By Sheetalnath Mahalungkar and Mike Ingram
In the cement industry, keeping equipment running is essential. Lost production due to equipment failure is not acceptable, especially during times of peak demand. Maintenance is expensive, but it is not an uncontrollable cost. As the industry has evolved with better and more efficient technology, scheduled or preventive maintenance (PM) has replaced reactive maintenance, resulting in better equipment availability. However, even with scheduled preventive maintenance, unpredictable failures can occur.
The industry’s approach is now shifting from scheduled maintenance to predictive maintenance (PdM), where new technology is used to constantly observe equipment conditions and predict potential failures. The source of an equipment abnormality is identified and corrected before an incident occurs.
In this reliability-centered maintenance (RCM) approach, efforts are focused on providing advance warning of signs of trouble to prevent sudden failure. Predictive maintenance is the current trend in the manufacturing industry. Condition monitoring through vibration and oil analysis is the latest technique for achieving higher equipment availability.
Early warning system
Figure 1. Rotating-machinery failures typically follow a pattern where vibration increases well before equipment breaks down.
Switzerland-based Holcim Ltd. is one of the world’s leading suppliers of cement and related construction materials, including mineral components, aggregates and ready-mix. It operates in more than 70 countries. Holcim (US) Inc., a wholly owned subsidiary, is one of the country’s largest makers of cement and mineral components. It includes 14 manufacturing facilities, 11 of which are cement plants.
Developments in technology, increases in product quality, and demand for product have driven the need for new methods to run equipment more reliably and at lower cost. The company is implementing many technologies to standardize processes.
The company has been proactive about equipment reliability and has been investing in the latest technologies available to monitor and predict possible equipment failures. It has a well-developed preventive maintenance program and has been moving toward condition-based maintenance in the past decade.
RCM is the center of maintenance activity at Holcim’s Portland cement manufacturing plant in
A kiln this size, if it is shut down due to equipment failure, can incur costs totaling thousands of dollars per hour in lost clinker production. At the same time, it strains the supply chain due to reduced cement production and inventory. This is the lost cost in production.
There is also additional maintenance cost due to sudden failure of equipment and consequential unplanned expenditures of material and overtime labor. The cost for damaged equipment has to be considered as well.
In an effort to avoid those costs, the plant has installed online vibration-monitoring systems on all critical equipment. The online transducers are connected to the centralized control room through PLCs. The equipment has settings for alarm and shutdown in case of excessive vibration.
Holcim had been effectively implementing PM programs for two decades, but a few failures in bearings and gears went undetected. The solution to this issue was answered in the new condition-monitoring techniques made available by the development in technology. Vibration analysis, oil analysis and infrared thermography can predict the failure of a bearing or a problem with a drive well in advance of unplanned equipment shutdown.