KWS Manufacturing

# Calculating Speed

## Question

I have several screw conveyors in my plant all running at different speeds. I need to increase the speed of a screw conveyor due to increased capacity. All my drive units are Dodge TA II shaft-mounted gear reducers utilizing belts and sheaves between the motor and gear reducer. How do I calculate the current output speed of a screw conveyor? Also, how do I increase the speed of a screw conveyor by 15-percent?

You need to know several inputs to determine the speed of a screw conveyor utilizing a shaft-mounted screw conveyor drive. The four basic inputs required are – motor speed (MS), gear reducer ratio (GRR), drive sheave diameter (D1) and driven sheave diameter (D2). Most motors are designed for 1750-rpm output speed. The most common shaft-mounted gear reducer is 25-to-1. We will use a gear reducer ratio of 25-to-1 for our example.

To determine the current speed, you can simply measure the outside diameter of each sheave. For demonstration purposes, we will use a drive sheave diameter of 3.5-inches, and a driven sheave diameter of 7.0-inches. Now we can easily calculate the screw conveyor output speed (SCOS) using the following formula –

SCOS = (Motor Speed (MS) / Gear Reducer Ratio (GRR)) X (Drive Sheave Diameter (D1) X Driven Sheave Diameter (D2))

SCOS = (1750 / 25) X (3.5 / 7.0)

SCOS = 35-rpm

If you would like to increase the speed of the screw conveyor by approximately 15-percent to a new screw conveyor output speed (NSCOS) of 42-rpm, then you can simply reduce the diameter of the driven sheave. The desired driven sheave size can be determined by the following formula –

D2 = (Motor Speed (MS) / Gear Reducer Ratio (GRR)) X (Drive Sheave Diameter (D1) X New Screw Conveyor Output Speed (NSCOS))

D2 = (1750 / 25) X (3.5 / 42)

D2 = 5.83-inches

KWS can help you solve even the most complex bulk material handling problems. Our team of experienced professionals has solved thousands of bulk material handling problems for almost 50 years. Please contact KWS today!! Inputs Needed to Determine Screw Conveyor Speed Typical Screw Conveyor Drive Mounted on Screw Conveyor