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Rapid Custom Oil Duct Strip DDP Supplier | High Compaction Transformer Insulation Support
- G4 grade high-density base material
- Excellent insulation performance
- Precise and stable dimensions
- Firm and reliable bonding
- Full customization available
- Good compatibility with insulating oil
Product Overview
Oil duct strip (also called oil duct support strip or winding duct spacer) is a core insulating component for oil-immersed power and distribution transformers. It consists of precision-cut high-density pressboard strips uniformly bonded onto a base of diamond dotted paper (DDP) via thermal curing process.
The raised pressboard strips create continuous vertical oil ducts between winding layers, enabling transformer oil to circulate and dissipate heat generated by the winding. Meanwhile, the DDP base paper provides inter-layer electrical insulation and maintains fixed strip spacing to prevent displacement under short-circuit electrodynamic forces.
Our oil duct strips are made from 100% sulphate wood pulp electrical pressboard (G4 grade), pre-compressed for high density and low shrinkage. The diamond dot adhesive coating is formulated for high bond strength and full compatibility with mineral and ester dielectric oils, ensuring no contamination or degradation over long-term operation at 105°C (Class A insulation).
Product Highlights
- High Mechanical Strength: Machine direction tensile strength up to 107.4 MPa, superior compressive performance vs traditional corrugated pressboard
- Excellent Dielectric Performance: Dielectric breakdown up to 35.7 kV/mm in transformer oil, high purity for partial discharge free operation
- Precision Dimension Control: Tight tolerance on thickness, width and strip pitch for consistent winding assembly
- Superior Oil Impregnation: G4 grade sulphate wood pulp base with excellent oil absorption and dielectric compatibility
- Multiple Strip Profiles: Rectangular, T-shape, trapezoidal and pigeon cauda strips available
- Low Shrinkage: Pre-compressed pressboard with uniform fiber orientation, minimal dimensional change under thermal cycling
- Certified Quality: Manufactured under ISO 9001, compliant with IEC 60641 standards
- Full Customization: Custom slit widths, strip heights, pitches and roll lengths to match your winding design
Applications
- Layer and section winding insulation in oil-immersed distribution transformers (10kV–35kV)
- Winding oil ducts in power transformers and rectifier transformers (up to 110kV)
- Oil cooling ducts in reactors and inductors
- Inter-layer spacing and support in amorphous alloy transformers
- Replacement and maintenance of transformer winding insulation systems
Technical Data Sheet
Part 1: Pressboard Strip (G4 Grade)
| Item | Typical Value | Test Value | Unit |
|---|---|---|---|
| Apparent Density | 1.1 – 1.2 | 1.18 | g/cm³ |
| Moisture Content | 4.0 – 9.0 | 5.7 | % |
| pH of Water Extract | 6.0 – 9.0 | 6.8 | – |
| Ash Content | ≤ 1.0 | 0.51 | % |
| Tensile Strength (MD) | ≥ 90 | 107.4 | MPa |
| Tensile Strength (CMD) | ≥ 50 | 101.3 | MPa |
| Oil Absorption | ≥ 7.0 | 12.29 | % |
| Shrinkage (MD) | ≤ 1.0 | 0.16 | % |
| Shrinkage (CMD) | ≤ 1.4 | 0.25 | % |
| Dielectric Breakdown (in Air) | ≥ 10 | 16.7 | kV/mm |
| Dielectric Breakdown (in Oil) | ≥ 24 | 35.7 | kV/mm |
| Conductivity of Aqueous Extract | ≤ 10.0 | 5.03 | mS/m |
Part 2: Diamond Dotted Paper (DDP Base)
| Item | Typical Value | Test Value | Unit |
|---|---|---|---|
| Base Paper Thickness | 0.25 ± 0.025 | 0.260 | mm |
| Apparent Density | 0.9 – 1.1 | 1.01 | g/cm³ |
| Moisture Content | 4.0 – 8.0 | 5.6 | % |
| Ash Content | ≤ 1.0 | 0.43 | % |
| Adhesive Coating Thickness | 0.006 – 0.012 | 0.011 | mm/side |
| Tensile Strength (MD) | ≥ 80 | 86.6 | N/mm² |
| Tensile Strength (CMD) | ≥ 35 | 48.1 | N/mm² |
| Dielectric Breakdown (dry) | ≥ 2100 | 2230 | V/layer |
| Bond Strength | ≥ 450 | 679 | kPa |
Standard Dimension Range
- Strip height: 2 mm, 2.5 mm, 3 mm, 4 mm, 5 mm (custom available)
- Strip width: 4 mm, 5 mm, 6 mm, 8 mm, 10 mm (custom slit available)
- Strip center pitch: 10 mm, 12 mm, 15 mm, 20 mm, 23 mm (custom pitch available)
- Standard width: 500 mm, 1000 mm (roll or sheet form)
- Insulation class: Class A (105 °C)
Our Services
Custom Manufacturing
- Full customization from drawings or samples: custom strip dimensions, pitches, widths and roll lengths
- OEM & ODM support for transformer manufacturers and insulation distributors
- Special profiles available: T-strip, trapezoidal strip, pigeon cauda strip and custom shaped strips
- Flexible MOQ for both standard and custom specifications
Sample Service
- Samples available for lab test
- Custom prototype samples available upon drawing submission
- Sample lead time: 3–5 working days
Quality Assurance
- 100% incoming raw material inspection
- In-process dimensional and visual inspection
- Final product testing per IEC standards
- Full traceability from raw material to finished goods
- ISO 9001 certified quality management system
FAQ
Q: Can you produce custom sizes according to our drawing?
A: Yes. We provide full custom cutting and fabrication service. Simply send us your drawing with strip height, width, pitch and overall dimensions, and we will manufacture to your exact specifications.
Q: What is your minimum order quantity?
A: MOQ is flexible. For standard sizes, we accept small batch orders. For fully custom specifications, please contact us for MOQ confirmation based on your design.
