A conveyor system is a common piece of mechanical handling equipment that moves materials from one location to another. Conveyors are especially useful in applications involving the transportation of heavy or bulky materials. Conveyor systems allow quick and efficient transportation for a wide variety of materials, which make them very popular in the material handling and packaging industries. They also have popular consumer applications, as they are often found in supermarkets and airports, constituting the final leg of item/ bag delivery to customers. Many kinds of conveying systems are available and are used according to the various needs of different industries. There are chain conveyors (floor and overhead) as well. Chain conveyors consist of enclosed tracks, I-Beam, towline, power & free, and hand pushed trolleys.
Conveyor systems are commonly used in many industries, including the Mining, automotive, agricultural, computer, electronic, food processing, aerospace, pharmaceutical, chemical, bottling and canning, print finishing and packaging. Although a wide variety of materials can be conveyed, some of the most common include food items such as beans and nuts, bottles and cans, automotive components, scrap metal, pills and powders, wood and furniture and grain and animal feed. Many factors are important in the accurate selection of a conveyor system. It is important to know how the conveyor system will be used beforehand. Some individual areas that are helpful to consider are the required conveyor operations, such as transportation, accumulation and sorting, the material sizes, weights and shapes and where the loading and pickup points need to be.
Increasing the service life of a conveyor system involves: choosing the right conveyor type, the right system design and paying attention to regular maintenance practices.
A conveyor system that is designed properly will last a long time with proper maintenance. Here are six of the biggest problems to watch for in overhead type conveyor systems including I-beam monorails, enclosed track conveyors and power and free conveyors. Overhead conveyor systems have been used in numerous applications from shop displays, assembly lines to paint finishing plants and more.
Poor take-up adjustment: this is a simple adjustment on most systems yet it is often overlooked. The chain take-up device ensures that the chain is pulled tight as it leaves the drive unit. As wear occurs and the chain lengthens, the take-up extends under the force of its springs. As they extend, the spring force becomes less and the take-up has less effect. Simply compress the take-up springs and your problem goes away. Failure to do this can result in chain surging, jamming, and extreme wear on the track and chain. Take-up adjustment is also important for any conveyor using belts as a means to power rollers, or belts themselves being the mover. With poor-take up on belt-driven rollers, the belt may twist into the drive unit and cause damage, or at the least a noticeable decrease or complete loss of performance may occur. In the case of belt conveyors, a poor take-up may cause drive unit damage or may let the belt slip off of the side of the chassis.
Lack of lubrication: chain bearings require lubrication in order to reduce friction. The chain pull that the drive experiences can double if the bearings are not lubricated. This can cause the system to overload by either its mechanical or electrical overload protection. On conveyors that go through hot ovens, lubricators can be left on constantly or set to turn on every few cycles.
Contamination: paint, powder, acid or alkaline fluids, abrasives, glass bead, steel shot, etc. can all lead to rapid deterioration of track and chain. Ask any bearing company about the leading cause of bearing failure and they will point to contamination. Once a foreign substance lands on the raceway of a bearing or on the track, pitting of the surface will occur, and once the surface is compromised, wear will accelerate. Building shrouds around your conveyors can help prevent the ingress of contaminants. Or, pressurize the contained area using a simple fan and duct arrangement. Contamination can also apply to belts (causing slippage, or in the case of some materials premature wear), and of the motors themselves. Since the motors can generate a considerable amount of heat, keeping the surface clean is an almost-free maintenance procedure that can keep heat from getting trapped by dust and grime, which may lead to motor burnout.
Product handling: in conveyor systems that may be suited for a wide variety of products, such as those in distribution centers, it is important that each new product be deemed acceptable for conveying before being run through the materials handling equipment. Boxes that are too small, too large, too heavy, too light, or too awkwardly shaped may not convey, or may cause many problems including jams, excess wear on conveying equipment, motor overloads, belt breakage, or other damage, and may also consume extra man-hours in terms of picking up cases that slipped between rollers, or damaged product that was not meant for materials handling. If a product such as this manages to make it through most of the system, the sortation system will most likely be the affected, causing jams and failing to properly place items where they are assigned. Any and all cartons handled on any conveyor should be in good shape or spills, jams, downtime, and possible accidents and injuries may result.
Drive train: notwithstanding the above, involving take-up adjustment, other parts of the drive train should be kept in proper shape. Broken O-rings on a Lineshaft, pneumatic parts in disrepair, and motor reducers should also be inspected. Loss of power to even one or a few rollers on a conveyor can mean the difference between effective and timely delivery, and repetitive nuances that can continually cost downtime.
Bad belt tracking or timing: in a system that uses precisely controlled belts, such as a sorter system, regular inspections should be made that all belts are traveling at the proper speeds at all times. While usually a computer controls this with Pulse Position Indicators, any belt not controlled must be monitored to ensure accuracy and reduce the likelihood of problems. Timing is also important for any equipment that is instructed to precisely meter out items, such as a merge where one box pulls from all lines at one time. If one were to be mistimed, product would collide and disrupt operation. Timing is also important wherever a conveyor must "keep track" of where a box is, or improper operation will result.
Since a conveyor system is a critical link in a company's ability to move its products in a timely fashion, any disruption of its operation can be costly. Most downtime can be avoided by taking steps to ensure a system operates at peak performance, including regular inspections, close monitoring of motors and reducers, keeping key parts in stock, and proper training of personnel.
Vertical lift conveyors contain two adjacent, parallel conveyors for simultaneous upward movement of adjacent surfaces of the parallel conveyors. One of the conveyors normally has spaced apart flights (pans) for transporting bulk food items. The dual conveyors rotate in opposite directions, but are operated from one gear box to ensure equal belt speed. One of the conveyors is pivotally hinged to the other conveyor for swinging the attached conveyor away from the remaining conveyor for access to the facing surfaces of the parallel conveyors. Vertical lift conveyors can be manually or automatically loaded and controlled. Almost all vertical conveyors can be systematically integrated with horizontal conveyors, since both of these conveyor systems work in tandem to create a cohesive material handling assembly line.
Like vertical conveyors, spiral conveyors raise and lower materials to different levels of a facility. In contrast, spiral conveyors are able to transport material loads in a continuous flow. A helical spiral or screw rotates within a sealed tube and the speed makes the product in the conveyor rotate with the screw. The tumbling effect provides a homogeneous mix of particles in the conveyor, which is essential when feeding pre-mixed ingredients and maintaining mixing integrity. Industries that require a higher output of materials - food and beverage, retail case packaging, pharmaceuticals - typically incorporate these conveyors into their systems over standard vertical conveyors due to their ability to facilitate high throughput. Most spiral conveyors also have a lower angle of incline or decline (11 degrees or less) to prevent sliding and tumbling during operation.
Like spiral conveyors, vertical conveyors that use forks can transport material loads in a continuous flow. With these forks the load can be taken from one horizontal conveyor and put down on another horizontal conveyor on a different level. By adding more forks, more products can be lifted at the same time. Conventional vertical conveyors must have input and output of material loads moving in the same direction. By using forks many combinations of different input- and output- levels in different directions are possible. A vertical conveyor with forks can even be used as a vertical sorter. Compared to a spiral conveyor a vertical conveyor - with or without forks - takes up less space.
Vertical reciprocating conveyors (or VRC) are another type of unit handling system. Typical applications include moving unit loads between floor levels, working with multiple accumulation conveyors, and interfacing overhead conveyors line. Common material to be conveyed includes pallets, sacks, custom fixtures or product racks and more.
Other types of heavy-duty roller conveyors are gravity roller conveyors, chain-driven live roller conveyors, pallet accumulation conveyors, multi-strand chain conveyors, and chain and roller transfers.
Gravity roller conveyors are easy to use and are used in many different types of industries such as automotive and retail.
Chain-driven live roller conveyors are used for single or bi-directional material handling. Large, heavy loads are moved by chain driven live roller conveyors.
Pallet accumulation conveyors are powered through a mechanical clutch. This is used instead of individually powered and controlled sections of conveyors.
Multi-strand chain conveyors are used for double-pitch roller chains. Products that cannot be moved on traditional roller conveyors can be moved by a multi-strand chain conveyor.
Chain and roller conveyors are short runs of two or more strands of double-pitch chain conveyors built into a chain-driven line roller conveyor. These pop up under the load and move the load off of the conveyor.
M.Marcu-Pipeline Conveyors (theory,photos,state of the art 1990-Pneumatic Pipeline conveyors with wheeled containers) at page 45 in: "Material handling in pyrometallurgy: proceedings of the International Symposium on Materials Handling in Pyrometallurgy, Hamilton, Ontario, August 26–30, 1990-Pergamon press"