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"Could purging old non-melt grease and replacing it with fresh non-melt grease cause overlubrication problems? Are there any other issues we should be concerned about with this type of grease?"
Non-melting grease is a high-performance lubricant that can aid in reducing equipment downtime and lubrication frequency when used in the proper environment. It generally offers elevated temperature performance (often up to 500 degrees F), resistance to oxidation, and excellent adhesive and anti-wear properties. Just as with any other type of grease, purging, greasing and overlubrication are frequent concerns with non-melting grease. However, there are some additional issues to keep in mind when utilizing this lubricant.
If feasible, it normally is better to perform greasing tasks while the equipment is in service. Remove the lower drain plug or relief cap, clean out any hardened grease and check for blockages. Next, clean the grease fitting to ensure any contaminants that have accumulated on the fitting are not pushed into the line.
Also, review your process for determining the amount of grease to add. This usually can be calculated by the number of shots based on weight or by employing a predictive maintenance technology such as vibration or ultrasound.
Slowly add new grease until the old grease begins to purge from the system at the drain plug or relief port. Be sure not to not overgrease. If grease does not purge from the system, there may be a blockage. After adding the new grease, clean and reinstall the drain or relief cap. Lastly, reinstall the grease fitting cap or add a dollop of grease on the fitting to minimize contamination.
Lines with blockages should be readdressed after a few days. For worst-case blockages, consider cleaning them out when the equipment is out of service and other maintenance tasks are performed. Following these steps should improve your purging and greasing process as well as minimize the likelihood of overgreasing.
There are some additional concerns regarding the use of non-melting grease. Although this grease is suited for high-temperature applications, you must take into account not only the additive melting point temperature but also the base oil melting point temperature. One property may function properly at a certain temperature, while another is just out of range. Oil burning off over time is a possibility that can result in hydrocarbon and thickener residue. Therefore, always review the product data sheets when selecting lubricants.
Another issue with this type of grease is the potential for thickening at lower temperatures. When choosing a lubricant for an application, it is key not only to understand the heat to which the grease will be subjected but the overall range of temperatures as well.
Finally, do not overlook grease compatibility. You must know which grease is being applied and if it is the correct one. Cross-contamination, especially with greases, is a common issue that can often lead to equipment failure and downtime.