Wood/Lignocellulosic Based Panel Products - Methods of Sampling

IS 7638: Scope - Key Specifications and Tables

Scope:
IS 7638 covers sampling and acceptance criteria for plywood, fibreboards, insulation boards, and particle boards as per related IS standards (Annex A).

Key Tables and Specifications:

1. Acceptance Quality Level (AQL) for Panel Products (Table 2, Clause 4.2)

Refer full table for all types.

2. Scale of Sampling and Permissible Defectives (Table 1, Clause 5.1)

IS 7638 - References Summary

IS 7638 refers to multiple Indian Standards that are integral to its provisions. Key points:

• The standard cites other IS codes as normative references; users should check the latest editions.
• Annex A (Page 4) lists these standards, which must be consulted for detailed specifications.
• Amendment No. 2 updates the list of referenced standards.
• Table 2 (Page 2) includes materials with their respective IS codes and minimum thicknesses:

Note:

• BWR = Boiling Water Resistant
• MR = Moisture Resistant

Always verify the latest editions of these IS codes for compliance and updates.

IS 7638 - Definitions (Clause 3.1) Overview

• Clause 3.1 defines terms used in the standard related to veneered products.
• The standard references related IS codes for specific materials:

• IS 7638 complements other standards for plywood, fibre hardboards, insulation boards, and particle boards (see Annex A).

Key Notes:

• Definitions clarify product types and their classification.
• Thickness 1.5 mm is typical for these veneer composites.
• Refer to the respective IS codes for detailed product specifications and grades.

graph LR
A[IS 7638 Definitions] --> B[Bamboo mat veneer composite]
A --> C[Coir veneered board]
A --> D[Medium density coir board]
B --> E[IS 14588]
C --> F[IS 14842]
D --> G[IS 15491]

For detailed design or manufacturing, consult the referenced IS codes directly.

IS 7638: Scale of Sampling - Key Points

1. Scale of Sampling (Clause 5.1, Table 1)

Sampling depends on lot size and Acceptance Quality Level (AQL):

• Format: Sample Size / No. of Sub-samples / Acceptance Number

2. Acceptance Quality Level (AQL) for Board Types (Clause 4.2, Table 2)

IS 7638: Number of Tests and Criteria for Conformity

Sampling Procedure (Clause 4.3.1.1)

• Sampling interval, ( r = \left\lfloor \frac{\text{Lot size}}{\text{Sample size}} \right\rfloor )
• Example: For 1330 boards, sample 32 → ( r = \lfloor 1330/32 \rfloor = 41 )
• Select every 41st board starting from a random point.

Acceptance Quality Levels (AQL) and Sampling (Clause 5.1.1 & Table 1)

• Acceptance number = max allowed defectives in sub-sample.
• Lot conforms if defectives ≤ acceptance number.

AQL Values for Panel Products (Table 2)

IS 7638: Sampling Methods for Panel Products

1. Sampling Scale & Acceptance Criteria (Clause 5.1, Table 1)

• Similar tables exist for AQL 2.5% and 4.0% with different acceptance numbers.
• Sampling is random and sub-samples are inspected individually.

2. Acceptance Quality Levels (AQL) for Panel Types (Clause 4.2, Table 2)

3. Sampling Method Summary

• Random sampling from the lot.
• Sample size and acceptance number depend on lot size and AQL.
• Defectives in sample ≤ acceptance number → lot accepted.
• Statistical quality control methods apply during production (Clause 397).

Visual Summary:

flowchart TD
    A[Lot Size] --> B{Select AQL}
    B --> C[Determine Sample Size & Sub-samples]
   

IS 7638: Inspection Procedures - Key Formulas & Tables

1. Statistical Quality Control (Clause 397)

• Uses Acceptance Quality Level (AQL) to determine sampling and acceptance criteria.
• AQL values depend on product type (see Table 2 below).

2. Table 2: AQL Values for Panel Products (Clause 4.2)

3. Sampling & Acceptance (Clause 5.1, Table 1)

• Acceptance Number = Max defects allowed to accept the lot.

Summary:

• Use AQL from Table 2 based on product type.
• Select sample size & acceptance number from Table 1 based on lot size and AQL.
• Inspect sub-samples

Acceptance Quality Level (AQL) - IS 7638 Summary

Definition (Clause 3.8)

• AQL = Maximum % defective considered satisfactory as a process average.
• Indicates the % defective level that will be accepted most of the time (~89-99%).

Key AQL Values for Panel Products (Table 2, Clause 4.2)

Sampling and Acceptance Criteria (Table 1, Clause 5.1)

IS 7638: Sub-sampling and Retesting Key Points

1. Sampling Procedure (Clause 4.3.1.1)

• Calculate sampling interval ( r = \lfloor \frac{\text{Lot size}}{\text{Sample size}} \rfloor ).
• Select every ( r^{th} ) board starting from a random board.

2. Scale of Sampling & Acceptance Criteria (Clause 5.1, Table 1)

• Similar columns exist for AQL 2.5% and 4.0% with different acceptance numbers.

3. Acceptance Quality Level (AQL) by Product Type (Clause 4.2, Table 2)

• Common AQL values:
  • 1.5% for most plywood, blockboard, particle board, etc.
  • 2.5% for some plywood types and veneered wood board.

4. Retesting (Clause 5.1.1)

• If initial lot passes, sub-samples (from those tested) are further tested.
• Lot is accepted if defectives in sub-sample ≤ acceptance number for the AQL.

Summary Formula for Sampling Interval:

[ r = \left\lfloor \frac{\text{Lot size}}{\text{Sample size}} \right\rfloor ]

Sampling Flow Diagram

flowchart TD
    A[Start: Lot Size] --> B[Calculate Sample Size & r]
    B --> C[Select every r-th board]
    C --> D[Conduct Tests on Sample]
   

IS 7638: Reporting and Documentation - Key Points

• Rounding Off Results:
  Follow IS 2:1960 for rounding numerical values in test reports to ensure consistency and accuracy.

• Disclosure Table for Veneered Boards:
  When reporting, refer to the following standards and minimum thickness (mm):

  Material	Applicable IS Code	Min. Thickness (mm)
  Bamboo mat veneer composite	IS 14588	1.5
  Coir veneered board	IS 14842 (BWR and MR)	1.5
  Medium density coir board	IS 15491 (Grades 1, 2, 3)	1.5

• Statistical Quality Control:
  Use IS 397 for methods on statistical quality control during production.
  Use IS 2500 (Part 2): 1985 for control charts on defect counts and attributes.

Summary for Reporting:

• Test values: Round per IS 2:1960.
• Material specs: Cite IS codes and thickness as per table.
• Quality control: Apply IS 397 and IS 2500 (Part 2) for statistical analysis.

flowchart TD
    A[Test/Analysis] --> B[Calculate final value]
    B --> C{Round off?}
    C -->|Yes| D[Apply IS 2:1960 rules]
    C -->|No| E[Report as is]
    D --> F[Include IS code & thickness per table]
    E --> F
    F --> G[Use IS 397 & IS 2500 for QC data]
    G --> H[Prepare final report]

This ensures clarity, standardization, and compliance in documentation under IS 7638.

IS 7638: List of Product Standards for Panel Products

Key Specifications & Tables

1. List of Relevant IS Codes (Annex A)

• Plywood: IS 303 (BWR, WWR), IS 709, IS 710, IS 1328, IS 4859, IS 4990, IS 5509, IS 5539, IS 7316, IS 10701
• Compregs: IS 3513 (Parts I-III)
• Blockboard: IS 1659 (Grades 1 & 2)
• Hardboard: IS 1658 (Standard medium & oil tempered)
• Particle Board: IS 3087, IS 3097, IS 3129, IS 3478
• Wood Wool Board: IS 3308
• Fibre Insulation Board: IS 3348
• Veneered Wood Board: IS 4834
• Medium Density Fibre Board: IS 12406
• Preliminated Particle Board: IS 12823
• Metal Faced Plywood: IS 13957
• Bamboo Mat Board: IS 13958
• Cement Bonded Particle Board: IS 14276

2. Acceptance Quality Level (AQL) for Sampling (Clause 1.5, Table 2)

IS 7638: Committee Composition & Sampling Specifications

Committee Composition (Annex B)

• Chairman: Shri V. Sivananda, Bangalore
• Members: Representatives from:
  • Public Works Departments (UP, CPWD)
  • Forest Departments (Assam)
  • Plywood Manufacturers' Associations
  • Directorate General of Technical Development
  • Indian Institute of Packaging
  • Federation of Indian Plywood and Panel Industry
  • National Test House, Calcutta
  • Ministry of Defence (R&D)
  • Industry representatives (e.g., Western Indian Plywood Ltd., Nuchem Ltd.)
  • Architects and Commerce Chambers

This multi-disciplinary committee ensures comprehensive standard formulation.

Sampling & Conformity Testing (Clause 5.2 & Table 1)

• If any sample fails, double the samples must be retested.
• Lot passes if all retested samples conform.

Table 1: Scale of Sampling and Acceptance Numbers

Summary

• The technical committee includes government, industry, and research experts.
• Sampling follows strict AQL-based procedures with doubling on failure.
• Acceptance numbers depend on lot size and AQL level.

This ensures robust quality control and stakeholder representation in IS 7638.