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January 19, 2011
Revised July, 2023
Revised July, 2023
When customers request suggestions for starting up a new screw press, we refer them to the Owners Manual. The key elements are as follows:
Re-tighten the nuts and bolts which likely will have come loose in transit. This is especially true of the bolts holding the screen.
Check that there is compressed air for the discharge cone and that there is oil in the gearbox.
Find out where the manual disconnect, stop button, or breaker is located. If there is an emergency of any sort it is important to know where to shut off the press.
Give quick safety instructions: keep hands out of the inlet hopper, and keep hands away from where they might get pinched by the cone actuator mechanism. The rest is obvious and normal.
Bump the press to make sure the direction of rotation is correct and that there is no severe rubbing. Check for tramp material which may have fallen into the press during installation. The direction of rotation is this: if you are sitting on the gearbox looking towards the discharge cone, the screw should be turning counter-clockwise.
Make sure the press liquor drain is hooked up and that there is a way for the press cake to be removed from the discharge area of the press.
If being used, make sure that the lubrication equipment is in place. Be sure that the grease hoses are full. The most critical item is having lubrication for the cone bushing(s).
Make sure the cone runs in and out. It may be jerky without the press in operation. With the screw turning, the in-out motion smooths out.
When ready to get going, set the cone air pressure very low, say one bar (15 psi). Turn on the press. If practical and safe, start feeding material into the press with the cone in the open (withdrawn) position. Assuming it does not jam and no funny noises or vibration are evident, ease the cone shut once some material is seen coming out of the cake discharge.
Monitor the motor amps while doing this. If the amps spike, the press is jamming. When this happens, stop feeding material into the press and leave the press running with the cone open. If the jamming is bad enough to trip out the motor, run the press in reverse to try and loosen the jammed material. Then switch back to forward in an effort to clear the press.
Assuming that there are no problems, expect the cone (shortly after it is shut) to gradually come open. Some cake should start coming out. At that point, increase the air pressure on the cone. Monitor the motor amps while doing this, backing off the feed or air pressure if the motor seems to be overloading.
Note: the initial press cake to come out will be damp or wet. That is because it has been merely conveyed to the discharge. The press needs to be full for squeezing action to occur.
Likely it is best to start out at full line frequency, either 60 or 50 Hertz, for maximum power (torque). Once relatively stable operation is achieved, try changing the drive frequency. Be prepared to lower the Hertz in order to get drier cake.
Check the level in the inlet hopper. Set the feed to the press to be such that the incoming material partly or barely covers the screw flights in the inlet hopper. That is the optimal level for the best press performance. If you can see the shaft of the screw when you look in the inlet hopper, the press is running half empty, which reduces throughput and dewatering.
Look for vibration or shuddering in the press. That would indicate that it may be getting close to jamming or tripping out.
Issue 229