Six Steps to Increasing Plant Up Time
Avoid unplanned downtime with a common-sense approach to your preventive maintenance.
By Therese Dunphy, Editor-in-Chief
Unplanned downtime. It’s an operator’s worst nightmare. It’s costly. It’s embarrassing. And, it’s avoidable. In today’s economic environment, many operators are trying to squeeze every last ounce of productivity out of their equipment. The challenge is to understand the difference between prodding a machine to peak efficiency and pushing it beyond its limitations. The first option leads to more tons per hour, more efficiency, and a better bottom line. The second can grind a plant to a halt, resulting in lost production and profits.
To avoid this costly scenario, remember these basic tips for keeping your plant up and running.
1. Operate equipment within its design parameters. Understand the key limitations to each piece of equipment. For example, review the crushing capabilities, volume limitations, and horsepower for each crusher at your operation. Based on the mineralogy of your deposit, know which engineering factor is most likely to limit the equipment’s production rate and respect it.
If pushed beyond intended operating conditions, equipment fatigue can set in. This damage is permanent and progressive. It often leads to premature equipment failure.
2. Practice preventive maintenance. Equipment manufacturers provide handy reference guides to their equipment with daily, weekly, monthly, and even periodic maintenance recommendations. These guidelines are developed to prolong equipment life and should not be relegated to the bottom of a drawer or filing cabinet. Keep them posted prominently and ensure that they are being followed.
When inspecting a screen, for example, check the screen tension, fastening system, and supporting structure. If using spray nozzles for dust control, check to see if water pressure has created an uneven wear pattern on screen media. Planned downtime can be arranged to work with, not against, the site’s production goals.
3. Identify the cause of equipment failure. As one crushing expert told Aggregates Manager, “Anyone with minimal mechanical aptitude is capable of changing a broken crusher part when it fails, but nine out of 10 times, the same crusher part will fail again because no one was able to identify and eliminate the root cause of the initial failure.”
By inspecting failed parts, gathering information from operations and maintenance personnel, and observing equipment trending information prior to failure, underlying problems can be pinpointed, and corrective action can be taken.
4. Take time for a lube stop. Aggregate operations create extreme operating environments. Selection and use of the proper lubricant helps improve equipment reliability and extend its life. Make sure the lubricant used on each piece of equipment — whether stationary or mobile — meets manufacturer specifications in terms of viscosity, oxidation stability, and additives. If the oil is too thin, equipment wear increases. If it is too thick, it requires more energy to lubricate moving parts.
To avoid cross contamination, label or color code storage containers, dispensing equipment, etc. And, don’t ignore the benefits of an oil analysis program to identify small problems before they become costly ones.
5. Stock wear parts on site. To keep equipment maintenance on the fast track, eliminate the need to wait for a part to be delivered by keeping standard wear parts on site. Common items such as screen media, crusher blow bars, liners, and rotors should be available for quick change outs. Remember to follow storage guidelines to keep consumables in proper condition.
6. Educate employees. Equipment is expensive and downtime can be even more so. Invest in employee training to ensure they understand how to operate and maintain equipment. Begin with an assessment of each employee’s current knowledge. Identify gaps in education and provide specific, measurable training that will improve their skills and prolong equipment life.
These six steps provide an overview of ways that aggregate producers can extend equipment life. Maintenance personnel and manufacturer representatives can provide specific guidance on additional procedures that can benefit your site. While trying to control costs, just remember that an investment in proper equipment maintenance and staff training is far less costly than the potentially catastrophic costs of unplanned downtime.
To keep equipment up and running, implement the following maintenance guidelines.
- Turn blow bars every 20,000 to 25,000 tons;
- Replace blow bars when they are 1.25 inches from the rotor surface; and
- Watch side liners for wear near the rotor and turn them between 50,000 and 75,000 tons, depending on mineralogy.
- Learn the wear pattern for your crusher type and maintain accordingly;
- Change wear liners at proper intervals; and
- Allow manganese to “work harden” by crushing softer or less abrasive material — when possible — after installing a new liner.
- Follow manufacturer recommendations for reduction ratios;
- Check liners daily for wear and begin inspecting for cracks and failure when they reach 25 percent of their expected life; and
- Change the liner if production rates decrease by 10 percent.
- Inspect screen media for excessive or patterns of wear;
- Ensure proper tension; and
- Check calibration of the screen’s throw to ensure proper material movement across the screen.