Electrical Insulating Tube

Electrical Insulating Tube is a general term for pipes with electrical‑insulation performance, divided into rigid insulating tubes and flexible insulating sleeves. Made of fiberglass‑epoxy composite, PVC‑U, CPVC, phenolic, PTFE and other insulating materials. Core functions: electrical isolation against short‑circuit, mechanical protection, moisture‑proof and chemical‑corrosion resistance. Widely used in HV/LV electrical equipment, transformers, switchgears, cable wiring, live‑line working and anti‑corrosion chemical systems.

Main material distinctions

‑Epoxy Fiberglass Tube (FRP / G10 / G11 / FR‑4): High mechanical strength and dielectric strength, working temperature 130‑155 °C, machinable. For high‑voltage apparatus, transformers, fuses, live‑line working tools, major export itemAlibaba.co…. ‑PVC‑U Electrical Conduit: Low‑cost, flame‑retardant, for building cable wiring; working temperature‑5~60 °C. ‑CPVC Chlorinated PVC Tube: Higher temperature‑resistance than PVC‑U up to 93 °C, acid‑alkali resistance, for chemical industry and high‑temp cable protection. ‑Phenolic Paper / Cloth Tube: Internal lead‑wire insulation for oil‑immersed transformers, good dielectric performance in oil, moderate cost. ‑Flexible Varnished / Silicone‑glass Sleeving: Bendable, for motor winding and small‑appliance wire harness protection. ‑PTFE Tube: Working temperature‑196~260 °C, superior chemical resistance, special high‑temperature & high‑frequency conditions.

1. Main Types

1. By stiffness

‑Rigid insulating tube: epoxy‑fiberglass, PVC‑U, CPVC, phenolic tube; rigid support for mechanical loads. ‑Flexible insulating sleeve: varnished glass‑fiber sleeve, silicone sleeve, heat‑shrink tube; bendable for wire‑harness protection.

2. By voltage class

‑Low‑voltage: ≤1 kV, building wiring, control cabinet internal wiring. ‑Medium‑high‑voltage: 3‑40.5 kV, transformers, switch‑gear, live‑line working components.

3. Size range

Rigid epoxy‑fiberglass tube: ID Φ8‑Φ500 mm, wall thickness 2‑30 mm, standard length 1000/2000 mm, custom cut‑to‑length available. PVC‑U / CPVC: DN16‑DN315. Flexible sleeve: ID 0.5‑50 mm, supplied in rolls. Color: natural green, brown, black, custom colors available.

2. Production Process

‑Epoxy‑fiberglass tube: Filament‑winding / pultrusion → high‑temp curing → cutting → precision machining → inspection. ‑PVC‑U / CPVC tube: Compounding & extrusion → sizing cooling → cutting → belling → inspection. ‑Flexible varnished sleeve: Glass‑fiber braiding → varnish impregnation → baking curing → slitting & rolling.

3. Key Features

‑Electrical properties: High breakdown strength & volume resistivity, prevent leakage and arc short‑circuit. ‑Epoxy‑fiberglass: Excellent strength‑to‑weight ratio, moisture & chemical resistance, can be turned/milled/drilled; avoid heavy impact. ‑PVC‑U: Low cost & easy installation; not for high‑temperature service. ‑Phenolic paper tube: Good insulation in transformer oil; insulation drops under humid ambient. ‑Flexible sleeve: Good bending performance for complex wiring; not for load‑bearing structures. ‑Limitations: Each material has definite maximum service temperature; over‑temperature causes insulation failure. Store dry, avoid sharp impact.

4. Typical Applications

Insulating structural parts for transformers, high‑voltage switch cabinets, fuses, disconnectors; live‑line working tool poles; cable protection pipes for buildings & factories; insulation for motor and appliance wire harnesses; chemical anti‑corrosion pipelines; new‑energy equipment insulation.

5. Standards

‑China: GB/T 13398‑2026 Insulating tubes for live working; GB/T 43815‑2024 PVC‑U electrical conduits; GB/T 5131 Epoxy glass‑cloth tubes; GB/T 7113 Flexible insulating sleeving. ‑International: IEC 60855‑1, IEC 60684; ASTM D149; NEMA G10/G11. ‑Russia / CIS: ГОСТ 17675‑87 Flexible electrical‑insulating tubes. EAC declaration required for EAEU export.

6. Selection Guidance

1. High‑voltage equipment: choose Epoxy‑fiberglass G10/G11. Low‑voltage building wiring: PVC‑U. High‑temp corrosive environment: CPVC or PTFE.
2. Oil‑immersed transformer internal parts: phenolic paper/cloth tube. Bendable wire‑harness: flexible varnished sleeve.
3. Order specification: material grade, ID × OD × length, voltage rating, temperature class, color, machining requirement, MTC mill test certificate required.
4. Epoxy products: forbid heavy impact. Phenolic paper tubes: strictly dry storage.

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