Matching Application to Use
Effective management of conveyor life begins with the selection of a system that matches the application for which it’s being used. Different applications require relatively different system components and configurations, especially as it applies to load requirements, operational conditions, cycles-of-use, materials conveyed, operational speeds, and usage period. When a conveyor system is improperly designed — i.e., oversized or undersized — value is wasted, regardless of the maintenance procedures employed.
For example, drive motors that are undersized — relative to the loads being conveyed — can overheat, which dramatically reduces motor life, ultimately reducing the value delivered for the dollars invested. Drive motors that are oversized are generally inefficient relative to energy usage, and in some cases, may impose a condition where torque levels are unacceptably high, thereby endangering related components and possibly creating a safety hazard.
Also, equipment with low quality components — such as chain, reducers, and bearings — can quickly fail under load and/or due to the intrusion of various types of contaminates, such as dust or moisture. This reduces not only the value received from the individual components, but if undetected, a resulting failure could cause a line down for repair. This ends up being very expensive for a small savings on an inferior component. Simply, in a system that is interdependent, every component is important to the life and value-producing ability of the system. This means that each component has to be properly specified, sized, and manufactured for the type of service to which it will be exposed.
Fortunately, PHC has teamed up with a number of quality “Product Providers” who along with our knowledge can help in selecting the best products for the equipment that we manufacture. The utilization of this “teamwork” can identify potential system problems, and aid in resolution before they cost anyone time, money, or the safety of their employees.
Planning to Avoid Emergency Repairs
Conveyor maintenance can and should be a straightforward, predictable process — not an emergency event. However, it can easily turn into one. When a system is not properly engineered and manufactured, there will be a significant increase in maintenance requirements, and safety, performance, and reliability may be very unpredictable. But with a properly designed conveyor system, maintenance follows a simple and predictable path.
The proper design of a conveyor system assures that power and loads are well balanced and that stress points are within controlled limits. The forces that occur at start-up and at stops can be quite surprising to anyone who is not familiar with conveyor engineering and the dynamics of applying power to a plastic chain or fabric belt — especially when it is loaded with a significant volume of product, possibly at multiple loading points.
Proper system design is a must for protection of the equipment investment, system safety, system availability, ease-of-maintenance, as well as the long-term, value-producing capability of the entire operation. Even though conveyor systems may be considered one of the safest methods for moving large volumes of material, safety and safety-related issues have to be an ongoing consideration in all maintenance activities.
Maintenance should only be performed with the conveyor system stopped and electrically locked out. No attempts should be made to adjust or touch a conveyor component while it is in operation. Also, it is important to check the entire conveyor for stray tools, parts, or other potential obstacles prior to restarting the system after maintenance activities have been performed.
Additionally, all protective guards and covers should be replaced prior to restarting the conveyor. Note: All personnel involved in the maintenance of a conveyor system should be thoroughly trained in both safety and system operations. Maintenance of a conveyor system is not a task for untrained or inexperienced individuals.
Predictive maintenance to eliminate surprises
There are two basic types of predictive maintenance. One type consists of replacing components at regularly scheduled intervals — usually during scheduled shutdowns — so that total failure of a component is avoided. Another, and somewhat similar, approach to predictive maintenance is to replace components as indicators of excessive wear or impending failure present themselves — which, in some cases, is far more frequent than standard guidelines advise.
An indicator of excessive wear, for example, would be the erosion of the wearstrips whether they be UHMW (ultra-high modular weight), or oil impregnated wood, to the point where the connecting bolts or fasteners are in danger of becoming exposed to the chain or belt in the foreseeable future. Such a condition would warrant the replacement of affected wearstrips at a scheduled shutdown, even if they had a longer life expectancy.
In most cases, however, the replacement interval suggested by the component manufacturer is an excellent guide. Replacement at these pre-determined intervals can go a long way toward preventing operational surprises that require “corrective” maintenance. An important guide to life of the bearings in rotating components is the L10 life. This is a clearly defined lab tested measure of bearing life expectancy under specific conditions. However, this does not apply if bearings are allowed to operate without lubrication or if bearings are overloaded — conditions which “preventive” maintenance activities are designed to minimize.
Preventive Maintenance Extends Component and System Life
Preventive maintenance for conveyors includes the re-lubrication of components at specified intervals, general housekeeping activities — such as removal of any build-up of material around components — as well as special attention to the square alignment of all components and splices. Preventive maintenance can also include the removal and replacement of worn or damaged conveyor sections, chain or belt and replacement of wear items — such as wearstrips, — at appropriate intervals. Maintenance intervals vary depending on the application, hours-of-use, quality of components, and system specifics, so it’s also important to take a look at the installation, operation, and maintenance guidelines provided by the equipment manufacturer.
Corrective maintenance, which involves the replacement of a component after it has demonstrated signs of imminent failure or has in-fact, failed, should be seen as a last resort. A proper system alignment also is a prerequisite for successful maintenance activities. Assuming the conveyor system is properly designed for the application, maintenance procedures begin with proper alignment of the system and its components.
It’s also recommended that conveyor systems be visually inspected on a regular basis by traversing the length of the system on both sides, if possible, while it is in operation and when it is stopped and electrically locked out. Inspection frequencies vary, dependent on operational conditions, but in general, they should occur daily.
Chain/belt surfaces and edges should be inspected for wear or damage. Splice points deserve special attention, especially because it is important to identify and repair damaged or failing splices at the earliest possible opportunity.
Attention to the condition and wear indicated on the chain/belting is important because the conveyor chain/belt is the single most expensive component of the conveyor system. In fact, most conveyor maintenance activities are directed to system components that could potentially damage the chain/belt, if they are ignored. This activity is designed to preserve the value of the chain/belt, and not the component, per se. Actually, conveyor components — such as bearings and wearstrips — are quite inexpensive relative to the cost of the conveyor’s belting.
Problems with bearings and rolling components may be prevented or minimized through the use of well-engineered — i.e. quality — components and through re-lubrication at appropriate intervals (when “relubricable” components are employed). Note: When using “relubricable” bearings, it is best to choose bearings with self-purging seals, which, upon re-lubrication, move contaminates away from the bearing area and push them out through the seal.
Good Housekeeping to Keep a Conveyor at Peak Performance
During visual inspection of a conveyor system, all areas of material buildup should be noted and subsequently removed at shutdown. No attempt should ever be made to remove built-up material while the system is in operation or not electrically locked out.
The causes of material buildup should always be explored, as it may be a sign of misaligned components, improperly fitted wearstrips, or overloading of the system. In general, all maintenance problems should be traced back to their root causes so that genuinely corrective actions can be initiated.
Impact and material transfer areas are exposed to extreme — and potentially damaging forces — and requires special attention, relative to wear and damage. Obviously, any damaged or worn component should be replaced as soon as it is practically possible (i.e., availability of replacement parts, enough shutdown time to accomplish change out, etc.). Likewise, unusually wet or dusty areas of the conveyor system warrant special attention during inspections. If problems are detected, it may be appropriate to retrofit these areas with specialized components and/or lubricants.
Qualified personnel should test all electrical and electronic systems on the conveyor periodically, while always referring to the recommendations of the equipment manufacturer. It is important to verify that all functional, interlock, and safety systems are operating as designed. (This area of inspection should include a check of emergency pull-cord and e-stop switches.)
Proper Equipment, Proper Maintenance
In the converting industry, as in virtually every other industry, preserving and protecting people, productivity, and profits is a full-time job. That’s why regular attention to the maintenance of an important system, such as conveying, is a vital part of the job, too. It is just too important to be left to chance and, when properly organized, it is efficient, effective, and non-disruptive. Ultimately, maintenance doesn’t cost, it pays — and it’s all about getting your money’s worth.
Protecting all parts
To obtain the optimum return on your conveyor investment, the following components that typically make up a conveyor system must be maintained:
- Take-up systems
- Catenary sag
- Control equipment
- Table top chain
- Return components
- Tail sections
- Impact-loading equipment
- Equipment guards
- Specialized components associated with site-specific activities
Check out our handy checklist to maintain efficient and long lasting operation of your conveyor system.