GRAPHALLOY Bushings and Bearings

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Thursday, December 11, 2014

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

Click here to learn more about GRAPHALLOY.

Monday, November 17, 2014

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.

Click here to

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

Thursday, October 23, 2014

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.

Thursday, October 9, 2014

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.

Click here to read more about GRAPHALLOY bushings.

Thursday, September 25, 2014

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.

Learn more about GRAPHALLOY by clicking here.

Tuesday, September 9, 2014

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

To learn more about GRAPHALLOY, click here.

Monday, August 18, 2014

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.

Wednesday, August 6, 2014

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 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.

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.

For more information about GRAPHALLOY, click here.

Tuesday, July 15, 2014

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.

Thursday, July 3, 2014

GRAPHALLOY® Survives Where Plastic Fails

A major oil company’s chemical plant was experiencing run dry failures with a multistage axially split cased pump in a hydrocarbon process service.  The plant was operating with batching requirements rather than continuous feed.  As a result of the batching requirement, the operators and instrumentation were unable to prevent run dry transients from occurring.

The plant engineers had approved modifying the pumps to incorporate plastic composite wear rings and sleeves on the rotating assembly.  These modifications were made in hopes of preventing pump failures during the dry running upsets.  After modification the pump continued to experience dry running upsets and the plastic composite materials failed.

This pump is a multistage volute style with a flow crossover so that some of the stages work in the opposed direction to help balance thrust.  The rotor utilizes stationary and rotating wear rings on the eye and hub side of the impellers as well as inter-stage bushings, center bushing and throttle bushing.

Operating conditions:
  • Temp: 350̊F
  • Flow: 370 GPM
  • TDH: 2020 ft
  • Speed: 3560 RPM
  • Motor Drive
After the failure of the plastic composite rings, engineers at Graphite Metallizing worked closely with the repair service company and the end user to upgrade the pump with GRAPHALLOY®  nickel-grade materials.  GRAPHALLOY allows the pump to survive dry running transients and avoid the issues associated with the original plastic composite rings. The plastic would melt as a result of the heat generated due to a lack of fluid between ring fits. The stationary wear parts were replaced with GRAPHALLOY inserts while the original metal rotating wear parts were put back into the pump.  Installing GRAPHALLOY as inserts into the metal stationary rings enabled the material to be installed in compression, taking advantage of GRAPHALLOY’s compressive strength.

The repair service company completed the installation and returned the pump to service.  Upon start-up the pump ran smoothly.  Over the next several months, this pump experienced four separate incidents where the pump was run dry for four to eight minutes.  GRAPHALLOY allowed the pump to operate through these transients without shutdown or failure because of its non-galling/self-lubricating features.

Since installing GRAPHALLOY, the plant operators have not observed any fluctuations in the pump’s performance (throughput and pressure) and vibration levels have remained constant.  The end user is pleased with the results of the GRAPHALLOY upgrade.

Read more about the success of GRAPHALLOY in pumps.

Thursday, June 19, 2014

GRAPHALLOY Material Receives Drinking Water System Approval

Graphite Metallizing Corporation continues to expand the GRAPHALLOY® product line to meet drinking water regulations worldwide.

Graphite Metallizing Corporation is pleased to announce that GRAPHALLOY® Grade GM 695.3 Bearings have been granted Water Regulations Advisory Scheme (WRAS) approval. This follows the recent certification of NSF/ANSI grades as Graphite Metallizing continues to expand the GRAPHALLOY product line to meet drinking water regulations worldwide.

Through a stringent testing process, WRAS approval indicates that the GRAPHALLOY bearings comply with the high standards set out by the water regulations within the United Kingdom.

In addition, WRAS approval specifies that GRAPHALLOY GM 695.3 Bearings are “suitable for contact with wholesome water for domestic purposes” because it has met the requirements of BS 6920-1:2000 (“Suitability of non-metallic products for use in contact with water intended for human consumption with regard to their effect on the quality of water”).

Bushings made of WRAS approved GRAPHALLOY are used in municipal water system pumps. These bushings have been found to operate for more than 10 years in these services and to provide solutions that eliminate requirements for lubrication systems, including pre-lubrication.

Thursday, June 12, 2014

GRAPHALLOY® Bearings Operate at -269°C

Turbomachinery International magazine reported on a project at Vienna University of Technology's Atominstitut using GRAPHALLOY at -269°C.

The article - "Maintaining Lubricity at Cryogenic Temperatures" - describes the key role of GRAPHALLOY in building a Rotating Sample Magnetometer to measure magnetic properties of samples, usually at temperatures near zero.

"When designing pumps, compressors, valves and ancillary components for cryogenic applications, one is concerned with more than the ability of the components to withstand the low temperatures without shrinking, becoming brittle, losing strength or cracking. 

Whenever there are moving parts, there is the need to minimize friction and wear, and to prevent sticking or galling. Unlike higher-temperature applications, the use of fluid lubricants in low temperatures is out of the question... 

Recently, the GRAPHALLOY material hit a new record low temperature application in a magnetometer. It was not quite as low as what the CAL will reach, since those can only be achieved in space, but it was not much warmer.

Click here to read the full article.

Tuesday, April 22, 2014

Is GRAPHALLOY A True “Run-Dry” Material?

GRAPHALLOY® is an alloy of carbon graphite and metal. The graphite provides continuous lubrication without the need for grease oil or other forms of lubrication. GRAPHALLOY deposits a thin film of graphite on the shaft to reduce friction and the metal impregnate help to transfer heat from the rubbing surface to the housing. GRAPHALLOY has much higher temperature limits than many thermoplastics available today. Run-Dry transients will not melt the GRAPHALLOY as it may do to other materials. Normally the pumps can be put back in service immediately after dry running transients while plastics usually require replacement.

For more answers to questions about GRAPHALLOY, click here.

Wednesday, April 9, 2014

GRAPHALLOY® Split Bushings for Continuous Screw Conveyor Service

Split Bushings that can withstand dust, chemical attack, caustic liquids and high temperature environments are now available from Graphite Metallizing.

Graphite Metallizing Corp now offers GRAPHALLOY® Self-lubricating Split Bushings (Type 1017) that can withstand dust, chemical attack, caustic liquids and high temperature environments. Designed for screw conveyors, these bushings directly replace standard metal or plastic bushings. The GRAPHALLOY bushings require no oil or other lubricants eliminating a potential contaminate to the conveyed product.

These Type 1017 bushings are split to provide for easy installation and replacement along the length of the conveyor. GRAPHALLOY Split Bushings for Continuous Screw Conveyor ServiceAdditionally, these split bushings provide superior performance in continuous duty operations and in applications where maintenance intervals are infrequent, or where useful life must be prolonged. One user recently extended the life of a conveyor from three months to two years, saving over $4,000 in one unit by replacing plugged bronze with a GRAPHALLOY bushing.

GRAPHALLOY, a graphite/metal alloy, is compatible with most industrial liquids and is not affected by submersion in most acids, alkalies, hydrocarbons or liquid gases. GRAPHALLOY does not deform under load and maintains dimensional stability. Because of their long life and self-lubricating qualities, GRAPHALLOY bushings are especially suitable for installations that cannot be accessed easily, or where performing regular maintenance is difficult. GRAPHALLOY products work where oil-based lubricants oxidize and where plastic bushings fail. GRAPHALLOY bushings are applied in refineries, paper mills, waste-to-energy plants, glass plants, steel mills and power plants.

GRAPHALLOY materials are self-lubricating, withstand temperature extremes from -400°F to +750°F (-240°C to 400°C) and thrive in harsh environments where other bearings fail. Special grades provide reliable service up to 1000°F (535°C) and higher in non-oxidizing atmospheres. GRAPHALLOY bushings and bearings are a proven solution for even the most challenging plant maintenance and new equipment design requirements.

For more information about GRAPHALLOY products, visit

Wednesday, March 5, 2014

GRAPHALLOY Installation Video

It is easy to install GRAPHALLOY® bushings in metal housings, once you know how. Click here to watch our video.

Tuesday, February 25, 2014

GRAPHALLOY Pump Bearings Excel in LNG Service

GRAPHALLOY® bearings and bushings are used in many low viscosity pump applications to help eliminate operational problems due to potential flashing and the low lubricity nature of these liquids.

Pumping fluids with low lubricity such as LNG and Natural Gas Liquids (NGLs) can be especially difficult for metallic bearings. The hydrodynamic film provided by these low lubricity liquids is unable to provide sufficient lubrication, which can lead to metal-on-metal contact, galling or seizing.

Recently, a customer contacted engineers at Graphite Metallizing with a special request. Their company was providing single-stage, axial-split case, double-suction, between bearings pumps for a Floating Liquid Natural Gas (FLNG) ship prototype. The customer contacted us because they knew that the non-galling, self-lubricating features of GRAPHALLOY would allow the pumps to continue working even when experiencing run-dry, flashing or cavitation.

The bushings were needed in a hurry. Because the pumps would be installed at the bottom of the ship, they needed to be in place before further construction could proceed. As the project manager described the situation, “timely completion of a multi-billion dollar project depends on timely delivery of our pumps.”

The project involved multiple pumps of several different sizes. A further complication was the need for metal holders in both 316 and duplex stainless steels. With tightly coordinated actions, Graphite Metallizing and the customer's personnel solved the problems of procuring the holders, re-machining the GRAPHALLOY bushings and adjusting the drawings. This was completed within an aggressive time frame so that the customer could honor its delivery commitments to the end user.

Click here for more information about GRAPHALLOY's success in troublesome pump applications. GRAPHALLOY bearings and wear rings allow for tighter clearances which improve reliability, lower vibration and increase efficiency in vertical and horizontal pumps.

Learn more about GRAPHALLOY.

Thursday, January 2, 2014

Cooperation Helps to Eliminate Pump Failures

World Pumps
November 2013

When a hot strip mill experienced failures in its Worthington 10-stage split case diffuser style pumps, the results were costly: each rebuild was put at approximately $85,000 when failure of seals, bushings and shafts made it necessary to rebuild the pumps every 18 to 24 months. Additionally, difficulties in running the two pumps supplying hydraulic pressure to the coiler resulted in reduced production and made for a higher scrap rate.

So the mill’s engineering team looked for a new repair provider and selected Hydro Inc, the engineering pump rebuilding company from Chicago, to apply new technology to the pumps, using GRAPHALLOY®, a self-lubricating graphite/metal alloy bearing material manufactured by the Graphite Metallizing Corporation. Hydro implemented engineered upgrades including A and B gap modifications, rotor centralization and manufacture of new impellers and diff users. Following its work at the steel mill, it is estimated that the mill has saved over $250,000 in potential rebuild costs.

Prior to the steel mill selecting the Chicago based company, it was found that the seals of the Worthington WT-810 split case pumps, which are designed to produce up to 1,400 PSI fluid pressure (with two split mechanical seals were originally used in the coupling and thrust ends of the stuffing box) would wear prematurely and would have to be replaced every six months.

The bronze bushings used on each of the ten stages failed every 18 to 24 months, and required a full element rebuild. The steel mill also experienced four broken shafts in one pump over the course of two years. Hydro’s engineers determined that this most likely occurred because the seals ran dry under various operating scenarios, and when this happened, they failed quickly. As a result of these failures, the two pumps that supplied hydraulic pressure to the coil ran inconsistently, resulting in lower than optimal production and a higher scrap rate.

A new approach was required to address the problem’s root cause, and after the mill contacted it, Hydro performed an inspection referred to as ‘rotor condition analysis’. This involved a review of field operating conditions including vibration, temperature, fl ow and past repair history.

This was followed by a thorough dimensional study to determine the physical condition of the pump. This analysis provided sufficient evidence to understand the pump’s problems and would serve as the basis for solving its performance issues.

Engineers from the Chicago company worked with the mill’s maintenance staff to identify the root causes of the pump failures, and it was found that the previous material used for the stuffing box seals and diffuser bushings performed well when fully lubricated but failed quickly under run dry conditions. Because there was no way to prevent the pump from running dry under certain operating scenarios, a new bearing material was key to solving this problem.

Hydro’s engineers also noted that the pump was being operated off its best efficiency point, close to shutoff, causing axial shuttling and hydraulic instability. The report additionally noted that the previous repair shop had provided a shaft manufactured from incorrect material and had not used accepted manufacturing techniques. This caused stress risers to occur in the threaded areas leading to shaft failure. After years of operation, there was also deterioration in the pump’s base plate and foundation as well as leaks throughout the piping system causing pressure drops which, in turn, contributed to the overall instability of the pump while in operation.

Hydro recommended upgrading the stuffi ng box and diff user bushings to Graphalloy because of its run dry capabilities. Graphalloy is a graphite/metal alloy with enhanced chemical, mechanical and tribological properties. This self-lubricating bearing material survives dry starts, flashing and loss of pumpage for prolonged periods without damage and allows immediate restarts. The material provides a constant, low coeffi cient of friction rather than just a surface layer, helping to protect against catastrophic failure. Graphalloy wear components also improve reliability under conditions such as low-speed operation, frequent starts and stops, and switching from standby to continuous running.

Hydro’s engineers recommended changing the A gap (between the impeller vane tip and diff user shroud) and B gap (between the impeller shroud and impeller vane tip) to reduce turbulent fl ow in the pump, increase rotor stability, and reduce axial shuttling and vibration.

The company’s team performed rotor centralization, a process they pioneered involving centering the rotating impellers within the stationary diff users and volutes. Hydro also manufactured new impellers and diff users using upgraded materials. The impellers were upgraded from bronze to high-grade special stainless steel. The diff users and return channels were upgraded from cast iron to high-grade special stainless steel.

The company also manufactured a new shaft using the proper grade of stainless steel. The maintenance department at the mill worked with its application engineering team to develop recommendations for structural changes to the pump’s mounting and to relieve piping strain. Rebuilding the pump Hydro utilized stringent practices in rebuilding the pump. Tighter fits and tolerances were achieved to improve pump efficiency. Precise manufacturing and balancing techniques were used to achieve a rotor balance of less than 1W/N (W = component weight and N = pump rotating speed) to reduce vibration thereby extending the life of the pump. The maximum shaft total indicator reading (TIR) was held to 0.001 in which is more stringent than the industry standard of 0.003 in TIR.

Because Graphalloy is non-galling, pumps can be designed with tighter clearances. Hydro was able to reduce the clearances between the bushings and shaft sleeves to 0.005 in or 0.0025 in per side. Pump elements were assembled in the vertical position to accommodate the much tighter assembly tolerances. It took checked the balancing the coupling with the rotor. Since even a perfectly rebuilt rotor cannot operate as intended if there are issues with the pump’s casing, Hydro inspected the casing and performed split line and line boring to restore the entire casing fits.

The project has surpassed the expectations of the mill’s management team, and the Graphalloy stuffing box and diff user bushings have lasted through two six-year pump rebuild cycles without any failures. When the pumps were disassembled during the scheduled rebuilds, only minimal wear was observed on the seals and bushings. The bushings and seals were replaced although they could have easily lasted many more years. The mill has estimated the design improvements have saved a quarter of a million dollars by avoided three rebuilds over six years, and that it has achieved improved reliability that eliminated lost production time. The rebuilt pump is now considerably more efficient resulting in reduced energy consumption. The pump requires substantially less maintenance, providing additional cost savings.

Click here to learn more about GRAPHALLOY.