Understanding Conveyor Systems

19 Oct.,2022

 

cotton conveyor belt

Conveyor Systems are mechanical devices or assemblies that transport material with minimal effort. While there are many different kinds of conveyor systems, they usually consist of a frame that supports either rollers, wheels, or a belt, upon which materials move from one place to another. They may be powered by a motor, by gravity, or manually. These material handling systems come in many different varieties to suit the different products or materials that need to be transported.

Important Conveyor Systems Specifications

Load Capacity per Unit Length

Manufacturers will offer this attribute in cases where the conveyor will be built to a custom length to permit users to determine loading margins.

Maximum Load Capacity

Associated with Load Capacity per Unit Length, this value can be stated for fixed length, purpose-built conveyors. This can also be known as flow rate.

Conveyor Belt System Speed/Rated Speed

Belt conveyors are typically rated in terms of belt speed in ft/min. while powered roller conveyors described the linear velocity in similar units to a package, carton, etc. moving over the powered rollers. Rated speed applies to apron/slat conveyors and drag/chain/tow conveyors as well.

Throughput

Throughput measures the capacity of conveyors that handle powdered materials and similar bulk products. It is often given as a volume per unit time, for instance, as cubic feet per minute. This attribute applies to bucket, pneumatic/vacuum, screw, vibrating, and walking beam conveyors.

Frame Configuration

Frame configuration refers to the shape of the conveyor frame. Frames can be straight, curved, z-frames, or other shapes.

Drive Location

Drives can be located in different places on conveyor systems. A head or end drive is found on the discharge side of the conveyor and is the most common type. Center drives are not always at the actual center of the conveyor, but somewhere along its length, and are mounted underneath the system. They’re used for reversing the direction of a conveyor.

Types of Conveyors

  • Belt
  • Roller
  • Powered Roller
  • Slat/Apron
  • Ball Transfer
  • Magnetic
  • Bucket
  • Chute
  • Drag/Chain/Tow
  • Overhead
  • Pneumatic/Vacuum
  • Screw/Auger
  • Vertical
  • Vibrating
  • Walking Beam
  • Wheel

Belt

Belt Conveyors are material handling systems that use continuous belts to convey products or material. The belt is extended in an endless loop between two end-pulleys.  Usually, one or both ends have a roll underneath. The conveyor belting is supported by either a metal slider pan for light loads where no friction would be applied to the belt to cause drag or on rollers. Power is provided by motors that use either variable or constant speed reduction gears.

The belts themselves can be made from numerous materials, which should correspond to the conditions under which the belt will be operating. Common conveyor belting materials include rubber, plastic, leather, fabric, and metal. Transporting a heavier load means a thicker and stronger construction of conveyor belting material is required. Belt conveyors are typically powered and can be operated at various speeds depending on the throughput required. The conveyors can be operated horizontally or can be inclined as well. Belt conveyors can be troughed for bulk or large materials.

Roller Conveyor Systems

Roller Conveyors use parallel rollers mounted in frames to convey product either by gravity or manually. Key specifications include the roller diameter and axle center dimensions. Roller conveyors are used primarily in material handling applications such as on loading docks, for baggage handling, or on assembly lines among many others. The rollers are not powered and use gravity, if inclined, to move the product, or manually if mounted horizontally. The conveyors can be straight or curved depending on the application and available floor space.

Powered Roller

Powered Roller Conveyors use powered rollers mounted in frames to convey products. Key specifications include the drive type, roller diameter and material, and the axle center dimension. Powered roller conveyors are used primarily in material handling applications that require the powered conveyance of the product. Various drive types include belts, chains/sprockets, and motorized rollers. Some of the uses of powered roller conveyors are food handling, steelmaking and, packaging.

Slat Belt Conveyor/Apron

Apron/Slat Conveyors use slats or plates made of steel, wood, or other materials typically mounted on roller chains to convey product. The slats are not interlocked or overlapping. Apron/slat conveyors are used primarily in material handling applications for moving large, heavy objects including crates, drums, or pallets in heavy-industry settings such as foundries and steel mills. The use of slats in heavy duty use cases prolongs the service life of the conveyor over other conveyor types that employ belts, which would wear out quicker under the exposure to heavy loads. These conveyor systems are usually powered and come in many sizes and load capacities.

Ball Transfer Conveyor

Ball Transfer tables or conveyors use a series of mounted ball casters to allow for unpowered, multi-directional conveyance of the product. Key specifications include the ball material and size. Ball transfer conveyors are used in material handling applications such as assembly lines and packaging lines, among others. When positioned where multiple conveyor lines meet, they are used to transfer products from one line to another and are often used in sorting systems. Many sizes and load carrying capacities are available. Ball transfer conveyors are not powered and rely on external forces to move the product along the conveyor.

Magnetic

Magnetic Conveyors use moving magnets mounted beneath stationary plates, tables, or other kinds of non-magnetic slider beds, to move magnetic (ferrous) materials, often in the form of machining scrap. Magnetic conveyors are commonly used as chip conveyors to remove ferrous chips from machining centers. Systems can be configured to use horizontal motion, vertical motion, or combinations. They can be beltless or may use a conveying belt instead of a slider bed. Underneath the conveying belt, a rail containing an electromagnet is used to attract ferrous materials to the belt. Because of the magnetic attraction of the product to the conveyor, these systems can also be used upside down.

Bucket

Bucket Conveyors or bucket elevators use multi-sided containers attached to cables, belts, or chains to convey products or materials. The containers remain upright along the system and are tipped to release material. Bucket conveyors are used in applications such as parts, bulk material, or food processing and handling. The conveyed material can be in liquid form or dry such as sludge, sand, manure, sugar, and grain. The systems can be used horizontally or can be inclined or vertical to change levels of the delivered products. Many sizes and load carrying capacities are available depending on the application.

Chute

Chute or Trough Conveyors are material handling systems that use gravity to convey product along smooth surfaces from one level to another. Key specifications include the chute material and the physical dimensions such as length and chute width. Chute conveyors are used for scrap handling, packaging, postal service package or mail handling, etc.  Chutes are designed to have a low coefficient of dynamic friction, allowing the product or material to slide easily, and can be straight or curved depending on the needs of the application.

Chain/Tow/Drag Line Conveyor

Drag/Chain/Tow Conveyors use mechanical devices attached to moving members, usually chains or cables, to drag or tow products. Drag conveyors are used for moving bulk materials in bins, flights, or other attachments and can have multiple discharge or loading points. Tubular drag conveyors use a fully enclosed system of chains to convey product in any direction. Chain conveyors use a chain, or multiple chains to move pallets or other hard-to-convey products. Tow conveyors use a towline such as cables or chains, usually in the floor or just above it, to tow product directly or to tow wheeled carts or dollies.

Overhead

Overhead Conveyors are mounted from ceilings that use trolleys or carriers moved by chains, cables, or similar connections. Overhead conveyors are primarily used in material handling applications where the product needs to be hung, such as dry-cleaning garment lines, paint lines, or parts handling systems, or for cooling and curing. Various types of overhead conveyor systems configurations are available including electric track, monorail, trolley, as well as inclined or ramped. Depending on the application, the load-carrying capacity may be critical. Most overhead conveyors systems are powered and controlled, while others are hand-operated conveyor belts.

Pneumatic/Vacuum

Pneumatic/Vacuum Conveyors use air pressure or vacuum to transport materials or items in or through closed tubes or ducts or along surfaces. Pneumatic/vacuum conveyors are used primarily in materials handling applications such as dust collection, paper handling, ticket delivery, etc. and in processes such as chemical, mineral, scrap, and food. Materials for the conveyors can be metallic or non-metallic depending on the media being conveyed. Various sizes are available depending on the load and throughput requirements. 

A screw conveyor in a winery pushes grapes to the press.

Image credit: Josef Mohyla/Shutterstock.com

Screw/Auger

Screw conveyors, sometimes known as spiral, worm, or auger conveyors use helical elements to move materials.  They consist of a helical screw element or steel auger that rotates around a central shaft, driving the work material according to the screw design and rotational direction. The helical screw functions within a casing, trough or compartment to take full advantage of the rotational force. Manufacturers use screw conveyors to transport materials such as flakes, grains, powders, seeds, and granules. Alternatively, these devices can be used to mix, agitate or blend such materials, or to maintain solutions. They are used widely in agricultural applications, from use in farm machinery like threshers and balers to factory-based grain and crop movers. A mini screw conveyor can also transport wet, non-flowing and caking materials that might otherwise be difficult to move, such as concrete. Other applications for screw conveyors are the conveying of various mechanical parts or to function as a bottling system conveyor. The screw can be of a paddle or ribbon design depending on the application and can be driven via a chain and sprocket, gears, or direct drive.

Types of screw conveyors include bottom conveyors and centerless screw conveyors. Bottom conveyors use multiple screws in an open trough. Centerless, or shaftless, screw conveyors do not contain a central shaft and instead consist of an empty helix. This design still moves the substrate but allows for more freedom within the casing.  Materials can be metal or non-metal depending on the media being conveyed.

Sets of augers used in the creation of custom screw conveyors

Image credit: Reinke & Schomann, Inc.

Vertical

Vertical Conveyors move products vertically between levels of conveying lines. Key specifications include the lift speed and maximum load height. Vertical conveyors move material or product to higher levels within a facility. They are further classified as continuous lifting or reciprocating. Various sizes and load capabilities are available depending on the application.

Vibrating

Vibrating Conveyors use rotary or linear vibration to move material along their system beds. Vibrating conveyors are used for moving dry, bulk materials such as aggregate, gravel, coal, etc. The bed of the conveyor vibrates to move the material along its length. The conveyor can be a trough, a tube, or a flat table top. Many sizes are available depending on the application.

Walking Beam

Walking Beam Conveyors use a combination of static supports and moving supports to index workpieces through manufacturing cells. Walking beam conveyors are used on automation and assembly lines, where items need to be placed in specific locations in a sequential manner. The item being supported at a stationary position is picked up by the walking beam and indexed to its next position, where another manufacturing step takes place. This movement repeats over the length of the conveyor. Walking beam conveyors can have single or multiple lines depending on the product.

Wheel Conveyor

Wheel Conveyors use unpowered wheels to move objects along their lengths by gravity or manual power. Wheel conveyors are used for item or package handling and are commonly employed for loading and unloading trucks and moving packages, pallets, etc. through facilities or along assembly lines. The conveyors are configured by the number of wheels and wheel spacing, depending on the load requirements and the application.

A belt conveyor in a potato processing factory.

Image credit: 279photo Studio/Shutterstock.com

Conveyor Systems Selection Considerations

When deciding on which conveyor system best suits your needs, a key consideration is the material is being transported. Some important characteristics to consider are size, flowability, abrasiveness, corrosiveness, moisture content, and the temperature at which it must be kept. The composition of the material, if powders, granules, pellets, fibers, or flakes are being conveyed, should also be considered, along with the particle size, weight, and density.

The function of the conveyor system itself may vary. The two main categories of moving material through a process are conveying and feeding. Conveying is the moving of materials from one or more pickup points to one or more drop points. The desired window of time for this movement should be considered, as well as the amount of pickup and drop points, the amount of material being moved, and whether or not cross-contamination between multiple materials is a concern.

Feeding is more time-sensitive and feeder systems need to be more precise than coveying systems. Material is usually moved from one pickup point to one drop point. The product being moved may have to be delivered in batches, or at a controlled, continuous rate.

An essential factor to consider before the selection of a conveyor system is the environment in which it will be used. High humidity, temperature, vibration, pressure, fragile or hazardous materials, and flammable products in the facility should all be discussed with a conveyor manufacturer to determine any potential risks and the countermeasures and workarounds needed. The size of the system compared to how much room in the workspace is available should be considered, along with how it will fit alongside existing equipment.

Conveyors systems are often relatively complex in their design and construction owing to their large scales and integration into different factory processes. Still, the modular nature of many conveyor components makes even long and complex systems readily achievable. Manufacturers of such systems can offer design assistance so that the conveyor suits the workspace.  

Additional Conveyor Systems Selection Factors

Cleats, high friction belting, buckets, etc. are common forms of preventing product slip. A heavily loaded inclined belt conveyor can slip backward when the drive is off. Such conveyors employ backstopping brakes that engage automatically with de-energization of their motors. Often, the brake is releasable to allow the conveyor to reverse for unloading prior to servicing. In some conveyors, a certain amount of slippage is desirable; those handling glass bottles on packaging lines will often employ some form of back-pressure relief to prevent breakage to the bottles as they accumulate in a staging area such as a filler infeed.

A conveyor belt is susceptible to static electricity as the belt is continuously pulled against the end pulleys. If electrical components are being conveyed, static electricity can be hazardous. Anti-static conveyor belt measures such as conductive belts or static control brushes should be considered to protect products.

Other safety considerations must be exercised due to often long conveyor lengths and their proximity to personnel. Live roller conveyors can be furnished with pop-out rollers that disengage from their drive belts if a person’s hand or foot slips between rollers. Crossovers can be used to permit people to pass over long sections of belt conveyors. Roller style conveyors often use manual or powered gate sections to accomplish this.

Conveyors often incorporate some type of soft starter or clutch mechanism to avoid overloading motors when starting fully loaded belts, chains, etc. Some belt conveyors are fitted with geared motor drives that incorporate internal motors and gear drives within the head rollers which eliminate the need for externally mounted motors and power transmission components.

While many conveyor systems are fixed and permanent, a great many are also portable and designed for loading trucks, railcars, silos, etc. Outfeed and infeed conveyors built specifically for packaging operations are often caster-mounted for easy transport within a facility. 

An overhead conveyor carrying the body of a car.

Image credit: TRAIMAK/Shutterstock.com

Conveyor Applications and Industries

Conveyor selection depends on product type, throughput or speed, elevation change, and in some cases, industry focus. Belt conveyors, for instance, come in a variety of sizes and can range from foot-long units used on packaging lines to mile-long systems used for mining operations. Conveyors can be hand powered—where products are moved along manually over rollers or wheels—or engine/motor powered, or gravity powered. In general, though, they are driven by AC and DC motors, either directly or through reduction gears, chains, and sprockets, etc. Products generally ride on the top surfaces of conveyors, though exceptions exist.

Overhead conveyors, as found at dry cleaners, slaughterhouses, or wherever floor space is a concern, suspend their loads from trollies which ride along overhead tracks. Other conveyors, such as screw and pneumatic types, convey their products through semi-enclosed troughs or tubes. These conveyors often handle dry products and powders. Some conveyors are designed to move products precisely between manufacturing operations. Walking beam conveyors are an example of this type. Other conveyors transport hard to handle products, such as cosmetic bottles, through fillers, labelers, and other processes by holding each container in individual pucks or pallets.

Conveyors are sometimes custom designed from modular components such as straightaways, curves, transitions, merges, dividers, etc. Manufacturers of such components often provide design expertise and installation assistance. Other conveyors are stand-alone systems, complete with drives and controls. Manual type roller and wheel conveyors can commonly be purchased in discrete sections and bolted up to form material handling systems of nearly any length. In general, powered conveyors employ head shafts and tail shafts where the head end provides the drive arrangement, and the tail end provides for adjustment of the chain or belt tension.

Conveyor Controls can be simple on/off varieties, slightly more sophisticated soft-start types which cushion loads upon startup, or variable frequency drives that can control the speed, acceleration, etc. of ac motors. Very long belt conveyors transporting ore and other products often rely on conveyor belt idlers to form troughs in the belts to better contain the conveyed materials.

Conveyor Systems - A Summary

This guide provides a basic understanding of conveyor system varieties, considerations for use, their applications, and industrial uses. For more information on related products consult our other articles and guides or visit the Thomas Supplier Discovery Platform to locate potential sources or view details on specific products.

Sources:

Other Conveyors Articles

More from Materials Handling