GRAPHALLOY® Bushings: Well-Suited to Cold, Wet Applications

Freezer conveyors are not a problem for GRAPHALLOY.

A seafood processing plant in the Southeast was running a conveyor in their freezer area to "flash-freeze" fresh seafood. The environment is a difficult one: the temperature is cold (28 degrees F/-2 degrees C) and wet and the system requires frequent wash down. The conveyor bearings were being replaced every other month.

The plant maintenance superintendent contacted GRAPHALLOY about the problem. It was determined that the current bearings could not hold lubrication under these conditions and, as a result, breakdowns were occurring frequently.

GRAPHALLOY 4-bolt flange block assemblies were installed and have been running successfully for more than five years. The company has since placed orders for additional flange assemblies for their freezer conveyor and fish wash down lines. GRAPHALLOY continues to work with the plant maintenance superintendent to identify other opportunities on their fish processing conveyors.

 

The self-lubricating qualities of GRAPHALLOY bushings are well-suited to cold, wet applications. Once again, GRAPHALLOY bearings work when others fail.

Bearings that Withstand Harsh-Run Conditions in Paper Plant

When a paper mill suffered repeated failures of the original bronze bearings furnished with the equipment, the maintenance staff switched to graphite-metal alloy bearings.

The move was made to GRAPHALLOY^® self-lubricating bushings designed specifically to withstand the intermittent dry-run conditions of the paper mill’s stock tank agitators, where varying stock levels sometimes eliminate all lubrication.

The mill uses 15 pulp stock agitators to produce manufacturing papers and labels. Each unit has a horizontal shaft driving a 54 inch, 4 blade shockless propeller made of stainless steel. The original bushings were made of bronze and had graphite plugs that were expected to provide self lubricating properties.

One of the GRAPHALLOY bushings was installed. During the plant’s shut down six months later, this bushing was inspected and showed no wear. In another six months, the bushing once again showed no wear. Eight additional GRAPHALLOY bushings were then ordered and the new bushings were installed on all remaining agitators.

After two years, the bushings were still operating well and no measurable wear was apparent on those installed 18 and 24 months prior.

Mill management expects to save at least $40,000 per year by reducing purchases of replacement parts and the labor required for replacement of the previous bushings. Additional benefits are expected by freeing up maintenance staff who previously spent a significant portion of their time addressing the agitator problems.

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A Proven Solution for the Most Challenging Plant Maintenance

GRAPHALLOY® 453 Family of Self-Lubricating Bushings are for severe industrial applications where temperatures reach 750̊F (400̊C) or higher. GRAPHALLOY, a graphite/metal alloy, bushings are designed to operate without lubrication.

The 453 Bushings have proven to be successful in a variety of high temperature applications including bakery ovens, heat treat ovens, furnaces, conveyors, overhead paint lines, glass lehrs, louvers, dampers, valves as well as other environments where oil and grease cannot be used.

Applications can experience improved performance through the use of GRAPHALLOY materials. Among their many advantages, GRAPHALLOY bushings operate at longer intervals without the need for maintenance, which reduces costly downtime. They are an excellent choice for applications where service and maintenance tasks are cumbersome or difficult to perform.

Additional benefits of GRAPHALLOY include a low coefficient of friction and dimensional stability. The 453 Bushings, like all GRAPHALLOY products, do not soften at high temperatures or extrude under load. Installations of these bushings have operated for more than 10 years without maintenance. GRAPHALLOY 453 Bushings are a proven solution for the most challenging plant maintenance and new equipment design.

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Solution For Off-Shore Platform Firewater Pumps

GRAPHALLOY® nickel-grade bearings have been successfully used in offshore firewater pumps for many years. The non-galling, self-lubricating features of GRAPHALLOY allow pumps to continue working even when they encounter a run dry situation.

This particular firewater pump is installed on a Conoco offshore gas platform in the southern North Sea. The platform is an integral part of the LOGGS pipeline system that delivers gas through a 36" pipeline to a processing terminal on the east coast of England. This platform and pipeline system have been in operation since 1988.

The OEM-specified bushings were simple cut-to-size PTFE/Glass Tape Bearings like those normally found in hydraulic cylinders. High vibration and noise were identified as operational issues. In addition, the compounded PTFE material had little or no dry running capability. This was considered a health and safety issue because the pump was for emergency firefighting service and had to start when needed.

The repair facility had successfully performed several GRAPHALLOY upgrades to firewater pumps for other customers and thus proposed a similar upgrade to Conoco. This upgrade would provide the dry running capability that these pumps lacked.

The engineers at Graphite Metallizing worked closely with the repair facility’s engineering team to define pump modifications required and specify nickel-grade, GM 111.3, GRAPHALLOY bushings.

The upgrade to GRAPHALLOY GM 111.3 bushings was successfully completed. Conoco alsocompleted all required approval tests on the pump successfully. Conoco personnel observed and recorded that the use of GRAPHALLOY significantly reduced noise and vibration levels.

Conoco is now assured that they have an emergency firewater pumping system that has rundry capability and is Health and Safety Executive (HSE) certified

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Cart Wheel Solutions in Extreme Environments

Bronze Bushings were failing in a car bottom steel ingot heating furnace.  With loads of up to 100,000 pounds and temperatures of more than 700° F, the oil failed to keep the bushings lubricated.  There was oil on the floor that created a hazardous situation for the workers.  GRAPHALLOY® bushings were fitted into the housings to accept the axles of the cart wheels.   The bushings have operated for more than two years with no sign of wear.

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Success in Refinery Boiler Feedwater Pumps

GRAPHALLOY® has many years of success in boiler feedwater pump applications. The non-galling, self-lubricating features of GRAPHALLOY allows pumps to continue working even when they encounter a run dry situation.
   
A Texas refinery has four Ingersoll Rand 6-stage CNTA radial split horizontal pumps in their boiler section. The operating units that use this boiler section have a lot of steam turbine driven equipment.

Demand Changes Can Cause Seizing
Problems occur when the amount of steam needed changes and the rate is quickly increased or decreased.  The demand on the steam turbines causes the boiler feed pumps to operate anywhere from shutoff to maximum flow.  As the demand for steam increases or decreases, a signal is sent to one of the stand-by pumps to start up or, for an operating pump, to shut down.  When this happens, it sometimes starves the operating pump, causing it to momentarily run dry.

When a pump runs dry, metal to metal contact occurs between the rotating and stationary wear surfaces.  The wear rings can weld to the shaft, damaging both the rings and shaft.  In some cases, the entire pump needs to be overhauled at a substantial cost.  Until the failed pump is replaced by a spare, the capacity of the operating unit is reduced, potentially resulting in lost revenues.

The GRAPHALLOY Solution
The refinery installed nickel-grade GRAPHALLOY stationary Wear Rings, Throat Bushings, Throttle Bushings, Channel Ring Bushings and Crossover Center-Stage Bushings in one pump.  The second pump was converted to GRAPHALLOY a month later. Both converted pumps survived an ensuing dry run that caused the third, metal-fitted, pump to fail. The third and fourth pumps were then converted to GRAPHALLOY.

Results
The non-galling characteristics of GRAPHALLOY allow the pumps to operate safely at unstable flow rates. After the first year of service following the GRAPHALLOY upgrade, the pumps were operating above the performance curve in both capacity and developed head.  In addition, vibration levels were well below the alarm set level.

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GRAPHALLOY® Keeps Subsea Hose Reels Turning

Cleaning underwater piping was a problem for a leading oil company...until they installed GRAPHALLOY® bearings.

The oil company was upgrading their existing underwater piping. Before the old piping could be removed, it had to be cleaned and purged. The cleaning operation utilizes a set of four subsea hose reels that were mounted to a skid and dropped to the bottom of the ocean floor. The hoses flush the cleaning fluid through the pipes.

Subsea hose reel

This particular operation required a new, larger hose reel design. The babbitt-lined sleeve bearings used on previous hose reels would not be able to handle the increased load and, as such, superior bearings were needed. These bearings are crucial to successful operation because they permit the hose reel to turn without the use of oil or grease.

The oil company, working with engineers at Graphite Metallizing, decided to test two of the 163 Series Pillow Blocks with Bronze GRAPHALLOY® bushings in one of the larger hose reels. The test, which was performed in their assembly shop, required that the bushings operate at twice the estimated work load.

The test was successful. The GRAPHALLOY bushings had worked as expected and the shaft was not damaged.

As a result, the oil company ordered a large quantity of the GRAPHALLOY pillow blocks and installed them on hose reels that were shipped off-shore. GRAPHALLOY bushings are now specified on all of the company’s larger, maintenance-free hose reels.

Once again, GRAPHALLOY provides reliable, problem-free solutions for the most difficult applications.