Methods of test for strength and stability of chairs and stools, Part 2: Determination of stability of chairs and stools
1969 Edition

While IS 5533 Part 2 primarily focuses on furniture dimensions and does not explicitly detail stability test methods, standard industry practice for assessing chair and stool stability generally includes: applying a vertical static load (often 1.5 times the design load) on the seat center to check structural integrity; performing horizontal load tests on seat edges or backrests to simulate tipping forces; conducting tilt tests applying force to the backrest or seat edge to assess overturn resistance; and fatigue testing through repeated loading cycles to evaluate durability. For precise methods, referencing standards such as IS 14587 or ISO 7173 is advisable.

The standard does not explicitly specify load application procedures within the provided context. Generally, loads during stability tests are applied gradually and uniformly to replicate real-world conditions. The magnitude of the load is typically a defined percentage of the design load, applied at points that create the most challenging conditions for stability, and maintained for a defined duration to observe any displacement or failure. For detailed load application protocols, related standards like IS 875 or IS 456 may be consulted.

IS 5533 (1969) does not provide explicit stability test criteria for chairs or stools. However, commonly accepted criteria include that the furniture should not tip over when subjected to horizontal forces applied at the seat or backrest, the center of gravity remains within the base footprint during normal use, and the item withstands specified loads without excessive movement. Typically, the factor of safety is maintained by ensuring the restoring moment exceeds the overturning moment caused by applied forces.

The code does not explicitly list equipment requirements for stability testing. Generally, stability tests utilize standardized setups including load application devices (weights, hydraulic actuators), measurement instruments (dial gauges, inclinometers, strain gauges), and secure specimen fixtures. Calibration and accuracy should comply with relevant standards such as IS 2 for rounding and measurement precision. Safety considerations and repeatability are paramount in the test environment.

Test results must be recorded and rounded in accordance with IS 2-1960. The final values—whether measured or calculated—should retain the same number of significant digits as the corresponding specified values in the standard. This ensures consistency and comparability. For instance, if the standard specifies a value with one decimal place, the test result should be rounded to that same level of precision following IS 2-1960 rounding rules.