technical of YOKE PLATE
1. Ultimate Tensile Strength (UTS)
1. UTS is the maximum axial force the yoke plate can withstand before mechanical failure.
2. Yoke plates are designed to match or exceed the ultimate tensile strength of the associated conductor or insulator string.
2. Working Load / Safe Working Load (SWL)
1. SWL is typically 1/2.5 to 1/3 of the UTS, ensuring safety during long-term operation.
2. Typical SWL Range:
30 – 100 kN, depending on the design, hole spacing, and steel grade.
3. Designed to handle combined mechanical loads from:
I. Insulator tension
II. Conductor weight and tension
III. Wind and seismic forces
3. Conductor Diameter Compatibility
1. Yoke plates do not clamp the conductor directly but connect conductor hardware like suspension clamps, tension clamps, or insulator strings.
2. However, the hole spacing and hardware sizing must match fittings that correspond to:
Conductor diameters between 18 mm to 40+ mm
3. Multiple hole types (oval/round) allow compatibility with:
Socket clevis, eye fittings, U-bolts, and ball and socket connections.
4. Slip Strength:
1. Since yoke plates are bolted and pinned, not clamped, slip strength is ensured through mechanical locking (i.e., no slippage should occur under rated load).
2. Pins and shackles used with yoke plates must withstand:
≥ 95% – 100% of connected component UTS
3. Failure to slip or deform is critical in maintaining alignment and load balance.
5. Temperature Withstanding Capacity:
1. Yoke plates must remain functional over a wide range of ambient and fault-induced temperatures.
2. Operating Range:
I. -40°C to +120°C (normal)
II. Up to 250°C short-term (during faults or lightning surges)
3. Steel properties and zinc coatings must remain stable within this range without warping or loss of strength.
6. Corrosion Resistance:
1. Used in highly corrosive environments like:
Coastal, industrial, or desert regions
2. Materials & Coating:
I. High-tensile mild steel / forged alloy steel
II. Hot-Dip Galvanized (HDG) as per IS 2629 / ASTM A153 / ISO 1461
3. Coating thickness: Minimum 80–100 µm
4. Optional paint or epoxy coatings for extra protection
7. Impact & Fatigue Strength:
1. Designed to withstand:
I. Dynamic loads, such as conductor galloping, switching surges, and wind-induced vibrations
II. Mechanical shocks during erection or maintenance
2. Fatigue-tested up to 10⁷ cycles
3. Should not crack, deform, or loosen under cyclic loading
8. Mechanical Endurance:
1. Mechanical lifespan: 25–40 years
2. Yoke plates are generally maintenance-free, requiring no replacements unless damaged.
3. Must retain:
I. Dimensional stability
II. Alignment under load
III. Rust and fatigue resistance
9. Design Safety Factors:
1. UTS vs SWL
≥ 2.5 – 3×
2. Pin/bolt shear safety
≥ 3× applied load
3. Thermal overload margin
~2× rated temperature
4. Fatigue resistance
≥ 10⁷ cycles
5. Corrosion protection
≥ 25 years in atmospheric exposure
Top 5 Quality Assurance
1. Standards Compliance
a. Yoke plates are manufactured according to relevant standards such as:
I. IS 2486 (Part 1 & 2)
II. IEC 61284
III. ASTM A153 (for galvanizing)
b. Ensures mechanical load-bearing capacity and safe use in high-voltage applications.
2. Raw Material Testing and Certification
I. Typically made from mild steel, galvanized steel, or alloy steel.
II. Each batch is supported by Material Test Certificates (MTCs).
3. Dimensional Accuracy and Tolerance Control
I. Yoke plates are precisely cut, drilled, and formed according to design drawings.
II. Dimensions (hole spacing, diameter, thickness) are checked using calibrated measuring instruments to ensure perfect alignment during assembly.
4. Hot-Dip Galvanizing and Corrosion Protection
1. All plates are hot-dip galvanized to a minimum zinc thickness of 85 microns as per IS 2629 / ISO 1461.
2. Zinc coating is tested for:
I. Thickness
II. Adhesion
III.Salt spray resistance to prevent rust and extend service life in outdoor conditions.
5. Final Inspection, Marking & Documentation
I. Each Yoke Plate is inspected for:
II. Surface defects, burrs, bends, and cracks.
III. Hole alignment and flatness.
IV. Marked with manufacturer’s logo, batch number, and size/type.