From calculating PV limits and thermal clearances to ensuring safe, fragile-part export packing. Find the right impregnation grade and navigate dual-use export rules for your high-temperature or submerged pump applications.
Complete RFQs are easier to review within 1-2 business days when drawings, graphite grade, quantity, and destination are included.
Sourcing graphite bearings requires more than sending a dimensional drawing. Running clearances, counterface material, PV limits, and export logistics determine success.
Graphite CTE (~4.0 x 10⁻⁶/°C) is much lower than steel (~12.0 x 10⁻⁶/°C). Using standard metal-bearing press fits will cause the expanding shaft to seize at high temperatures.
Dry-running PV limits cap around 15,000 (psi × fpm). High PV applications require metal-impregnated graphite (e.g., antimony) to increase thermal conductivity.
High-density graphite (>1.72 g/cc) may trigger EAR 1C107 or MOFCOM licenses. Furthermore, fragile bearings require separated foam trays to prevent shipping damage.
Matching the graphite impregnation to the operating environment is critical to avoid premature wear or chemical degradation.
| Material Family | Best Fit Application | Key Risk / Constraint | Validation Step |
|---|---|---|---|
| Resin-impregnated graphite | Submerged pumps, chemical mixers, food processing (<250°C / 482°F) | Temperature limit strictly bound by the resin (PTFE, furan, phenolic). PV limits ~0.5 N/mm²m/s. | Chemical compatibility check + temperature verification |
| Metal-impregnated (Babbitt) | Low temp, high load (<150°C / 302°F) | Babbitt alloys melt around 223°C to 248°C. High ambient or friction temp will cause bearing failure. | Max ambient and friction temperature calculation |
| Metal-impregnated (Antimony/Copper) | High PV limit (up to 15,000 dry), dry running pumps (<400-500°C) | Antimony alloys may trigger specific export compliance reviews. Requires hard counterface shaft (HRC 45+). | Export ECCN check + load calculation |
| Electro-graphite / Plain Carbon | High temperature ovens, conveyors (<350°C plain, <500°C electro in air) | Oxidation occurs above 400°C in air; lower structural strength compared to metal-impregnated. | Atmosphere review (air vs inert) + maintenance interval planning |
Metal shafts expand significantly as temperature rises, pushing outward against the bearing ID.
Graphite expands at a fraction of the rate of steel. The bearing ID remains relatively stable.
Without calculating a larger initial running clearance, the rapidly expanding shaft will bind and seize inside the slowly expanding graphite bearing.
Prepare these inputs before requesting a quote to ensure an accurate engineering review.
Carbon graphite has a very low coefficient of thermal expansion (CTE) of approximately 4.0 x 10⁻⁶/°C, compared to steel at ~12.0 x 10⁻⁶/°C. As the assembly heats up, the metal shaft expands faster than the graphite ID. A typical starting point is 0.001" to 0.003" per inch of shaft diameter, but this must be calculated for the specific operating temperature to prevent seizure.
The PV limit (Pressure × Velocity) determines the heat generation capability of the bearing. For dry-running carbon bearings, the PV limit typically maxes out around 15,000 (psi × fpm). Exceeding this limit causes the bearing to overheat and wear rapidly. Impregnating graphite with metal (like antimony) increases its thermal conductivity, raising the allowable PV limit significantly.
Yes. Depending on the material's density (>1.72 g/cc) and grain size, it may fall under US BIS EAR ECCN 1C107 or China's MOFCOM graphite export controls (artificial/high-density graphite). Exporters often require an end-use certificate and destination verification before shipping, alongside proper die-cut foam tray packing to prevent transit chipping.
Yes. The graphite acts as a solid lubricant, transferring a microscopic film onto the metal shaft. However, the counterface shaft must be hard (minimum HRC 35, ideally HRC 45+) and have a smooth finish (Ra 8-16 microinches) for this transfer film to establish properly without rapid wear.
Send your dimensional drawings, shaft material, RPM, load, operating temperature, and destination country. We will calculate PV limits, check clearances, and quote the ideal grade with export-safe packaging.
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