Huahao Sealing supplies carbon graphite bushings, journal bearings and thrust washers for the inner rotor of magnetic drive pumps. Furan-resin-impregnated grades replace phenolic with Tg 260-300°C, Td5 340°C and 65% char yield at 700°C, extending dry-start tolerance by about 2.4×; antimony-impregnated grades (M106D/M106H) cover the 500°C high-temperature sections. Self-lubricating at friction coefficient 0.04-0.15 with 8-70 W/m·K thermal conductivity, sized to CQB-series and OEM bearing housings, custom-built from your drawing.
Magnetic pumps transmit torque across the containment can between inner and outer rotors, eliminating the dynamic seal point — and with it the leakage warning channel. A liquid-free start shows no visible symptom for the first seconds; by the time it is noticed the bearing is already burned.
Full dry friction is established 0.3 s after a dry start, PV spikes instantly to 2.1 MPa·m/s — far above the 0.8-1.2 MPa·m/s recommended limit for phenolic-impregnated carbon graphite — and the face temperature crosses the resin Tg of 180°C within 8 seconds.
The inner-rotor journal bearing cannot be grease-lubricated from outside; it is lubricated and cooled only by the pumped medium itself, so the bearing material becomes the single point of failure of the whole pump.
Eddy-current heating in the containment can is dumped straight into the medium in the bearing gap, thinning the liquid film and accelerating ageing of the impregnant.
Once the impregnation layer is sheared off, exposed graphite pores and resin debris form three-body abrasive wear between shaft and bushing, multiplying the wear rate in solids-bearing media.
Furan-resin-impregnated bushing grades (M140K / M120K) substitute phenolic with Tg 260-300°C, Td5 340°C and 65% char yield at 700°C, extending dry-start tolerance about 2.4× while the residual carbon film keeps lubricating after decomposition
For hot or long-duty service, switch to antimony-impregnated grades (M106D / M106H) rated 500°C, which have no resin glass-transition step at all and run stably with anti-oxidation treatment
The layered graphite crystal forms a self-lubricating transfer film on the shaft — friction coefficient 0.04-0.15 — so lubrication persists at the instant of flow loss and the journal is not smeared
Thermal conductivity of 8-70 W/m·K drains friction heat out of the bearing gap, suppressing hot spots and thermal cracking; pairing with a SiC counterface dissipates further and resists particle erosion
Bushings are fitted to CQB-series and OEM bearing-housing dimensions, with optional axial grooves or spiral helices to flush particles and establish a liquid film, custom-ground to micron tolerances from your drawing
| Temperature | -50°C ~ 500°C (grade dependent) |
| PV Value | 0.8 – 1.2 MPa·m/s continuous; 2.1 MPa·m/s dry-start spike |
| Dry-Start Tolerance | ~13.5 s on furan grade vs ~4 s on phenolic |
| Coefficient of Friction | 0.04 – 0.15 (dry) |
| Grade | M140K / M120K (Furan) / M106D / M106H (Sb) |
| Mating Face | SiC / WC |
The two have different boundaries. SiC is very hard (HV2500), wear and corrosion resistant, but brittle and not self-lubricating — chipping is likely under dry running or when particles jam. Carbon graphite self-lubricates through its layered structure, survives short dry starts and can absorb fine particles without smearing the journal. Inner-rotor journal bearings in magnetic pumps therefore stay on carbon graphite in most cases; SiC suits continuously flooded, clean media, or serves as the counterface.
Check the running side first: an abnormal temperature difference across the containment can (normally stable at 5-8°C; ≥12°C works as an early warning) usually appears before the face temperature alarm. On teardown inspect three things — radial wear and out-of-roundness of the bush bore, discoloration and radial cracking of the surface, and smear marks on the journal. The graphite bushing is a sacrificial part: after a dry-run event, replace it and re-measure the diametral clearance instead of judging by hand.
It comes down to thermal margin. Phenolic impregnation has Tg around 180°C and Td5 about 260°C, so a dry start crosses glass transition in roughly 8 seconds. Furan impregnation has Tg 260-300°C, Td5 about 340°C and a 65% char yield at 700°C, extending dry-start tolerance about 2.4×, and the residual carbon film keeps lubricating after decomposition. Phenolic is sufficient for cool, clean media; choose furan where dry-run risk, vaporization or elevated temperature exists; above 220°C go straight to antimony-impregnated grades.
Life is governed mainly by solids concentration and particle size rather than the material alone. Three measures matter most: select harder antimony or heat-resistant furan impregnated grades; cut axial grooves or spiral helices and open the clearance slightly so particles are flushed out instead of crushed into the interface; and add filtration or reverse flushing at the bearing inlet. Send us the solids content, particle size distribution and temperature and our engineers will specify the grade and the expected replacement interval.
