GRAPHALLOY Bushings and Bearings

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Thursday, September 16, 2010

Submerged Pillow Blocks - 20 Years of Service in an Abrasive Environment

GRAPHALLOY® Pillow Blocks - Reliable in Wastewater Treatment

After two decades of reliable service, the GRAPHALLOY bushings in a wastewater treatment plant were replaced with new GRAPHALLOY bushings.

A large condominium complex in the Northeast maintains this wastewater treatment facility on its premises. Wastewater treatment is a chemical and biological process that removes contaminants from household sewage. This process produces wastewater and solid waste suitable for discharge back into the environment.

The condominium complex used a Rotating Biological Contactor (RBC), a type of mechanical aeration treatment system, to treat the wastewater. The RBC is a secondary treatment process that allows the wastewater to come into contact with a biological medium. This process removes pollutants from the wastewater before releasing it into a nearby body of water.

An RBC unit consists of a large disc with radial and concentric passages slowly rotating in a concrete tank so that the surface of the wastewater passing through the tank almost reaches the shaft. As a result, nearly 40% of the total surface area of the disks is always submerged in the ambient wastewater. The rotation and exposure to oxygen allows organisms to multiply and cause the biological degradation of organic pollutants.

This facility had two RBC systems - one of which was running at all times. Each system had GRAPHALLOY pillow blocks at either end and each pillow block contained GRAPHALLOY bushings that had been installed in 1988.

Using the imprint code from the outside of the casting, Graphite Metallizing was able to identify the pillow blocks used in the unit. The maintenance manager at the condominium complex removed two of the pillow blocks and drove the insert assemblies to the Graphite Metallizing manufacturing facility in Yonkers. Once the units were disassembled, the original bushings proved to still be functional after 20+ years of operation in the abrasive conditions. The old bushings were removed and new GRAPHALLOY bushings were manufactured and installed in the housing.

GRAPHALLOY provided reliable, long-lasting service in this difficult wastewater treatment application. The original bushings provided service 20+ years after installation.

Thursday, September 2, 2010

Chemical Plant Experiences Bushing Failure in Gear Pumps

The Competition Said "No" but GRAPHALLOY® Said "Yes"

A chemical plant in Tennessee was experiencing rapid bushing failure in their gear pumps. These bushings were failing after only a few weeks of operation.

When plant representatives contacted this carbon bushing manufacturer about the problem, they were told that there was "no solution". The bushing manufacturer - our competitor - claimed that the viscosity of the polymer being pumped was simply too thick.

Unhappy with this response, the chemical plant engineers contacted Graphite Metallizing for assistance. After studying the problem, our engineers promptly responded by saying "yes, we can help" and that GRAPHALLOY bushings were the solution.

The pump that was failing was a positive displacement, herringbone-type gear pump with internal bushings lubricated by the pumped liquid. The pumpage is a polymer with heavy viscosity (150 -10,000 CPS) similar to a thick latex paint. The temperature can range from 80 degrees to 140 degrees F with a speed of 520 -1,750 RPMs and a load of 155 - 1,980 pounds. This pump has very high bushing loads because of the meshing gear forces. The calculated PV values were up to 500,000 - over four times the maximum recommended level for GRAPHALLOY in submerged services.

The GRAPHALLOY engineers provided a solution designed for applications involving the transfer of viscous liquids. Grade GM 119.3 bushings were recommended because of their load-bearing and corrosion-resistant capabilities. GRAPHALLOY engineers also recommended slight design changes to improve reliability.

The initial order was shipped to the customer and immediately installed.

The pumps fitted with GRAPHALLOY bushings have been operating for over one year without failure...six times the life of the competitor's bushings.

The success of these GRAPHALLOY bearings demonstrates the potential for GRAPHALLOY upgrades in chemical plants. If you have a pump that may benefit from GRAPHALLOY, please contact us with details about your application.