Gypsum wallboard is everywhere. The construction industry uses this material as much as possible because of its durability, versatility, and affordability.
Given the massive quantity of gypsum wallboard used each year, the manufacture of this wallboard needs to be a robust process that can produce boards at an incredibly fast rate.
Carbon graphite plays a critical role in making this possible.
Specifically, carbon graphite bearings support the rollers on which each gypsum board travels over during drying in large continuous board dryer ovens. Each of these ovens can have hundreds of rollers, so it is very important that the bearings that support these rollers are well-engineered for a long life with minimum maintenance.
Common Problems in Continuous Dryers
Consistent and accurate drying ensures the end product meets acceptable quality standards. Ensuring that the right amount of moisture is removed from the gypsum to bring the material to its final hardened state is essential.
If too much moisture remains, the boards will be weak and brittle. If the board is over-dried, the board will be too heavy, which will lead to sagging. Either of these conditions will result in poor material quality and lost profits.
Proper maintenance of continuous board dryer ovens is critical to achieve consistent results. But it can be difficult. Major repairs require the whole oven to be shut down and cooled off before maintenance crews can access certain locations.
These units are also incredibly massive, so maintenance or repair are often not quick, simple tasks. Between cooling off the ovens, doing the repairs, and heating the ovens back up, a lot of time goes by – time that would be better spent producing gypsum wallboard.
How Carbon Graphite Saves Board Dryers
To prevent the complications that often arise when operating and maintaining board dryer ovens, it is necessary to thoroughly engineer an oven designed specifically to mitigate the need for frequent maintenance or repair. Manufacturers can take advantage of unique materials such as carbon graphite to minimize the required maintenance efforts.
Carbon graphite is a self-lubricating material with excellent wear resistance, so constantly applying lubrication or frequently replacing worn bearings is something maintenance crews do not have to worry about when using carbon. There are two different carbon grades which are very popular in board dryer ovens, each of which has its own advantages:
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Copper Impregnated Carbon Graphite
These grades do well in the lower temperature zones of the oven, as they are often only rated for continuous use at 750°F. The copper impregnation fills the porosity of the carbon graphite and improves the material’s wear resistance. -
Oxidation Inhibitor Impregnated Graphite
These grades are nearly exclusively used in high temperature zones, as they have been engineered to withstand extended durations at temperatures up to 1,000°F. On top of their thermal resistance, they have excellent dry running capability.
In order to improve ease of maintenance even further, carbon graphite manufacturers often provide board dryer bearing assemblies with “quick replacement” features. This essentially means that maintenance crews are able to quickly remove and swap out the carbon graphite portion of the bearing assembly without dismounting the full assembly. Since there are often hundreds of bearings in a single dryer oven, this feature is immensely helpful.
The hanger bearing on the left is designed with a locking mechanism that allows users to easily remove the carbon in the axial direction. On the right, the clip on top of the bearing allows the carbon to be quickly removed radially.
There are other benefits to using carbon graphite bearings aside from ease of maintenance. Unlike plastic bearings, carbon graphite will not “cold form,” or distort under loads. This is a major benefit of carbon graphite, as board dryer bearings see considerable amounts of stress throughout their life.
Carbon graphite bearings also have much greater temperature resistance than their plastic counterpart and will not melt at elevated temperatures. This is especially important in the event of a flash fire in the board dryer, which can cause extensive damage to non-carbon bearings.
Finally, and perhaps most importantly, the self-lubricating properties of carbon graphite eliminate the need to apply any lubrication to the bearings. This is incredibly beneficial not only in terms of cost savings, but in time savings as well. Constantly adding lubrication to hundreds of bearings each day can quickly become overwhelming and extremely costly.
The switch from plastic bearings to carbon graphite bearings in conveyor ovens is a trend seen in many industries, not just wallboard manufacturing. Conveyor ovens used in food production, metal treating, ash drag out systems, etc. are all increasingly taking advantage of carbon graphite bearings.
Across industries, carbon graphite has proven to be the longest lasting and most cost effective bearing option. As the mechanical carbon graphite industry rapidly improves due to technological advances, board dryer bearings are seeing drastically improved wear rates and temperature resistance. These two factors in particular are driving the major increase in carbon graphite board dryer bearings we see today.
