Conveyor Systems

Chapter One – What is a Conveyor System?

A conveyor system is a mechanism designed for transporting packages, products, supplies, parts, and equipment for various purposes such as production, shipping, or relocation. The different types of conveyor systems include pneumatic, screw, belt, and roller. The design of each system depends on the characteristics of the materials being moved, such as their weight, dimensions, and transportability.

Though conveyor systems are essential for material handling and production, they are also used in various production applications such as sintering, part and assembly finishing, and part washing. In most cases, these systems are automated, but non-automated designs using chutes and rollers are also common in retail, material handling, and shipping applications.

Chapter Two – What Are The Conveyor System Requirements

A conveyor system can be integrated into an operation in numerous ways to boost efficiency and speed. Before deciding to install a conveyor system, it's crucial to consider several important factors. Each system is tailored to meet the specific demands of its intended application.

Space

Conveyor system manufacturers assess the available space to determine the optimal system design. This process involves identifying interaction points, clearances, obstructions, and any potential areas that could hinder material movement. While automated systems are the most common, the specific application will dictate whether the system should be motorized or manual.

Load Capacity

After the system layout and pattern have been established, the next step is to determine its material carrying capacity. Overloading the system can lead to damage or operational interruptions. Factors influencing load capacity include the system's overall length, bed width, and drive system.

Speed

The speed of a conveyor system is measured in feet per minute (fpm). The average speed for most conveyor systems is 65 fpm, which is roughly equivalent to the pace of a person carrying a 50 lb package. However, this speed can be adjusted up or down to suit specific applications.

Powder or Liquid Material Handling

Handling powdered materials involves different parameters compared to conveying systems for solid, bulky items. A well-designed powder and liquid conveying system must be adequately sealed to prevent any escape of the materials. The movement of powdered, granular, and chip-type materials can result in dust buildup, which must be addressed in the system design and may require filtration. As with other conveyor systems, a careful examination of the material's characteristics is essential.

Configuration

Conveyor systems come in a wide variety of shapes, designs, sizes, and forms. They can be vertical, angled, horizontal, curved, or equipped with pockets, slats, and z-frames. Each system is tailored to meet a specific application, making it impractical to cover all possible configurations. However, it is important to understand that there are very few limitations on integrating a conveyor system, regardless of the application.

Drive System

The drive in an automated conveyor system provides the power to move materials. It includes a counter bearing to ensure continuous movement along the belt. These drives can be designed to move items in both directions and can be positioned at the system's middle, end, or beginning. Overhead systems, while similar, often use chain or sprocket drives. For liquids, granular materials, and powders, conveyor systems may utilize pneumatic power or screw drives.

Drive systems can feature single or variable speeds based on their design. Typically, they use a motor-driven gear system. Variable speed drives have gained popularity in modern conveyor systems because they enable adjustments to material flow.

Safety

Drive systems can feature single or variable speeds based on their design. Typically, they use a motor-driven gear system. Variable speed drives have gained popularity in modern conveyor systems because they enable adjustments to material flow.

In the image below, observe the emergency stop button, the keyed motor activation, and the symbols indicating conveyor operation.

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Chapter Three – Types of Conveyor Systems

Conveyors come in a wide range of types, designs, and processes. The most common types include belt, roller, and overhead conveyors, which fall into two main categories: overhead and floor-mounted. Conveying systems offer numerous benefits and are a standard component of large-scale operations.

Belt Conveyors

Belt conveyors are the most common and straightforward type of conveyor and can operate at variable speeds. They consist of a moving belt mounted on a steel frame that supports both the belt and the materials being transported. If the belt is supported by a frame underneath, it is known as a sliding style. When the belt is supported by closely spaced rollers, it is referred to as a roller belt style.

Gravity Roller Conveyors

Gravity roller conveyors consist of a series of evenly spaced rollers attached to a side frame. These rollers create a surface for placing materials for movement. When the conveyor is tilted or angled, materials move by gravity. While gravity roller conveyors can handle items of varying sizes, care must be taken to prevent larger materials from colliding with smaller ones. These conveyors are commonly used by shipping companies for loading and unloading trucks.

Chain Conveyors

Chain conveyors can feature one or multiple sets of chains that come into contact with the bottom of the items being transported. Materials rest on these chains as they move. Chain-driven conveyors are well-suited for items with uneven bottom surfaces or those that are very heavy. They can support pallets placed directly on their robust frames. Due to the nature of the items they handle, chain conveyors typically operate at a slower pace.

Motorized Roller Conveyors

Motorized roller conveyors utilize motors positioned along the conveyor frame to power evenly spaced rollers. This design resembles a gravity conveyor but includes the addition of motors. The number of motors depends on the load being moved and the overall system design. Rollers are connected by either a chain or belt. Some systems are equipped with sensors that start and stop the motors to prevent pieces from bunching together.

Slat Conveyors–

Slat conveyors are designed similarly to chain conveyors but use flat slats connected to the chain instead of a belt. In this way, they resemble belt conveyors, with slats serving as the conveyor surface in place of the belt.

Slat conveyors are similar to chain conveyors, but they use flat slats connected to the chain instead of a belt. This design makes them comparable to belt conveyors, with slats providing the conveyor surface in place of the belt.

Overhead Conveyor Systems

There are various types of overhead conveyor systems, each with a distinct design but serving similar functions. The primary purposes of overhead conveyors are to optimize floor space and facilitate the efficient and easy movement of parts and components.

Enclosed Track Conveyor - An enclosed track conveyor features an enclosure that fully covers the trolley connectors, leaving only a small gap for trolley movement. This design protects the track from wear and simplifies the incorporation of bends and curves into the system.

Open Track Conveyors - Open track conveyors use I-beams as the track and do not have an enclosure covering it. They are easy to install and are well-suited for long, straight configurations.

Chain overhead conveyors use a continuously powered chain that travels along a track. Pendants are attached to the chain at regular intervals, allowing parts or products to hang from them. In other designs where pendants are not used, pusher dogs can move trolleys along a second track positioned below the chain track. This configuration is known as a power and free system.

Monorail Conveyors

Monorail conveying systems use carriers to transport materials over long distances and are ideal for this purpose. The rails are suspended from the building structure and receive power through signal lines from conductor lines embedded within the mounted rails. Monorail conveyors effectively utilize overhead space in the production area. In some designs, the carriers can lower to the production level and then rise out of the way when not in use.

Power and Free Conveyors

Power and free conveying systems are designed to transport parts through production and assembly processes. Items move from one workstation to another, stopping at each station for work before continuing to the next. This type of system is a specialized form of overhead conveyor system.

The distinctive design of power and free systems enables products to be buffered along the conveyor path, start and stop automatically, and offers high versatility and adjustability. Unlike continuous flow chain conveyors, power and free systems allow for individual loads to be halted for adjustments.

Inverted Conveyors

Inverted conveyors are floor-mounted and can function as power and free conveyors. They typically use a drive system that does not rely on belts or chains.

Paternoster Conveyors

Paternoster conveyors are a vertical conveying system featuring equally spaced load carriers connected to a chain drive, operating in a continuous loop. They are also referred to as platform conveyors.

Chute Conveyors

Chute conveyors consist of a smooth, flat surface made from wood, metal, or plastic, angled within a frame that can be straight, spiral, or circular. Items slide down the surface due to gravity.

Screw Conveyors

Screw conveyors are used to transport bulk materials such as granular products, chips, and loose substances. They feature a rotating helicoid mounted on a shaft inside a pipe. Also known as auger, helix, or spiral conveyors, screw conveyors have blades designed to lift the material upwards.

Pneumatic Conveyors

Pneumatic conveyors move bulk materials using pressurized air to push the material through a sealed pipeline. As the pressure increases within the pipeline, powders or granular materials are lifted and transported through the pipe.

Vibratory Conveyors

A vibrating conveyor utilizes vibrations to move materials along a trough, making it suitable for items like grains, various solids, vegetables being harvested, and quarried rocks. The vibrations create a gentle, continuous motion that transports products through the conveyor. Each type of vibratory conveyor is designed for its specific application, with significant differences between those used in mining and those designed for harvesting or food production.

One of the major advantages of vibrating conveyors is their outstanding performance in the harshest conditions and environments.

Chain on Edge Conveyors (COE)

A chain on edge conveyor is a single-strand chain conveyor that operates on its side, utilizing a roller chain that moves within a plate-supported channel. This design allows the chain to flex along the horizontal axis, enabling it to navigate horizontal turns and vertical curves. The ability to make various twists and turns makes the chain on edge conveyor more versatile than traditional chain-driven conveyors.

Skid Conveyor

Skid conveyors are a type of floor-mounted conveyor that moves products on fixtures equipped with longitudinal runners known as skids, allowing movement both longitudinally and transversely. Key elements of a skid conveyor system include power rollers, pivot tables, shuttle carriages, and two-strand chain systems. These conveyors are appreciated for their efficiency and quiet operation. Variations in skid conveyor systems arise from the diverse components and control systems that can be incorporated.

Friction Conveying System

A friction conveying system employs a motor to drive a friction wheel made of non-metallic material, generating the driving force. The system includes a friction drive, load-bearing track, switch, stopper, trolley, elevator, and steel structure. Friction conveying systems offer a safe alternative to power and free systems, providing the advantages of cleaner and quieter operation. They feature a flexible layout, modular construction, easy speed adjustment, straightforward expansion, and a low overall cost.

The primary purpose of friction conveying systems is to support operations with high production rates. Depending on their design, these systems can be inverted or overhead. They transmit force directly to a skid, slide, pallet, or carrier using a friction wheel.

Chapter Four – How does a Conveyor System Work?

Conveyor systems are a crucial component of a larger production process. To understand how a system functions, it's essential to examine all aspects of the overall production process and how the various components interconnect. Much of the system's functionality is established during the design phase. Once operational, the system's intricate mechanics become vital to the efficiency and success of the operation.

How a Conveyor System Works

To narrow the discussion on conveying systems, the information below focuses on belt conveying systems, as they are the most commonly used.

Belt

Belt conveyors operate using motorized pulleys with a thick, durable belt looped around them. When the motor is activated, the belt is pulled between the pulleys.

Support System

The support system ensures the belt moves smoothly by holding the material without sagging. During the design phase, the weight capacity of the frame is determined, and the frame is constructed to meet the operational requirements.

Pulleys

Conveyor belt systems typically include at least two pulleys: a drive pulley and a tail or return pulley. Positioned between them are idler or dummy pulleys that are driven by the belt. The drive pulley moves the load, while the tail pulley returns the belt. As illustrated in the diagram, idler pulleys play several roles in guiding the belt, including controlling its tension.

Belt Cleaner

The purpose of a belt cleaner is to remove any carryback that remains on the belt after the load has been discharged. Carryback is a common issue in all belt systems and is a major cause of belt malfunctions.

Drive

The drive for the belt can be located in various positions in the conveying system. For most belt conveyors, the drive is located at the discharge or head of the belt. Other locations can be anywhere along the belt depending on the design. AC motors are generally used to power the pulley that moves the belt.

Chapter Five – What Are Conveyor System Applications

As automation and production technology have advanced, conveyors have quickly become a crucial component in material processing and movement, significantly enhancing the speed of various production operations.

Conveyor System Applications

Sintering

Sintering is a production process that heats a material just below its melting point to shape and form it. Conveyors are used to transport the material into high-temperature furnaces for the sintering process.

Packaging

A packaging conveyor is designed to assist with product packaging, such as placing finished products in containers, efficient labeling, or preparation of products for shipping. The function of a packaging conveyor system is to move products from completion and assembly for shipment. They provide a safe method of moving materials and avoid the need for employees to carry heavy items.

Production Line

A production line conveyor is designed to bring work to workers, eliminating the need to move the assembly crew. The advantages of a production line conveyor include efficiently moving products through each step of the assembly process, allowing tasks to be performed effectively. Raw materials enter at the start of the assembly process and are transformed into a completed product by the end.

Pharmaceutical

The pharmaceutical industry needs specially designed conveying systems that can be installed in sterile environments while remaining flexible, reliable, and easily accessible to prevent contamination. Pharmaceutical conveyors handle products moving in and out of sterilization processes that use toxic chemicals, necessitating the use of materials that can withstand such exposure.

Metalworking

The growing demands in metal production have led to an increased use of conveying systems to boost productivity and efficiency. Conveying systems enable precise and accurate completion of various metalworking processes. They accelerate cutting and molding operations, facilitating the rapid production of large quantities of products. Press-out conveyors, in particular, are used to remove molded pieces from the pressing line or transfer them to other operations.

Airport

While airports use people-moving conveyors, the primary conveying system is designed for luggage handling. This system streamlines the process of transporting luggage from the check-in counter to the airplane and from the airplane to the baggage claim area. These highly sophisticated and complex systems minimize manual handling and efficiently move packages and bags. Airport conveying systems include various types, such as angled, vertical, and horizontal conveyors.

Mining

Conveyors are crucial for mining operations, efficiently moving raw materials while withstanding harsh conditions. Since many mining sites are in remote locations difficult for trucks to access, mining conveyors eliminate the need for truck access roads. Although mining conveyors come in various sizes and lengths, most are inclined and handle several tons of material. To prevent spillage or gaps, they must be evenly loaded. Depending on their design, they can operate at speeds of up to 100 feet per minute.

Automotive

The automotive industry employs various types of conveyors for material handling, facilitating the movement of parts and car bodies between operations. These conveyors are particularly effective for transporting heavy items like doors, bumpers, chassis, and frames.

Food Processing

Food conveyors transport food and organic materials efficiently and cost-effectively compared to manual labor. The term "food conveyor" encompasses various systems, including rollers, belts, and dumpers, used to move food products through the manufacturing process. Like all conveying systems, food processing conveyors are tailored to meet the specific needs of the manufacturer and application. What sets them apart is the need to comply with stringent governmental regulations for sanitation and cleanliness.

Printing

Printing conveyors, used in screen printing, employ conveyor dryers to dry screen-printed materials. While other drying methods exist, conveyor dryers are preferred for high-volume production and come in various types. During the drying process, hot air is applied to the garment at a controlled temperature and with an even flow as it moves along the conveyor system.

Chapter Six – What Are The Benefits of a Conveying System

Conveyors have become integral to manufacturing, mining, production, and finishing operations. They enhance efficiency, reduce labor costs, and contribute to higher volumes and increased production. Additionally, conveyors help prevent injuries by automating material handling tasks.

Regardless of the industry, conveyors have consistently proven to enhance production processes.

Benefits of Conveying Systems

Time Savings

Materials can be moved quickly and easily from one location to another or between different levels.

Continuous Operation

Materials can be continuously loaded and unloaded over extended periods without interruption or stoppage.

Automated Unloading

Conveyors can be designed to automatically unload materials, eliminating the need for manual labor.

Control of Movement

Conveying systems feature speed controls to regulate the rate at which items move, reducing concerns about handling issues or breakage.

Directional

While older conveying systems could only move in one direction, modern conveyors equipped with CNC controls can move both forward and backward, allowing for greater flexibility in adjusting manufacturing operations.

Low Maintenance

TMost conveyors require minimal maintenance; however, some types with motors and components need regular checks and replacements. Maintenance needs vary based on the conveyor's usage and operating environment.

Safety

Conveyors are the safest method for transporting materials through a facility or production floor. They are equipped with built-in on/off switches, emergency stop buttons, and speed controls. The image below shows a safety cable stop for conveyors.

High Volume

Conveyors are integral to automated systems, capable of moving hundreds or even thousands of tons of material per hour or per day.

Chapter Seven – What Are Some Conveying System Malfunctions

Continuous use of a conveying system can lead to various malfunctions. Many of these issues can be prevented through regular maintenance checks.

Conveying System Malfunctions

Mistracking

Mistracking, also known as belt drift, occurs when the belt shifts to one side. A misaligned belt can cause significant damage through uneven wear or by damaging items on the belt. The image below shows a belt that has drifted to the left.

Seized Rollers

Mistracking issues may be linked to a seized roller, which can cause sharp edges and potentially shut down the system. As conveyor systems are typically made of metal, a seized roller can develop these sharp edges.

Slippage

Slippage on a belt conveyor can happen if the tension is either too high or too low, leading to belt stretching and subsequent slippage.

Blockage

Conveyor systems are designed to operate continuously without interruption or stoppage. Any form of blockage can be damaging to the system and lead to major repairs.

Carryback

There are several types of carryback, with the most common being when material adheres to the belt and continues past the transfer point before falling off. An example of carryback is shown at the bottom of the image below.

Spillage

When a belt conveyor is overloaded or overly packed, materials can spill off the sides. This issue may arise due to inadequate employee training or problems upstream in the system.

Unload or Chute Blockage

Unload problems arise when material does not flow correctly from the conveyor at the offload point, potentially causing the entire system to shut down.

Pneumatic Systems

Pneumatic blower packages are highly reliable and typically have a long operational life. The first indication of a problem is often a change in system pressure, which can signal issues such as feeding problems, buildup in the line, uneven feed, or a clogged pipe. In most pneumatic conveying systems, potential problem areas include the blower package, conveying line, bin vents, filter, or airlocks. The image below shows product buildup in the line.

Screw Conveyors

Fatigue in a screw conveyor occurs when material accumulates in the pipe as the conveyor turns. A gap always exists between the pipe wall and the screw blades, where material collects and hardens. As the screw turns, this material breaks up and moves along in solid form. Occasionally, solidified material can remain, causing the screw to work harder and placing additional strain on its centerline.

Conveyor System Maintenance

Although a conveying system may appear to be a single machine, it is actually a complex system of interconnected components that rely on each other to function effectively. To maintain a conveying system and prevent issues, it is crucial to inspect each individual component and understand its role in the overall operation.

Repair or Replace

Deciding to replace a component in a system involves several cost factors, including system downtime, sourcing the correct component, and hiring a specialist for the replacement. These expenses can be mitigated through regular maintenance and monitoring of the system.

Motor

The motor is a crucial component of a conveying system. Most motor failures are due to issues with bearings and windings, with bearings being the primary cause. Bearing failures are often related to lubrication problems, which can be prevented through regular maintenance and lubrication. Additionally, the motor's temperature should never exceed its recommended operating range.

Pulley Bearings

Pulley bearings are fully lubricated to protect against water and contaminants. When regularly inspected and maintained, they typically do not require repairs. Manufacturers recommend scheduling maintenance based on the frequency of system use.

Cleaning

Regardless of the system type, regular cleaning is crucial. Belts, rollers, chains, motors, slats, and all accessible areas should be cleaned routinely. This is particularly important for systems handling products with treatments or coatings, as these substances can lead to contamination and potential damage to components.

Belt Tracking

Premature wear on belt conveyors can result from improper belt tracking, which should be checked each time the belt is activated. Issues with belt tracking may arise from misuse, environmental factors, or inadequate maintenance. Neglecting these aspects can lead to costly repairs.

Pneumatic Pressure

Many conveying systems include pneumatic components. Regular maintenance should involve adjusting pressure, flow control, and regulators as needed. It is crucial to maintain pipeline pressure according to system specifications, as excessive pressure can damage individual components.

Grounding

Conveying systems can be affected by stray voltages, which may short-circuit the system. Proper grounding can help prevent this issue.

Chapter Eight – What Are The Conveying System Safety Requirements

The Occupational Safety and Health Administration (OSHA) offers guidelines for operating conveying systems, while the American National Standards Institute (ANSI), in conjunction with the American Society of Mechanical Engineers (ASME), provides safety standards for conveyor design.

Every year, OSHA and ASME review and update these requirements to incorporate new technology and advancements.

OSHA Guidelines

1926.555(a)

General requirements.

1926.555(a)(1)

A motor stoppage switch must be located at the operator position. The system should have a warning light with sound that activates when the system is turned on.

1926.555(a)(2)

Remote operations must have a stoppage switch at the motor.

1926.555(a)(3)

Emergency stop switches prevent reactivation of the system until the emergency switch is reset to "ON".

1926.555(a)(4)

Protective coverings and safeguards are required for screw conveyors.

1926.555(a)(5)

Overhead conveyors must be equipped with protective coverings underneath, even if the conveyor is positioned away from employees.

1926.555(a)(6) & 1926.555(a)(6)

Warning signs should be posted at crossovers, aisles, and passageways.

1926.555(a)(7)

Conveyors should be locked out or have warning signs posted during routine maintenance.

1926.555(a)(8)

Conveyors must be built and maintained in accordance with the ANSI B20.1-1957 Safety Code for Conveyors, Cableways, and Related Equipment.

ASME Guidelines

Safety standards for conveyors are outlined in ASME B11.0-2020, which addresses the safe use of machinery and specifies various safety devices to be included in the installation and construction process.

ASME B20.1-2018

ASME B20.1-2018 provides guidelines for the design, construction, maintenance, and operation of conveying systems with a focus on safety and hazard prevention. It is intended for industrial conveyors and does not apply to those designed for transporting people.

ASME B20.1-2018 is part of a set of specifications that also includes ASME B20.1, ANSI B11.19, ANSI A1264.1, and ANSI 244.1. These standards cover safety guidelines for conveyors and walking surfaces.

ASME B20.1 and ANSI B11.19

ASME B20.1-2018 outlines requirements for the construction, installation, maintenance, inspection, and operation of conveying systems.

ASME B20.1, ANSI B11.19, ANSI B11.0

These provide additional details on safety procedures for permanent, temporary, and portable conveyors.

Conclusion

• Conveying systems are an essential part of automation and production.
• Each conveying system is developed to fit a specific application.
• Though belt conveying systems are the most and easily recognizable, other types include screw, pneumatic, chute, and roller.
• As with any form of machine, conveying systems require regular maintenance.
• Safety is essential with conveying systems. OSHA and ASME provide guidelines and regulations regarding the use and construction of conveying systems.

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