TechnoServe Inc. brought the digester, hydraulic press and spindle press into a rural community together with the business management training to create small-scale palm oil processing enterprises.
However there were engineering problems with plant layout and matching the throughput of machine components. For instance:
1. The press and digester stations were typically separated from each other. Extra labour was required to load the cages from material discharged from the digester. The extra labour added to production costs.
2. The digester works much faster than the press; therefore there is always digested material awaiting the press. The digested mash cools during the waiting period. The cooling process reduces oil extraction efficiency, reducing plant throughput. The digester discharge and press loading activities were performed too close to the floor from the viewpoint of hygiene.
3. The surface area of the press plates and cage diameters were too large and therefore reduced the transmitted pressure of the hydraulic presses. Reduced pressure meant reduced extraction efficiency. Operating pressure was measured at 30-40 psi in the hydraulic press cylinder.
4. The manual presses were not ‘women friendly’ since a great deal of muscle power was required to pump the hydraulic system all day. In the peak season the work was difficult for even two young, able-bodied men. The press cages were heavy and unyielding to manipulation by women.
5. The frequent start/stop operation was injurious to the engine and increased fuel consumption. There was idle power in the drive engine as the digester led the press in performance by about 30 minutes. The idle power could be used to drive the hydraulic system. There was, therefore, the opportunity to move to semi-continuous technology.
TechnoServe Inc. sought to address the above-mentioned defects by producing a sturdy, hygienic, mechanically semi-continuous operation that can be handled also by female processors. The aim was achieved through:
• Equipment layout design changes to link the digester and press stations through an operating table on which press cages can slide between stations so that the digested mash always remains above ground. The digester and press stations were arranged so that one operator could manipulate both units.
• Changing to a high-pressure motorised press developing about 70 tonnes (versus the current 30-40 tonnes) cylinder pressure. The higher cylinder pressure was to be transmitted to a narrower press cage with smaller (4 mm diameter) holes using a smaller diameter (270 mm-diameter) press plate. The existing cages are usually 460 mm in diameter with 10 mm drilled holes. The new cages conserve pressure better.
• The hydraulic fluid is pumped using a power take-off pulley connected to the continuously running digester shaft. Thus the prime mover engine supplies the pressing power. The press/release mechanism is a spindle-operated valve, which is held up or down. No real strength is required to hold down the valve handle to operate the press.
• The smaller press cages permit easy manipulation by women since movement is by sliding the cages on a metal table connecting the elevated digester chute and press station.