BY Sandy Lender
Learning to use blending and loadout controls at the asphalt plant is only one portion of today’s plant operator’s job. AsphaltPro asked a number of controls and plant OEMs to share specifically how the plant operator or ground personnel can participate in the routine maintenance of controls to keep unplanned downtime at bay. Here are some suggestions for your operation, in alphabetical order by responding company.
How an operator troubleshoots controls varies greatly depending on the company he works for, their safety policies. In some cases he can’t even open the cabinet to look at the controls; the work must be done by an electrician. If he suspects it is an electrical problem, an electrician is called in. If he suspects a mechanical problem, several other types of specialist could be called in until the problem is identified and enough people are on site to solve all aspects of the problem. Some controls systems…will detect a component failure for the operator and pop up a help screen with troubleshooting instructions to guide the operator to the problem resolution step by step. Other systems may simply post an error message and the operator must determine the cause and resolve it on his own. And finally, some systems only sound an alarm and maybe blink a light to indicate the area of concern.
A good maintenance program can prevent many issues from occurring. Electrically, each wire termination point should be tightened at least once a year. Loose wiring is a frequent cause of intermittent failures which can be difficult to identify. Safety systems should be checked on a regular basis. Lubrication and cleaning of the equipment is also critical. A good operator will learn the sound of a properly operating plant and is attune to any changes to that sound or noises that are not typical. These can be early indications of a maintenance need before a shutdown occurs and save thousands of dollars in repair cost and lost production.
Caretaking of the controls themselves, like any other computer based system, requires typical IT skills to make sure the system stays virus free, that hard drives are working properly and not getting cluttered, that the computer is staying cool and that the computer itself is free of accumulated dust on its components.
Windows security updates and proper firewall management is important to combat the ever increasing threat of malware attacks. If a system does not need to be connected to the internet 24/7, disconnect it for absolute guarantee that a virus will not penetrate through that connection; only reconnect it when needed. Hard drive utilities are built into the operating system for maintaining the hard drive. Check the temperature of the computer cabinet and clean air filters like you would for your home AC system. Canned air can be purchased for blowing dust off of the motherboard and other electronic components. Dust on a circuit board traps heat in the electronics and can also short out sensitive circuits causing premature failure.
Libra Systems, Inc.
Plant control automation is the heartbeat of an asphalt plant and is interfaced to the various plant devices, including solenoids, motors, limit switches, valves, tachometers, load cells and thermocouples. When these devices fail, or are prevented from performing their intended function, the symptoms of the problem are typically first noticed at the automation. A modern automation system will include input/output (I/O) diagnostic screens help to pinpoint the problem area, or assistance can be provided from the automation manufacturer. Plant automation is only as accurate as the sensors that are sending the required information, so it is very important that all of these devices and the interconnecting wire are maintained in good working order.
When troubleshooting electrical problems, it is very helpful for the operator to have access to a multi-meter, which measures current, voltage and resistance. Current clamps also allow electric current to be measured without having to make physical contact or disconnect the conductor.
It is important to control the environment by keeping dust around the computers and electronics at a minimum.
Temperature and air quality can prolong the life of most automation components. With this in mind, it is a good idea to blow out the PC and printer once or twice a year to prevent dust from blocking sensors and or burning out fans.
Electrical wiring should be clean, orderly and easily traceable. All wires should be labeled. Wiring diagrams should be current and maintained in a secure location.
The power source supplying power to parts of the automation should be protected from power fluctuations such as brown outs or surges. This is best accomplished in many applications by connecting the proper equipment to an online uninterruptible power supply (UPS). This not only protects from voltage interruptions but also isolates this equipment, making it less vulnerable to damage when power interruptions or surges occur.
It is important that solenoid valves are maintained and function properly for the accuracy of the plant automation when weighing materials during batch plant and silo loadout operations.
Weighbridges on a continuous mix asphalt plant must be checked regularly for accuracy. This includes string lining the belt, weighing idler checks for correct positioning of the idlers and visual checks for any materials that may be stuck in the weigh bridge, which can affect accurate weighing of the material being measured by the automation.
Thermocouples that measure temperature should be calibrated and checked for accuracy periodically.
David L. Enyart
SYSTEMS Equipment Corp.
Every year I work with many customers to update their controls to the latest PC/Windows/touch screen equipment now available. The goal of this automation in addition to making a quality product, is to give the plant team a greatly enhanced view of the complete process, such as annunciating possible problems before they become serious, comparing expected results with actual results with settable ranges of acceptable tolerances, reminding the operator when a production change is made of any additional settings that could possibly affect the product quality….This being said, we often find that once it’s installed, the plant team who ran the plant with the old controls does not embrace the enhanced features now available to them. If no new approach to plant troubleshooting or plant maintenance is implemented the overall effect will be no improvement in results.
New automation will not repair failed equipment, correct a bad mix design, or remove the plant team’s responsibility to maintain the plant effectively. New automation will provide the plant team with top notch tools to assist in maintaining a quality plant, a quality process and a quality product when utilized to their fullest.
The plant team needs to understand their controls, trust their controls and act on the information provided by their controls….As a team, a continuous improvement approach to plant quality will result in less down time, lower costs and higher quality.
As the equipment manufacturer, it is our ongoing responsibility to assist the plant team. Supporting them with a continuous improvement approach to their job with ongoing product support and training when it is needed most. Working through the issues with the team and empowering them with the knowledge required to face future issues on their own. We know that the plant operator and the entire plant team, when working together, with the proper tools, will always make the difference.