Solving Subpar Pump Performance by Finding the Right Material

A petrochemical manufacturing plant recently faced material-related issues with two fractionator pumps at its performance products plant in Texas. Pump performance was gradually falling off to a point where the pump could not keep up with demand.


By Eric Ford, Vice President, Graphite Metallizing Corporation
Pump Engineer, November 2014 

A petrochemical manufacturing plant in Texas was experiencing frequent pump failures, as often as once every year, on their Worthington model 3UNX-105 multistage pumps. The pumps were being used to transfer Tert-Butyl alcohol at a temperature of 110°F, suction pressure of 10 psi, and a discharge pressure of 500 psi. The fractionator had an operating pump, an installed spare pump, and spare rotors in a warehouse as backups. A spare rotor would be installed into the failed pump, while the damaged rotor was pulled from service and sent for repairs.

The Area Maintenance Engineer started looking for a longer-lasting option to reduce costs. While the pump was originally supplied with stainless steel bushings and impeller wear rings, these were subject to galling on start-up, and during upset conditions. An upgrade to PEEK material resolved the galling issue, but over time the resin binder started to break down allowing critical clearances to increase and pump performance to drop off. The repair shop suggested switching to a higher,more expensive grade of PEEK.

This idea was rejected as there was no guarantee that the new PEEK material would hold up any better as it had not been tested or used in this service before. After more research, the decision was made to replace the bushings and wear rings with nickel-filled GRAPHALLOY^® graphite/metal alloy components, which allow the graphite layers to slide against each other resulting in excellent dry lubrication, is stable chemically, unaffected by ordinary solvents, and can withstand high temperatures without deformation or burning.

The pump internals are 300 series stainless steel. The supplier provided wear rings that were finish machined and installed into the pump’s 300 series stainless steel housings. The new material was installed into the eye and hub-side stationary rings, as well as the throat, throttle and center bushings. The first GRAPHALLOY-fitted spare rotor was installed into the pump. The damaged rotor with the PEEK bushings was sent to the shop and fitted with new graphite-based components.

The pump has been through several start/stop cycles and over a year in continuous service without any indication of increasing wear ring clearance or degradation. It has exceeded the runtimes of the previous bushings

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GRAPHALLOY Bearings: A Component of Power Generation at The Geysers

GRAPHALLOY Helps Generate Reliable Geothermal Power

The Geysers is the largest geothermal power field in the world. Because geothermal power is constant (and nearly free), The Geysers have become one of the most reliable energy sources in Northern California. Currently, the Calpine Corporation owns and operates 19 of 21 power plants at The Geysers. Calpine and their predecessors have used GRAPHALLOY to solve a critical pump application problem.

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(Image courtesy of DOE/NREL, Credit - David Parsons)

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.

To learn more about GRAPHALLOY bushings, click here.