The quality of Crude Palm oil is determined by the percentage of Free Fatty Acid, the percentage of dirt, the percentage of Moisture and the Dobi Index (Bleachibility index).
The generally accepted standards for good quality Crude Palm oil are
1. Free Fatty Acid – Below 5%
2. Dirt in oil Below 0.01 %
3. Moisture in oil Below 0.1 %
4. Dobi Value Above 250.
FFA. (Free Fatty Acid)
The main cause of FFA being above 5% is due to the crop quality. FFA increase once the crop is harvested. Any delay in processing either in the plantation or the mill will cause the FFA to increase. The mill can reduce the increase the FFA rise by processing the crop as soon as it arrives at the mill. This is achieved by having a minimum balance every day. The balance FFB at the end of each processing day should be equivalent to two hours mill processing capacity. This quantity is required so that when the mill starts the old FFB can be processed to produce fibre and shell for boiler fuel. During the two hours of processing the fresh FFB can be sterilised so that the mill can process FFB continuously.
Dirt and Moisture.
The quantity of dirt and moisture in the pure oil before the purifier depends on the efficiency of the clarification tank. The dirt in the pure oil is reduced in the clarification tank due to dirt settling out in the clarification tank as it is denser than pure oil. If the clarification tank is not function efficiently then the quantity of dirt will be too much for the oil purifier to remove and dirt in the production oil will be above the allowed limit.
The clarification tank is working efficiently when the oil layer is always more than 500 mm. To achieve this at all times it is suggested that the skimmer height is set to 10 cm. The skimmer height is the difference between the level of the oil outlet at the oil skimmer and the sludge outlet
Picture of a Typical Continous Clarification Tank
Once the correct setting of the skimmer height is achieved in a mill and clean oil is flowing out of the clarification tank, then the skimmer height is correct. At the end of the processing shift it is wrong to decrease the skimmer height to recover the oil in the clarifier tank. The oil layer must be left in the tank so that when the mill is started up the next day clean oil is obtained. The operation of the clarification tank is explained in an other article on this site.
The purifiers must be in operation correctly to remove most of the remaining dirt and some moisture.
To remove the balance of moisture the oil has to pass through the vacuum dryer.
To manage the CPO quality the following samples must be taken and analysed.
Sample | Frequency | Location | Analyse For | Remarks |
| Oil after Clarifier | Once every two hours | Outlet of Clarifier. | Dirt and Moisture | If dirt more than 0.1% and/or Moisture >0.5%. Increase skimmer height. Check that the oil outlet pipe of the Clarifier tank does not have any holes. |
| Production Oil | Every Two Hours | After oil purifier | Dirt and Moisture | If dirt more than 0.01% and/or Moisture >0.1%. Clean the purifier. If automatic cleaning purifier then, shorten the automatic cleaning cycle. |
If a problem is suspected then the frequency of the sampling must be increased and the operation of the clarifier examined.
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