Insulating Oil for X‑Ray Machines: Properties, Types & Maintenance
Dielectric Oil in High‑Voltage X‑Ray Equipment
X‑ray generators use mineral‑based insulating oil for:
- Electrical insulation: Prevents arcing between high‑voltage components (cathode/anode, cables).
- Thermal management: Convects heat from anode/target.
- Corona suppression: Fills voids in solid insulation.
Key Properties
| Property | Typical Spec |
|---|
| Dielectric strength | >30 kV (2.5 mm gap) |
| Viscosity @ 40°C | 8‑12 cSt |
| Flash point | >140°C |
| Pour point | <‑40°C |
| Water content | <20 ppm |
| Neutralization number | <0.01 mg KOH/g |
| PCB content | Non‑detectable (<1 ppm) |
Common Types
- Naphthenic mineral oil (most common) – good low‑temp flow, high solvency.
- Paraffinic mineral oil – higher oxidation stability.
- Synthetic esters (e.g., Midel 7131) – biodegradable, higher fire point; used in eco‑sensitive sites.
- Silicone oil – wide temp range; niche applications.
Maintenance & Testing
- Annual DGA (Dissolved Gas Analysis) – detects arcing, overheating, partial discharge.
- Moisture (Karl Fischer), dielectric breakdown, acidity, interfacial tension, furans (paper aging).
- Filtration / reclamation if parameters drift.
- Replace per manufacturer interval (typically 10‑20 years) or if DGA indicates active fault.
Safety
- Non‑PCB, low toxicity, but treat as industrial chemical.
- Spill containment; proper disposal (recycle/incinerate per EPA).
- Fire risk low but present; Class B extinguishers.
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