General Problems, Their Causes and Solutions
Position of Oil Flow
The heaviest flow of oil from the cage is normally at the feed section, If this does not happens and the oil flows from further along the cage at the centre or discharge end, it is a indication that the expeller is not getting sufficient feed. In an expeller, the pressure is generated according to the volume of material fed to it. When the cage is not running full of meal, much pressure is lost, and when the pressure is lost, good extraction will not take place and cake will contain more percentage of oil. The fed from the cooker should be regulated, so that the feed hoper is always full.
When the expeller is properly working, good amount of oil also flows through the intermediate chamber, but very little oil trickles out from the last chamber.
Abnormal Discharge of Foots
In expellers when properly prepared and cooked meal is pressed a small percentage of oily meal known as foots is discharged along the cage. These foots are normally mixed with the meal in the kettle and thus disposed off in the process. If it is allowed to accumulate, they result in the development of acidity.
Sometimes there is an abnormal discharge of foots from the cage. It means that the pressure on the meal is being lost and the discharged cake will be containing more oil content. This may be due to improper cooking of the meal or increased interspaces between the cage bars. Low fibrous material in the meal is also a frequent cause of an abnormal discharge of ‘foots’.
The cause of such abnormal discharge of foots, should be immediately removed, otherwise it will give heavy losses to the efficient working of the mill.
Expeller Refuses to Feed
If after running the expeller for sometime in good order, and a good cake has been made, the expeller then refuses to take sufficient feed to give desire pressure and a good tough cake, the indication is that the oil is collecting in the press cage instead of quickly flowing out through the bars.
This generally occurs with more oily seeds and irregular feeding. When sudden rush of oil content cannot escape quickly. This oil mixes with the incoming meal, forms a spongy mass, which the worms cannot grip and is, therefore, allowed to churn in the cage as an oily paste. If this happens the door of the feed chamber should be opened and oily mass is allowed to run out. The feed should be stopped and a few pieces of dry broken cake should be run, which will clear the whole cage. The feed from the cooker should then be opened and working resumed. If this defect becomes persistent, the chamber should be opened and the spaces between the cage bars of the feed section should be slightly enlarged by inserting suitable spacers between them.
Material Entering Pressure Cone
Sometimes oil creeps in between the cone bore and the sleeves and retards the ready movement of the cone in or out. This oil becomes hard in between the cone and sleeve, due to presence of uncoagulated albuminoids in the oil which is released by improperly cooked meal. This happens because he cone remains hot due to friction and the albumen gets baked into an extremely hard thin cake resembling a thin strip of ‘Bakelit’. It is this deposit which retards the free movements of the cone in or out.
To avoid such problems, the meal is properly cooked so that all albuminoids are coagulated and left in the cake , The cone should also be taken out at least once in 24 hours When this is done, The sleeve on which it slides should be thickly greased, which will prevent albumen penetration too far.
Effect on Worms
The Pressing worms of an expeller usually get the heaviest wear & tear, which generally starts from the last worm i.e.worm which is nearer to the cone. If this worm is changed from time to time. The wear and tear on other worms is generally minimised. If worm out worms are allowed to continue, they create space between the bars and top rim of the worm, this prevents the material being forced forward and therefore keep churning in the feed section. This results low capacity and yield of the machine.
Sometime oil drips continuously fro the discharge end along the cake. This indicates that worms and collars are not properly fitted in the shaft and oil finds passage in between them and flows to the entire length of the shaft. This difficulty can be removed by putting thick brown paper rings in between the worms and collars etc.