Indian Standard Code IS 5391
1992 Edition

The frame must have at least three legs to prevent tipping and can be made from mild steel tubular pipes with a minimum wall thickness of 1.25 mm or aluminium tubular pipes with at least 2 mm wall thickness and 25 mm outside diameter (either square or round). Additionally, mild steel flats with a minimum thickness of 5 mm are permissible. The seat is typically constructed from a single piece of mild steel sheet at least 1 mm thick or aluminium sheet not less than 1.6 mm thick, ensuring structural strength and absence of sharp edges. Alternative materials like suitable plastics, timber, or timber-based products may also be used.

Adjustable chairs should have an overall height of no less than 800 mm measured at the highest position. The seat clearance width must be at least 450 mm. Seat height should be adjustable within the range of 400 mm to 480 mm from the floor, with a recommended fixed height of 435 ± 5 mm as per related standards. The backrest should be inclined between 95° and 105° relative to the horizontal seat plane to promote ergonomic posture. Additionally, the chair's structure must distribute loads evenly, avoid excessive strain on any supports, and maintain stability against sudden shifts in user weight.

The standard permits joining components using riveting, bolting, or welding. The recommended welding techniques include gas welding as per IS 1323:1982, arc welding following IS 816:1969, and resistance spot welding in accordance with IS 819:1957. For aluminium parts, welding should conform to IS 2812:1964 guidelines. These methods ensure structural integrity and compliance with the specified requirements.

Strength testing must be conducted according to IS 5416 (Part 1):1988, verifying that the chair can withstand sustained and impact loads with uniform load distribution and without undue stress on any support. Stability testing follows IS 5416 (Part 2):1988, ensuring the chair does not tip when subjected to sudden lateral forces. Swiveling chairs require vertical axle supports capable of bearing 1500 N without wobbling. These tests confirm that chairs are safe, stable, and durable under typical operating conditions.

Initially, all chair parts must be deburred, with dents and sharp edges removed, followed by pickling, scrubbing, and rinsing to eliminate grease, rust, and scale. Immediately after pickling, a phosphating treatment conforming to Class C of IS 3618:1966 should be applied, following IS 6005:1970 procedures to enhance corrosion resistance and paint adhesion. Surface imperfections are filled with putty meeting IS 110:1983, and aluminium primer conforming to IS 2074:1979 is applied. Painting involves one or more enamel coats complying with IS 151:1985, IS 2932:1974, and IS 2933:1975. Aluminium components must be anodized to provide additional corrosion protection.