technical of ISOLATOR CLAMPS
1. Ultimate Tensile Strength (UTS)
1. Definition: The maximum force the clamp can withstand before failure.
2. Typical Value:
I. For forged or cast Aluminum Alloy: ≥ 45–60 kN
II. For Copper Alloy clamps (used for copper busbars): ≥ 60–70 kN
3. Standard: Tested as per IEC 61284 / IS 5561
2. Working Load / Safe Working Load (SWL)
1. Definition: Maximum continuous load the clamp can handle safely during normal operation.
2. Value:
I. Typically 30–40% of UTS, providing sufficient margin.
II. For example, if UTS = 60 kN ⇒ SWL = 20–24 kN
3. Conductor Diameter Compatibility
1. Definition: Acceptable range of conductor diameters that the clamp can hold.
2. Typical Range:
I. Suitable for ACSR, AAAC, AAC conductors with diameters between 12 mm – 40 mm
3. Design Variants:
I. Bolted, compression, or wedge-type for different installation needs.
4. Slip Strength:
1. Definition: Resistance to axial slipping under tensile load.
2. Requirement:
I. Should be ≥ 95% of conductor’s rated tensile strength.
II. Must prevent slippage under wind load, thermal expansion, or short-circuit force.
5. Temperature Withstanding Capacity:
1. Operating Temperature:
I. –40°C to +105°C (continuous)
II. Up to 250°C during short-circuit conditions
2. Material Selection: High-grade aluminum alloy or copper with good heat dissipation.
6. Corrosion Resistance:
1. Coating:
I. Hot-dip galvanized (for steel)
II. Anodized aluminum / Tin-plated copper for high atmospheric resistance.
2. Salt Spray Test: Should pass ≥ 1000 hours as per ISO 9227.
3. Environment: Designed for coastal, industrial, and high-humidity zones.
7. Impact & Fatigue Strength:
1. Performance:
I. Withstands vibrations due to wind or switching shocks.
II. Survives thermal cycling without mechanical failure or loosening.
2. IEC Vibration Test: 10–30 million cycles without degradation.
8. Mechanical Endurance:
1. Requirement:
I. Retain clamping force, alignment, and conductivity for ≥ 30 years of service.
II. No loosening, fracture, or fatigue in long-term operations.
9. Design Safety Factors:
1. Standard Factor of Safety:
I. ≥ 2.5 to 3.0 times the SWL.
2. Purpose:
I. Accommodates extra stresses due to environmental effects, aging, and mechanical loads.
Top 5 Quality Assurance
1. Raw Material & Metallurgical Test
a. Verification of Aluminum or Copper Alloy composition (per IS 617 / ASTM B179).
b. Testing includes tensile strength, elongation %, and Brinell hardness.
2. Dimensional & Fitment Accuracy
a. Every clamp must match approved drawings (length, diameter, bolt hole size).
b. Conductor seating and terminal alignment checked by GO/NO-GO gauges.
3. Surface Finish & Coating Inspection
a. Ensure uniform galvanization or anodizing without blisters or peeling.
b. Minimum coating thickness:
I. Galvanization ≥ 80 µm
II. Anodization ≥ 15 µm
4. Electrical Contact Resistance Test
a. Must maintain contact resistance ≤ 1.0 µΩ over full service life.
b. Checked after mechanical and thermal stress testing.
5. Type & Routine Testing Compliance
a. Type Tests:
I. Tensile test
II. Slip test
III. Temperature rise test
IV. Salt spray test
b. Routine Tests:
I. Visual, dimensional, torque, and hardness testing