Bearings and the environment – MRO . Magazine
Since their inception as a standard mass-produced product in the late 19th century, rolling element bearings have reduced friction and thus reduced the energy consumption of rotating equipment. During the first 50 years, the focus was on converting current applications using sliding bearings to the use of bearings with rolling elements; However, over the past 75 years, it has been recognized that most roller assemblies will be supported by some type of rolling element bearing.
Here are some examples of how rolling element bearings are affected and maintained today
Prevent the release of toxic substances
The pulp mill had poor ID fan reliability. Each time the fan went down, the facility had to report to the Ministry of Environment (MOE) that some unwanted gases had been released. At one point, the MOE determined that the frequency of fan failures was excessive, and the facility had to take corrective action. The solution was to bring in some bearing experts to ensure that best practices were used for mounting and operating the fan.
The first step was to inspect the bearings that had been taken out of service to understand the reasons for the shortened life. The second step was to ensure that mill workers were using the proper techniques to mount the bearings. The third step was to carefully monitor the operation of the fan. This was achieved by installing a continuous vibration
Bearing notes indicate several installation issues, which ended up in bearings that were previously axially loaded. Also, there were many checks that were not missed, both during installation and during monitoring during operation.
Corrective actions have been taken to ensure and monitor oil levels are correct, to keep assembly vibration low and to monitor operating temperatures. As a result, reliability is improved, and the environmental impact of fan malfunctions is eliminated.
Suitable quantities and frequencies for grease
While doing a lubrication survey at a steel mill, I was inspecting the area of the slugging transmission windings. It was powered by single-block ball bearings that rotated at less than 10 rpm in a relatively clean part of the mill. Under each bearing was a pile of grease that was cleared from the bearings while they were re-lubricated once a week.
The strange thing is that electric motors use “sealed for life” bearings that last 5-10 years at 1500 rpm without lubrication; However, when bearings of the same size are placed in unit blocks and rotate at 10 rpm, somehow, they must be lubricated every week.
While working with the facility, the appropriate re-lubrication frequency was calculated based on speed, temperature and degree of contamination, and it was determined that the bearings could operate without maintenance; Without any additional grease.
Many bearings of this type do not need re-lubrication at all in their life, and a correct calculation of the lubrication requirements will end up reducing the amount of lubrication without purpose being added to the bearing, thus ending up getting washed out and sent to a landfill.
The use of degradable grease
Conventional lubricants based on mineral and synthetic oils are ultimately biodegradable through a slow decomposition rate. Under some conditions, they can exist as pollutants in groundwater for nearly a century. However, with regard to lubricating oil, it is difficult to find an oil that can provide adequate lubrication and is biodegradable. As such, there aren’t many options for users who want a “green” grease.
Use of SRBs . Sealed Bearing
Given the cost and difficulty in obtaining good quality, cost-effective bio-degradable grease, sealed bearing is a worthy consideration, especially now that sealed spherical roller bearings are more readily available. With sealed SRBs, the bearing itself can be fed with high-quality bearing grease and the bore on both sides of the sealed bearing can be filled with inexpensive, environmentally friendly grease. Because the bearing requires much less grease to lubricate compared to a seal, the assembly will not eject excessive amounts of grease that may not dissolve quickly.
To protect the bearing from wet, dirty environments, a biodegradable “green” grease can be used to seal and disinfect the housing bore without worrying about the buildup of less ground-friendly grease.
Calcium sulfonate grease
There is a lot of “anti-EV” debate about the use of lithium in electric vehicle batteries. What is true is that lithium-based greases are the most common grease for use in bearings, and they pass through the bearings and are then discarded with no opportunity for recycling.
However, recently there has been an increase in the popularity of calcium sulfonate grease, which in many cases, can provide similar or better performance in bearings. This is an example of how alternative greases can be available that can be more earth friendly in ways other than those related to disposal.
Best Practices for Toxic Waste Disposal and Recycling of Scrap Items
The world-class rebuilding workshop will have the proper procedures for disposing of recyclable materials while the machine is being disassembled. There should be special bins for disposal of expected waste, such as excess grease, oils, (contaminated) solvents, grease or oil-filled rags. In addition, recyclable metals can be collected or separated into aluminum, steel, and yellow metals. Other than seals and grease, bearings are 100 percent recyclable.
Special bearings help the environment
In one particularly challenging application, the compressor draws sour natural gas from wells, and a hybrid bearing has been developed that can withstand the challenging conditions that have occurred due to the condensation of hydrogen sulfide and other gases in the bearing lube oil.
Using stainless steel and high nitrogen porcelain rolling elements, the bearing was able to withstand these conditions. This was important because every time the compressor was taken out of service, toxic gas was vented into the atmosphere. With the time between compressor shutdowns, spanning from months to years, a significant reduction in pollutants was achieved, and greater compressor reliability allowed planned maintenance more often than unplanned downtimes.
In both this case and the fan case, the impulse to fix the problem was a fine for the gas release. Perhaps if companies can keep score on their own in the fight against pollution, progress can be made without losing dollars in fines.
Douglas Martin is a heavy-duty machinery engineer based in Vancouver. He specializes in rotating equipment design, fault analysis and lubrication. You can reach him at email@example.com.
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