Created by Ankur Sharma, Gurudayal Srivastava, Vikram Singh, Sanket Tamhane

1. WHAT ARE CENTRIFUGES?

• THESE ARE THE DEVICES USED FOR SEPARATING IMPURITIES FROM FUEL OIL & LUBE OIL

• IMPURITIES CAN BE SOLID (ASH,METAL PARTICLE ETC) OR LIQUID (CHEMICALS & WATER)

2. WHAT IS THE PRINCIPLE ON WHICH PURIFIER WORKS?

• WHEN BOWL/TANK IS ROTATED, CENTRIFUGAL FORCE WILL THROW ANY PARTICLE WITH DENSITY GREATER THAN THE OIL TO THE PERIPHERY OF BOWL.

• FORCE OF SEPARATION CAN BE GIVEN BY THE STOKE’S FORMULA I.E.,

• F = Π/6 X D3 ( ρw – ρo ) w2 r ------------(2)

WHERE D = DIAMETER OF IMPURITY PARTICLE/OIL GLOBULE

( ρw – ρo ) = DENSITY DIFFERENCE BETWEEN WATER & OIL.

W = ANGULAR VELOCITY OF THE DISC.

R = EFFECTIVE RADIUS/ DISTANCE OF IMPURITY PARTICLE FROM BOWL CENTRE. FOR THIS DIAMETER OF BOWL TO BE INCREASED. BUT THERE IS LIMITATION BECAUSE OF BALANCING PROBLEM.

3. WHAT IS INTERFACE?

• WHEN SEPARATION STARTS BY CENTRIFUGAL FORCE, IT FORMS THREE ZONES I.E.

1. HEAVIER LIQUID/PARTICLE PHASE NEAR PERIPHERY OF BOWL

2. LIGHT LIQUID/CLEAN OIL PHASE NEAR CENTER OF THE BOWL. &

3. MIDDLE NEUTRAL PHASE .THIS GRADUALLY BECOMES LESS & EVENTUALLY FORMS THIN DIVIDING LINE BETWEEN THE TWO ZONES .THIS DIVIDING LAYER IS CALLED INTERFACE OR E-LINE.

• THE POSITION OF INTERFACE DECIDES THE DEGREE OF PURIFICATION

• THE OPTIMUM POSITION OF INTERFACE IS BETWEEN EDGE OF DISC STACK & THE OUT SIDE EDGE OF THE TOP DISC.

• POSITION OF INTERFACE CAN BE FIXED BY USING CORRECT SIZE OF GRAVITY DISC.

4. WHAT IS GRAVITY DISC?

• GRAVITY DISC IS A RING FITTED AT THE TOP OF DISC STACK FROM WHERE WATER (HEAVIER PHASE) IS PASSING OUT.

• OUTSIDE DIAMETER OF GRAVITY DISC IS FIXED & INSIDE DIAMETER CAN VARY DEPENDING UPON SPECIFIC GRAVITY OF THE OIL TO BE PURIFIED. FOR THIS PURPOSE DIFFERENT SETS OF GRAVITY DISCS ARE SUPPLIED WITH EVERY CENTRIFUGE.

• THE SIZE OF THE DAM RING CAN BE SELECTED WITH THE FOLLOWING DATA.

A) VISCOSITY OF THE OIL. B) SPECIFIC GRAVITY OF THE OIL.

C) TEMPERATURE OF THE OIL. D) TEMPERATURE OF WATER.

5. METHODS TO SELECT CORRECT SIZE OF GRAVITY DISC?

1. USING THE MONOGRAMS GIVEN IN MANUAL WHICH IS BASED ON OIL DENSITY & SEPARATING TEMP.

2. BY USING THE FORMULA.

3. BY TRIAL & ERROR METHOD.

6. WHAT IS TRIAL & ERROR METHOD?

• IF THE GRAVITY DISC (INSIDE DIAMETER) IS CORRECT SIZE , INTERFACE WILL BE FORMED BETWEEN EDGE OF DISC STACK & OUTSIDE EDGE OF THE TOP MOST DISC . WITH THIS CLEAN OIL OUTLET IS CLEAR OF WATER & WATER DISCHARGE IS CLEAR OF OIL .

• IF INSIDE DIAMETER IS TOO LARGE, THE INTERFACE WILL BE FORMED OUTSIDE THE TOP DISC EDGE. CLEAN OIL WILL PASS TO THE WASTE THROUGH WATER OUTLET & CLEAN OIL OUTLET WILL BE CLEAR OF WATER.

• IF INSIDE DIAMETER IS TOO SMALL, THE INTERFACE WILL BE FORMED WITHIN THE DISC STACK & SEPARATING EFFICIENCY WILL REDUCE. WITH THIS CLEAN OIL WILL CONTAIN WATER & THE WATER DISCHARGE WILL BE CLEAR OF OIL.

7. HOW ARE THE FOLLOWING FACTORS AFFECT INTERFACE?

8. HOW AND WHERE SEPARATION OF IMPURITY IS DONE?

9. WHAT IS THE DIFFERENCE BETWEEN PURIFIER AND CLARIFIER?

PURIFIER

• THE LOWER DISC HAS HOLES

• SEPARATES WATER & HEAVY SOLID IMPURITIES

• TWO OUTLETS ON TOP, EACH FOR WATER & OIL

• TOP DISC WITH NECK.

• GRAVITY DISC ON TOP OF DISC STACK.

• REQUIRE SEALING WATER WHILE STARTING.

• PROVIDED WITH AUTOMATIC CLEANING ARRANGING.

CLARIFIER

• THE LOWER DISC HAS NO HOLES.

• SEPARATES ONLY FINER PARTICLES.

• THERE IS ONLY ONE OUTLET ON TOP.

• DISC WITHOUT NECK

• CLARIFIER DISC WITH SMALLER NECK

• DOES REQUIRE SEALING WATER.

• TO BE CLEANED MANUALLY

10. WHAT IS MANUAL CLEANING AND SELF CLEANING?

MANUAL CLEANING

• IN THIS TO CLEAN THE BOWL AND DISC, THE BOWL PART IS TO BE DISMANTLED, AND THE DISCS ARE TO BE TAKEN OUT.

• THESE ARE TO BE CLEANED WITH DIESEL OIL AND PLAIN CLOTH. THE BOWL IS ALSO TO BE CLEANED IN A SIMILAR FASHION.

• IN CASE PARTS OF THE BOWL IS CLEANED THOROUGHLY AND THE OTHER PARTS CLEANED POORLY, CAUSE UNBALANCE OF THE BOWL WHICH FURTHER RESULT IN VIBRATION AND DAMAGE TO THE BEARING.

• ALSO IMPROPER CLEANING RESULTS IN PLUGGING IN SOME PARTS WITH SLUDGE WHICH FURTHER AFFECTS THE PERFORMANCE OF THE BOWL OPERATIONS.

SELF CLEANING

• A SELF CLEANING CENTRIFUGE DOES NOT REQUIRE DISMANTLING.

• WATER WASH IS GIVEN DURING RUNNING PERIOD ONLY.

• FOR THIS THE BOWL IS CONSTRUCTED WITH A CONICAL SURFACE AND HYDRAULICALLY OPERATED OPENING AND CLOSING VALVE MECHANISM.

• THE SLUDGE DISCHARGE TAKES PLACE THROUGH A NUMBER OF SLOTS IN THE BOWL WALL. DURING NORMAL RUNNING CONDITIONS THESE SLOTS ARE CLOSED BY THE SLIDING BOWL.

• FOR THIS, SLIDING BOWL IS FORCED UPWARDS AGAINST A SEAL RING BY THE PRESSURE OF THE OPERATING LIQUID CONTAINED IN THE SPACE BELOW IT.

• THIS OPERATING LIQUID OUTER BALANCES THE DOWNWARD PRESSURE FROM THE PROCESS LIQUID INSIDE THE BOWL.

11. WHAT ARE THE REASONS FOR PURIFIER OVERFLOWING?

1. WRONG SELECTION OF GRAVITY DISC, GRAVITY DISC OF BIGGER SIZE.

2. TOO MUCH RATE OF THROUGHPUT

3. TOO LOW FUEL OIL TEMP

4. TOO MUCH SLUDGE INSIDE THE BOWL

5. LOW SPEED OF BOWL ROTATION

6. OIL IS EXCESSIVELY HEATED UP.

7. SEALING RING OF BOWL IS LEAKING

8. OPERATING WATER FAILURE

9. BOWL HAS NOT CLOSED PROPERLY

10. OIL PAIRING DISC ARE WORN OUT

11. OPERATING WATER FLOW IS NOT PROPER

12. HEIGHT OF BOWL IS NOT PROPERLY ADJUSTED

13. CLUTCH PADS ARE WORN OUT OR SLIPPING

12. WHAT ARE THE REASONS FOR WATER CARRIED AWAY WITH OIL?

1. GRAVITY DISC IS SMALLER.

2. INTERFACE WILL SHIFT INWARD

3. FEED RATE IS TOO HIGH

4. BOWL DISC IS DIRTY

5. THROUGHPUT IS TOO HIGH

13. WHAT ARE THE REASONS FOR EXCESSIVE VIBRATION?

1. Sludge too much

2. Foundation damper & spring failure

3. Bearing failure

4. Worn gear

5. Uneven wear of frictional clutch

6. Motor speed too high or too low

7. Height adjustment is not proper

8. Shaft is bend

9. Foundation bolts are loose

14. WHAT ARE THE REASONS IF PURIFIER IS NOT DESLUDGING?

1. DOWN BELOW PAIRING DISC AND WATER HOLES ARE CHOCKED.

2. SLIDING BOWL IS SEIZED

3. DESLUDGING WATER PRESSURE IS NOT SUFFICIENT MAY BE FILTER IS CHOCKED OR SOLENOID VALVE IS NOT OPERATING.

15. WHAT ARE THE REASONS IF BOWL IS NOT GETTING CLOSED?

1. OPERATING WATER LINE PRESSURE IS NOT BUILT UP.

2. SEALING RING IS LEAKING

16. WHAT ARE THE REASONS WHY HAVN’T GET ENOUGH RPM WHEN PURIFIER IS RUNNING?

1. Improper touching with friction clutch (worn out frictional clutch)

2. Touching with break

3. Excessive sludge in the bowl

4. Bearing failure

5. Motor running at overload

6. One phase power failure (Single phasing)

7. Sump oil level too high

8. Vertical shaft and horizontal shaft are out of alignment

17. WHY NEED SEALING WATER?

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

18. HOW TO ADJUST BOWL HEIGHT?

By turning vertical shaft adjust screw

By shim by bowl body

19. HOW TO CHANGE 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.

20. HOW TO CANGE PURIFIER TO 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.

21. WHAT IS PAIRING 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. It is used to remove oil and water from purifier. It works on centripetal force.

22. WHY MULTIDISC PROVIDED?

To separate the liquid into thin layer & create shallow settling distance between discs.

Improving separation of oil from heaver liquids & solids particle

23. WHAT ARE ALL TRIPS & ALARMS ARE PRESENT IN PURIFIER?

1. Back Pressure shutdown- this measures the discharge oil pressure and alarms and initiates a shut down when below a set value.

2. Heavy phase overflow- Oil has a much higher viscosity than water. The heavy phase outlet is led to a small catchment tank contain a float. The outlet from the tank is restricted in such a way that water flows freely but oil tends to back up. This initiates an alarm and shut down

3. Bowl not open- this may be done in several ways, typically by a lever switch operated by the discharged sludge hitting a striker plate. The other method is by measuring the motor current, when the bowl opens the bowl speed is dragged down due to friction effects of the discharging sludge and water. The motor current rises until full speed is re-established. This is detected by a current sensing relay

4. Water in oil- This found on modern designs which have a detection probe mounted in the oil discharge

5. High temperature alarm and shut down

6. Low control/seal water pressure-Where control water is supplied via a fixed small header tanks a float switch may be fitted.

24. WHAT IS DRIVE OF PURIFIER?

• THE DRIVE FOR THE CENTRIFUGE IS TAKEN FROM A STANDARD CONSTANT SPEED HORIZONTAL SHAFT TYPE ELECTRIC MOTOR RUNNING AT 1450-1720 RPM WITH AC SUPPLY OF 60 CYCLE. WITH WORM WHEEL BOWL REVOLVES AT A SPEED OF ABOUT 6000 RPM.

• NORMALLY CENTRIFUGAL FRICTION TYPE COUPLING IS USED TO CONNECT THE MOTOR AND THE PURIFIER CROSS SHAFT WHICH HOUSES THE WORM WHEEL ON IT WITH INBUILT WORM.

• THE MATERIAL USED FOR WORM IS HARDENED STEEL WHERE AS THAT FOR WORM WHEEL IS PHOSPHOR BRONZE.

• THE SPINDLE UNIT WHICH IS VERTICAL IS FITTED WITH BALL BEARINGS AND SLEEVE. THE TOP PART OF THE SPINDLE CARRIES BOWL AND THE LOWER IS FITTED WITH CYLINDRICAL WORM (REMOVABLE).

• THE SPINDLE IS DRIVEN THROUGH THIS CYLINDRICAL WORM WHICH ITS DRIVE FROM THE WORM WHEEL. THE WHOLE OF THIS ASSEMBLY IS TOTALLY ENCLOSED IN AN OIL BATH AND LUBRICATION IS THEREFORE AUTOMATIC.

25. WHAT IS AN ALCAP SYSTEM?

• THE BASIC ALCAP CLEANING SYSTEM COMPRISES:

• AN FOPX SEPARATOR

• A WATER TRANSDUCER WT 200, AN EPC-400 CONTROL UNIT, AND

• A WATER DRAIN VALVE.

• AN OIL FEED PUMP, A STRAINER, AND OIL HEATING SYSTEM ARE SUPPLEMENTARY EQUIPMENT TO THE BASIC CONCEPT.

WORKING:

Changes in refinery techniques are resulting in heavy fuel oils with increased density and usually contaminated with catalytic fines. These are small particles of the catalysts used in the refining process. They are extremely abrasive and must be removed from the fuel before it enters the engine. The generally accepted maximum density limit for purifier operation is 991 kg/m3 at 15*C.

In the ALCAP separation system the separator has no gravity disc and operates, to some extent, as a clarifier. Clean oil is discharged from the oil outlet and separated sludge and water collect at the periphery of the bowl. When the separated water reaches the disc stack, some water will escape with the cleaned oil. The increase in water content is sensed by a water-detecting transducer in the outlet .

The water transducer signal is fed to the MARST 1 microprocessor which will discharge the water when a predetermined level is reached which is 0.2% above the reference value. The water will be discharged from sludge ports in the bowl or, if the amount is large, from a water drain valve.

It can be used for oil whose specific gravity is more than 1.

26. WHAT ARE THE BENEFITS OF ALCAP SYSTEM?

• CONSTANT OPTIMUM SEPARATION EFFICIENCY IS MAINTAINED SINCE SEPARATED WATER DOES NOT ENTER THE DISC STACK.

• SIMPLE OPERATION: NO ADJUSTMENTS OF THE CLEANING PLANT ARE REQUIRED DUE TO FLUCTUATIONS IN DENSITY, VISCOSITY, FLOW RATE AND TEMPERATURE.

• SINGLE STAGE OPERATION: ONE ALCAP CLEANING SYSTEM REPLACES ONE PURIFIER/ONE CLARIFIER IN SERIES.

• VIRTUALLY NO OIL LOSSES.

• WIDE OPERATING RANGE AS ANY FUEL OIL WITH DENSITY UP TO 1010 KG/M3/15°C CAN BE EFFICIENTLY CLEANED WITH RESPECT TO WATER AND SOLID PARTICLES. SEPARATION EFFICIENCY IS NOT AFFECTED EVEN WHEN CLEANING FUEL OILS WITH A HIGH WATER CONTENT.

SOME POINTS TO REMEMBER

1. Friction clutch is provided as the starting torque is too high so power required is high.

2. Bowl speed is higher than motor speed.

3. Pure diesel oil purifier cannot be changed for heavy oil as they don’t have heater.

4. Pure clarifier cannot be changed to purifier as they don’t have oil outlet.