AN INTRODUCTION TO CONVEYOR TYPES .SELECTION AND USES
The conveyor is quite broad, but generally applies to mechanical devices that transport solids. These can be either bulk solids or powders. Furthermore, conveyors may be either powered or unpowered. some of major conveyor types, including :
(1) conveyor belts,
(2) overhead conveyors,
(3) roller conveyors,
(4) chutes conveyors,
(5) screw conveyors.
1- conveyor belts
Conveyor belts can be used to transport solids as well as powders, but are not used to transport liquids or gases in any normal capacity. You can find conveyors belts implemented heavily in the following applications:
• Mining
• Food industry
• Pharmaceuticals
• Postage processing
• Manufacturing
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| FIG 1 |
The basic components of a conveyor belt include a drive mechanism, which powers the motion of the belt, and the belt itself, which transfers this motion to the conveyed material and provides support. There are a number of different options in belt structure and material and there are also many ways to power the belt. Any conveyor belt system is composed of:
• The belt
• The drive mechanism
• The guidThe belt runs in a continuous loop along the guidance
mechanism, at some point passing through the drive mechanism, which provides power, and the entire system is Bsupported by an underlying structure to transfer the loads to the ground. Figure 2 shows the basic layout of a conveyor belt system.ance mechanisms
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| FIG 2 |
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| FIG 3 |
The belt tension is one of the most significant quantities that influences aspects of the belt’s behavior and performance. The working tension of the belt and selected speed determines the necessary power the motor must provide Tension is usually reported in units of PIW, pounds per inch width of belt. Here is a quick formula that can be used
PIW = (HP(1 + K)(33,000))/SW
where:PIW is the unit tension,
HP the motor horsepower,
K a numerical drive factor,
S the belt speed,
W the width of the belt.
Drive Mechanism The drive mechanism of the conveyor belt consists of the motor, speed reducer, and drive pulley.
Selection Specification
The following design parameters have a notable impact on belting type, drive type, and general sizing:
Load details
• Weight
• Dimensions
• Loading method
• Chemical reactivity
• Temperature
Goal transport speed
Path of conveyor
• Length
• Inclines
• Turns
Function of belt
• Accumulation
• Pure transport
• Concurrent action (painting, cooking, etc.)
Selecting the Correct Belt
• The type of belt used (plied or wire mesh) is strongly dependent on the function intended.
• The weight of the belt affects the requirements on the drive selection.
• The tensile strength required is dependent on the load characteristics.
• For plied belts, interply strength places requirements on the diameter of pulleys.
• The surface material determines how the belt interacts with the load.
2- Overhead Conveyors
the overhead conveyor offers an ideal transport method. All overhead conveyor systems are composed of a track, a coupling device to allow motion along this track, some form of carrier for the load, and in some cases a means to provide power to the system. Each of these components comes in a number of variations. The automotive, garment, and food industries, among others, all use overhead conveyors.
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| FIG 4 |
chain.
The power and free configuration consist of two tracks, one powered and one unpowered or “free.” The primary advantage of such a system is the ability to separate trolleys from the drive chain. This makes accumulation and intermittent transfer possible, something of which the continuous chain variants described above are not capable. Power and free conveyors may make use of both of the track types discussed previously. Usually, the drive chain passes through an enclosed track, while the free track onto which the trolleys are attached may be either enclosed or I-beam.
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| FIG 5 |
The sprocket drive consists of a motor–reducer combination that powers a toothed sprocket or gear
The friction drive has a configuration similar to that of the sprocket drive. the caterpillar drive uses a separate continuous-drive chain using a sprocket drive and then uses a parallel transfer through the drive dogs to power the main drive chain. Some of the benefits of this configuration over the sprocket drive include easier relocation, compatibility with many different conveyors for reapplication, and more flexibility in location along the drive chain.
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| FIG 6 |
below.
1. Define the requirements
a. Load dimensions
b. Transport speed
2. Select the basic conveyor type
3. Specify the track path, considering
a. Load dimensions
b. Transport speed
c. Space available
4. Select the chain
a. Type
b. Necessary chain pull
c. Appropriate pitch
d. Linking method
5. Select the drive mechanism
a. Type
b. Torque and horsepower requirements
c. Location in system
3- Roller Conveyors
roller conveyors consist of an arrangement of rollers, cylindrical steel components, upon which the load moves. Roller conveyors find use primarily in bulk applications Roller conveyors are used over belts in scenarios where more diverse loading, unloading, and accumulation options are required.
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| FIG 7 |
The various types of roller conveyors are classified by how they are powered, if at all. These types
include:
• Free roller : human powered
• Gravity roller : not driven; uses gravity and an incline to move packages down from a height
• Belt-driven roller : driven by a belt or belts at the end of, or underneath, the rollers
• Chain-driven roller : driven by a chain or chains attached at the ends of the rollers
• Lineshaft roller : driven by a rotating shaft to which individuals rollers are belted
The rollers contact the load, supporting and transporting it forward. The most basic roller is simply a long steel cylinder mounted on a shaft supported by bearings which allow it to rotate.but not move in a translational manner
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| FIG 8 |
Powered roller conveyors use drive systems that provide torque to all or intermittent rollers. The four most used are:
1. Belt-driven
2. Chain-driven
3. Line shaft-driven
4. Individually driven
Selection Specification The basic steps of the selection process for roller conveyors are outlined below:
1. Identify application
a. Load characteristics
b. Conveyance need: Powered? Unpowered? Accumulation?
2. Select type of roller conveyor; consider:
a. Load aspects and needs
b. Cost
c. Adaptability
3. Select and size rollers
a. Type
b. Roller selection
c. Bearings
4. Specify path
5. Select drive (if necessary)
a. Based on type of load and conveyor
b. Torque and horsepower requirements
The selection of roller conveyor type depends mostly on the weight of the load. For powered roller conveyors, line shaft conveyors are the most cost-effective for lighter loads, chain driven can be used for heavier loads, and individually powered are the most adaptable and suitable for very heavy loads. Gravity or unpowered conveyors suffice for simple directing or facilitation of intermediate-weight loads.
4- Chute Conveyors
The chute conveyor serves the role of connecting components in the materials flow chain. They are simple in the fact that there are no moving parts in the chutes themselves, but if poorly designed or implemented, chutes can be the source of some of the biggest complications. Their primary application is containing and guiding material. They are used in handling most substances besides gases, and rely on gravity to motivate motion.
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| FIG 9 |
They vary in complexity with application. For open chutes, the main geometric parameters of interest are the width, height, length, and angle of declination. If there is a turn in the chute, the radius of this turn is important to consider to prevent package jamming and flow backup.
In closed chutes, the cross section, which encompasses the previously mentioned dimensions, is one of the most important factors. The curvature of the chute, which can be related to the instantaneous angle of declination, also affects flow rates and clogging. Open chutes are generally found
in simpler applications with larger solids (not powders or particulate solids). They guide material imprecisely, as the goal is only to convey the individual loads to the next conveyor. Major concerns in regard to open chutes include:
• The coefficient of friction between the chute material and load base
• Angle of declination necessary to overcome this sliding friction without tumbling loads
• Width necessary to prevent jamming, especially in turn sections
• Exit speed of loads from chute Closed chutes find more frequent
use in bulk solids handling such as mining and grain processing. The responsibilities attributed to closed chutes are:
• To guide material onto a conveyor belt, at the speed of the belt, in the direction in which the belt is traveling
• To eliminate spillage
• To enclose material dribbles
• To enclose material from operating personnel
• To eliminate dust liberation
the mass flow rate, usually labeled Q. Using continuum mechanics provides a flow rate of
Q = 𝜌VA
where:
ρ the bulk density (kg/m³),
V the velocity (m/s),
A the cross-sectional area (m²).
Q in kg/s.
5- Screw Conveyors
The screw conveyor of today is mechanized and used in many industries. Some examples include the grain, mining, and sewage industries. Screw conveyors can be implemented horizontally, on an incline, or vertically. The simplicity of the design leads to predictable behavior and reliable service
in most applications
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| FIG 10 |
The basic screw conveyor consists of several components:
• The screw itself
• The shaft
• The shaft supports
• The trough and covers
• The drive mechanism
The characteristic component of the screw conveyor, the screw itself, is responsible for converting
rotary motion into translational motion in the material conveyed.
Some important characterizing quantities include the diameter and the pitch. The pitch of the screw is the distance between adjacent planes of the flight and is a characterization of the steepness of the inclined plane. Pitch values are usually given in terms of diameters. Some examples are illustrated in Fig.11
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| FIG 11 |
The possible types of screw design are nearly endless. Some more “exotic” designs include variable pitch, ribbon, or cut and folded screws (Fig. 12). Each design possesses its own advantages and has a specific effect on thematerial being transferred.Some exotic screw designs: (a) variable; (b) ribbon; (c) cut and folded
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| FIG 12 |
Selection Specification The selection of screw
conveyor system components is outlined below.
1. Define the material to be conveyed.
a. Maximum particle size
b. Bulk density
c. Chemical reactivity
d. Temperature
2. Define the capacity and distance conveyed.
3. Using the requirements outlined above, size and select the conveyor.
a. Diameter
b. Screw pitch
c. Screw materials (considering temperature, abrasiveness, and corrosivity)
4. Calculate the horsepower required.
5. Select the motor and drive arrangement.
6- Skatewheel Conveyors
Similar to a roller conveyor, skatewheel conveyors consist of many small wheels mounted on a horizontal grid. The transfer concept is the same as for roller conveyors, but there is much less contact area with loads. Skatewheel conveyors are predominantly unpowered and used to transport boxes or other flat-bottomed loads. They can be gravity conveyors when mounted on inclines, but more often they are usedmerely to facilitate human-powered movement of packages.
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| FIG 13 |
7-Bucket Conveyors
As the name implies, this conveyor relies on buckets to move material in a vertical or inclined path. The buckets are mounted as illustrated in Fig. 14. The materials are loaded in at the bottom, drawn up inside the upright bucket
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| FIG 14 |
8- Vibrating or Oscillating Conveyors
vibrating conveyors are used for smaller particulateloads, such as pills or diamonds, while oscillating conveyors have a larger amplitude, lower-frequency motion, and handle slightly larger objects, such as hot metal castings.
This form of conveyor is generally used only over a short distance and is helpful in separating materials into a single layer for further conveyance on a belt.
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| FIG 15 |
9- Pneumatic Conveyors
Pneumatic conveyors rely on air or gas pressure to move materials through a network of tubes or pipes. A simple form of this conveyor with which you may be familiar is implemented at many drive through banks. The tube system that transports canisters between your car and indoor tellers is a pneumatic conveyor. For bulk solids and industry uses, the idea is about the same, only on a larger scale. Some industry applications include grain handling, fine powders, pharmaceuticals, and food processing.
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| FIG 16 |
10- Cart-on-Track Conveyors
This conveyor is designed to transport discrete loads. A mine cart can be viewed as one manifestation of the cart-on-track method.
The difference between different forms of cart-on-track conveyors is the manner in which they are powered. Many are human powered, some have motors mounted on each cart, and others rely on a line shaft concept similar to that used in roller conveyors. This is illustrated in Fig. 17.
The central rotating shaft is coupled to each cart, motivating it along the supporting tracks. Usually, flat cart conveyors are used for large package handling, and bucket carts can be used for bulk solid handling.
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| FIG 17 |
11- Vertical (Elevator) Conveyors
Vertical conveyors are implemented when very heavy loads need to be moved through a height. Usually, they are run intermittently, only requiring use sporadically. If more regular vertical transfer is required, other conveyance methods such as belts or overhead conveyors are recommended. Vertical conveyors are basically freight elevators, but are not constructed with considerations toward carrying people. Unless specially designed, you should not use this conveyance device for moving people.
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| FIG 18 |
Great article on roller track manufacturers! I appreciate the detailed information about the various types of roller tracks available
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