In part one of this two part Series, Timken’s Principal Product Development Engineer, Kuldeep Mistry covered the basics of what makes up bearing grease and oil. In this second portion of the interview, Kuldeep tells us how grease knowledge can help us make better choices for our motion system.
Bearing Tips: Can you explain a bit further why selecting the right grease for a bearing is critical? What are the hazards of making the wrong selection?
Kuldeep Mistry: The main benefits of using the right grease the production uptime, followed by the customer’s quality specifications like performance, noise, lower torques, minimize operating temperatures and reduce component wear.
The correct choice of grease also minimizes preventative maintenance costs, minimizes the repair costs and safety expenses. It also helps to stay compliant with environmental legislation and avoids any related cost. Finally it also avoids machines’ replacement costs.
For example: if a bearing costs $100.00 a piece and it takes one hour to replace that bearing, and if we say the labor cost is $40.00/hr , then it can cost up to $140.00 per bearing to replace a bearing. And in a plant, if there are thousands of bearings, this leads to a big number as the total annual replacement cost for 1,000 Bearings is $140,000.
Here’s another example of why it is important to select the right grease. The downtime in the process industries can cost anywhere from 10,000.00 to $100,000.00 per hour. And if we assume it is $50,000.00 per hour, and if the line is shut down for three hours, it can cost as much as $150,000.00 for the production time, for the loss in the production. So it is very critical to select the right grease for the bearing.
BT: Can you elaborate a little further?
KM: Sure. Grease selection is very important for a bearing and the main reason is that these bearings are used in multiple applications. They can be used in the automotive applications, aerospace industries, metal industries, agriculture, construction, power generation, wind, mining, marine and many more.
All of these industries or applications require different bearings and different bearing performance due to different environment and operating conditions. Hence, we need grease that suits those requirements.
For example, power generation and metal industries, which include paper mills, aluminum mills, and steel mills. These applications have extreme temperatures, heavy loads, slow to medium speeds and wet conditions. There are metal-working fluids used in the applications, which can be very corrosive. So, to address these operating environments, we need to have grease which can match the requirements of this application. Calcium sulfonate thickened grease is the appropriate choice because it has excellent high temperature properties, works well in wet conditions however, the correct NLGI grade and high base oil viscosity is critical. .
Now, there is other group of applications like construction and off-highway, where there are agriculture, mining, cement plants, off-road and earth-moving equipment. There again, the needs are extreme temperature, high load, slow speed, dirty environments with shock loads and high sliding wear. And here, you may need calcium sulfonate thickened grease but you also need a solid lubricant for extreme conditions. Thus, addition of moly disulfide (MoS2), known as “moly” or graphite. can address the requirements of extreme temperature and protection in wet conditions.
Automotive applications, for example, typically have moderate loads, moderate speeds and moderate temperatures. Here, lithium-complex grease is perfect. Lithium-complex grease has excellent overall grease properties and it has great shear stability and it even works great at high temperatures.
The ball bearings are typically found in lightly loaded pillow blocks or idler pulleys, conveyors, electric motors, fans and pumps. Polyurea grease can be an excellent fit for ball bearing applications because it has the water resistance, rust protection properties and excellent oxidation properties needed to perform well for the given application.
Lastly, if you have a food grade requirements, specific greases are required for the food and beverage or pharmaceutical industry. There, the greases may come in contact with food, so the grease needs to be FDA approved. Hence, the greases thickened with aluminum-complexnot only provide the right properties for that environment, but it is not harmful if it comes in contact with the food.
There are many other applications and they can have different operation conditions as well as environment thus, need specific grease for operation. Timken carries grease line that is designed to various applications where our bearings operate.
BT: Are there any other factors necessary to consider before using grease for a bearing?
KM: Grease fill is a critical factor and it is dependent on the operation condition, then there is grease compatibility with the seals, interchanged greases, mating materials, other components is important and also consideration of grease re-lube intervals which is operating temperature dependent is crucial.
BT: Have any of the industries that you specified shown a greater need for innovation over others? Is anyone leading the pack in terms of asking you for new technology with lubrication?
KM: That is a very good question. Although there is no straightforward answer, Timken is growing and growth is a process; we are penetrating different markets, more applications, and newer components to create bearing sales opportunity. This diversified bearing opportunity needs the greases to support the lubrication needs.
I can give you one example, our rail business needed special rail grease that would work at arctic region that is very low temperatures. So we had to develop a grease to address the specific lubrication needs. We were involved in the whole process, worked closely with the grease suppliers, monitoring each and every step. We developed the rail grease which meets all the rail specifications and can perform great at the operation temperatures as low as -60°C or lower. So, you can see how a change in market space for same application creates opportunities for new developments.
Apart from that, some of the other challenges that we have seen is developing greases for developing countries. In the developing countries, cost is a significant concern. It’s challenging to sell US exported greases in developing countries due to its high price that is affected by multiple reasons. So, we work with the suppliers in the developing countries to use their raw materials and to make sure that it meets the same specs and performance requirements of a US product at cost-competitive pricing.