Which end does the screw conveyor drive go on?

 

The screw conveyor drive, also called the reducer, refers to the motor/gear reducer assembly used to drive the screw conveyor. A screw conveyor drive can be mounted in a number of ways to drive the screw conveyor, including a shaft mount with torque arm, low speed coupling with a base mount, chain reduction assembly or screw conveyor adapter. All these configurations serve the same purpose and over the last 15 years screw conveyor drives with screw conveyor adapters have begun to dominate the market due to the easy of installation and lower overall costs.

There are two options on where to install the screw conveyor drive: the inlet or discharge end of the screw conveyor. Because of the considerations below the discharge end is preferred. In cases where the screw conveyor drive must be mounted on the inlet end, alternative shaft seals and thrust limiting methods should be considered in the design of the screw conveyor.

 

Considerations

1. Shaft Seal – The shaft seal is used to seal the screw conveyor at the shaft locations to keep the product in and contaminants out. The advantage of the screw conveyor adapter is it has a shaft seal built in so for most applications the need to add additional sealing is not needed. The basic type of screw conveyor adapter shaft seal is some form of lip seal. This usually consists of multiple lips seals in a labyrinth configuration to keep product in the screw conveyor. In horizontal conveying applications with mostly granular products this seal works well. For more difficult applications like flood feed inlets, inclined conveyors or dusty products these seals can fail and when they do so allow an avenue for contaminants to enter the gearbox case and destroy the internal gearing. Placing the screw conveyor drive on the discharge end helps protect the shaft seal and reduces the likelihood of contaminating the gearbox.

2. Tension – The screw in the screw conveyor is made of flighting wrapped around a center pipe and then bottled at each end. A single screw is pretty stiff because of the pipe in the center but as the screw gets longer the stiffness decreases and then adding hangers decreases it even more. The screw is like a spring out of a pen. When you try to squeeze it between your fingers it will bow in the middle but if you pull the spring it will straighten out. To keep the screw from bowing in the middle, it is best to put the screw conveyor drive on the discharge end.