Kiln maintenance can be extremely difficult in cement plants because of the harsh conditions associated with this industry.
As the physicist and mathematician William Thomson Kelvin said, “What is not defined, cannot be measured. What is not measured, cannot be improved. What is not improved, will always degrade.”
To determine the current health of the rotary kiln’s rotational components that require lubrication, an assessment should be conducted during which lubricant health and lubrication practices are reviewed and scored against industry standards and best practices.
All necessary information is gathered including lubricant specifications based on the kiln manufacturer’s requirements, lubrication points, and operating conditions. With the completion of the assessment, a detailed list of lubricant types, application amounts, application methods and a detailed oil analysis programme should be provided. Additionally, lubrication-related reliability solutions may be suggested to protect the lubricant, extend its lifespan, and enhance its performance.
Lubricant selection
Even though kiln manufacturers recommend lubricants that provide baseline protection from friction and wear, the operating conditions in the cement industry often require a high-performance lubricant to provide optimum wear-reducing protection. Determining factors in lubricant selection include operating temperature, load size, and speed of machinery. Lubricants are not all formulated the same. In high-impact, heavily contaminated applications such as those found in cement plants, a high-performance lubricant can have a significant impact on reducing operating and maintenance costs.
Open gears
Kilns and ball mills are two of the most critical pieces of equipment for cement plants; downtime is not an option for these applications.
However, their open gears regularly suffer from pitting and other wear due to insufficient lubrication and shock loading. The use of asphaltic-based open gear lubricant is still a common practice with many end users, and the use of these opaque lubricants means that wear cannot be seen by maintenance personnel. Instead, elevated temperatures and vibration are the first indicators that there are problems.
Lubrication best practices for open gears include selecting the right lubricant and the right method of application to combat these challenges. Choosing wisely will help protect the gears from wear, increase uptime, and, in most cases, dramatically reduce gear set operating temperatures, lubricant consumption, energy consumption, and waste disposal. This will lead to a cleaner, safer working environment.
The right choice for open gears is a heavy-duty, high-viscosity lubricant with extreme pressure, anti-wear additive package. A typical open gear lubricant will have a Timken rating of 70 lb or more in order to reduce wear and extend gear life. In the past, open gear lubricants were asphaltic-based, had Timken ratings of 20 – 25 lb, and relied on excessive volume for adequate protection. Most open gear lubricants on the market today use a variety of thickeners, such as graphite, silica and traditional soap thickeners. Nonetheless, even with the newer types of lubricants, operators still report issues with excessive consumption, leading to lubricant buildup around the shrouds, poor drainage, and significant housekeeping challenges.
Other concerns include needing to be heated for pumpability, plugging spray system nozzles, not spraying in low temperatures, drawing in contaminants, obscuring the gear from visual inspection, and not reducing gear temperatures.
Lubrication Engineer’s (LE) Pyroshield Syn Hvy and XHvy open gear lubricants were designed specifically to provide outstanding protection for high-load, heavy-shock applications, such as the large shrouded open gears used in the cement industry. Pyroshield Syn open gear lubricants are non-asphaltic and environmentally friendly, containing no heavy metals. They are translucent in use, enabling cement plant maintenance teams to inspect their open gears daily with the use of a strobe light. In addition, LE’s unique conversion process for Pyroshield allows kilns and ball mills to be converted without having to stop production.
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