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Carbon Graphite Bearings for Pump Service

Determine the right carbon graphite bearing grade for your pump service. Our selector evaluates fluid media, temperature, and shaft speed to recommend resin, antimony, or PTFE-impregnated graphite for reliable operation in challenging environments.

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Primary Users: Pump OEMs, maintenance engineers, reliability specialists, and procurement teams

Last Technical Review: September 23, 2026

Carbon graphite bearings and bushings for high-performance pump service

Step 1: Determine Bearing Grade & Risks

Use this tool to narrow down the carbon graphite material family based on your pump's operating parameters.

Pump Application Parameters
Select the operating conditions to determine the appropriate carbon graphite bearing grade.

Design Methodology & Evidence

Why we recommend specific impregnations for different pump services.

Hot Water & Condensate Risks
In boiler feed pumps and hot condensate systems, liquid water can flash into steam within the microscopic pores of standard resin-impregnated graphite. This rapid expansion causes a failure mode known as "blistering," where the bearing surface spalls off. Antimony impregnation fills the porosity with a high-strength metal that conducts heat away and resists this mechanical damage, making it the industry standard for severe water service.
Chemical Compatibility Boundaries
Phenolic resin-impregnated graphite provides excellent resistance to most acids, salts, and organic solvents up to roughly 200°C. However, strong oxidizing agents (like fuming nitric acid, concentrated sulfuric acid, or halogens) will attack the resin. In these specific services, PTFE (fluoropolymer) impregnation is required, which lowers the maximum continuous operating temperature to approximately 250°C.
Impregnant Temperature Limits
Maximum continuous operating temperatures before impregnant degradation or oxidation begins.
Running Clearance Guidelines
General diametrical clearance requirements based on lubrication state.
ConditionClearance (% of Shaft Ø)Notes
Wet (Hydrodynamic)0.1% – 0.3%Fluid film prevents seizure; tighter clearance improves stability.
Dry Running0.3% – 0.5%Larger clearance required to dissipate frictional heat.
Critical Note: Carbon graphite has a lower coefficient of thermal expansion than steel housings. Interference fits must be calculated at the maximum operating temperature to prevent the bearing ID from shrinking and seizing the shaft.
PV Limits (Pressure-Velocity)
Theoretical limits for bearing load capacity and wear life.
Operation TypeAbsolute LimitDesign Limit
Dry Running~15,000 psi·ft/min7,500 – 10,000
Wet (Fully Submerged)Variable (Viscosity dependent)> 50,000 psi·ft/min
Design Margin: Actual operating PV should be kept at 50%–70% of the absolute material limit to account for edge loading, start/stop cycles, and abrasive particles.

Reference Sources

  • Impregnant limits in hot water and condensate
    Supports the recommendation that antimony-impregnated graphite is preferred for boiler feed and hot condensate pumps to prevent the blistering often seen with standard resin grades.
  • Dry running and PV limits
    Explains that unlubricated (dry) or gas-running conditions require strict PV (Pressure-Velocity) management and oxidation-inhibited grades to prevent rapid wear and thermal degradation.
  • Chemical compatibility and PTFE impregnation
    Highlights that while phenolic resin covers most acids, strong oxidizers require PTFE impregnation, limiting the maximum operating temperature compared to standard grades.
  • Running clearances for carbon bearings
    Specifies diametrical clearance guidelines of 0.1%-0.3% for hydrodynamic fluid film operation, and larger 0.3%-0.5% clearance for unlubricated dry running to manage heat.

Frequently Asked Questions

Why choose carbon graphite for pump bearings instead of bronze or plastics?
Carbon graphite is self-lubricating, chemically inert, and dimensionally stable at high temperatures. Unlike plastics, it does not swell in liquids or creep under moderate loads. Unlike metals, it will not gall or seize against the shaft if the pump runs dry temporarily.
Why does boiler feed water require a special graphite grade?
Hot water and condensate lack lubricity and can penetrate the microscopic pores of standard resin-impregnated graphite. Upon flashing to steam, the rapid expansion causes surface "blistering." Antimony-impregnated graphite provides the strength and thermal conductivity to prevent this failure mode.
What is the maximum operating temperature for these bearings?
It depends on the impregnant. Babbitt is limited to ~150°C. Phenolic resin operates up to ~200-260°C. PTFE handles up to ~250°C. Antimony can reach ~400°C. Unimpregnated, oxidation-inhibited graphite can exceed 500°C in air, and much higher in reducing atmospheres.
Can carbon graphite bearings run dry?
Yes, they have excellent dry-running capabilities. However, friction generates heat. In a dry-running application, the PV (Pressure x Velocity) limit is significantly lower than in submerged operation to prevent exceeding the material’s thermal limit.
How do I specify the correct shaft fit and clearance?
Graphite has a lower coefficient of thermal expansion than steel. When pressed into a metal housing, the bearing ID will shrink. You must calculate the installed ID and specify a running clearance that accounts for the maximum operating temperature. We can assist with these calculations during the RFQ process.

Ready to specify your pump bearings?

Send us your pump parameters, drawings, and chemical duty. We will verify the grade and assist with interference fit and clearance calculations.

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