Chapter 1: Belt Conveyors and their Components
What is a Belt Conveyor?
A belt conveyor is a system that moves materials, goods, and even people from one place to another. Belt conveyors are different from other ways of moving things because they use a belt instead of chains, spirals, hydraulics, etc. to move things. It uses a loop of flexible material stretched between rollers that are moved by an electric motor.
Since the nature of the things being moved varies, so does the belt material according to the system it is used in. It frequently appears as a rubber or polymer belt.
Components of a Belt Conveyor
A typical belt conveyor system has a frame, idler rollers, head and tail pulleys, belt, and belt.
Head Pulley
The head pulley is joined to the actuator and the electric motor. It moves the conveyor by acting as the pulling force. The head pulley is at the point where the conveyor dumps its load. This is called the discharge end of a belt conveyor. Since it drives the whole system, it is often necessary to increase the belt’s grip by putting a rough jacket over its outside. The jacket is known as a legging.
The diameter of the head pulley is usually the biggest of all the pulleys. In some systems, more than one pulley can act as a drive pulley. The head pulley is the drive roller with the biggest diameter that is at the end where the belt comes off.
Return or Tail Pulley
This is at the end of the belt conveyor where the goods are being loaded. It sometimes has a wing shape that lets material fall away from the belt and onto the support members, which cleans the belt.
In a simple belt conveyor, the tail pulley will be mounted on guides that usually have slots to let the tension of the belt pass through. In other belt-conveying systems, we’ll see, the tension of the belt is left to another roller called the “take-up roller.”
Idler Roller
These are rollers used to support the belt and load, prevent sagging, align the belt, and clear up carryback along the length of the belt (material left sticking on to the belt).
Idler rollers can perform any one of the aforementioned tasks or all of them, but they will always support the belt in whatever environment.
The following is a list of the various idler roller types available for various purposes:
Troughing Idlers
Three idler rollers will be arranged in a way on troughing idlers that causes the belt to form a “trough.” They are situated on the side of the belt conveyor that is carrying the cargo. While the two on the ends can be modified, the idler in the centre is immovable. This allows for flexibility in the trough’s depth and angle. When these idlers are used, spillages will be decreased and the cross-sectional area of the belt conveyor will remain constant. Stability depends on maintaining a consistent cross-sectional area.
Rubber Disk Idler
Rubber discs are positioned along the roller axis of this idler at predetermined intervals. In order to reinforce the belt edge, which is prone to tearing, the rollers are significantly closer together at the extreme ends. The evenly spaced discs will separate any associated carryback or leftover material and lessen material accumulation on the belt’s underside. This is a frequent reason for tracking errors (when the belt shifts to one side of the system and causes misalignment).
Screw Idler Roller
Sometimes the discs are shaped like a screw, and the idler is called a rubber screw idler roller. It will still do the same thing. A screw idler roller is shown in the picture below. Rubber helix can also be used to make the screw idler. Most of the time, screw idlers are used where a scrapper that gets rid of carryback wouldn’t work, like on mobile belt conveyors.
Trainer Idler
Trainer idlers make sure the belt goes in the right direction. It keeps you from getting lost. It does this with the help of a central pivot that turns the roller back to the middle if the belt moves to the side. It also has two guide rollers that help keep the belt in place.
Conveyor Belt
The belt is probably the most complicated part of setting up a belt conveyor. The tension and strength are important because the belt takes a lot of abuse when it is being loaded and moved.
The need for longer lengths of transport has pushed researchers to find new materials, but this always comes at a cost. Stronger belts that follow strict rules about being green tend to be more expensive to set up, and sometimes the costs are so high that they are hard to justify. On the other hand, if you try to save money, the belt usually breaks, which means your operating costs will be high. Most of the time, the cost of the belt should be less than half of the total cost of the belt conveyor.
Some of the parts of a belt are:
Conveyor Carcass
Since this is the belt’s skeleton, it needs to have the tensile strength to move the belt and the lateral stiffness to support the load. It must also be able to absorb the force of a load. The belt is a loop, so it needs to be joined. This is called splicing. Some methods of splicing involve bolts and fasteners, so the carcass must be able to provide a solid base for these fasteners.
The frame is usually made of steel cord or textile ply. Textile ply is made of fibers like aramid, polyamide, and polyester. Even when there is only one ply, a PVC-coated textile carcass is often used. There can be even six layers of meat on a carcass. The carcass can also include the edge protection that is very important in bulk conveyor belts.
Conveyor Covers (Top and Bottom & Sides)
This is a flexible material made from rubber or PVC. The covers are exposed directly to the weather and the working environment. Depending on how the covers will be used, they need to be carefully chosen. Most of the time, you need to pay attention to flame resistance, low-temperature resistance, grease and oil resistance, anti-static, and food grade.
The side of the conveyor that carries the load, the angle at which the conveyor is tilted, and how the belt is used in general all have special features. It can be rigid, smooth, or cleated.
Steel belt conveyors are also used in places like scrap conveyors in CNC machines because they don’t wear out as quickly as other materials.
Belts made of PVC, PU, and PE are also used in the food processing industry to keep food safe and limit contamination.
Plastic belts have only been around for a short time, but they are slowly becoming more popular because they are useful in so many ways. They are easy to clean, can be used in a wide range of temperatures, and work well with viscosity. They can also handle saltwater and substances that are alkaline or acidic.
Conveyor Frame
The frame will be different depending on how much it needs to carry, how high it needs to be, and how far it needs to go. They can be made in a simple way that looks like a cantilever. They can also be made of trusses if they need to hold more weight. Aluminum extrusions are also used for simple and light-weight tasks.
The design of the frame is an important part of the design of a conveyor. If the frame isn’t made well, it can:
- Belt running out of track
- Structural failure which results in:
- Long downtimes which translate to delays in production
- Injuries and casualties
- Costly Spillages
- Expensive fabrication methods and installation.
On the frame, you can also attach things like walkways and lights, as shown above. In some lighting situations, the materials will need sheds and guards to keep them safe. Chutes for loading and unloading can also be attached. To avoid unplanned overloading, it’s important to know about all of these possible add-ins.
Chapter 2: Types of Belt Conveyors
This section will talk about the different kinds of belt conveyors. Among these are:
Roller Bed Belt Conveyor
This type of conveyor belt has a surface of rollers just under the belt. The rollers are close together, so there isn’t much sagging of the belt.
They are good for both long and short distance travel. In some cases, they can be so short that they only need two rollers for the whole system.
The roller belt conveyor is one of the best ways to load using gravity. If the rollers were loaded by hand, the shock would damage them easily because they usually have bearings on the inside. Because of these bearings and the smooth surface of the rollers, there is a lot less friction, which makes it easy to move.
Roller bed belt conveyors are mostly used in places where things are sorted, put together, moved, and inspected by hand. Some examples are:
-Airport baggage handling
-The sorting of courier items, including at post offices
Flat Belt Conveyor
One of the most popular types of conveyors is the flat belt conveyor. It is frequently used to move things inside a building. For internal transportation, the belt must be pulled by a number of motorized rollers and pulleys.
Belts made of fabrics, polymers, and natural rubber are used on the flat belt conveyor. Because of this, it can carry many different kinds of materials. It is also easy to line up because the tail pulley is usually set up so it can be moved to line up the belt. Most of the time, it is a slow-moving conveyor belt.
Some uses for flat belt conveyors are:
-Lines that move slowly
-Apps for washing down
-Light, dusty business meeting
Modular Belt Conveyor
Flat belt conveyors use a “seamless” loop of a flexible belt. Modular belt conveyors, on the other hand, use a series of rigid pieces that fit together and are usually made of plastic or metal. They work more like the chain on a bike.
They have a huge advantage over flexible belts because of this. It makes them strong because they can work in a wide range of temperatures and PH levels.
When a section of the belt gets damaged, it is easy to just replace that section. With flexible belts, the whole belt would have to be replaced. Modular belts can go around corners, in straight lines, up and down hills, and in and out of valleys with only one motor.
Even though other conveyors can do the same thing, it is more complicated and costs more money. When you need an “unusual” width that is longer than the length of the conveyor, it will be much easier to do this with a modular belt conveyor.
Since modular belt conveyors aren’t made of metal, are easy to clean, and can let gas and liquids through, they can be used in:
-Food handling
-Fluid handling
-Metal detection
Cleated Belt Conveyor
Cleated belt conveyors are always made with a stopper or cleat. The cleats work to divide the belt into equal sections. When the conveyor goes up and down, these parts stop particles and materials from rolling back or falling off.
The cleats come in a variety of sizes and shapes, such as:
Inverted Capital T
This cleat will stand at a 90-degree angle to the belt to give fragile items support and movement. It works best for light jobs and moving small parts, packaged goods, and food.
Forward- Leaning Capital L
Because of how it’s oriented, it can easily resist leverage forces. It can be used to scoop granules and hold them up against gravity. It can be used to hold light to medium-weight granules.
Inverted V Cleats
These cleats are less than 5 cm high, but they have the same effect as a trough. They can be used to move heavy or large amounts of material because their cleat is short and can withstand high impacts.
Lugs and Pegs
These cleats are used to help water run off after washing things like vegetables and fruits. Lugs and pegs are a cheap way to move things that don’t need to be held up the whole length of the belt, like big boxes or rods. They can also be used to move only products that are bigger than a certain size and even hold single products in place.
Cleated Belt Conveyors can also be used to:
-Escalators are different from cleated belt conveyors in that they move loose items up a steep incline.
Curved Belt Conveyor
This conveyor has a frame that is already bent, so it can carry items around tight corners. It is used in places where space is limited and where winding conveyors would save space. The curves can be as steep as 180 degrees.
Modular plastics with pieces that fit together are used, but only if the conveyor has a straight part before it curves.If the belt is largely curved, flexible flat belts will be employed.
Incline/Decline Belt Conveyor
On inclined conveyors, keeping things from falling off the belt requires a tighter tension force, more torque, and traction on the belt surface. So, they will have a gear motor, a centre drive, and a take up. The belt must also have a rough surface to make it easier to grip.
Like cleat conveyors, these move objects up an incline without letting them fall off. They can also be used to speed up the way fluids move in response to gravity.
Sanitary Washdown Conveyor
Health and safety rules usually require sterilisation and rough washing in the pharmaceutical and food industries. Washdown and sanitary conveyors are made to handle these kinds of sanitary tasks. Most of the time, thin, flat belts are used in this setting.
Belt conveyors with sanitary wash-down stations are used for things that come from places like freezers and furnaces. They have to work sometimes in hot oil or glaze. Because they can work well in greasy places, they are sometimes used to get oil drums and crates off ships
Troughed Conveyors
A troughing belt conveyor is not a separate type of belt, since troughing can be added to any type of conveyor.
It uses a belt that looks like a trough because the idler rollers under it are also shaped like a trough.
The centre roller of the troughing idler rollers has a horizontal axis of rotation, while the axes of the two outer rollers, called “wing rollers,” are tilted away from the horizontal. Most of the time, the angle is around 25 degrees. The top idler rollers are the only ones that get troughed; the bottom ones never really do.
Higher troughing angles will damage the belt in a way that can’t be fixed. If the belt is troughed at sharper angles, it will keep its cup shape and be hard to clean, hard to track, and might even break in the middle. It could also decrease the amount of surface contact with the idler rollers, which would make the belt conveyor system less effective.
Most of the time, trough belts only work in one plane, either horizontally or at an angle of up to 25 degrees. The belt must have a large enough radius so that it can still touch all of the rollers in the troughing idler. If the angle of the troughing is sharper, the belt won’t touch the centre idler roller. This weakens the belt’s structure and the overall efficiency of the conveyor system.
Magnetic Belt Conveyor
Magnetic belt conveyors are used to move and control pieces and parts made of ferrous metal. They move materials with the help of ferrite or neodymium magnets. They are great for moving small parts that wouldn’t fit on a traditional belt conveyor. Magnetic belt conveyors work the same way that regular belt conveyors do. Magnetic belt conveyors are different from other types of conveyors because they use magnets to take advantage of the magnetic properties of the material.
On a magnetic belt conveyor, the magnets are spread out along the bed of the conveyor and have enough power to fight against the force of gravity. Since the strength of the magnets can be changed to meet different needs, the size of the materials doesn’t have much of an effect on how well a magnetic belt conveyor works.
Types of Magnetic Belt Conveyors
Magnetic Belt Conveyors: Magnetic belt conveyors are the most common type of magnetic conveyor because they are easy to build and use. They have a metal belt that is magnetised with either permanent magnets or a series of electromagnets that make iron-based materials stick to the belt.
Magnetic belt conveyors work just like regular belt conveyors, except that they have magnets on them. They are used to move cans of goods, parts, ore, and other metals with magnetic properties. They can move products vertically, up slopes, and upside down.
Magnetic Separator Belt Conveyors – Magnetic separator belt conveyors are a special kind of magnetic conveyor that is used to separate ore from loose dust and debris. As things move along the belt, things that aren’t magnetic fall to the side, while things that are magnetic stick to the belt. There are both dry and wet types of magnetic separator conveyors. The difference between the two is that the dry type doesn’t need materials to be wet in order to separate them, while the wet type does.
Chapter 3: Design and Selection of Belt Conveyors
When making a conveyor belt, the most important things to think about are:
– Choice of motor and gearbox
– Speed of belt
– Tension and take-up
– Material to be moved
– Distance to be moved
– Working conditions, such as temperature, humidity, and so on.
Motor and Gearbox Selection
To help choose the motor, you must first know how much pulling force the conveyor needs.
For a simple horizontal conveyor, the effective pulling force is given by the formula below:
Fu=µR · g(m+ mb+ mR)
Where:
Fu=Effective pulling force
µR =Friction Coefficient when running over roller
g = Acceleration due to gravity
m =Mass of goods conveyed on the whole length of the conveyor
mb =Mass of Belt
mR =Mass of all rotating rollers minus mass of drive roller
For a system on an incline, the effective Pulling force is given as below:
Fu=µR · g · (m + mb+ mR) + g · m · sina
Where
Fu =Effective Pulling Force
µR =Friction Coefficient when running over roller
g = acceleration due to gravity
m = mass of goods conveyed on the whole length of the conveyor
mb =Mass of Belt
mR =Mass of all rotating rollers minus mass of drive roller
a =Angle of inclination
Once the pulling force is known, it’s easy to figure out the torque and, from there, the right motor and gearbox.
Speed of Conveyor
The speed of the conveyor will be the circumference of the drive pulley multiplied by the revolutions per unit time.
Vc=D · F
Vc =Speed of conveyor belt in ms-1
D =Diameter of drive pulley in meters.
F =Revolutions of drive pulley per second
Tension and Take-up of the Belt
Take-up is an important part of keeping and getting the right amount of belt tension. This will make the process and its mechanical stability much better.
When the tension is right, the belt will wear evenly, keep the material in the trough evenly, and run in the middle when it goes over the idlers.
The length and width of every conveyor will always stretch a little bit. Most of the time, it’s fine for a new belt to stretch by 2 percent more than its original length. Since this fraction will make the belt longer, there will be a slack in the whole belt. To keep the right amount of tension, this slack will have to be taken up.
The stretch will be bigger the longer a conveyor is. Using the 2 percent stretch, a belt that is 2 metres long can stretch by 40 mm, but a belt that is 200 metres long will stretch by 4 metres.
Take up is also a good idea when the belt needs to be fixed. In this case, the take-up is just let go, and it’s easy for the staff to do maintenance.
Types of Belt Conveyor Take-Ups
There are many ways to set up take-ups, and each has its own pros and cons. The most common types of belt conveyor take-up are the gravity take-up, the screw take-up, and the horizontal take-up.
Screw Take-Up
The screw take-up takes up all the slack in the belt by using mechanical force. It does this by adjusting a threaded rod that is attached to one of the rollers, usually the tail roller. This threaded rod will be on each side of the roller, so it can also be used to get the roller in the right place. Since this method is done by hand, it is often called “manual take-up.”
The top angle take-up is a different style. Even though it is also popular, it needs a big, heavy tail frame to archive. The guards must also be big.
Screw take-ups are the easiest and most common way to control belt tension on short conveyors. They are inexpensive and work well.
Gravity Take-Up
Screw take-ups are usually not made to handle the length of the stretch that happens in conveyors longer than 100 metres. In these situations, the best way to tighten the belt is to let gravity do the work.
A gravity take-up assembly has three rollers. Two of them are bendy rollers, and the third is a gravity or sliding roller that controls the tension of the belt. A counterweight that will be attached to the gravity take-up roller pulls down on the belt to keep the tension from gravity. The bend rollers direct the slack in the belt around the gravity take-up roller.
The full take up assembly is built into the bottom of the frame of the conveyor and keeps the belt taut all the time. This self-tensioning system makes it easy for the take-up to adapt to sudden changes in tension or load.
So, the gravity take-up method always keeps the belt at the right tension and keeps it from getting damaged by sudden spikes in load or tension. Gravity tensioners don’t need as much maintenance as the screw take-up method because they can tighten themselves.
Most of the time, they need to be fixed when the belt has reached the end of its life. That’s when it will have stretched enough that the assembly will have gone as far as it can. When this happens, the conveyor belt will either need to be replaced or cut and vulcanized. Gravity take-up systems are also called automatic take-up systems because they adjust themselves.
Horizontal Take-Up
The horizontal take-up can be used instead of the gravity take-up, but only when there isn’t enough room for both.
This take-up is similar to gravity take-up, but the assembly is placed vertically behind the tail roller instead of below the belt. This is especially helpful when the conveyor is on a slope and there isn’t any extra room under the conveyor.
Because the horizontal take-up won’t fall below the conveyor, a weight box is used to tighten the belt with a system of cables and pulleys. The cables that are attached to the tail pulley ride on a carriage that can be moved in and out of position.
Chapter 4: Applications and Benefits of Belt Conveyors
This chapter will talk about how belt conveyors can be used and what their benefits are. It will also talk about common belt conveyor problems, what causes them, and how they affect the environment.
Applications of Belt Conveyors
Conveyor belts are used in many different ways in many different industries. These things are:
- Mining Industry
- Bulk handling
- Processing plants
- Taking ores from the shaft to the ground level
- Automotive Industry
- Assembly line conveyors
- CNC machines’ scrap conveyors
- Transport and Courier Industry
- Baggage handling conveyors at airports
- Packaging conveyors at courier dispatch
- Retailing Industry
- Warehouse packaging
- Till point conveyors
Other conveyor applications are:
- Food handling industries for grading and packaging
- Power generation conveying coal to the boilers
- Civil and construction as escalators
Chapter 5: Types of Belt Conveyor Pulleys
Pulleys are an important part of belt conveyors that can’t be left out. They help keep the drive belt tight and change the direction of the belt’s movement. Belt conveyor pulleys can be smooth, have a rubber coating, or be made of cast rubber. They can be drive, tension, motorized, snub, wing, or bend pulleys.
Motorized Pulley or Motor Drum
Motorized pulleys are what move a belt conveyor system. They have a sealed motor and a protected drum on the outside that is driven by an electric motor. The drum is what moves the conveyor belt. As with most pulleys, motorized pulleys come in a variety of shapes and sizes to meet the wide range of needs of conveyor manufacturers.
Drive Pulley or Head Pulley
The drive pulley is what moves a conveyor belt. Its surface is covered with chevrons or diamonds to create enough friction between the belt and pulley to move the conveyor belt. They can be single or double sided and have one or two drives. How many drive pulleys a conveyor system has depends on how big the system is.
Bend Pulley
A bend pulley changes the way a belt conveyor is wound so that it forms a loop. They are used as the tail roller of the tensioning device and can make the belt go in a different direction. Bend pulleys look the same as return pulleys, but their diameter is smaller.
Tension Pulley
A tension pulley is a type of return pulley that is used to tighten the conveyor belt and put more force on the pulley. Tension pulleys are solid pulleys because they need to be able to stand up to the forces that are put on them. They have more than one purpose and can be put anywhere along the belt or used as return pulleys. They want to be as close as possible to the pulley that moves the belt.
Snub Pulley
The driving pulley and the snub pulley collaborate. The surfaces that touch the driving pulley and the belt are made larger by using it. Snub pulleys are perfect for systems that demand high drive power or in contaminated environments because they create friction between the conveyor belt and the driving pulley.
Wing Pulley
A wing pulley is used to move things off the return belt. It cleans itself all the time and has great grip. There are many different kinds of wing pulleys, such as spiral, heavy duty, and herringbone.
Magnetic Pulley
Magnetic pulleys are part of magnetic conveyor belts, which are used to separate ferrous materials from non-ferrous materials. They are made of steel and have permanent magnets inside of them. Like all magnetic conveyors, they can pick up both big and small pieces of iron.
Crowned Head Pulley
A crowned head pulley has a cylindrical middle and tapered ends to help a conveyor belt move without wobbling. They are used with flat-belt drives to make them more stable and increase their strength. Crowned head pulleys use their tapered ends to force a flat conveyor belt back to the middle.
Chapter 6: Advantages and Problems with Belt Conveyors
Most people think that belt conveyors are an easy and convenient way to move, sort, pack, and ship goods and products. They have been around for years in different forms and have made a huge difference in the efficiency of the supply chain.
Advantages of Belt Conveyors
The advantages of belt conveyors include:
- It is a cheap way of moving materials over long distances
- It doesn’t degrade the product being conveyed
- Loading can be done at any place along the belt.
- With trippers, the belts can offload at any point in the line.
- They do not produce as much noise as their alternatives.
- Products can be weighed at any point in the conveyor
- They can have long operating times can even work for months without stopping
- Can be designed to be mobile as well as stationary.
- Have less dangerous hazards to human injury
- Low Maintenance costs
Common Belt Conveyor Problems
Even though belt conveyors have their benefits, they are complicated pieces of equipment that need to be watched and managed. Among the things that need to be looked at are:
Problem 1: The Conveyor Runs to One Side at a Certain Point in the System.
The causes of this would include:
- Material building upon the idlers or something causing the idlers to stick
- Idlers no longer run square to the path of the conveyor.
- Conveyor frame tilted, crocked, or no longer level.
- Belt was not spliced squarely.
- Belt is not loaded equally, probably loaded off-center.
Problem 2: The Conveyor Belt Slips
The causes of this would include:
- Traction is poor between belt and pulley
- Idlers stuck or not rotating freely
- Worn out pulley legging (the shell around the pulley that helps increase friction).
Problem 3: Overstretching of the Belt
The causes of this would include:
- Belt tensioner is too tight
- Belt material selection not done properly, probably “under belted”
- Conveyor counterweight is too heavy
- The gap between idler rolls is too long
Problem 4: The Belt Wears Excessively at the Edges
The causes of this would include:
- Belt is loaded off-center
- High impact of material on the belt
- Belt running against conveyor structure
- Material Spillage
- Material is trapped between belt and pulley
Environmental Effects On Belt Conveyors
Water, petroleum products, chemicals, heat, sunlight, and cold all influence the belt conveyor’s performance and life.
The causes and the effects can be categorized as:
Moisture Effects
- Belt rots and cracks
- Belt loose adhesion
- Causes slippage
- Steel carcasses can rust
Effects of Sunlight and Heat
- Rubber will dry out and weaken
- Rubber will crack
- Rubber may have more slack and thus reduce belt tension
Cold Effects
- Belt stiffens and becomes harder to guide and train
- On incline systems, frost can build up and cause slippage
- Ice can build up in chutes and clog them
Effects of Oil
- Rubber will swell
- Rubber will lose tensile strength
- Rubber will lose tensile strength
- The belt will wear quicker
- Rubber will lose adhesions
Conclusion
A belt conveyor is a system that moves materials, goods, and even people from one place to another. Belt conveyors are different from other ways of moving things because they use a belt instead of chains, spirals, hydraulics, etc. to move things. Depending on how the belt conveyor will be used, it is important to know how it is built and what it can be used for.
