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.

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.

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.

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.

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. Additionally, 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 www.graphalloy.com.

GRAPHALLOY Installation Video

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

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.