Furniture - Storage units - Determination of stability

IS 13089: Scope Overview

• Standard Covered: IS 13089:1991 corresponds to ISO 7171:1988.
• Field of Application: Specifies methods for testing strength and stability of furniture, particularly chairs, stools, tables, and trolleys.
• Equivalent Indian Standards:
  • IS 5416 (Part 1 & 2): Methods for chairs and stools (strength & stability).
  • IS 5967 (Part 1 & 2): Methods for tables and trolleys (strength & stability).

Key Points:

• The standard defines test procedures rather than design formulas.
• It ensures furniture safety and durability through standardized testing.
• No direct formulas or tables are provided in the scope; they appear in related IS codes (IS 5416, IS 5967).

Summary Table of Related IS Codes

If you need formulas or test procedures, refer to IS 5416 and IS 5967 for detailed methods on load application and stability criteria.

IS 13089 - Normative References Summary

IS 13089 adopts key International Standards (ISO) related to furniture testing, with equivalent Indian Standards (IS) specified for national use:

Key Points:

• IS 5416 covers strength and stability tests for chairs and stools.
• IS 5967 covers strength and stability tests for tables and trolleys.
• These IS standards are identical in content to the referenced ISO standards.
• The Indian Standards replace ISO standards where applicable, maintaining consistency in testing methods.

Usage:

• Refer to IS 5416 and IS 5967 for detailed test methods and specifications on furniture strength and stability.
• These references ensure uniformity in test procedures for furniture under IS 13089.

flowchart LR
    A[IS 13089] --> B[ISO 7173]
    A --> C[ISO 8019]
    B --> D[IS 5416 (Chairs & Stools)]
    C --> E[IS 5967 (Tables & Trolleys)]
    D & E --> F[Strength & Stability Test Methods]

This ensures compliance with recognized international and national testing protocols.

IS 13089 - Test Equipment and Conditions (Clause 3 & 3.5)

• Test Equipment: Use equipment as per referenced IS or ISO standards (e.g., IS 5416 for chairs, IS 5967 for tables).
• Test Conditions: Follow prescribed procedures; if design is not covered, adapt tests closely and document deviations.

Key Tolerances (Clause 3.5):

Notes:

• Ensure calibration of force application devices within ±5% accuracy.
• Masses used for loading must be within ±0.5% of specified weight.
• Dimensional measurements during testing must be accurate within ±0.5 mm.

This ensures repeatability and reliability of strength and stability tests for furniture as per IS 13089.

flowchart LR
    A[Test Setup] --> B[Apply Load (Force ±5%)]
    B --> C[Measure Deflection/Failure]
    C --> D[Record Mass (±0.5%)]
    D --> E[Check Dimensions (±0.5 mm)]
    E --> F[Evaluate Compliance]

IS 13089 does not explicitly provide detailed formulas or tables for the stability of unloaded storage units. However, based on general principles and related standards (like ISO 7172), the key aspects are:

Stability of Unloaded Unit

• Definition: Ability to resist overturning moments due to external forces without load.
• Critical Parameters:
  • Height (h)
  • Base width (b)
  • Center of Gravity (CG) height (h_cg)
  • Overturning moment due to applied force (M_o)
  • Restoring moment due to weight (M_r)

Key Formula:

[ \text{Stability ratio} = \frac{M_r}{M_o} = \frac{W \times \frac{b}{2}}{F \times h} ]

Where:

• (W) = weight of the unit
• (F) = lateral force applied at height (h)

Unit is stable if: [ M_r \geq M_o \quad \Rightarrow \quad \frac{W \times b/2}{F \times h} \geq 1 ]

Typical Specifications:

• Base width (b): Should be maximized relative to height for better stability.
• Height to base ratio: Usually < 3 for good stability.
• Fixing: Units may be anchored to walls for enhanced stability.

Recommended Test (from ISO 7172):

• Apply lateral force at 75% of unit height.
• Measure force at which overturning occurs.

graph LR
A[Weight (W)] --> B[Restoring Moment (W × b/2)]
C[Lateral Force (F) at height h] --> D[Overturning Moment (F × h)]
B --> E[Stability Check]
D --> E

Summary: Ensure the restoring moment from weight and base width overcomes overturning moment from lateral forces for stable unloaded units.

IS 13089: Stability with Loads on Movable Parts (Vertical Force)

Key Points from IS 13089 & Related ISO Standards

• Stability Definition: Ability of furniture to resist overturning forces.
• Vertical Force Application (Clause 3.1): Use a device applying vertical force (fixed or gradually increasing) without restricting furniture movement.
• Test Reference: ISO 7172 (Tables) and ISO 7171 (Storage units) provide detailed test methods.

Typical Stability Test Setup

General Stability Formula (Conceptual)

[ M_{resisting} \geq M_{overturning} ]

Where:

• ( M_{resisting} = W \times d_{cg} ) (weight × horizontal distance of center of gravity from pivot)
• ( M_{overturning} = F_v \times h ) (vertical force × height at which force is applied)

Furniture is stable if:

[ W \times d_{cg} \geq F_v \times h ]

Summary

• Apply vertical force at specified points on movable parts.
• Use ISO 7171/7172 for detailed test procedures.
• Verify overturning moment does not exceed resisting moment.

graph LR
A[Vertical Force \(F_v\)] --> B[Overturning Moment \(M_o = F_v \times h\)]
C[Weight \(W\)] --> D[Resisting Moment \(M_r = W \times d_{cg}\)]
B --> E{Stability Check}
D --> E
E -->|Stable| F[No Overturning]
E -->|Unstable| G[Overturning Occurs]

This approach ensures furniture stability under vertical loads on movable parts per IS 13089 and ISO references.

IS 13089 references stability of furniture storage units under loads, aligned with ISO 7171 principles.

Key Concepts for Stability with Loads on Open Shelf:

• Stability = resistance to overturning due to vertical (gravity) and horizontal (lateral) forces.
• Forces considered:
  • Vertical load (W) on shelves.
  • Horizontal force (H) simulating tipping or impact.

Fundamental Stability Criterion:

[ \text{Overturning Moment} \leq \text{Restoring Moment} ]

Where:

• Overturning Moment (M_o) = H × height of force application (h)
• Restoring Moment (M_r) = W × half of base width (b/2)

Stability Check Formula:

[ H \times h \leq W \times \frac{b}{2} ]

• h = vertical height where horizontal force acts.
• b = width of base footprint resisting overturning.
• W = total vertical load (self-weight + shelf load).

Practical Specifications:

• Furniture must resist a minimum horizontal force (e.g., 50 N to 100 N) without tipping.
• Base width b should be maximized or anchoring provided.
• Load distribution on shelves must be uniform to avoid eccentric moments.

Typical Table Extract (Example):

graph LR
A[Horizontal Force (H) at height h] --> M_o[Overturning Moment = H × h]
B[Vertical Load (W) at base width b] --> M_r[Restoring Moment = W × (b/2)]
M_o -->|Should be ≤| M_r

Summary: Ensure ( H \times h \leq W \times \frac{b}{2} ) by adjusting load, base width, or anchorage to maintain stability of open shelf furniture.

IS 13089: Test Report Requirements – Key Points

• Test Validity: Results apply only to the tested specimen. For generalization, the specimen must represent the production model.

• Non-Covered Designs: If test procedures don't cover a design, conduct tests as closely as possible to the standard and document deviations.

• Test Equipment & Conditions: Must comply with prescribed conditions to ensure reliability.

• Equivalence Table: IS 13089 references international standards (ISO 7173, ISO 8019) with corresponding Indian Standards (IS 5416, IS 5967) for strength and stability testing of furniture.

Note: Detailed test procedures and formulas are found in referenced IS codes (IS 5416, IS 5967).

flowchart LR
    A[Test Specimen] --> B{Is specimen representative?}
    B -- Yes --> C[Apply test results to production]
    B -- No --> D[Conduct new tests on representative specimen]
    C --> E[Report test results]
    D --> E

IS 13089 - Tolerances Summary (Clause 3.5):

• Forces: ± 5%
• Masses: ± 0.5%
• Dimensions: ± 0.5 mm

These tolerances apply unless otherwise specified in the standard.

Additional Notes:

• The tolerances ensure uniformity and reliability in furniture testing (strength, stability).
• Dimensions tolerance of ±0.5 mm is critical for manufacturing precision.
• Force tolerance ±5% accounts for testing variability.
• Mass tolerance ±0.5% ensures consistency in material weight measurements.

Related Standards for Reference:

flowchart LR
    A[Tolerances in IS 13089] --> B[Forces ± 5%]
    A --> C[Masses ± 0.5%]
    A --> D[Dimensions ± 0.5 mm]

Use these tolerances as baseline limits for quality control and testing compliance in furniture design and manufacturing.

IS 13089: Deviations and Special Cases - Key Points

• Deviations in Testing:
  When a design or test procedure is not explicitly covered, perform the test as closely as possible to the standard method. Document all deviations clearly.

• Tolerances (Clause 3.5):
  Unless otherwise specified, use the following tolerances:

  • Forces: ± 5%
  • Masses: ± 0.5%
  • Dimensions: ± 0.5 mm

• Special Cases:
  No explicit formulas or tables are provided for special cases. The approach is to adapt the standard procedure and record deviations.

Summary Table: Tolerances

This ensures consistency while allowing flexibility for non-standard designs or tests.