•          Replace the gravity disc, which is smaller than the heavy oil                                           
•          Open heater by pass vale.
•          Closed the F. O heater steam in/out valves.
•          Open heater drains v/v.

Why Multi-disc provided in purifier: 

•         To separate the liquid into thin layer. 
•         Thereby create shallow settling distance between discs.                          
•         Improving separation of oil from heaver liquids & solids particle

Need of  sealing water in purifier :

   To seal the water outlet & to prevent the overflow of oil from the water outlet.

 Gravity disc: 

       The gravity disc is important part of purifier, which set the location of the oil and water interface.

                       http://www.marinesite.info/2014/04/what-is-gravity-disc-of-purifier.html

Selection of gravity disc 

1 . Separation temperature 

2. density of oil at this temperature 

3. desired through put of oil and by using of nomogram .

If the gravity disc is too large and/or the outlet line back pressure is too high, the interface will be too close to the periphery of the bowl and fuel will be carried over into the water outlet. 

                                                                                                                                                  Conversely, if the gravity disc is too small and/or back pressure is too low, the interface will be too close to the centre of the bowl and purification will be inefficient, with water being carried over in the purified fuel.

Paring disc

It is a stationary impeller mounted in a chamber at the neck of the bow.

It function is convert the rotating energy into a pressure head.

PURIFIER STARTING PROCEDURE:

Before starting purifier or any other machinery, first check and observe the machinery for lub oil level, is there any job going on with that machinery, brake is free, no obstruction nearby, check for leaks around the machinery etc.

 If you are starting the purifier first and fore most ,

1.       Check the valve line up on your own.
2.       Check the operating water tank level if fitted/open water line valve
3.       Check sludge valve is open.
4.       Ensure before purifier filter is cleaned and purged properly.

Starting the Purifier

• 1. Ensure valves are open, the lines are set from settling tank to service tank.

  2. Start the purifier feed pump with the 3-way re-circulation valve in a position leading to settling tank.

  3. Open the steam to the heater slightly ensuring the drains are open so that the condensate drains. close the drains once steam appears. If steam controller is working fine, do not throttle the inlet/outlet valve of steam line. open fully. By throttling the steam valve slowly the valve seat will erode causing steam to leak always.) 

  4. Start the Purifier motor.

  5. Check for vibrations, check the gear case for noise and abnormal heating.

  6. Note the current (amps) during starting. It goes high during starting and then when the purifier bowl picks-up speed and when it reaches the rated speed, the current drawn drops to normal value.

  7. Ensure the feed inlet temperature has reached optimum temperature for separation as stated in the Bunker Analysis report and nomogram ( bunker delivery note gives the density of the fuel and using this we can get the separation temperature and gravity disc size from the nomogram)

  8. Now check whether the bowl has reached the rated speed by looking at the revolution counter, if provided. The revolution counter gives the scaled down speed of the bowl. The ratio for calculation can be obtained from the manual.

  9. Now, after the bowl reaching the rated RPM, check for the current attaining its normal value.
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• De-sludge Procedure

  10. Open the bowl closing water/operating water, which closes the bowl. (Ensure sufficient water is present in the operating water tank or water line valve is open).close after 30 secs.

  11. Now after 10 seconds, open the sealing water to the bowl.

  12. The sealing water should be kept open till the water comes out of the waste water outlet.

  13. Once the water overflows through the waste water outlet, stop the sealing water.

  14. Now open the de-sludge water/bowl opening water. (This is done to ensure the bowl has closed properly). During de-sludge we can hear a characteristic sound at the opening of the bowl. then close.approx.3 seconds.

  15. Repeat the steps 10, 11 ,12 & 13.

  16. Open the 3-way re-circulation valve such that the dirty oil feed is fed into the purifier. observe the 3 way valve cylinder position

  17. Wait for the back pressure to build up.

  18. Check for overflowing of dirty-oil through waste water outlet & sludge port.

  19. Now adjust the throughput to a value specified in the manual. Correspondingly adjust the back pressure, too.

  20. Now the purifier is put into operation. Change over the clean-oil filling valve to service tank.

  
  

  Checks after starting the purifier during regular watches:

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• 1. Adjust the throughput, back pressure, temperature of feed inlet if necessary

  2. gear case oil level, motor amps, general leakages, vibration have to be monitored

  3. De-sludge every 2 hours for heavy oil purifiers & every 4 hours for lubricating oil purifiers.                                                                                                                                                                                                                                                                                             

  Stopping of Purifiers:                                                                                                                      

  1. De-sludge the purifier after stopping the feed inlet.

  2. Shut down the steam inlet to the oil.

  3. Stop the purifier after filling up the bowl with water.

  4. Apply brakes and bring up the purifier to complete rest.

  5. If any emergency, the purifiers has emergency stops, on pressing it, will stop the purifiers immediately shutting off the feed.

  Thus we have seen in detail how to start the purifier after carrying out all safety checks and we have also seen how to stop it.
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Purifier overflow reasons:

1. Incorrect  gravity disc size (if this is the reason it will happen only on bunker change)
2. Excessive sludge deposit inside the bowl (purifier will vibrate, also motor Amps will increase slightly)
3. Sealing water low (if you are in doubt with this point, manually increase the sealing water amount/duration. this may be due to clogged filter in water line. usually water line used to have a filter before solenoid ,to avoid solenoid valve being affected by debris in water. clean the filter)
4. Excessive back pressure or service tank valve closed
5. Feed oil temperature high or low(with the large deviation of temperature in purifier inlet oil this may happen.)
6. Orifice plat installed wrongly in the inlet side( this is a human error, it will happen after overhaul or bowl routines).
7. Excessive feed rate (Always set the feed rate with normal operating temperature, around 98 deg.c)
8. Main Sealing ring leakage, between bowl and hood.
9. Low rpm or wrong direction(low rpm mainly by friction pad worn out)
10. Leaking three way valve

In case of overflow of purifier, as a junior engineer you just close the feed valve.
if you know the de sludge operation carry on. otherwise inform senior engineers.

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