technical of multi-bolt aluminum parallel groove clamp
1. Ultimate Tensile Strength (UTS)
1. Not used for primary load-bearing, but UTS still matters for clamp body and bolts.
2. Clamp Body (Aluminum Alloy – LM6 / LM25 / A356):
I. UTS ~ 150–250 MPa
3. Bolts (Hot Dip Galvanized Steel or Stainless Steel):
I. UTS ~ 400–800 MPa depending on bolt grade (e.g., 8.8 grade steel = 800 MPa)
2. Working Load / Safe Working Load (SWL)
1. While PG clamps are not designed to carry tension, SWL applies to:
I. Mechanical grip strength on the conductor
II. Resistance to separation under wind-induced vibration
2. Safe working mechanical grip: 3–5 kN, depending on size and conductor material
3. Bolted joint must maintain integrity under typical line vibration and conductor weight
3. Conductor Diameter Compatibility
1. Designed to connect two conductors in parallel
2. Sizes vary; typical compatibility:
I. Min: 6 mm (ACSR/AAAC)
II. Max: 40 mm (for large transmission conductors)
3. Multi-bolt design ensures uniform pressure distribution on both conductors, reducing hot spots and deformation.
4. Slip Strength:
1. Critical to maintain electrical and mechanical contact integrity under vibration and expansion
2. Slip strength requirement: ≥ 5–10 kN, depending on size and tightening torque
3. Enhanced by:
I. Serrated inner surfaces
II. Proper tightening of bolts (torque ≥ 20–50 Nm depending on design)
5. Temperature Withstanding Capacity:
1. Operating temperature: –40°C to +85°C continuous
2. During high-current flow: withstands up to 150°C to 200°C temporarily
3. Expansion must not compromise clamp grip or contact resistance
4. Tested for thermal cycling to simulate conductor heating/cooling
6. Corrosion Resistance:
1. Clamp body (Aluminum): inherently corrosion-resistant in open air
2. Bolts (HDG steel or SS):
I. Zinc coating ≥ 80 µm (for HDG bolts, as per IS 2629/ASTM A153)
3. For high-corrosive areas, clamps may be anodized or epoxy-coated
4. Electrolytic corrosion controlled by using bimetallic connectors or inhibitors
7. Impact & Fatigue Strength:
1. Withstands:
I. Wind-induced conductor vibrations (galloping, aeolian vibration)
II. Mechanical shocks during installation or maintenance
2. Bolted connections and clamp body tested for 10,000+ vibration cycles
8. Mechanical Endurance:
1. Service life: 25–40 years, depending on corrosion zone
2. Retains mechanical grip and electrical conductivity under:
I. Repeated thermal expansion
II. Conductor movement
III. Seasonal loading and environmental changes
9. Design Safety Factors:
1. Mechanical design factor: ≥ 2.5 on slip strength
2. Electrical design:
I. Maintains low contact resistance over life
II. Meets or exceeds standards for thermal and mechanical cycling
Top 5 Quality Assurance
1. Type & Routine Testing as per IEC 61284 / IS 5561
a. Mechanical grip test (minimum slip force verification)
b. Temperature cycling test
c. Short-circuit current test (for high-current passage and expansion simulation)
d. Contact resistance measurement (<100>
2. Material Testing & Certification
a. Aluminum body tested for:
I. Composition (Al-Si-Mg alloys as per ASTM B108)
II. Tensile strength and elongation
b. Bolts & nuts tested for:
I. Galvanizing thickness
II. Hardness (Brinell or Rockwell)
III. Thread conformity (gauge test)
3. Dimensional Inspection
a. 100% check of:
I. Groove width and depth
II. Bolt hole alignment and spacing
III. Surface finish and casting integrity (no cracks or voids)
b. Templates/gauges used for consistent tolerance control
4. Corrosion & Environmental Resistance Testing
a. Salt spray test (ASTM B117): ≥ 500–1000 hours for marine/industrial zones
b. Moisture ingress test for clamps with sealing (if any)
c. Bimetallic compatibility testing (if Cu-Al contacts are used)
5. Traceability & Documentation
a. Each clamp marked with:
I. Manufacturer name/logo
II. Size/type code
III. Batch number
b. Supplied with:
I. GTP (Guaranteed Technical Particulars)
II. Routine test reports
III. ISO 9001 compliance certificate
IV. Optional third-party inspection reports (CPRI/ERDA)