Hopper Feeder Drive Design Part 1 of 2

Video explains how to design a hopper feeder belt conveyor drive. For a free copy of the power calculation program go to: rulmecacorp.com/bulk-handling...
0:00 Introduction
0:15 Agenda
0:35 Purposes of Hoppers
3:59 Continuous Flow Question
5:06 Hopper Metering Question
5:58 Bulk Conveyor Components
6:48 Effective Tension
8:10 CEMA Tension Equation
8:39 Required Power
9:18 Special Hopper Load
For text, screen shots, and equations go to:
rulmecacorp.com/how-to-unders...
This video explains the purposes and functions of hoppers and serves as an introduction to the company’s two-part tutorial on how to design hopper feeder conveyors.
It includes three parts: the purposes of hoppers, standard conveyor belt loads, and special hopper loading. A separate video will be present arching theory, calculating hopper drag load, and pressure relief tips.
The four purposes of hoppers are:
• Material storage
• Material blending
• Interface between batch loading and continuous flow
• Material metering
Material Storage: Bins and silos are the best examples of how a “hopper” may be used to store material until it is required by the plant downstream.
Material Blending: Multiple hoppers may be used for material blending. For example, in a multiple “pant-leg” configuration, each pant-leg contains a different ingredient and has a hopper feeder conveyor at the bottom.
Interface between batch loading and continuous flow: Hoppers may be used as an interface between batch and continuous material flow. A clamshell ship unloader, for example, removes coal in batches, one clamshell load at a time, and deposits material into the hopper. The hopper accumulates the material and continuously feeds it onto the dock conveyor.
Material Metering: Metering hoppers are designed to supply material onto conveyors at various rates. Speeding up or slowing down feeder conveyors will increase or decrease the rate of material flowing on the feeder conveyor.
Continuous Flow: If a conveyor with a belt speed of 100 feet per minute (fpm) transfers 1,000 tons per hour (tph) to another conveyor, which has a belt speed of 200 fpm, what is the rate of output from the second conveyor? The answer is 1,000 tph because the flow is continuous. A different belt speed simply means that the material cross section in the trough of the faster conveyor will be smaller than the slow conveyor. When material flows continuously belt speed does not affect the carrying rate.
Metering Hopper: Assume the amount of material in the hopper is unlimited and the output is unrestricted. If the hopper feeder conveyor moves material at 1,000 tph at a belt speed of 100 fpm it will move material at 2,000 tph at a belt speed of 200 fpm. That is because the handling rate is linearly proportional to the belt speed.
The Conveyor Equipment Manufacturers Association (CEMA) conveyor design manual explains how to calculate standard bulk conveyor belt loads in a continuous material flow situation. Notice that material continuously flows through the feed chute onto the conveyor and through the discharge chute off of the conveyor.
The drawing shown in the video highlights key features of a typical conveyor belt: drive pulley, troughing idlers, loading skirts, feed chute, tail pulley, return idlers, and gravity take-up with two snub pulleys. The drawing does now show other items such as belt cleaners and slider beds.
Te, effective belt tension, is essential to know to calculate the power required to drive the conveyor belt.
This equation is beyond the scope of this short presentation, but it’s taken from the CEMA belt conveyor design manual.
Te = LKt (Kx + KyWb + 0.015Wb) + Wm(LKy + H) + Tp + Tam + Tac
It shows us how we to calculate the belt tension required to overcome:
• Gravity
• Friction
• Momentum
Once we know the effective belt tension, Te, we can calculate the power required to drive the belt. Required power equals the required belt pull times the belt speed.
Required power = Te x V
Since Te is expressed in pounds and V, belt speed, is expressed in fpm, the product equals a certain number of foot-pounds per minute.
Since 1 HP = 33,000 ft-lbs/min, the required power can be converted from ft-lbs/min to HP, and then a drive system can be selected.
Now let’s examine “special hopper loading” on a feeder belt conveyor. As mentioned previously, we have a certain amount of material in the hopper, which exerts a vertical force on the conveyor beneath it. This “additional vertical force” on the feeder conveyor results in an extra horizontal force against the sidewall of the hopper.
This “extra horizontal force” is another component of belt drag, as illustrated here, and must be added to the effective belt tension, Te, for the conveyor to calculate total required hopper feeder conveyor power.
In part two, we’ll discuss arching theory, calculating hopper drag load, and pressure relief tips.

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