teak squares

IS 3731: Scope & Key Specifications

• Scope: IS 3731 covers classification and grading of seasoned timber based on defects, primarily for structural use.

• Defect Evaluation:
  Defects like shakes are quantified in units of defects as per IS 3364 (Part 2) - 1976.
  Example from Table 6.6.2:

• Permissible Defects:
  Clause 3.2.1 states the total defect units must not exceed twice the allowed units for the timber grade.

Summary Diagram of Defect Evaluation Process

flowchart TD
    A[Identify Shake Defect] --> B[Measure Length & Width]
    B --> C[Calculate Units of Defect (from Table 6.6.2)]
    C --> D[Sum Units of Defects]
    D --> E{Is Total ≤ 2 × Allowed Units?}
    E -- Yes --> F[Grade Accepted]
    E -- No --> G[Grade Rejected]

This ensures timber quality conforms to structural safety requirements.

IS 3731: Key Definitions & Defect Units

• Reference Standards:
  Definitions mainly per IS 707-1976 and defect evaluation per IS 3364 (Part 2)-1976.

Units of Defects for Shakes (Clause 6.6.2)

Units of Defects for Knots (Clause 6.4.3)

Important Specification (Clause 3.2.1)

• Total defect units shall not exceed twice the permitted units for each grade.

This system quantifies wood defects to control quality in timber grading per IS 3731.

IS 3731: Grading of Teak Squares – Key Points

• Purpose: Establish uniform grading rules for teak squares to standardize internal trade and replace varied specifications.
• Grades Based on Defects: Teak squares are graded primarily by the extent and type of visible defects affecting quality and conversion loss.
• Inspection Philosophy: No absolute rule; grading relies heavily on expert judgment considering the general quality and probable loss during conversion.
• Rounding Off: Test results must be rounded as per IS 2-1960 rules, matching the significant figures of the specified values.

Typical Defects Considered for Grading

• Knots
• Cracks and shakes
• Sapwood percentage
• Worm holes
• Decay or rot

Grading Criteria (Summary)

Practical Note:

• Grading is subjective; the grader's experience is crucial.
• Defect limits are revised periodically based on field experience.

flowchart LR
    A[Teak Square] --> B{Inspection}
    B -->|Minimal Defects| C[Grade I]
    B -->|Moderate Defects| D[Grade II]
    B -->|Higher Defects| E[Grade III]
    C --> F[High Quality Use]
    D --> G[General Use]
    E --> H[Utility Use]

For detailed defect limits and exact grading tables, refer to the full IS 3731 document.

IS 3731 - General Requirements: Key Points & Tables

1. Defect Limits (Clause 3.2.1)

• The value from Clause 3.2 (units of defects) shall not exceed twice the permitted units of defects for each grade.

2. Marking of Squares (Clause 7.1)

All squares must be marked at ends to indicate:

• Supplier's ID: Abbreviated initials
• Grade 1: Square mark
• Grade 2: Triangle mark
• Grade 3: One star '*', cross 'x', or '+'

3. Units of Defects for Shakes (Clause 6.6.2 & Table)

Units of defects are evaluated per IS 3364 (Part 2)-1976. Sample values:

Summary

• Defect units control quality limits.
• Marking ensures traceability and grade identification.
• Use IS 3364 for detailed defect evaluation.

flowchart LR
    A[Wood Squares] --> B[Marking at Ends]
    B --> C[Supplier ID]
    B --> D[Grade 1: Square]
    B --> E[Grade 2: Triangle]
    B --> F[Grade 3: Star/Cross]
    A --> G[Defect Evaluation]
    G --> H[Units of Defects ≤ 2x Permitted]
    G --> I[Refer IS 3364 for Shakes]

IS 3731: Measurement of Dimensions - Key Formulas & Tables

1. Length Measurement (Clause 5.2)

• Measure length end-to-end, accurate to the nearest 0.05 m.
• Use the shortest length parallel to longitudinal edges as the effective length.

2. Defect Units Evaluation (Based on IS 3364 Part 2 - 1976)

Notes:

• Units of defects quantify the severity of imperfections.
• Moisture content determination methods are referenced but detailed in separate IS codes.

flowchart LR
    A[Measure Length] --> B{Length at corners}
    B --> C[Take shortest length parallel to edges]
    D[Identify Defects] --> E{Type?}
    E -->|Shake| F[Refer Table 6.6.2]
    E -->|Knot| G[Refer Table 6.4.3]
    E -->|Hole| H[Refer Table 6.5.3]
    F & G & H --> I[Calculate units of defect]

This concise framework ensures standardized measurement and defect evaluation per IS 3731.

IS 3731: Evaluation of Defects in Timber

Key References:

• Defect evaluation and measurement generally follow IS 3364 (Part 2)-1976.
• Defects not explicitly listed can be treated as equivalent defects based on size, location, and distribution (Clause 6.8.1).
• Defects not equivalent or not listed require values from IS 3364 (Part 2)-1976 (Clause 6.8.2).

Defect Units for Holes (Clause 6.5.3 & Table 6.5)

General Notes:

• The unit value quantifies the severity of defects.
• Sum of defect units helps decide timber usability.
• For defects not covered, use IS 3364 (Part 2) tables or consider equivalence per Clause 6.8.1.

Summary Diagram

flowchart LR
    A[Defect Identification] --> B{Is defect listed?}
    B -- Yes --> C[Use IS 3364 (Part 2) values]
    B -- No --> D{Can defect be equivalent?}
    D -- Yes --> E[Assign equivalent defect units]
    D -- No --> F[Refer IS 3364 (Part 2) for values]
    C --> G[Calculate total defect units]
    E --> G
    F --> G
    G --> H[Evaluate timber utility]

Use IS 3364 (Part 2)-1976 for detailed defect tables and measurement methods.

IS 3731: Permissible Limits of Defects - Key Points

1. Defect Units and Evaluation

• Defects are quantified in units, based on size and number.
• Holes are evaluated per IS 3364 (Part 2)-1976.
• Example units for holes (Clause 6.5.3):

2. Permissible Defect Limits for Squares > 5 m (Clause 3.2)

For squares longer than 5 m:

[ \text{Permissible defects} = \frac{L}{5} \times \text{Permissible defect value for grade} ]

• L = length of the square in meters.
• The permissible defect value depends on the grade of the material.

3. Maximum Defect Units (Clause 3.2.1)

• The defect units shall not exceed twice the permissible number for each grade.

4. Defect Values for Unlisted Defects (Clause 6.8.2)

• For defects not listed or not equivalent, refer to IS 3364 (Part 2)-1976 for defect values.

This system allows quantifying defects in units, applying limits based on size, number, and material grade, ensuring quality control in structural steel products.

flowchart TD
    A[Defect Size & Number] --> B[Convert to Defect Units (IS 3364)]
    B --> C{Length of Square > 5 m?}
    C -- Yes --> D[Calculate Permissible Defects = (L/5) × Grade Limit]
    C -- No --> E[Use Grade Limit Directly]
    D & E --> F[Check Defect Units ≤ 2 × Grade Limit]
    F --> G[Accept or Reject Material]

Inspection and Record Keeping as per IS 3731

Key Points:

• Inspection Principles: Follow IS 6534-1971 for grading and inspection of timber squares.
• Record Keeping: Use the pro forma in Table 1 for each teak square inspected, capturing:
  • Identification mark
  • Dimensions (Length, Breadth, Width)
  • General defects (Curvature, Taper, Wane)
  • Specific defects (Knots, Holes, Shakes, Checks, Splits)
  • Total units of defects and remarks

Table 1: Pro Forma for Grading of Teak Squares (Summary)

Defect Evaluation (Example for Shakes per IS 3364 Part 2-1976)

Additional Specifications:

• Maximum Defect Units: Total defect units must not exceed twice the permitted units per grade (Clause 3.2.1).
• ISI Certification Mark: Teak squares may carry the ISI mark as per Clause 7.1.1, ensuring compliance and quality control.

flowchart TD
    A[Start Inspection] --> B[Identify Teak Square]
    B --> C[Measure Dimensions]
    C --> D[Check General Defects]
    D --> E[Evaluate Specific Defects]
    E --> F[Calculate Defect Units]
    F --> G[Record in Pro Forma (Table 1)]
    G --> H{Defect Units ≤ Permitted Limit?}
    H -- Yes --> I[Grade and Approve]
    H -- No --> J[Reject or Reclassify]
    I --> K[Apply ISI Mark (Optional)]
    J --> K

IS 3731: Sampling and Consignment Grading for Teak Squares

Key Definitions

• Consignment (Clause 2.3): One lot of ≤ 100 teak squares offered for inspection at a time for a particular grade.

Grading Limits (Clause 3.1.2 & 3.2.1)

• Grade 2:
  • Max defects per single square: 4.0 units
  • Average defects per consignment: ≤ 1.5 units
• Defect Value Limit (Clause 3.2.1):
  The total defect value for any square shall not exceed twice the permitted defect units for the grade.

Sampling & Inspection

• Inspect all squares in a consignment (≤ 100 units).
• Calculate defect units per square.
• Confirm average and individual defect units are within limits.

Summary Table for Grade 2

flowchart TD
    A[Consignment ≤ 100 squares] --> B[Inspect each square]
    B --> C[Calculate defect units per square]
    C --> D{Defect units ≤ 4.0?}
    D -->|Yes| E[Include in consignment average]
    D -->|No| F[Reject square]
    E --> G{Average defect units ≤ 1.5?}
    G -->|Yes| H[Consignment accepted]
    G -->|No| I[Consignment rejected]

This ensures uniform quality control for teak squares in trade per IS 3731.

IS 3731 - Marking and Identification of Teak Squares

Key Specifications (Clause 7.1 & 7.1.1):

• Marking at ends of squares must indicate:

  • Supplier’s identification: Abbreviated initials
  • Grade 1: Marked by a square
  • Grade 2: Marked by a triangle
  • Grade 3: Marked by one star (*) or cross (x)

• ISI Certification Mark (optional):

  • May be stamped on teak squares
  • Indicates compliance with IS standards under ISI supervision
  • Use governed by Indian Standards Institution (Certification Marks) Act

Summary Table of Marking Symbols

Notes:

• Markings ensure traceability and quality assurance.
• ISI mark confirms product conformity and quality control.

flowchart LR
    A[Teak Square End] --> B[Supplier ID (Initials)]
    A --> C{Grade}
    C -->|Grade 1| D[Square (▢)]
    C -->|Grade 2| E[Triangle (▲)]
    C -->|Grade 3| F[Star (*) or Cross (x)]
    A --> G[Optional ISI Mark]

This marking system facilitates easy identification and quality verification of teak squares per IS 3731.

IS 3731: Key Defect Units for Timber (per IS 3364 Part 2 - 1976)

Notes:

• Units of defect quantify the severity of timber defects for grading.
• These values help evaluate timber quality and permissible defect limits.
• Refer to IS 3364 (Part 2) - 1976 for detailed defect evaluation procedures.

flowchart LR
    A[Timber Defects] --> B[Shakes]
    A --> C[Holes]
    A --> D[Knots]
    B --> B1[20×10 mm → 0.10 units]
    B --> B2[40×15 mm → 0.20 units]
    B --> B3[80×25 mm → 0.66 units]
    C --> C1[≤5 mm → 0.01 units]
    C --> C2[>5 to ≤10 mm → 0.03 units]
    D --> D1[≤50 mm → 0.01 units]
    D --> D2[>50 to ≤100 mm → 0.04 units]

This summary aids quick defect quantification per IS 3731.