NEMA G7 silicone glass fiber tubing is high-temperature thermoset composite tubing constructed from continuous woven glass cloth impregnated with silicone resin binder. Engineered for continuous duty in Class H (180 °C) operating environments, G7 glass tubing provides high arc endurance, low dielectric dissipation, and excellent structural stability under elevated thermal stress.
1. NEMA G7 Glass Tubing Technical Property Matrix
Standardized properties and certified test parameters for NEMA G7 / IEC 60893 SI GC 202 silicone glass composite tubing across thermal, electrical, and medium compatibility limits:
| Specification Parameter | Standard Test Method & Conditions | NEMA G7 Tubing Value |
|---|---|---|
| Continuous Operating Temperature | IEC 60216 Thermal Index (20,000 hrs aging) | Class H (180 °C Continuous Duty) |
| Arc Resistance | ASTM D495 (High-voltage, low-current arc) | ≥ 180 Seconds |
| Thermal Aging Exposure Test | IEC 60216 (200 °C short-term thermal stress) | Retains ≥ 50% axial tensile strength after 1,000 hrs |
| Flammability Rating | UL 94 Vertical Burning Test | UL 94 V-0 Rated |
| Axial Tensile Strength | ASTM D638 / ISO 527 (23 °C) | ≥ 120 MPa |
| Dielectric Strength (Wall Thickness) | ASTM D149 / IEC 60243 (In 90 °C Transformer Oil) | ≥ 10.0 kV/mm |
| Applicable Chemical Media | Immersion Exposure Compatibility | Compatible with mineral transformer oil, ozone, SF6 gas, and mild organic solvents. Not recommended for concentrated strong acids. |
2. Dimensional Specifications & Precision Tolerances
NEMA G7 tubing is manufactured using standard mandrels or custom tooling to meet precise physical envelope requirements:
- Inner Diameter (ID) Range: Standard tooling from 6.0 mm up to 300 mm. ID tolerance maintained within ± 0.10 mm to ± 0.25 mm depending on mandrel diameter.
- Outer Diameter (OD) & Wall Thickness: Wall thickness ranges from 1.0 mm up to 25.0 mm. Outer diameter precision can be centerless ground to achieve tolerances within ± 0.05 mm.
- Standard Tube Lengths: Standard manufactured lengths are 1000 mm and 1200 mm, cut to custom length specifications upon request.
3. Machining Capabilities & Custom Tooling Services
NEMA G7 silicone composite tubes exhibit good machinability when utilizing correct carbide or diamond-coated tooling:
- CNC Milling & Turning: Can be turned, threaded, chamfered, and grooved on standard metalworking equipment. High-speed dust extraction is required during dry machining.
- Custom Mandrel & Tooling Fabrication: For non-standard inner diameters or oval/square profile tubing, custom steel mandrels can be manufactured for low-volume B2B prototyping and high-volume production runs.
4. Frequently Asked Questions (FAQ)
Q: What is the main difference between NEMA G7 tubing and NEMA G11 tubing?
A: NEMA G7 tubing uses silicone resin rated for Class H (180 °C continuous) with superior arc resistance (≥ 180s) and ultra-low dielectric loss. NEMA G11 tubing uses modified epoxy resin rated for Class F (155 °C continuous) with higher mechanical tensile and hoop strength. Select G7 for higher heat, SF6 gas, and arcing environments; select G11 for high dynamic mechanical load at 155 °C.
Need Custom Dimensions or Tooling for NEMA G7 Tubing?
Contact RDS Composite technical sales team for custom Mandrel tooling, certified TDS datasheets, and direct B2B volume pricing.
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