GRAPHALLOY® Specified for Nuclear-Service Pump Components

A nuclear-products operation recently contacted Graphalloy about replacement case rings and a channel bushing for a pump used in heavy-water service. Legacy drawings specified nickel-grade GRAPHALLOY for all three components. After reviewing the fluid, operating temperature, mating material, and running clearances, a Graphalloy engineer confirmed the appropriate material family and quoted the replacement parts to the original drawings.

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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.

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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.

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Self-Lubricating Bearings for Low Viscosity Liquids

The use of GRAPHALLOY® bearings and wear rings when pumping low viscosity fluids allows tighter clearances, improving reliability, lowering vibration and increasing efficiency in vertical and horizontal pumps.

Graphite Metallizing Corporation announces a range of custom GRAPHALLOY® bearings and wear rings designed for pumping low viscosity fluids such as Natural Gas Liquids (NGLs), LNG, CO2 and other light hydrocarbons.

GRAPHALLOY bearings are used in vertical and horizontal pumps for low viscosity service to help eliminate operational problems due to the poor lubricity of these liquids. The non-galling, self-lubricating features of GRAPHALLOY allow pumps to continue working even when experiencing run-dry, flashing or cavitation.

According to Graphite Metallizing Corporation, light hydrocarbons can be especially difficult for metallic bearings because the hydrodynamic film provided by these low lubricity fluids is unable to provide enough lubrication, which can lead to metal-on-metal contact, galling or seizing of the pump.

Using GRAPHALLOY bearings and wear rings allows tighter clearances, improving reliability, lowering vibration and increasing efficiency in vertical and horizontal pumps.