Practical Operational Guidelines
For successful operation of the expellers few hints are given here. They will serve as general guides for the operators and will assist in removing most of the difficulties generally faced by them.
Before starting any expeller the following points should be carefully ascertained.
That the pressure worm shaft will revolve in the correct direction i.e in an anti-clockwise direction when looking from the driving end of the expeller. However this should be ascertained from the instructions available from the makers.
That the pressure cone is with drawn right out of the barrel.
That there is no foreign matter in the expeller or kettle. The driving pulleys should be pulled round by hand for a few revolutions to check this and to ensure that the machines run freely.
That all parts of the machine are will lubricated, all grease cups and oil baths should be filled with necessary lubricants. Grease should also be liberally applied to all gears and pinions.’
That the cage of the expellers properly cleaned and the interspaces are perfectly clear. If the interspaces are blocked it will prevent the oil from flowing out and the cake will not be properly formed.
A few minutes before starting th e expeller, steam of about 15-25 lbs.per sq.inch pressure should be admitted to the jacket of the tempering trough or the heating kettles as the case may be, and the first meal entering the heating device should be will cooked before pressings commenced. However, if pressing is immediately commenced the meal may not be properly cooked, and as the expeller in continuously drawing its feed from the cooker. It will be difficult to catch up with the demands of the expeller of providing a properly cooked meal. When pressing is started after the first charge to the cooker is properly treated, the supply of fresh meal should be continued to the cooker and the machine will continue to draw the proper meal throughout.
Advancing the Cone
When the meal starts to come out of the discharge and , it is advisable to advance the pressure cone into the pressure cage, a little at a time, so as to gradually build up the pressure in the cage for the formation of the cake. Attempts to suddenly push the cone right in at once, may result in the blockade of the cage, and will create difficulties in the right formation of the cake. When the expeller has worked in this way for some time, the cone is then so adjusted as to get the best yield of oil, the thickness of the cake varying according to the nature of seed, between 1/8” -3/8”. When the expeller is working continuously it is always advisable to run the pressure cone back at least once in 24 hours to ensure that it does not get fixed in one position.
If at any time. The expeller shows a tendency to choke, the cone is withdrawn a little away, until the discharge of the cake starts freely, then the cone can be again turned t the original position.
Thickness of the Cake
The position of the cone governs the thickness of the cake that will be produced. But different manufacturers may have their own requirements regarding thickness and oil contents of the cake, it is not possible to define a standard thickness of the cake for all materials.
It may be taken as a rule that the cake from more fibrous material cannot be made as thin as that from the less fibrous materials.
It may be taken as a rule that the cake from more fibrous material, cannot be made as thin as that from the less fibrous materials. For example, decorticated cotton seed can be compressed to a much thinner cake than undecorticated cotton seed, yet the oil contents of the two cakes may remain the same.
The first pressed cake of those oily materials which are usually pressed twice such as groundnut, castor seed, sesame, copra, etc. Must be much thicker than the cakes of second or single pressing of seeds. First pressed cakes are generally 3/8”-5/8” thick whilst final cakes are 1/8”-3/16” thick. First pressed cakes are general found to fall in to pieces readily on leaving the discharge, but this is quite in order as the low pressure necessary to reduce the oil content to about 20-25% is not sufficient to make hard cake.
If the material is once pressed such as decorticate cotton seed. Well rolled linseed, or rape, the cake is about 8” thick. Soya, undecorticated cotton seed, dry maize greem meal etc. Will make a cake about 3/16” thick. Second pressed groundnut. Copra or castor cake should be about 1/8”-5/16” thick. These thicknesses are only as guide but the cake all right when the cake is tough and the cone side of the cake is brightly polished, without being burnt, and the outside is slightly polished.
Stopping the Machine
When the machine is intended to be stopped, first the feed should be stopped and then the cone should run out to its extreme position in order to pass out any meal left in the cage. A handful of dry whole seeds are then run from the feed chute and the machine should be stopped when this is seen emerging out from the cake end. This will ensure the readiness fro stating the machine again without any difficulty.
In case of starchy meal, instead of dry whole seeds, a small quantity of oily foots should be fed to the expeller through the feed hooper, when the soft oily material is seen to be emerging from the cake discharge end, the expeller may be stopped. The soft foots will not bake in the heat of the press cage and expeller will be ensured in ready condition for staring up again.
Care should always be taken to see that the feeding is uniform and sufficient and the meal is properly cooked.
From time to time the expeller box should be opened to see that the worms etc. Are in good condition. All bolts, nuts, should also be properly checked.
All these guidelines will ensure efficient and economic working of the expellers.