The importance of gear cleaning and how lubricant contamination can cause major problems

In incidents where excessive foreign particles have entered the gear guard or where continuous contamination has occurred, it is imperative to conduct proper gear cleaning and relubrication, according to AGMA 9005 requirements, to ensure no damage was caused to the gear.

Problems caused by contaminated lubrication

• Abrasive wear on gear teeth
• Excessive vibration
• Corrosion
• Buildup in the root of the gear tooth can cause the pinion and gear not to mesh properly

A proper cleaning and flushing program, as per ASTM E2905, needs to be developed to minimize gear teeth contamination. This helps the asset to reach the expected 25-year lifecycle as per the stringent industry standard AGMA 6014 – Gear Power Rating for Cylindrical Shell and Trunnion Supported Equipment.

Finding the right cleaner

Cleaners formulated with Extreme Pressure additives are designed to remove contamination and lubricant buildup on girth gears and pinions prior to inspection or any related maintenance procedures. The cleaning times are typically less than an hour. Clean gear teeth allow the engineers to provide an accurate onsite failure analysis, as per AGMA 1010-F14, to determine the possible failure modes, their severity and how they might impact the operational function of the mill.

Removing built-up contaminated lubricant ensures that an accurate inspection of the gear teeth can take place using digital inspection methods such as Eddy Current Array. The new technology enables 60% faster gear inspections with outstanding accuracy when compared to the use of conventional methods. Hence, wiping or rinsing girth gear teeth is not required for this process.

Flushing away old lubricant goes a long way

Open gear flushing is a new practice recommended to be performed once a year, a bit like an oil change on a car. This is meant to remove contamination and lubricant buildup on girth gears and pinions prior to inspection or any related maintenance procedures.

Using flushing lubricants proves exceptional for:

• NDT inspections
• Pinion changeouts
• Alignment
• Visual inspections
• Slurry ingress flushing

Flushing contamination can be conducted without having to shut down the mill to remove slurry ingress when the lubricant contains high levels of EP & AW additives to protect the gear teeth during the flushing process to avoid any damage such as wear or scuffing as the pinion and gear mesh.

Bottom line

Although risks of contamination can be minimized, they can never be eliminated entirely. Progressive wear and reduced asset life can, however, be prevented by:

• Proactively cleaning the gear to conduct a thorough inspection
• Flushing the gear
• Cleaning the gear after an incident that caused excessive particle infiltration into the lubricant

Metso Outotec is a provider of expert solutions to ensure the reliability, integrity and longevity of a grinding mill’s most critical components while minimizing downtime. Through close monitoring with the use of advanced instrumentation, annual girth gear inspections and preventive maintenance practices, our services offering can bring significant risk improvement solutions and safety and sustainability benefits to your entire grinding operation.