By Steve Hall, SEPCO
In order for any manufacturing businesses to function properly and reach all necessary targets and Key Performance Indicators (KPIs), it is vital that they have the correct, high functioning equipment. However, equipment failure may result for many reasons. Often, and regardless of industry, this equipment failure is caused by lubrication contamination. When kept clean and dry, lubricants can ensure successful machine operation and provide years of wear protection. The struggle then to achieve months, or even weeks, of service life between oil changes is because of contamination ingress.
Provided that dirty oil is not poured into a machine, the most common reason for lubrication contamination is a failed oil seal. A well-designed oil seal or bearing isolator often solves this contamination problem in even the toughest applications. In the Southeastern part of the U.S., two paper mill repair shops learned this lesson after experiencing issues and high prices with their existing bearing isolators. After research and contemplation of a new design, both locations chose different technology and products, and experienced decreased costs and greater uptime.
The Problem
Two paper mill repair shops in the Southeast U.S. wanted to ensure that the rotating equipment in their possession – whether it be repaired or rebuilt — had a long operational lifespan. After all, the rotating assets used in paper mills, including pumps, are often in dusty, dirty environments, or even outdoors. This makes them prime suspects for lubrication contamination. The first paper mill repair shop, which shall be called Shop 1, used magnetic bearing isolators in its pumps for the mill. When compared to lip seals or compound labyrinth bearing isolators, magnetic type bearing insulators are much more costly.
“Where I work, we were using magnetic type bearing isolators, at a much higher cost,” said Ray Oliver, the rotating equipment specialist for the first Southeastern paper mill. Oliver wanted to find and implement a less expensive solution that also effectively protected the equipment. In the second Southeastern paper mill repair shop, or what shall be known as Shop 2, Joe Dixon, the precision rebuild specialist, also needed a solution to replace the existing, less effective oil seal technology for use on his rebuilds.
The Solution
An effective systems approach examined the bearing housing environment from an energy balance perspective. Some traditional bearing isolators successfully prevent contamination while operating, though others do not. The bearings that do prevent contamination though, utilize centrifugal force to expel any contaminants that may enter the bearing housing. This is also true of the improved, system-focused bearing isolator that is now used by both Shop 1 and Shop 2. However, during shutdown, contaminants may still enter the bearing housing with some isolator designs because of the housing’s energy balance. Bearing housings interact with the environment that they are situated in. A bearing house will always try to be in equilibrium with its surroundings (see Figure 2). During operation, housings vent to atmosphere because they are at an overall higher temperature and pressure than the atmospheric side. After shutdown however, the housings’ internal temperature cools. Since cool air is denser than warm air, the bearing housing consumes the air inside and begins to create a vacuum. It is because of this that the air enters from outside the bearing housing until reaching equilibrium. Moisture and dust will also migrate in with this air, contaminating the lubricant if an effective oil seal is not installed.
To block contamination during shutdown, some bearing isolators are designed to focus on the system and have a different design. As moisture and dust enter the system-focused isolator, the energy decreases as they move through a tight-clearance, axial throttling gap, and then through a longer radial gap (labeled as mist coalescing rings in Figure 3). There, the contaminants are confined within the internal condensate trap. Then they are allowed to drain out through a small static weep hole at the six o’clock position. These contaminants never reach the lubricant, even during shutdown.
The repair shop experts from both Shop 1 and Shop 2 switched to the SEPCO EXP system-focused bearing isolator. According to Oliver, this was for several reasons, as it is not only more cost efficient, but also easier to install, repair, and maintain.
Dixon, the expert at Shop 2, has been equally successful. In his opinion, the system-focused bearing isolator is most advantageous because “the rotor is cupped over the outside of the stator making it a double labyrinth seal,” he said. “I use the unitized feature on certain applications so that I know the seal will not separate.” For Dixon, it is also vital that the company be able to manufacture and supply any size or configuration that may be needed in operation.
It is through innovation and evaluation of existing system designs that both Shop 1 and Shop 2 were able to improve its processes and ensure ongoing success and profitability. It is for this reason that innovation is vital in all areas of the pump industry, regardless of sector. Through examination and outside-of-the-box thinking, the future of the industry as a whole can be safeguarded.
About the Author
Steve Hall, Southeast regional manager, has worked with SEPCO for 22 years. Before that, he was a mechanic, machinist, and electrician in several industries. Hall has been in field service on rotating equipment in several different plants and with various maintenance crews for more than 12 years. He may be reached at steveh@sepco.com.