asbestos cement pipes and fittings for sewerage and drainage

IS 6908: Scope on Dimensions and Tolerances

Key Specifications from Clause 3.4 & 4.4:

• Main dimensions must follow the manufacturer's catalogue (Clause 4.4.1).
• Dimensional tolerances apply to:
  • Wall thickness (excluding machined ends)
  • External diameter (finished ends)
  • Nominal length

Table 2: Permissible Deviations on Sizes

Notes:

• Thickness tolerance excludes machined ends.
• External diameter tolerance applies to finished ends.
• Length tolerance varies with nominal diameter.

Summary Diagram of Tolerances:

flowchart LR
    A[Wall Thickness] -->|Tolerance| B[-1.5 to -4.0 mm]
    C[External Diameter] -->|Tolerance| D[±1.0 to ±1.5 mm]
    E[Nominal Length] -->|Tolerance| F[+50 to -40 mm]
    style A fill:#f9f,stroke:#333,stroke-width:1px
    style C fill:#bbf,stroke:#333,stroke

IS 6908: Key Specifications on Dimensional Tolerances (Clause 3.4.4)

Additional Notes:

• Thickness deviations exclude machined ends.
• External diameter deviations apply to finished ends.
• Nominal length deviations vary with pipe size.
• Main dimensions must conform to the manufacturer's catalogue (Clause 4.4.1).

This table ensures pipes meet strict manufacturing tolerances for thickness, diameter, and length to guarantee fit and performance.

flowchart LR
    A[Manufacturer's Stated Dimensions] --> B[Check Thickness Tolerance]
    B -->|Within Permissible Deviation| C[Check External Diameter]
    C -->|Within Permissible Deviation| D[Check Nominal Length]
    D -->|Within Permissible Deviation| E[Accept Pipe]
    B -->|Out of Tolerance|

IS 6908: Classification of Pipes by Crushing Strength

Key Formulas:

• Ultimate Crushing Load (UCL) per meter length = Load per unit area × Nominal Diameter (m)

  Where load per unit area for classes:

  • Class 1 = 60 kN/m²
  • Class 2 = 90 kN/m²
  • Class 3 = 120 kN/m²

• Minimum crushing load at rupture ≥ 15 kN/m

Table 1: Minimum Ultimate Crushing Load (kN/m)

Note: For diameters/classes outside this table, dimensions must be mutually agreed.

Recommendations:

• Select pipe class to ensure factor of safety ≥ 1.3 against crushing, considering installation and bedding conditions.
• Crushing load per meter must never be less than 15 kN/m regardless of class.

flowchart TD
    A[Nominal Diameter (m)] --> B[Load per unit area (kN/m²)]
    B --> C[Ultimate Crushing Load (kN/m)]
    C --> D{Compare with Table 1}
    D -->|≥ Min Load| E[Accept Class]
    D -->|< Min Load| F[Review Design]

This classification ensures pipes withstand expected loads during installation and operation safely.

IS 6908: Dimensions and Geometrical Characteristics

Key Points from Clauses 3.4 & 4.4:

• Main dimensions must follow the manufacturer's catalogue (Clause 4.4.1).
• Dimensional tolerances are specified in Table 2 (Clause 3.4.4) for wall thickness, external diameter, and nominal length.

Table 2: Permissible Deviations on Sizes

• Thickness tolerances exclude machined ends.
• Diameter tolerances apply to finished ends.

Summary:

• Thickness tolerance decreases with increasing thickness.
• Diameter tolerance varies with nominal diameter size.
• Length tolerance typically ±50 mm or as per catalog.

flowchart TD
    A[Manufacturer's Catalogue] --> B[Main Dimensions]
    B --> C[Thickness Tolerances]
    B --> D[External Diameter Tolerances]
    B --> E[Nominal Length Tolerances]
    C --> F[Table 2: Thickness Deviations]
    D --> G[Table 2: Diameter Deviations]
    E --> H[Table 2: Length Deviations]

For detailed design, always refer to the manufacturer's catalogue and IS 6908 Table 2 for precise tolerances.

IS 6908 – Jointing of Asbestos Cement Pipes

Types of Joints (Clause 5.1)

• Asbestos cement couplings with rubber sealing rings
• Cast iron detachable joints with rubber sealing rings, bolts, and nuts

Key Specifications

• Hydrostatic Pressure Test (Clause 5.4):
  Joint must withstand 0.25 MPa (2.5 bar) internal pressure per IS 5913:1989, even at max angular deviation.

• Rubber Rings (Clause 5.3):
  Must comply with IS 5382:1985 and be compatible with the joint type.

• Material Standards (Clause 5.2):

  • Asbestos cement couplings: conform to Clause 3.1 of IS 6908
  • Cast iron joints: conform to IS 8794:1988

Summary Table

Testing Method Reference

• IS 5913:1989 – Hydrostatic pressure testing procedure for joints.

flowchart LR
    A[Pipe Ends] --> B[Rubber Sealing Ring]
    B --> C[Coupling / Cast Iron Joint]
    C --> D[Bolts & Nuts (for cast iron)]
    D --> E[Joint Assembly]
    E --> F[Hydrostatic Pressure Test @ 0.25 MPa]

This ensures leak-tight, pressure-resistant joints suitable for asbestos cement pipelines.

IS 6908: Sampling and Testing Key Points

Sampling (Clause 7.2 & 6.1)

• Sampling Method: Samples must be taken either before or immediately after delivery, as per purchaser's choice.
• Sample Size: Typically, samples should be representative of the batch and taken according to the standard procedures outlined in IS 6908.
• Testing Authority: Tests are performed on written instruction from the purchaser or their representative.

Testing Criteria (Clauses 3.5 & 4.5)

• Tests include:
  • Physical characteristics: Dimensions, surface finish, and appearance.
  • Mechanical characteristics: Tensile strength, yield strength, elongation, hardness.
  • Chemical characteristics: Composition analysis to ensure conformity with specified grades.

Acceptance Criteria (Clause 7)

• Acceptance is based on compliance with specified physical, mechanical, and chemical properties.
• If samples fail, the batch may be rejected or retested as per the standard.

Typical Testing Parameters (from IS 6908 & related standards):

flowchart LR
    A[Sample Collection] --> B{Before or After Delivery?}
    B -->|Before| C[Sample taken pre-delivery]
    B -->|After| D[Sample taken post-delivery]
    C & D --> E[Testing as per IS 6908]
    E --> F{Test Results}
    F -->|Pass| G[Batch Accepted]
    F -->|Fail| H[Retesting or Rejection]

Summary:
Ensure sampling is representative and timely. Testing covers physical, mechanical, and chemical properties. Acceptance depends on conformity with IS 6908 criteria.

IS 6908: Criteria for Acceptance

1. Sampling & Testing (Clause 6.1)

• Samples for independent tests are taken before or immediately after delivery.
• Tests must follow IS 6908 procedures on purchaser's written instruction.

2. Dimensional Tolerances (Clause 3.4.4 & Table 2)

3. Physical, Mechanical & Chemical Characteristics (Clauses 3.5 & 4.5)

• Must comply with specified IS 6908 requirements.
• Includes tensile strength, yield strength, elongation, chemical composition limits.

Summary:

• Dimensional tolerances are critical for acceptance.
• Thickness, diameter, and length deviations must be within Table 2 limits.
• Independent tests are purchaser's right.
• Compliance with mechanical & chemical specs is mandatory.

flowchart LR
    A[Sample Taken]

Manufacturer's Certificate - IS 6908 Key Points

• Clause 8.1:
  The manufacturer must ensure pipes/fittings conform to IS 6908 requirements and provide a certificate stating the class of pipes/fittings to the purchaser.

• Dimensional Tolerances (Clause 3.4.4, Table 2):
  Permissible deviations on thickness, external diameter, and nominal length are as follows:

• Main Dimensions (Clause 4.4.1):
  Must comply with the manufacturer's catalogue.

• Testing (Clause 7.2.1):
  Tests per Clauses 3.5 and 4.5 on samples selected as per Clause 9.

Summary for Manufacturer's Certificate

• Confirm compliance with IS 6908.
• State pipe/fitting class.
• Include dimensional tolerances per Table 2.
• Reference catalogue dimensions.
• Confirm tests conducted on representative samples.

flowchart TD
    A[Manufacture Pipes/Fittings] --> B[Conduct Tests (Clauses 3.5 & 4.5)]
    B --> C[Check Dimensions per Catalogue & Table 2]
    C --> D[Verify Compliance with IS 6908]
    D --> E[Issue Manufacturer's Certificate]
   

IS 6908: Inspection by Sampling Summary

• Reference Standard: Sampling, inspection, and acceptance follow IS 7639:1975.

• Inspection Lot Definition:

  • Items must be of the same diameter and class.
  • Lot size varies by pipe diameter:

• Sampling Procedure:

  • Samples are taken either before or immediately after delivery per purchaser’s instruction (Clause 6.1).
  • Inspection can be 100% (each item) or by sampling (Clause 7.1 & 7.2).

• Acceptance Criteria:

  • Defined in Clause 7, based on sample test results.
  • Follow IS 7639 for detailed acceptance levels and sampling plans.

Key Points:

• Sampling ensures quality without testing every pipe.
• Lot sizes and sampling plans must be agreed upon.
• Independent testing can be requested by purchaser.

flowchart TD
    A[Inspection Lot] --> B{Diameter?}
    B -->|Up to 100 mm| C[Lot: 200-800 pipes]
    B -->|125 to 250 mm| D[Lot: 100-400 pipes]
    B -->|300 mm and above| E[Lot: 100-200 pipes]
    C --> F[Sampling per IS 7639]
    D --> F
    E --> F
    F --> G{Acceptance Criteria}
    G -->|Pass| H[Accept Lot]
    G -->|Fail| I[Reject Lot / Re-inspection]

For detailed sampling plans and acceptance numbers, refer to IS 7639:1975.

IS 6908: Marking of Pipes and Fittings (Clauses 10.1 & 10.1.1)

Pipes and fittings must be legibly and indelibly marked with:

• Manufacturer's name or trade-mark
• Date of manufacture
• Nominal diameter
• Class of pipe and fittings
• Pictorial warning sign as per IS 12081 (Part 2):1987
• Optionally, the Standard Mark may also be included.

Dimensional Tolerances (Clause 3.4.4, Table 2)

Summary Diagram of Marking Elements

graph LR
A[Pipe/Fitting] --> B[Manufacturer's Name/Trade-mark]
A --> C[Date of Manufacture]
A --> D[Nominal Diameter]
A --> E[Class of Pipe/Fitting]
A --> F[Pictorial Warning Sign (IS 12081 Pt 2)]
A --> G[Standard Mark (Optional)]

Note: Markings ensure traceability, quality

IS 6908 - Safety Rules Sheet (Clause 11)

• Requirement:
  All deliveries of asbestos cement pipes and fittings must be accompanied by a Safety Rules Sheet as per IS 11769 (Part 1): 1987.

• Purpose:
  To ensure safe handling, transportation, storage, and installation of asbestos cement pipes and fittings, protecting workers and users.

• Key Points (Typical Safety Rules):

  • Use protective gear (gloves, masks) to avoid asbestos dust inhalation.
  • Handle pipes carefully to prevent breakage and dust release.
  • Store pipes in a dry, ventilated area, avoiding direct sunlight.
  • Clean up dust and debris with wet methods, not dry sweeping.
  • Dispose of waste according to environmental regulations.

• Marking:
  Each pipe/fitting may bear the Standard Mark (Clause 10.1.1) ensuring conformity.

Reference Table Summary (Clause 11.1)

Diagram: Safety Process Flow for Handling Pipes

flowchart TD
    A[Receive Pipes & Fittings] --> B[Check for Safety Rules Sheet]
    B --> C{Safety Gear Available?}
    C -- Yes --> D[Handle Pipes Carefully]
    C -- No --> E[Procure Safety Gear]
    D --> F[Store Properly]
    F --> G[Install Pipes]
    G --> H[Clean Work Area Safely]
    H --> I[Dispose Waste Properly]

For detailed safety rules, always refer to IS 11769 (Part 1): 1987 along with IS 6908.

IS 6908 - Composition of Technical Committee (CED 2)

The Technical Committee for Cement and Concrete (CED 2) comprises experts from diverse organizations related to cement, concrete, construction, and research. Key points:

• Chairman: Dr. H.C. Visvesvaraya (University of Roorkee)

• Members: Representatives from:

  • Cement companies (e.g., Orissa Cement Ltd, The Associated Cement Companies Ltd)
  • Government departments (CPWD, Central Water Commission)
  • Research institutes (CSIR Structural Engineering Research Centre, Central Building Research Institute)
  • Industry bodies (Indian Roads Congress, Builders Association of India)
  • Testing and standards organizations (National Test House, BIS ex-officio member)
  • Engineering consultants and contractors (Larsen & Toubro, Gammon India)

• Alternate members are nominated for most representatives to ensure continuity.

Specifications Summary:

• Composition covers multidisciplinary expertise ensuring comprehensive standard development.
• Includes academia, industry, government, and research institutions.
• Ensures balanced representation for cement and concrete materials, testing, and application.

If you need formulas or tables related to physical, mechanical, or chemical characteristics (Clauses 3.5, 4.5), please specify, as the committee composition itself does not include formulas.

graph TD
    A[Technical Committee CED 2] --> B[Chairman: Dr. H.C. Visvesvaraya]
    A --> C[Members]
    C --> D[Cement Industry]
    C --> E[Government Departments]
    C --> F[Research Institutes]
    C --> G[Industry Bodies]
    C --> H[Testing & Standards]
    C --> I[Engineering Consultants]

This structure ensures diverse expertise for standard development and review.