Marine Centrifuge
Marine Centrifuges are devices used by ships to remove any contaminants from liquids such as fuel and oil. Removal of Contaminants is done with a high-speed centrifugal force that separates the solid particles from the liquid. It is essential to ship operation and maintenance, as it keeps the fuel clean for use in the ship’s engines.
Marine centrifuges can also be used to separate solid particles from liquids such as water or sewage, ensuring marine vessels’ clean and safe operation. They are designed to withstand harsh conditions, making them ideal for use in a marine environment.
A centrifuge is a high-speed machine used to separate or remove contaminations from fuel and Lube oils. It is mandatory to undertake this Treatment to separate and remove water and solid impurities before supplying to the marine engine. A centrifuge works on the principles of centrifugal force, accelerating molecules to physically separate the particles of different masses in a gradient along the periphery of a rotating container.
A centrifuge separates the particles from a solution according to their size, shape, density, viscosity of the molecule, and rotor speed.
In this post on centrifuge machines, we will discuss the complete process and uses of centrifuge machines and the devices used to carry out Lubricating and fuel Oils Treatment.
Centrifuges are the most important machineries on board ships. 4Th Engineer is responsible to maintain the centrifuges on board a merchan ship.
Introduction
Hence in light of the above reasons, it becomes essential to consider the pre-treatment of fuel oil. For performing the Pre-treatment, centrifuge machine is the most reliable and proven methods.
Important terminology used in Separators
- Clarifier disc: – This disc is optional and replaces the gravity disc in the separator bowl for the clarifier mode. The function of the disc is to seal off the heavy phase outlet in the bowl hood eliminating the liquid seal.
- Sludge discharge: – Sludge expulsion from the separator bowls
- Interface:- Interface is the boundary layer between the lighter phase (Oil) and heavier phase ( Water) in the separator bowl.
- Phase: – There are two phases in the separator. The heavy phase separation of heavy liquid, e.g., water, and the lighter phase is the lighter liquid separation, e.g., oil.
- Throughput: – The feed of the liquid to the separator per time unit and expressed in M3/ hour or Litres /hour.
- Sediment (sludge):- Solids that are separated from a liquid.
- Gravity disc: – The function of the gravity disc is to position the interface between the disc stack and the outer edge of the top disc. A gravity disc is used only in the separator for the purifier mode.
- Water seal: – Is the seal of water in the solid space of the separator bowl to prevent the lighter phase from leaving the bowl through the heavier phase when the separators work in purifier mode.
Tips for safe operation of Centrifuge
- Ensure the bowl is completely assembled and all fastenings securely tightened before starting the separator.
- Always stop with the emergency stop button before discharging a vibrating separator.
- Always begin to disassemble a separator after it has come to a complete standstill.
- Follow the instructions in the instruction book to set the discharge intervals.
- Be serious about the alarms. Ascertain the cause of alarm and eliminate the cause before resuming separator operation.
- Use a suitable separator for the right liquid.
- Always use thepower supply frequency as stated on the machine plate.
- Clean the operating system at specified intervals to avoid sludge discharge malfunction.
- Only a fully trained person with complete knowledge of installation, operation, maintenance, and emergency procedures should handle the separator.
- Use only genuine spare parts and the special tools supplied by OEM.
THE NEED FOR CLEANING OF ENGINE LUBRICATING OIL
During the engine operation, oil gets contaminated, depletion of additives and degradation of oil. Hence to restore the lubricant properties, the oil needs treatment. This treatment is done partially by the engine-mounted centrifugal filters.The lubrication oil contamination level should be kept low for the engine’s excellent and safe operation.
Most of the impurities are produced in the engine except a few coming from external sources like oil refill and vent pipes.The oil in medium-speed engines gets contaminated through combustion products in the combustion chamber, though blow-by, and with the fuel through the fuel injection system.
To restore the lube oil properties, the oil should be purified through a centrifugal filter up to some extent. To clean the oil of the engines running on HFO, separate seprators should be used.
Categories of centrifuge machine
Centrifugal Purifier Working Principle
The dirty oil is supplied to the center from the settling tank. Then due to centrifugal force, the separation between oil and Water occurred due to their different density.Water, heavier than oil, is thrown out toward the wall of the bowl, whereas the oil is positioned in the center. Water is applied first because if the oil is supplied directly to the purifier, it will come out from the waterside. Water is provided preferably, 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, also known as E-line.The position of this interface within the purifier is very important for correct operation; a gravity disk achieves this interface at the outlet.
Several gravity discs are provided with the purifier. This Gravity disk (a.k.a Regulating Ring) has a different diameter for the different densities of oil to be purified, so if the oil is being changed, the gravity disk has to be changed.
A large-diameter gravity disk that does not break the seal should be used as a thumb rule. A blind disc is at the top disc stack.
Purifier
A Purifier is a centrifuge arranged to separate two liquids of different densities as water from fuel oil. Correct size gravity disc is the main component of a purifier. The gravity disc or the dam ring creates the interface between the ware and fuel oil. On board, marine ship spate purifiers’ are used for the Lube oil and Fuel oil. Lube oil is purified through centrifugation. Fuel oil is separated through centrifugation and gravity separation.
Bowl assembly is surrounded by an outer framework. In the outer framework, there are several inlet and outlet connections for feeding the liquid and discharge after the treatment. Dirty oil enters through the center of the bowl, passes away through the stack of discs and the outlet is through the top.
Interfaces of two liquids are formed due to Centrifugal separation. Correct positioning of the interface is achieved by Gravity Disc.
Various sizes of gravity discs are provided to suit the fuel with different densities of fuel.
Clarifier
A clarifier is a centrifuge machine that separates solids and liquids, such as particles, sediments, and oil, from the separation process. With this process, the liquid gets cleaned. The primary difference between a clarifier and a purifier is that a purifier separates one liquid from another liquid and solids. A clarifier separates a solid from a liquid, known as double-stage separation.
Oil having little or no water is cleaned in a clarifier. The collection of impurities takes place at the periphery of Bowl. Maximum efficiency is achieved in this process since the machine runs at maximum separating efficiency. No gravity disc is required since the interface is not required to be maintained in this type of process.
Lube Oil Treatment
Lube oil of Diesel Engines are contaminated due to the daily continuous operation. Rotating parts attribute to the metal deposits. Combustion products attribute to the carbon and sludge deposits which ultimately carried along with the Lubricating oil and in this process Lubricating oil gets contaminated.To get rid of above contaminants oil need to be cleaned with the process of centrifuge machine.
Fault Finding- centrifuge machine
Separator Vibration
A separator will vibrate while passing through its critical speeds during Starting and stopping. Vibration also exists up to some extent during the operation of the separator. Operators should get acquainted with these expected conditions. Excessive vibration with noise is a positive indication of severe abnormality in the separator. Under such circumstances, the separator should be stopped immediately and investigated the cause. Carry out the condition monitoring at specified intervals and record the level of vibrations. The level of vibration shouldn’t exceed 9 mm/s.
| Cause | Corrective Action |
| Bowl Unbalance Improper CleaningWrong AssemblyWrong Disc stack CompressionBowl assembled with the parts from other separator | Check the assembly and cleaning after dismantling the separator |
| Abnormal deposition of sludge in the sludge space | Clean the separator Bowls |
| Wrong adjustment of Paring Disc height | Stop the separator, measure and re-adjust the correct height. |
| Bent Bowl Spindle | Change the Bowl Spindle with a new one |
| Worn out frame feet | Replace the frame feet |
| Worn or damaged bearings | Renew the bearings |
| Top bearing spring of spindle broken | Renew the springs |
Smell
| Cause | Corrective Action |
| It is Normal after starting; friction pad slippage causes the smell. | No action is to be taken. If the smell continues when the separator has gained full speed, stop the separator and change the worn-out friction pads. |
| Too low oil level in the sump | Check and top up the oil level to the correct level |
Noise
| Cause | Corrective Action |
| Wrong Height of Paring Disc | Stop the separator, and adjust the height |
| Worn or damaged bearings | Replace all the bearings |
Too low Speed of centrifuge machine
| Cause | Corrective Action |
| Friction pads are slippery with oil or warned out | Clean or replace the friction pads |
| Leaky or non- operative bowls | Dismantle and check the bowls |
| Motor failed | Repair / replace the motor |
| Damaged Bearings | Replace all the bearings |
| Incorrect fitment of transmission parts ( 60 Hz Pulley for 50 Hz Pulley) Power Supply | Change the belt transmission to suit the supply frequency. |
Too High Speed of centrifuge machine
| Cause | Corrective Action |
| Incorrect fitment of transmission parts (50 Hz Pulley for 60 Hz Pulley) Power Supply | Change the belt transmission to suit the supply frequency. |
Too high starting power
| Cause | Corrective Action |
| Incorrect fitment of transmission parts ( 60 Hz Pulley for 50 Hz Pulley) Power supply | Change the belt transmission to suit the supply frequency. |
| Incorrect direction or rotation | Change the phase connection of motor |
Too low starting power
| Cause | Corrective Action |
| Incorrect fitment of transmission parts (50 Hz Pulley for 60 Hz Pulley) Power Supply | Change the belt transmission to suit the supply frequency. |
| Friction pads are slippery with oil or warned out | Clean or replace the friction pads |
| Motor failed | Repair / replace the motor |
Too long starting time taken by centrifuge machine
| Cause | Corrective Action |
| Friction pads are slippery with oil or warned out | Clean or replace the friction pads |
| Wrong Height of Paring Disc | Stop the separator, and adjust the height |
| Worn or damaged bearings | Replace all the bearings |
| Motor failed | Repair / replace the motor |
Separating Operations
Accidently opening of bowl of centrifuge machine during operation
| Cause | Corrective Action |
| Chocked strainer in the water supply | Clean the strainer |
| Insufficient water in the operating water system | Ensure the opening of the water supply valve |
| Incorrect fitment of Hoses between supply valve and the separator | Correct the fitment |
| Clogged operating side nozzle | Clean the nozzle |
| Defective rectangular ring in discharge slide | Replace the rectangular ring |
| Defective valve plugs | Replace all the plugs |
| Leaky supply valve for opening water | Correct the leakage |
Failure of Bowls to open for sludge discharge
| Cause | Corrective Action |
| Chocked strainer in the water supply | Clean the strainer |
| Insufficient water in the operating water system | Ensure the opening of the water supply valve |
| Incorrect fitment of Hoses between supply valve and the separator | Correct the fitment |
| Clogged operating side nozzle | Clean the nozzle |
| Defective rectangular ring in discharge slide | Replace the rectangular ring |
Poor Separation results of centrifuge machine
| Cause | Corrective Action |
| Wrong Operating temperature | Adjust the temperature |
| Clogged disc stack | Clean the disc stack |
| Too high throughput | Adjust the throughput |
| Filled sludge space | Clean and re adjust the time of sludge discharge |
| Too low bowl speed | Inspect the motor andpower transmission including the clutch |
| Wrong direction of bowl rotation | Check the electrical connections to themotor |
Bowls Failure to close in centrifuge machine
| Cause | Corrective Action |
| Clogged nozzle in operating slide | Clean the nozzle |
| Reversed Hoses | Adjust |
| Defective rectangular ring in discharge slide | Replace the rectangular ring |
| Defective or missing valve plugs in operating slide | Replace valve plugs |
| No water | Turn on water supply. |
Maintenance procedure
(Credit:- https://shipfever.com/purifier-basic-principle-working/)
- 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 a complete stop and not rotating.
- All seals to be renewed.
- Clutch drive to be checked and lining renewed if required.
- Gearbox to be checked for abnormal wear. Bearing to be within makers running period limit. Gearcase lubricating oil to be renewed.
- 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.
- Before closing top cover, turn the bowl by hand. To test if it’s free of obstruction.
- After running up to normal speed the operation of the purifier shall be checked especially the separating efficiency of the purifier with regard to the selection of the correct gravity disc or plug.
- Correct torque should be employed as mentioned by the maker.
- Necessary entries shall be made in the record.
A centrifuge is a 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.
Centrifugal Separators
( Credit:-https://www.sciencedirect.com/topics/engineering/centrifugal-separator)
Centrifugal separators utilize centrifugal action for the separation of materials of different densities and phases. They are built in stationary and rotary types. Various modifications of stationary units are used more than any other kind
In centrifugal or cyclone separators, centrifugal forces act on a droplet at a force several times greater than gravity, as it enters a cylindrical separator. This centrifugal force can range from 5 times gravity in large, low velocity unit to 2000 times gravity in small, high pressure units. Generally, centrifugal separators are used for removing droplets greater than 100 μm in diameter, and a properly sized centrifugal separator can have a reasonable removal efficiency of droplet sizes as low as 10 μm
Best Marine Engineering Books
| Product Image | Title | Buying Option |
|---|---|---|
  | Pounder's Marine Diesel Engines and Gas Turbines |  |
  | Diesel Generator Handbook |  |
  | Reeds Diesel Engine Troubleshooting Handbook |  |
  | Marine Diesel Engines: Maintenance, Troubleshooting, and Repair |  |
  | Troubleshooting and Repairing Diesel Engines |  |
  | Introduction to Marine Engineering |  |
  | How To Become Marine Engineer |  |
  | General Engineering Knowledge for Marine Engineers |  |
  | Marine Auxiliary Machinery |  |
  | Lamb’s Questions and Answers on the Marine Diesel Engine |  |
  | Pounder’s Marine Diesel Engines and Gas Turbines |  |
  | Marine Electrical Equipment and Practice |  |
  | A Pocket Book of Marine Engineering: Questions and Answers |  |
FAQ
Blog Conclusion
We hope you enjoyed our article on the Centrifuge machine. We know that the students are always excited to get an article like this and learn more about the topics they want to learn more about. We tried to break the content down in a way that makes it easy to understand the fundamentals of the Centrifuge machine and how it works. If you have any questions or concerns, please don’t hesitate to reach out to us athttps://marinediesel.co.in/contact-us/. Thank you for reading, we would love to hear from you!
