The PBI facility, as part of their planned maintenance period, worked on one of the two reactors late last year. During the cleaning process, high-pressure water damaged one of the bushings on one of the reactors. Two of these specially made GRAPHALLOY® bushings are used in each reactor, which makes the polymer used to produce the fibers at the plant.
“I’ve been the plant engineer at PBI for over 14 years,” said Larry Canterbury. “I work on capital projects and help with equipment selection, installation and support the maintenance teams here at PBI.”
PBI is the trade name for polybenzimidazole, and PBI Performance Products is the sole producer of PBI fiber in the world. This fire-resistant material has been used since the 1960s to make protective uniforms for firefighters, and the fabrics have also been used for high heat and flame applications in electrical, industrial, aerospace, motorsports and military applications and even for NASA.
“When we realized that the cleaning process had caused damaged to the bushing, we went through our files to determine if we could find the original provider of these specialized bushings. We found that these bushings came from Graphalloy back in the late 1980s,” Canterbury said. “At first I was worried that the original provider might not be around. When we looked up Graphalloy, we learned they’ve been operating for over 100 years and are still operating – to our immense relief!”
In March 2020, Canterbury reached out to Chris Speer, territory sales manager at Graphalloy, with the original drawings for their 16-inch bushing.
“He told me about how high-pressure water impacted the end of this bushing, and that the cleaning process cracked a part of the graphite-impregnated material,” Speer said. “I was not surprised at all to hear our bushing had performed so well for so long, and I was happy to share with Larry that we still had the original drawings for his custom bushing. Within a day or so, we were able to confirm that we could offer a replacement bushing for his reactor.”
The reactors are critical equipment for this manufacturing facility. Even though the original bushing had been damaged, it did not impede the reactor’s ability to operate. The decision to purchase a replacement bushing was done pre-emptively, to make sure all equipment could be properly maintained and continue to operate to the highest standards. The order was placed last spring for a custom Graphalloy bushing with an outer diameter of 17.5 inches and an inner diameter of 11.5 inches, making it one of the largest bushings installed at the PBI manufacturing facility.
This Graphalloy bushing was originally selected to fit around the slow-moving reactor shaft for the following reasons.
- Reliable in severely high-temperature applications – The Graphalloy bushing is engineered to work at extremely high temperatures – up to 1000°F. It will not “gum” or seize in these very hot instances, making it perfect for the high-temperature reactor at PBI’s manufacturing facility.
- Self-lubricating – The Graphalloy bushing does not require grease or oil, thereby minimizing maintenance and enabling continuous operation of the reactor, whose shaft rotates at varying speeds. In high-temperature applications, oil-based lubricants may burn off or oxidize and plastics typically fail, so having a self-lubricating bushing was ideal for this specific application.
- Withstands run-dry events – Because the Graphalloy bushing operates reliably without lubrication, it is engineered to survive run-dry events. This eliminates the potential for galling or seizing in severely hot conditions. In this particular application, heated oil is pumped through the bushing. This oil has a temperature of more than 662˚F, so as the oil expands and heats up, the Graphalloy bushing provides a reliable bearing surface.
“The bushings act as a bearing on the floating end of the shaft,” Speer explained. “That’s what is so cool about it. It replaces a bearing. If you’re not having a problem with your bearings, then you don’t need a Graphalloy bushing because it is more expensive than a bearing – but it runs so much longer. When you look at the expense versus how long your machine can keep running, the savings down the line are significant, especially in terms of less down-time, reliable operation and reduced maintenance expenses.”
- Chemically-resistant – The Graphalloy bushing is insoluble in most industrial liquids. It works in acids, alkalis, hydrocarbons, water and liquid gases. This Graphalloy bushing was ideal for the reactor’s agitator shaft and the chemicals being processed to make the fire-resistant material.
- Low coefficient of friction – The Graphalloy bushing has a constant, low coefficient of friction because it is not just a surface layer but solid Graphalloy material throughout. For this reason, Graphalloy has manufactured bearings, bushings, thrust washers and other components for a range of industries, including nuclear-power-generation utilities and other manufacturers.
“I was very impressed with the team at Graphalloy,” Canterbury said. “Graphalloy confirmed they could provide a replacement within eight weeks, and then the coronavirus really hit the U.S. in March. Graphalloy is located in Yonkers, and we all have been watching how hard New York has been impacted by COVID-19. Through it all, they’ve been operating as an essential business, and they never stopped communicating with us. We all agreed it would be best to push the delivery to June, but I’m very pleased with them overall, especially with their responsiveness.”
Graphalloy recently shipped the first bushing, and PBI plans to place an order for a second bushing at the end of the year.