technical of TRUNBUNCKLES
1. Ultimate Tensile Strength (UTS)
1. UTS is the maximum axial load the turnbuckle can withstand before failure.
2. Depends on:
I. Material (Mild Steel, Forged Steel, Galvanized Steel)
II. Diameter of rods and eye ends
III. Threading length and integrity
3. Verified as per IS: 2486, ASTM F1145, or DIN 1480 standards.
2. Working Load / Safe Working Load (SWL)
1. Ensures safe tensioning of:
I. Stay/Guy wires
II. Overhead conductors
III. Structural members of lattice towers
2. SWL = UTS / Safety Factor (typically 2.5 to 3)
I. M12
10 – 15 kN
II. M16
20 – 25 kN
III. M20
25 – 35 kN
IV. M24
35 – 50 kN
3. Conductor Diameter Compatibility
1. Turnbuckles do not directly hold conductors but are part of the stay system.
2. They are compatible with:
I. Stay/Guy wires: 7/3.15 mm, 7/4 mm, 7/4.72 mm
II. Messenger wire fittings
III. Installed using thimbles and eye nuts to match cable diameter
3. Connection points like eye–eye, hook–eye, or jaw–jaw are selected to suit specific conductor stay configurations.
4. Slip Strength:
1. Turnbuckles are designed to avoid any slippage or loosening under load.
2. Lock nuts or jam nuts on both threaded ends
3. Thread engagement ≥ 90%
4. No axial slip under 95% of rated load
5. Once tightened, turnbuckles maintain position even under vibration or line movement.
5. Temperature Withstanding Capacity:
1. Designed for all-weather outdoor use.
2. Operating Range:
I. -40°C to +120°C (continuous)
II. Up to 250°C transient (e.g., fault current heat on clamps)
3. Material retains full mechanical strength over temperature range.
6. Corrosion Resistance:
1. Made from carbon steel or forged steel, turnbuckles are built to withstand high and low temperatures.
I. Normal Operation
-40°C to +120°C
II. Short-term Fault Events
Up to 250°C
2. No mechanical degradation under normal or fault-induced thermal expansion.
7. Impact & Fatigue Strength:
1. Turnbuckles are frequently subjected to:
I. Sudden line tension changes
II. Wind-induced vibrations
III. Mechanical shocks during installation
2. Fatigue resistance:
I. No cracking or thread deformation under >10⁶ load cycles
3. High-grade forged steel bodies perform well under
Top 5 Quality Assurance
1. Compliance with Standards
a. Turnbuckles are manufactured according to standards like:
I. IS 2486 (Part 1 & 2) – Hardware fittings for overhead lines.
II. IS 4091 – For galvanized stay fittings.
III. ASTM F1145 – For dimensional and mechanical specifications.
b. Ensures the turnbuckle meets load-bearing and safety requirements for electrical installations.
2. Raw Material Testing and Certification
a. Made from forged steel, malleable iron, or mild steel.
b. Each batch is tested for:
I. Chemical composition to ensure the correct grade of metal.
II. Mechanical properties such as tensile strength, yield strength, and ductility.
c. Supported by Material Test Certificates (MTCs) for full traceability.
3. Mechanical Strength and Load Testing
a. Turnbuckles are subjected to:
I. Tensile load tests to verify the Ultimate Tensile Strength (UTS).
II. Thread integrity tests to ensure smooth and secure tension adjustment under load.
III. Slip and deformation resistance under tensioned conditions.
b. Verifies safe working performance in field applications.
4. Galvanizing and Corrosion Resistance
a. All turnbuckles are hot-dip galvanized as per IS 2629 / ISO 1461.
b. Galvanizing is tested for:
I. Zinc coating thickness (typically ≥85 microns).
II. Adhesion and coating uniformity.
III. Optional salt spray testing for aggressive environments.
c. Ensures durability and long service life in outdoor and coastal installations.
5. Final Inspection, Marking & Documentation
a. Each unit is inspected for:
I. Surface finish, thread smoothness, absence of cracks, and dimensional conformity.
II. Proper working of adjustment mechanism (eye-eye, hook-eye, or jaw-jaw types).
b. Marked with:
I. Batch number, size/type, and manufacturer’s logo.
c. Delivered with:
I. Inspection report
II. Certificate of Conformance (CoC)
III. Mechanical and galvanizing test certificates