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July 6, 2006
The first thing to take into account in a screw press installation is to make provision for both bypassing the press and handling overflow from the inlet hopper. Solutions can take a wide variety of forms. Questions to be asked include: What will happen to excess material if the press will not take the flow being fed to it? What will happen if, over time, screw press capacity declines? This can be due to things like screw wear or changes in the material being fed to the press.
Spill containment is another consideration, especially in agricultural installations. Under certain conditions, it is possible that the flow being fed to a screw press will all purge out the cake discharge, at a consistency unchanged from what it was when it went into the press.
Making provision for future maintenance is very important. Room should be left at the cake discharge end of the machine so that the screw can be removed. The screw comes out through the cake discharge hole.
When it comes to rigging, the first consideration must be safety. Also, be sure to properly support the press when lifting it from the truck. Do not lift just one end, as it is possible for the frame to deflect, which in turn can shift the screw positioning within the press. Interference between the screw and the screens can result.
As for mounting a screw press, do not bolt or weld the press down to a level foundation! Instead, first set the press where it is to be installed. Next, place shims between the press frame and the steelwork (or concrete pedestals or foundation) to fill any gap where the press is to be anchored. Only after this shimming should the press be pulled down tight. Doing otherwise will likely rack the frame of the press, and this can cause screw-to-screen interference.
The press should be mounted solidly to a foundation or structural steel. If a press goes into a jammed condition while operating, without the press being anchored in place, the frame of the press can twist. If tramp metal is big enough, it can cause such a jam.
To suit individual situations, the press can be installed with the cake discharge tilted upwards a few degrees. In fact, this is the preferred installation position, as it improves press liquor drainage. When the angle is more than 15º, consult the factory as it is likely that the oil level in the gearbox will have to be adjusted.
In order to get the motor out of the way, hollow shaft gearboxes can be rotated 90º or 180º. This, too, requires adjustment of the oil level, as indicated in the operating manual. If the press is too long to be installed in a given space, the drive can be changed. Presses with hollow shaft gearboxes can be changed to right-angle drive gearboxes. Presses with in-line drives (motor direct coupled to a concentric gearbox) can be changed to a belt drive, with the motor mounted either above or to one side of the gearbox. In extreme cases, we go to a parallel shaft gearbox with the input and output shafts on the same side. This puts the motor next to the inlet hopper of the press. In all cases where the drive is to be changed in this manner, the change must be made at the time of order entry, not after we have built the press.
Issue 175