Code of Practice for Use and Laying of Ductile Iron Pipes

IS 12288: Foreword - Key Points & Specifications

• Purpose: Provides guidelines for the proper use and laying of ductile iron pipes.
• Scope: Covers centrifugally cast (spun) ductile iron pressure pipes used for water, gas, and sewage pipelines.
• Rounding Off: Final test or analysis values must be rounded per IS 2-1960:
  • Retain the same number of significant digits as the specified value.

Important Notes:

• The code emphasizes correct trench excavation and preparation for underground pipelines (see Clause 4.2).
• Ensures compliance by specifying how to interpret test results, maintaining consistency in measurements.

Summary Table: Rounding Off Values (per IS 2-1960)

flowchart TD
    A[Pipe Specification] --> B[Material: Ductile Iron]
    B --> C[Manufacturing: Centrifugal Casting]
    C --> D[Use: Water, Gas, Sewage]
    D --> E[Installation: Trench Excavation & Preparation]
    E --> F[Testing & Analysis]
    F --> G[Rounding Off per IS 2-1960]

This ensures standardized quality and installation practices for ductile iron pipes.

IS 12288: Scope - Key Specifications & Guidelines

• Rounding Off Values (Clause 0.3):
  Final test or analysis results must be rounded per IS 2-1960, retaining the same number of significant figures as specified in IS 12288.

• Cutting Tools (Clause 5.4.1):
  Use hand or power hacksaws with blades having 1 mm tooth pitch for pipe cutting.

• Field Survey Plans (Clause 2.3):

  • Survey strip width: approx. 500 m along pipeline route.
  • Vertical profiles scaled between 1:100 to 1:125 for complex crossings.
  • Built-up areas: use 1:1250 scale plans.
  • Urban areas: include trial trenches to locate utilities.

• Trench Width (Clause 4.2.1):

  • Minimum clearance: 200 mm on each side of the pipe at trench bottom.
  • Extra width required for timber supports, strutting, and handling specials.
  • Exceptions apply for rock excavation.

Summary Table: Trench Width Clearance

flowchart TD
    A[Start: Pipeline Route Survey] --> B[Field Survey - 500 m strip]
    B --> C{Area Type?}
    C -->|Urban| D[Use 1:1250 scale + trial trenches]
    C -->|Built-up| E[Use 1:100 to 1:125 scale]
    E --> F[Detail special crossings]
    D --> F
    F --> G[Trench Excavation]
    G --> H[Maintain 200 mm clearance each side]
    H --> I[Place timber supports if needed]
    I --> J[Pipe Laying & Cutting]
    J --> K[Use hacksaw with 1 mm pitch blade]

This concise scope ensures proper planning, excavation, and handling for pipeline installation per IS 12288.

IS 12288 Terminology Key Points & Specifications

• Rounding Off Values (Clause 0.3):
  Final test or analysis results must be rounded per IS 2:1960.

  • Retain the same number of significant figures as the specified value.

• Rock Definition (Clause 4.3):
  'Rock' means as defined in IS 1200 (Part 1) - 1974 (Earthwork measurement).

• Sheeting & Bracing Removal (Clause 4.4.2):

  • Remove sheeting/bracing 900 mm below street level or existing surface, whichever is lower, if left in place.
  • Other sheeting can be removed after backfilling or when safe to do so without damaging structures.
  • Removal before filling is allowed only if it ensures protection of work and adjacent structures.

Relevant IS Code References Summary

Practical Notes:

• Always cross-check rounding with IS 2 for compliance.
• For excavation, consult IS 1200 for rock classification.
• Follow safety and structural protection rules strictly during sheeting removal.

flowchart TD
    A[Start Excavation] --> B{Is sheeting left in place?}
    B -->|Yes| C[Remove sheeting 900mm below street level]
    B -->|No| D{Backfilling complete?}
    D -->|Yes| E[Remove sheeting safely]
    D -->|No| F[Remove sheeting only if safe]
    E --> G[Protect adjacent structures]
    F --> G

This diagram summarizes safe sheeting removal per IS 12288.

IS 12288: Site Preparation and Excavation Key Points

1. Trench Width (Clause 4.2.1)

• Minimum clearance 200 mm on either side of the pipe between sheeting faces.
• Extra width to allow timber supports, strutting, planking, and handling of specials.

2. Cutting High Grounds (Clause 4.12.1)

• Bottom width must accommodate pipeline, supports, service passage, and side drains.
• Side slopes for cuttings:

3. Sheeting & Bracing (Clause 4.4.2)

• Sheeting left in place must be removed up to 900 mm below street level.
• Other sheeting removed after backfilling or safely before filling, ensuring protection.

4. Cleaning-Up (Clause 10.3)

• Remove all surplus materials, tools, temporary structures.
• Haul away dirt, rubbish, excess earth to dump.
• Leave site clean as per authority satisfaction.

Typical Trench Section (Fig. 1 reference)

graph LR
  A[Pipe] -->|200 mm clearance| B(Sheeting)
  B --> C[Timber Supports & Strutting]
  C --> D[Backfill]

Summary:

• Maintain 200 mm clearance for pipe laying.
• Follow slope ratios for excavation stability.
• Proper sheeting removal for safety and compliance.
• Clean site post-excavation.

IS 12288: Key Specifications & Formulas for Laying Ductile Iron Pipes

1. Excavation & Trench Preparation (Clause 4.2)

• Trench width: Minimum 300 mm wider than pipe diameter.
• Depth: Sufficient for pipe cover as per design loads.
• Bedding: Uniform, firm base with sand or fine gravel for pipe support.

2. Laying Above Ground (Clause 5.2)

• Ground should match pipe curvature subtending an angle of 120° at pipe center.
• Pipes supported on:
  • Saddles
  • Rollers
  • Rocker supports (as per authority)
• Pipes may rest directly on non-aggressive soil.

3. Cutting Pipes (Clause 5.4.1)

• Use hand/power hacksaw with blade teeth pitch: 1 mm.

Typical Arch Length for Pipe Shell (120° Arc)

[ \text{Arch length} = \frac{120}{360} \times 2\pi r = \frac{1}{3} \times 2\pi r = \frac{2\pi r}{3} ]

Where:

• ( r = \frac{D}{2} ) (pipe radius)

Summary Table: Pipe Support Methods

flowchart LR
    A[Trench Excavation] --> B[Uniform Bedding]
    B --> C{Pipe Laying}
    C -->|Above Ground| D[Supports: Saddle/Roller/Rocker]
    C -->|On Ground| E[Non-aggressive Soil]
    D --> F[Pipe Curvature 120° Arc]

For detailed dimensions and installation, refer to IS 12288 clauses and figures.

IS 12288: Key Points on Joints and Jointing

Types of Joints (Clause 6.0)

• Flexible Joints:
  • Push-on joints
  • Mechanical joints (compression of rubber gasket)
• Rigid Joints:
  • Flanged joints

Jointing Procedure (Clause 6.3)

• Clean all parts (socket inside & spigot outside)
• Correctly locate components
• Centralize spigot in socket (use lifting gear if needed)
• Follow manufacturer’s instructions strictly
• Inspect and clean glands and gaskets

Flexible Joint Design (Clause 6.1)

• Allow angular deflection & axial movement (thermal expansion, ground movement)
• Use elastomeric gaskets
• Leave a gap between spigot end and socket back for movement
• Require external anchorage at bends, dead ends, valves, tees to resist thrust

Anchorage for Flexible Joints (Clause 5.8)

• Anchor at all changes in direction & dead ends to resist internal pressure thrust
• Design anchor blocks per IS 5330-1984
• Spacing of transverse anchors for steep pipelines:

Typical Jointing Steps (Summary)

flowchart TD
    A[Clean socket inside & spigot outside] --> B[Inspect & clean gaskets]
    B --> C[Apply lubricant if required]
    C --> D[Centralize spigot in socket]
    D --> E[Push spigot into socket to required depth]
    E --> F[Check joint alignment & sealing]

Note: For thrust block design, refer IS 5330-1984 for safe bearing pressures and block dimensions.

IS 12288: Handling, Stacking, and Storage of Pipes

1. Handling & Transportation (Clause 7.2 & 7.3)

• Loading: Pipes must be secured to prevent movement.
  • Pyramid loading: Bottom layer restrained by broad wooden wedges.
  • Straight-sided loading: Supports along vehicle sides; better vehicle capacity utilization.
• Off-loading:
  • Use cranes preferably.
  • For pipes ≤ 400 mm NB, skid timbers & ropes may be used.
  • Smooth lifting without jerks; use guide ropes to control pipe movement.
  • Hooks must engage pipe ends securely, passing over protective packing.
  • Avoid sling lifting of bundles; for single pipes, use broad webbing slings, not chains.

2. Stacking (Clause 7.4 & 7.4.1)

• Foundation: First layer on firm, level solid timbers.
• Stack height: Max 2 m.
• Avoid: Pipes resting on sockets.
• Square stacking:
  • Layers at right angles.
  • Spigots and sockets alternate.
  • Sockets project beyond spigot ends.
  • Pipes rest directly on those beneath; careful placement to avoid damage.

Summary Table for Stacking

flowchart TD
    A[Loading] --> B[Secure pipes on vehicle]
    B --> C{Loading method}
    C -->|Pyramid| D[Wedges on bottom layer]
    C -->|Straight-sided| E[Side supports]
    A --> F[Transportation]
    F --> G[Off-loading]
    G --> H{Method}
    H -->|Crane| I[Use hooks & guide ropes]
    H -->|Skid timbers| J[For pipes ≤ 400 mm]
    G --> K[Safe lifting: no jerks]
    L[Stacking] --> M[First

IS 12288: Testing of Pipelines (Hydraulic Testing)

Key Specifications & Procedures

• Test Objectives (Clause 8.1):

  • Check mechanical soundness and leak tightness of pipes/fittings.
  • Leak tightness of joints.
  • Soundness of construction work, especially anchorages.

• Test Pressure (Clause 8.3):
  Test pressure ≥ max of:
  a) Maximum sustained operating pressure
  b) Maximum static pressure + 5 N/mm²
  c) Max sustained/static pressure + max calculated surge pressure

• Test Duration:
  Maintain full test pressure for ≥ 10 minutes after stabilization.

• Pressure Measurement:
  Measure at the lowest point or adjust for static head to avoid exceeding max pressure there.

• Testing Length (Clause 8.2):
  Can be full pipeline or sections depending on water availability, joints, elevation differences.

Maximum Field Hydrostatic Test Pressure (Table 1, Clause 8.5)

• These pressures are 0.5 N/mm² higher than pipe pressure ratings.
• Applies only if pipeline and fittings are properly anchored.

Testing Sequence Summary

flowchart TD
    A[Complete Pipeline Laid & Jointed] --> B[Section Testing (optional)]
    B --> C[Complete Pipeline Test]
    C --> D[Fill Pipeline with Water]
    D --> E[Pressurize to Operating Pressure]
    E --> F[Wait for Stabilization (time varies)]
    F --> G[Increase Pressure to Test Pressure]
    G --> H[Maintain Pressure ≥ 10 mins]
    H --> I[Inspect for Leaks, Defects & Anchorage Soundness]

This ensures safe, reliable pipeline operation per IS 12288 standards.

IS 12288: Flushing and Disinfection of Mains – Key Points

1. Flushing (Clause 9.2)

• Flush mains after pressure testing with water at sufficient velocity to remove dirt and foreign matter.
• Use water from the distribution system or approved source.

2. Disinfection Methods (Clause 9.2 & 9.3)

• Continuous Feed Method:
  • Inject chlorine (liquid chlorine or hypochlorite) at constant rate.
  • Use hypochlorinator or solution feed chlorinator with booster pump.
  • Operate all valves and hydrants during disinfection.

3. Post-Disinfection (Clause 9.4)

• Prevent backflow of strong chlorine into supply line.
• Flush chlorinated water until chlorine residual equals normal system levels.
• Conduct bacteriological tests; repeat disinfection if standards not met.

Summary Flow Diagram

flowchart TD
    A[Pressure Testing Completed] --> B[Flush Mains at Sufficient Velocity]
    B --> C[Disinfect with 20-50 mg/l Chlorine]
    C --> D[Maintain Contact Time of 24 Hours]
    D --> E[Check Residual Chlorine ≥ 10 mg/l]
    E --> F{Residual OK?}
    F -- Yes --> G[Flush Chlorinated Water to Normal Levels]
    F -- No --> C
    G --> H[Bacteriological Test]
    H --> I{Test Passed?}
    I -- Yes --> J[Commission Main]
    I -- No --> C

Note: Ensure all consents for disposal of chlorinated water are obtained and treatment is done if necessary (Clause 8.6).

IS 12288 – Restoration and Cleaning-up Key Points

Restoration of Damaged Surfaces (Clause 10.2 & 4.5)

• Restore all disturbed property (pavements, shrubbery, fences, poles) to original condition.
• Use sound stone blocks, bricks, or asphalt paving blocks for pavement restoration.
• Permanent pavement restoration only after backfill is properly compacted and supports pavement.
• Separate and preserve surface materials suitable for reuse during excavation.

Cleaning-up (Clause 10.3)

• Remove all surplus materials, tools, and temporary structures.
• Haul away dirt, rubbish, and excess earth to a dump.
• Leave site clean and to the satisfaction of the authority.

Disinfection & Testing (Clause 9.4)

• Prevent backflow of chlorine solution into supply lines.
• Flush chlorinated water until chlorine residual matches system levels.
• Conduct bacteriological tests; repeat disinfection if standards are not met.

Summary Table

flowchart TD
    A[Excavation] --> B[Separate Surface Materials]
    B --> C[Work Execution]
    C --> D[Backfill & Compact]
    D --> E[Restore Surface with Sound Materials]
    E --> F[Clean-up Site]
    F --> G[Disinfection & Testing]
    G --> H[Final Approval by Authority]

This ensures structural integrity, environmental safety, and compliance with IS 12288.