technical of PARALLEL GROOVE CLAMPS
1. Ultimate Tensile Strength (UTS)
1. Clamp Body (Al Alloy):
I. UTS: 150–250 MPa, depending on casting quality and grade
2. Bolts (HDG Steel or SS):
I. UTS: 400–800 MPa (e.g., Grade 8.8 bolts: 800 MPa)
2. Working Load / Safe Working Load (SWL)
1. While not designed to carry tension loads like suspension clamps, SWL applies to:
I. Bolt tightening torque holding the conductors
II. Mechanical grip and vibration resistance
2. SWL is typically 30–40% of UTS
3. For a typical multi-bolt PG clamp, this equates to ~3–6 kN holding capacity on each side.
3. Conductor Diameter Compatibility
1. Compatible with:
I. Aluminum/ACSR/AAAC conductors: 6 mm to 40 mm diameter
II. Copper conductors (in bimetallic clamps): 6 mm to 30 mm
2. Available in various groove depths and jaw designs to fit specific strand profiles
3. Supplied in matched sets: e.g., 7/3.15 ACSR or 6/4 AAAC, etc.
4. Slip Strength:
1. PG clamp must not slip under conductor expansion/contraction, vibration, or surge currents
2. Typical minimum slip strength:
I. 5–10 kN, based on torque-tightened grip and serrated/contoured jaw design
3. Must retain contact under:
I. Wind-induced motion (aeolian vibration)
II. Load cycling and thermal expansion
5. Temperature Withstanding Capacity:
1. Operating range: –40°C to +85°C
2. Short-term peak tolerance: up to 250°C under fault or surge currents
3. Conductive surfaces designed to avoid hot spots or thermal runaway
6. Corrosion Resistance:
1. Aluminum alloy body: inherently corrosion-resistant
2. HDG bolts/nuts: ≥80 µm zinc coating (IS 2629 / ASTM A153)
3. Bimetallic PG clamps: include copper or tin-plated inserts to prevent galvanic corrosion
4. Optional epoxy or anodized coating for harsh environments
7. Impact & Fatigue Strength:
1. PG clamps must endure:
I. Installation shocks, minor hammering
II. Conductor galloping or twisting
III. Thermal fatigue from load fluctuations
2. Vibration testing: ≥10,000 cycles without loosening or conductor damage
8. Mechanical Endurance:
1. Service life: 25–40 years, depending on environment
2. Must withstand:
I. Seasonal expansion/contraction
II. Wind vibration
III. UV, rain, dust exposure
3. Clamp pressure retention tested for long-term contact reliability
9. Design Safety Factors:
1. Mechanical design factor: ≥2.5 to 3.0
2. Electrical safety includes:
I. Low contact resistance (<100 micro-ohms="micro-ohms">
II. Adequate surface area to dissipate heat under fault conditions
III. Anti-slip and anti-vibration design using contoured or serrated grooves
Top 5 Quality Assurance
1. Mechanical & Electrical Type Testing (as per IS 5561 / IEC 61284)
a. Slip test (under tensile pull)
b. Contact resistance test (<100>
c. Short-circuit current test (e.g., 25–30 kA for 1 second)
d. Thermal cycling test (simulate heating/cooling over 1000 cycles)
2. Material Certification & Composition Analysis
a. Aluminum alloy: LM6 / LM25 grade compliance per IS or ASTM standards
b. Copper insert (if bimetallic): Purity ≥99.9%
c. Bolts and nuts checked for:
I. Proof load
II. Galvanizing thickness
III. Thread pitch and tolerances
3. Dimensional & Visual Inspection
a. Groove depth and width inspection for correct conductor fit
b. Threaded hole alignment and casting integrity
c. Visual checks for:
I. Burrs
II. Cracks
III. Incomplete casting or surface voids
4. Corrosion Resistance Testing
I. Salt spray test (ASTM B117) for ≥500–1000 hours
II. Bimetallic corrosion simulation (if applicable)
III. Confirm longevity under high-humidity or coastal installations
5. Traceability & Documentation
a. Each clamp marked with:
I. Manufacturer name or logo
II. Conductor size range
III. Batch number or heat number
b. Supplied with:
I. Routine Test Report
II. GTP (Guaranteed Technical Particulars)
III. ISO 9001/14001 compliance
IV. Optional third-party test reports (CPRI/ERDA)