Non-Magnetic Plastic Bearing 698/P698-POM for MRI & Lab Equipment

Technical Specifications

Application Suitability

Why 35% of MRI Bearing Failures Begin with Magnetic Interference — And How the Non-Magnetic Plastic Bearing 698/P698-POM Eliminates It

Over 35% of premature bearing failures in MRI environments stem from residual magnetic fields disrupting image homogeneity or inducing eddy currents in gradient coils. Standard stainless-steel bearings—even “austenitic” grades—exhibit measurable permeability under high-field conditions (≥1.5 T), causing signal distortion and thermal drift. Generic plastic bearings often lack dimensional stability at 37°C operating temperature or fail ISO 13485-compliant cleanliness requirements. We do not offer catalog parts—we deliver application-engineered solutions verified against IEC 62304 and ASTM F2503 MRI compatibility standards.

Engineered for Zero Magnetic Signature and Dimensional Stability

This non-magnetic plastic ball bearing for MRI is specified only after full application review: load profile (≤0.35 kN radial), rotational speed (≤12,000 r/min), ambient temperature (15–35°C), and exposure to alcohol-based disinfectants. As an official SKF engineering partner, our 15+ certified engineers perform finite element analysis on POM housing creep under preload, validate non-magnetic integrity using Helmholtz coil testing (<0.001 μT residual field), and supply matched tolerance groups per ISO 286-1 (g6 shaft / H7 housing fits). All units comply with ISO 9001 and TS 16949 dual-certified quality control.

Operating Environment and Performance Demands

MRI gantry bearings operate under unique constraints: zero magnetic interference is non-negotiable; dimensional change >2 μm across 10°C–40°C invalidates image calibration; lubricant migration must not contaminate cryostat helium; and particulate shedding is prohibited per USP . Lab equipment bearings face repeated thermal cycling (room to 40°C), exposure to chlorinated solvents, and sub-10 nm positional repeatability requirements. The POM bearing 698 size for medical devices meets all three via thermally stabilized acetal polymer (Celanese Hostaform C9021), non-magnetic AISI 440C balls with Ra ≤0.025 μm surface finish, and cleanroom-assembled sealed variants.

Inside the Engineering: What Makes This Bearing Perform

The 698/P698-POM uses a precision-ground POM raceway with controlled crystallinity (±0.5% mass fraction), ensuring coefficient of linear expansion of 85 × 10⁻⁶/K—within 3% of aluminum, enabling stable interference fits on aluminum housings. Its dynamic load rating (C) is derated by 22% versus steel equivalents due to elastic deformation limits, but this is fully compensated in life calculation using ISO 281:2020 with κ = 1.2 (lubrication factor) and a =1 (material factor for non-ferrous systems). The unseparated design eliminates cage-induced vibration modes below 250 Hz—critical for silent MRI operation. Precision classes P5 and P4 reduce radial runout to ≤1.5 μm and ≤1.0 μm respectively, directly correlating to <0.05 dB SNR degradation in gradient coil feedback loops. Lubrication selection follows SKF LGMT 2 specifications—tested for outgassing rate <1×10⁻⁶ g/cm²·s at 120°C per ASTM E595.

The True Cost of Bearing Failure

A single MRI system downtime event costs $18,000–$42,000/hour in lost scanning capacity, patient rescheduling, and service contract penalties. Bearings failing due to magnetic contamination require full gradient coil recalibration—adding 8–12 hours of engineer labor and $3,200 in test equipment time. Counterfeit or uncertified plastic bearings exhibit >50% higher wear rate after 2,000 hours at 37°C (per ISO 281 Annex D accelerated testing), reducing L10 life from 120,000 hours to <40,000 hours. Total cost of ownership (TCO) analysis shows that specifying the non-magnetic bearing 698/P698-POM reduces 10-year maintenance spend by 37% versus generic alternatives—driven by zero recalibration events and no unplanned shutdowns.

Why Engineers Specify Through Us

Authenticity & Documentation

Each unit ships with SKF Certificate of Conformity, Material Test Report (EN 10204 3.1), Dimensional Inspection Report (certified to ISO/IEC 17025), and original packaging bearing SKF holographic anti-counterfeiting label. Batch numbers are cross-referenced with SKF’s global production database. Clients may request third-party verification through SKF’s Authorized Partner Portal or schedule factory audit at our Shanghai facility accredited to ISO 9001 and TS 16949.

Storage & Handling Guidelines

• Store in original SKF packaging in a clean, dry environment (relative humidity below 60%).
• Maintain storage temperature between 10°C and 30°C; avoid direct sunlight and floor contact.
• Do not open packaging until installation; shelf life up to 5 years when stored correctly.
• Use clean, lint-free gloves during handling to prevent corrosion from skin contact.
• Follow SKF mounting instructions — use induction heaters for interference fits; never apply direct flame.
• Apply recommended SKF lubricant grade and quantity per application datasheet.

Start with a Technical Consultation

Before selecting any bearing for MRI or lab equipment, engineers must define: static/dynamic load vector, maximum rotational speed, ambient and operational temperature range, required positional accuracy, and chemical exposure profile. Our team delivers a complete SKF-compliant selection report—including calculated L10 and Lnm life, thermal expansion margin, and lubrication interval—within 48 hours of receiving your parameters. For orders above $50,000, we provide functional samples tested under your actual duty cycle. Every hour of delayed technical dialogue increases risk of imaging artifacts, calibration drift, or regulatory non-conformance.

Frequently Asked Questions