The 1978 edition of IS 802 Part 2 outlines detailed procedures for the fabrication, galvanizing, inspection, and packaging of structural steel elements used in overhead transmission line towers across India. This standard guides engineers and fabricators to maintain quality, durability, and safety by adhering to nationally accepted practices in steel tower component production.
Overview
The 1978 edition of IS 802 Part 2 outlines detailed procedures for the fabrication, galvanizing, inspection, and packaging of structural steel elements used in overhead transmission line towers across India. This standard guides engineers and fabricators to maintain quality, durability, and safety by adhering to nationally accepted practices in steel tower component production.
Audience
Contents
Structure
This section defines the extent of the code and specifies that design drawings must include all relevant dimensions such as member lengths, slopes, cross-section sizes, bend and gauge lines, bolt details including diameter and quantity, gusset plate dimensions, hole locations, and relative positioning of components. Manufacturers are required to provide all inspection gauges and templates. Bolt spacing and edge distances must comply with prescribed minimum values to ensure structural integrity.
Detailed design dimensions must be included in drawings, covering member lengths, section sizes, slope indicators, bend and gauge lines, hole placements, and bolt details. Drawings should comply with IS 696-1972 for general arrangement and IS 962-1967 for technical drawing conventions. Shop drawings need to clearly show member sizes, hole positions, edge distances, and any clipping or notching for fabrication.
Steel grades must be distinctly marked to ensure proper placement. Manufacturers are responsible for using correct steel grades and may be required to conduct laboratory testing to confirm quality. Materials have to be straightened without hammering, avoiding twists and sharp bends, ensuring adjacent members have proper contact within tolerances.
This section details identification of materials, adherence to fabrication tolerances as per clauses 6.2 to 6.5 and IS 7215-1974, and the operations of cutting, drilling, welding, and assembling. Maintaining dimensional accuracy and surface condition is emphasized throughout fabrication.
Holes must be cylindrical with diameter equal to bolt diameter plus 1.5 mm clearance. Minimum bolt spacing and edge distances vary with bolt size and are specified in a tabulated form. Holes close to bending lines are drilled or punched after bending using templates or jigs to maintain location accuracy.
Maximum deviation in hole diameter between opposite sides is limited to 0.8 mm. Consecutive hole spacing tolerance is ±0.5 mm. Straightening must be done by pressure only without hammering, ensuring no sharp bends or twists. General tolerances not specifically addressed follow IS 7215-1974.
Bundles and packages must be clearly and durably marked to prevent loss or damage during transport. Markings include manufacturer details, identification numbers, quantity, weight, destination, and handling instructions. Manufacturers must also supply gauges and templates for inspection.
Shop drawings should include all fabrication details to facilitate temporary assembly of one complete tower type. This temporary erection, performed either horizontally or vertically, verifies dimensional accuracy and fit before starting mass fabrication. Any discrepancies found must be corrected.
Surface preparation must conform to IS 1477 (Part I) with primer and finishing coats as per IS 1477 (Part II). Hot-dip galvanizing is required for bolts and fasteners (IS 5358-1969), structural members (IS 4759-1968), and spring washers (IS 1573-1970) ensuring adequate corrosion resistance and coating thickness.
Inspectors are granted free access during reasonable hours to fabrication facilities to verify compliance. The manufacturer must provide all necessary inspection tools such as gauges and templates to facilitate accurate checking of dimensional and fabrication standards.
Packing must prevent damage or loss during transit with clear marking on each bundle or package. Smaller items like bolts and nuts are to be packed in double-layer gunny bags with proper tagging. Protective packing and handling instructions should be provided for all components.
Manufacturers are obligated to guarantee conformity with the standard upon purchaser request. They must supply calibrated gauges and templates for inspection and ensure packing prevents damage with proper identification markings. Documentation supporting compliance should be clear and signed.
Frequently Asked
IS 802 Part 2 specifies that the maximum difference in hole diameter between the two sides of a plate or angle should not exceed 0.8 mm, ensuring minimal taper. Consecutive hole spacing tolerance is ±0.5 mm. Holes must be cylindrical with a diameter equal to the bolt diameter plus a 1.5 mm clearance. Other fabrication tolerances follow clauses 6.2 to 6.5 or IS 7215-1974 when unspecified, ensuring precise fit and structural integrity during assembly.
According to IS 802 Part 2 (1978), bolts and fasteners should be hot-dip galvanized following IS 5358-1969. Structural steel members require hot-dip zinc coating complying with IS 4759-1968, while spring washers must meet galvanizing requirements as per IS 1573-1970. These standards ensure adequate corrosion protection and durability of the transmission tower components.
Steel components must be straightened using pressure only, avoiding hammering to prevent material damage. Members should be free from twists and sharp bends, which are grounds for rejection. Mild steel angle sections up to 75x75 mm with thickness up to 6 mm can be cold bent up to 10°, while larger or thicker sections require hot bending. Holes near bends must be drilled or punched after bending using templates to maintain positional accuracy, ensuring structural soundness.
Inspection must be performed at the manufacturing site before dispatch. Inspectors are allowed access at reasonable times and facilities to verify that fabrication complies with IS 802 Part 2, including dimensional accuracy, weld quality, surface treatment, and packing. Inspections should not disrupt production unnecessarily and ensure components meet all quality standards prior to shipment.
Bolts must protrude 3 to 8 mm beyond the nut after tightening to ensure proper fastening. Holes near bend lines are to be drilled or punched after bending using templates or jigs to maintain accuracy. Minimum bolt spacing and edge distances depend on bolt diameter as specified. Additionally, bolts should not connect members thicker than three times their diameter, and generally should fasten no more than three stressed members (excluding gussets and packings) to minimize bending stresses, ensuring secure and reliable assemblies.
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