technical of stay set
1. Ultimate Tensile Strength (UTS)
1. UTS includes strength of rod, welded eye, and stay plate anchorage.
2. Compliant with IS 4091, IS 2486, and REC construction standards.
2. Working Load / Safe Working Load (SWL)
1. SWL is typically 1/3 of UTS, ensuring operational safety.
2. Typical SWL Range:
15 – 30 kN, depending on rod size and installation depth.
3. Must support:
I. Static pole loading
II. Wind and ice loading
III. Sudden load shifts due to conductor faults
3. Conductor Diameter Compatibility
1. While the stay set doesn't directly interface with conductors, it is selected based on:
I. The mechanical load exerted by the conductor on the pole
II. Matching the tensile strength of the stay wire (typically 6–12 mm, 7-strand)
2. Compatible with stay wires of:
I. 6 mm to 12 mm (1/4" to 1/2") diameter
II. Used for LT, 11 kV, 33 kV, and even 132 kV poles
4. Slip Strength:
1. Slip strength is applicable to:
I. Eye-to-wire connections
II. Rod-to-plate joints
2. There must be no slippage under working or fault conditions
3. Slip resistance ≥ 95% of guy wire RTS, verified by pull tests
4. Ensured by:
Proper locking of nuts and washers
Deep eye bends or thimbles to lock guy wire securely
5. Temperature Withstanding Capacity:
1. All components operate in extreme outdoor environments:
I. Normal Range: -40°C to +70°C
II. Short-term max: Up to 250°C during lightning or fault discharge
2. No deformation, warping, or loss of strength in hot/cold cycles
6. Corrosion Resistance:
1. Exposed to soil, rain, dust, and polluted air.
2. Must resist:
I. Soil acidity and moisture (stay plate)
II. Atmospheric corrosion (stay rod, nuts)
7. Impact & Fatigue Strength:
1. Must endure:
I. Pole vibrations
II. Wind loading
III. Earth movement / soil settlement
IV. Mechanical shock during installation
2. Designed to tolerate millions of small stress cycles
3. Should not crack, loosen, or bend during lifetime
8. Mechanical Endurance:
1. Typical service life: 25 – 40 years
2. Operates maintenance-free if:
I. Galvanization is intact
II. Nuts are properly torqued
3. Resists mechanical creep, corrosion degradation, and fatigue failure
9. Design Safety Factors:
1. UTS vs SWL
≥ 2.5 to 3×
2. Eye Bend Strength
≥ 95% of stay wire RTS
3. Soil pullout resistance
Based on plate area & soil type
4. Fatigue Cycle Strength
≥ 10⁷ cycles
5. Corrosion Life
≥ 25 years (with HDG)
Top 5 Quality Assurance
1. Compliance with Applicable Standards
a. Stay sets are designed and manufactured in accordance with:
I. IS 4091, IS 2486, and utility-specific standards.
II. Hot-dip galvanizing as per IS 2629 / ISO 1461.
b. Ensures the assembly meets required mechanical strength, safety, and environmental durability.
2. Raw Material Testing
a. Components like stay rods, thimbles, bow (eye) plates, and nuts are typically made of mild steel or forged steel.
b. Each material batch undergoes:
I. Chemical composition analysis (to verify grade)
II. Mechanical property testing (tensile strength, elongation)
c. Backed by Material Test Certificates (MTCs) for traceability.
3. Mechanical Load & Dimensional Testing
a. Stay rods and assemblies are tested for:
I. Ultimate Tensile Strength (UTS) — Should match or exceed the rated strength of the stay wire.
II. Thread strength and torque capacity for nuts and rods.
III. Dimensional accuracy of threaded sections, eye ends, and hole sizes.
b. Ensures proper load transfer and secure fitting in the field.
4. Corrosion Protection and Galvanizing
a. All metallic parts are hot-dip galvanized, with:
I. Zinc coating thickness ≥ 85 microns.
II. Adhesion testing and salt spray testing to validate corrosion resistance.
b. Protects components from rust and degradation in outdoor conditions.
5. Final Inspection, Marking & Documentation
a. Complete stay sets are subjected to:
I. Visual inspection for defects, surface finish, and bending.
II. Fitment checks of all parts (rod, plate, nuts, thimble).
b. Marked with batch number, manufacturer’s ID, and sometimes component size.