Logs for Plywood
1988 Edition

IS 656: Introduction and Key Specifications

• Scope: This standard defines requirements for logs used in plywood manufacturing.
• Standard Mark Usage (Clause 7.1.1):
  • Logs may bear the BIS Standard Mark, confirming adherence to IS 656 under the surveillance of BIS.
  • The use of this mark is regulated by the Bureau of Indian Standards Act, 1986.
• Role of BIS:
  • Oversees standardization, marking, and certification processes.
  • Conducts ongoing inspection, testing, and quality control activities.
• Updates and Revisions:
  • Indian Standards are reviewed periodically and updated accordingly.
  • Users should ensure they are referencing the most current edition or amendments.
• Rounding Procedures (Clause 0.4):
  • Test outcomes must be rounded according to IS 2:1960.
  • The precision of significant digits must align with the values specified.

BIS Regional Offices Contact Information

This introduction frames the quality assurance and compliance requirements for logs used in plywood production as per IS 656.

Scope of IS 656: Specifications for Logs in Plywood Manufacture

• Objective: Establishes criteria for logs intended for use in plywood production.

• Volume Calculation Formula:
  [ V = \frac{1}{4\pi} \times G^2 \times L ] where:

  • (V) = Log volume in cubic meters
  • (G) = Girth of the log in meters
  • (L) = Length of the log in meters

• Marking Provisions: Logs may be marked with the BIS Standard Mark to certify compliance with quality and inspection requirements under BIS supervision.

• Rounding Guidelines: Final measurement or test results must be rounded as per IS 2:1960, maintaining the number of significant digits specified.

• Quality Assurance: Logs should fulfill the minimum quality criteria defined in the standard (Clause 5).

Volume Calculation Parameters

flowchart LR
    G[Girth (G) in meters] -->|Square| G2[G squared]
    G2 -->|Multiply| Prod1[Multiply by Length (L)]
    L[Length (L) in meters] --> Prod1
    Prod1 -->|Multiply by 1/(4π)| V[Volume (V) in m³]

Refer to IS 656 Clause 5 and 7.1.1 for full details on quality and marking requirements.

IS 656: Definitions and Essential Terms

1. Terminology:

• As per Clause 2.1, terms conform to those defined in IS 707-1976 (Seasoned Timber).
• Curvature Limit (Clause 5.2.1): Maximum permitted deviation from a straight line connecting log ends is 30 mm per meter length.

2. Rounding Off Results (Clause 0.4):

• Final test or calculated values should be rounded according to IS 2-1960.
• The count of significant digits retained should match the standard’s requirements.

3. Marking Information (Clause 7.1.1):

• Logs may carry the Standard Mark, indicating conformity with BIS quality control.
• Usage of this mark is controlled by the Bureau of Indian Standards Act, 1986.

Curvature Tolerance Table

Decision Flow for Timber Straightness

flowchart TD
    A[Timber Sample] --> B[Measure Straightness]
    B --> C{Is deviation ≤ 30 mm per meter?}
    C -- Yes --> D[Accept Timber]
    C -- No --> E[Reject or Rework]

This ensures compliance with timber quality as per IS 656.

IS 656: Timber Species for Logs - Highlights

• Reference: Species classification and definitions refer to IS 707-1976 (Timber Seasoning Code).

• Selection Criteria:

  • Logs must be from timber species mutually agreed upon by supplier and purchaser, generally from those identified in IS 707.

• Preservative Treatment:

  • Timber species require prophylactic treatment following Table 2, Group 9 of IS 401-1982 to protect against pests and decay.
  • This treatment should be applied immediately after felling.

Relevant Standards and References

Common Timber Groups from IS 707

Treatment Details (per IS 401-1982 Table 2, Group 9)

• Preservative: Copper Chrome Arsenate (CCA) or equivalent
• Application: Pressure impregnation or brushing
• Purpose: Protection against fungal decay, termites, and insects

flowchart LR
    A[Timber Species Selection]
    B[Classification per IS 707-1976]
    C[Agreement Between Supplier & Purchaser]
    D[Prophylactic Treatment]
    E[IS 401-1982 Table 2 Group 9]
    F[Immediate Treatment Post-Felling]

    A --> B --> C --> D --> E --> F

Consult IS 707 and IS 401 for exhaustive species listings and treatment requirements.

Specifications for Log Dimensions Under IS 656

Key Measurement Guidelines:

• Length Measurement (Clause 4.3.1.1):

  • When a napha or chain groove exists on one end, length is measured from the opposite end to the midpoint of the outer edge of the napha/chain groove and the initial felling cut on the snouted end.
  • Length values should be rounded down to the nearest 0.01 m.
  • Irregular or uneven ends may be trimmed for measurement accuracy.

• Girth Measurement (Clause 4.3.2):

  • Girth is taken as the circumference at the midpoint along the length of the log, measured in meters.

Summary Table of Log Dimensions

Notes:

• Logs must be from species agreed upon by buyer and supplier.
• Measurement methods ensure uniformity critical to veneer quality.
• Uneven ends may be excluded for precise measurement.

flowchart LR
    A[Log End with Napha/Groove] --> B[Measure to Midpoint of Outer Edge of Napha]
    C[Opposite End] --> B
    B --> D[Determine Length]
    E[Mid-Length Point] --> F[Measure Circumference (Girth)]

These procedures provide consistent log sizing for veneer production in line with IS 656.

Summary of Quality Criteria in IS 656

Essential Quality Points (Clause 5 and related):

• Rounding Off:
  All final test results or calculations should be rounded following IS 2:1960, retaining the prescribed number of significant figures.

• Marking (Clause 7.1.1):
  Logs may bear the Standard Mark, signifying compliance with IS 656 under BIS supervision.

  • This mark guarantees product quality through rigorous inspection, testing, and control processes.
  • Its usage is regulated by the Bureau of Indian Standards Act, 1986.

• Quality Control:
  Logs supplied must satisfy minimum quality requirements to be economically and technically suitable for plywood manufacturing.

Log Volume Calculation (Clause 4.3.3)

[ V = \frac{G^2}{4\pi} \times L ]

• (V) = log volume in cubic meters
• (G) = girth (circumference) in meters
• (L) = length in meters

Notes:

• Logs must meet minimum quality benchmarks to ensure plywood grade standards.
• BIS standards are periodically updated; users should verify they have the latest version.

flowchart TD
    A[Received Logs] --> B[Quality Inspection]
    B --> C{Complies with IS 656?}
    C -- Yes --> D[Apply Standard Mark]
    C -- No --> E[Reject or Reprocess]
    D --> F[Supply to Plywood Manufacturer]

For comprehensive specifications, consult the full IS 656 and IS 2:1960 for rounding rules.

Protection Guidelines for Plywood Logs as per IS 656

• Defect Restrictions (Clause 5.2.9):
  The total number of defects such as knots, wounds, bird pecks, and bark pockets must not exceed 4 within every 3-meter segment of the log.

• Log Quality:
  Logs must satisfy minimum quality standards to meet plywood manufacturing requirements.

• Storage and Handling Recommendations:

  • Keep logs elevated on platforms or sleepers to prevent ground moisture absorption and fungal growth.
  • Cover logs with waterproof tarps or sheets to shield from rainfall.
  • Avoid direct sunlight exposure to reduce drying cracks and splitting.
  • If logs are stored longer than 3 months, apply preservative treatments.

Defect Limits Table (per 3 m log length)

Preservation and Storage Flow

flowchart LR
    A[Log Harvesting] --> B[Transport and Storage]
    B --> C{Storage Conditions}
    C -->|Off Ground| D[Store on sleepers/platforms]
    C -->|Cover| E[Use waterproof covers]
    C -->|Shade| F[Protect from direct sunlight]
    C -->|Extended Storage| G[Apply preservative treatments]

Note: For detailed preservative specifications and application methods, see IS 13601 (Preservative Treatment of Timber).

Marking Requirements for Logs as per IS 656

Clause 7.1: Marking Details

Each log shall be clearly and permanently marked on both ends with:

• Supplier’s identification mark (abbreviated initials)
• Length of the log
• Mid-length girth (circumference)

Clause 7.1.1: Use of Standard Mark

• Logs may optionally bear the BIS Standard Mark to confirm compliance with Indian Standards.
• Use of this mark is governed by the Bureau of Indian Standards Act, 1986.
• The Standard Mark signifies that logs have undergone strict inspection, testing, and quality control supervised by BIS.

Additional Notes:

• Length measurement should follow the procedure illustrated in Figure 1 (measurement to the outer edge of napha or chain groove).
• Ends of logs must be coated to prevent splitting as per IS 1141-1973.
• Rounding of measurement and test values should comply with IS 2-1960.

Marking Summary Table

flowchart LR
    A[Log Ends] --> B[Mark Supplier ID]
    A --> C[Mark Length]
    A --> D[Mark Mid Girth]
    A --> E[Optional: BIS Standard Mark]

References:

• IS 656: Clauses 7.1, 7.1.1
• IS 1141-1973 (End Coating)
• IS 2-1960 (Rounding Off)