Code of practice for laying asbestos cement pressure pipes

Scope of IS 6530:

IS 6530 covers the design and installation of asbestos cement pressure pipes, focusing on:

• Hydraulic thrust transfer via thrust blocks (Clause 7.1)
• Pipe deflection and curvature limits (Clause 6.4, Fig. 6)
• Trench width specifications for pipe bedding (Clause 4.1.1)

Key Specifications & Tables

1. Thrust Blocks (Clause 7.1):

• Required to transfer hydraulic thrust from fittings/pipes to soil.

2. Trench Width (Clause 4.1.1):

• For pipe diameter ( D ) (in meters):
  • ( D \leq 0.5,m \Rightarrow ) trench width = ( D + 0.4,m )
  • ( D > 0.5,m \Rightarrow ) trench width = ( D + 0.6,m )
• Minimum trench width:
  • (0.6,m) for trench depth (\leq 1.5,m)
  • (0.8,m) for trench depth (> 1.5,m)

3. Deflection & Radius of Curvature (Table 1, Clause 6.4):

IS 6530 Key References & Tables

1. Thrust Blocks (Clause 7.1)

   • Used to transfer hydraulic thrust to soil.
   • Size depends on pipe diameter and soil bearing capacity.

2. Deflection & Radius of Curvature (Table 1, Clause 6.4)

   Angle of Deflection (°)	Displacement (mm) for Pipe Length (m)	Radius of Curvature (m) for Pipe Length (m)
   	1	2
   1	20	35
   2	35	70
   3	50	100
   4	70	195
   5	85	170

3. Testing & Disinfection (Clause 12.1)

   • Follow IS 3114-1965 (CI pipes) or IS 5822-1970 (welded steel pipes) for disinfecting potable water pipelines.

4. Additional References

   • IS 3114: Code of practice for laying cast iron pipes.
   • IS 5822: Code of practice for laying welded steel pipes.

Summary Diagram: Thrust Block Function

flowchart LR
    Pipe_Fitting -->|Hydraulic Thrust| Thrust_Block
    Thrust_Block -->|Load Transfer| Soil_Bearing_Section

Contact: For detailed standards and updates, refer to Manak Bhavan, New Delhi or regional offices listed in the code.

IS 6530: Handling and Unloading of Pipes

Key Specifications & Procedures

• Unloading by Hand (Clause 3.1.1):

  • Pipes ≤ 60 kg: Hand-passed by two persons.
  • Pipes > 60 kg: Use two ropes forming loops; slide over planks with slope ≤ 45°.
  • Planks must be rigid; only one pipe at a time.
  • Ropes tied opposite unloading side.

• Unloading Location (Clause 3.1):

  • Pipes should be unloaded directly at the trench site if ready, avoiding extra handling.

• Storage (Clause 3.2.2):

  • Store on firm, level, clean ground.
  • Use wedges at bottom layer for stability.

Deflection & Radius of Curvature (Clause 6.4, Table 1)

Thrust Blocks (Clause 7.1)

• Used to transfer hydraulic thrust from fittings/pipes to larger soil bearing area.
• Essential for preventing pipe movement under pressure.

flowchart TD
    A[Pipe Unloading] -->|≤ 60 kg| B[Hand Passing by 2 Persons]
    A -->|> 60 kg| C[Use

IS 6530: Excavation and Trench Preparation - Key Points

• Excavation Timing (4.2.1):
  Excavation should closely follow the laying operations to prevent trench side collapse and flooding.

• Trench Slope (4.2.2):

  • Slope ratio depends on soil type:
    • Stable soil: 1:1 (45°)
    • Loose soil: flatter slope, e.g., ¾:1 or ½:1
  • This prevents side collapse.

• Soil Disposal (4.2.5):

  • Excavated soil should be placed on one side, leaving a 0.5 m wide bench for safe worker movement.

• Shoring (4.2.8):

  • Required in loose or deep trenches to protect workers.

Typical Trench Slope Table (for reference)

Simple formula for bench width:

[ \text{Bench width} \approx 0.5,m ]

graph TD
A[Start Excavation] --> B{Soil Type?}
B -->|Stable| C[Slope 1:1]
B -->|Loose| D[Slope ¾:1 or ½:1]
C --> E[Place excavated soil on one side leaving 0.5m bench]
D --> E
E --> F{Depth > safe limit?}
F -->|Yes| G[Shoring required]
F -->|No| H[Proceed with laying operations]

Summary: Follow slope guidelines, keep excavation close to laying, maintain a 0.5 m bench, and shore deep/loose trenches for safety.

IS 6530: Soil Conditions and Bedding Key Points

1. Backfill Material (Clause 10.3)

• Initial backfill must be free of large stones and dry lumps.
• In stony areas, use shaved trench sides material.
• In bogs/marshes, avoid vegetable matter; use gravel or crushed stone instead.

2. Trench Bed Excavation (Clause 4.2.9)

• Excavate trench bed to pipe grade ensuring uniform support along pipe length.
• Avoid pipes resting on humps, joints, or earth mounds (see Fig. 2).
• Correct laying: pipes rest evenly on made-up bed.

3. Rock Encounter (Clause 5.5)

• Provide 150 mm cushion of fine earth or sand under pipes.
• Excavate extra depth if needed.
• For slopes > 30°, anchor pipes to prevent sliding.

4. Trench Width (Clause 4.1.1)

• Minimum trench width:
  • 0.6 m for depths ≤ 1.5 m
  • 0.8 m for depths > 1.5 m

Summary Table for Bedding Width

flowchart LR
    A[Excavate Trench to Pipe Grade] --> B[Provide Uniform Support]
    B --> C{Soil Condition}
    C -->|Rock| D[Excavate Extra Depth + 150mm Sand Cushion]
    C -->|Bog/Marsh| E[Use Gravel/Crushed Stone Bedding]

IS 6530: Jointing of Pipes – Key Formulas, Tables & Specifications

1. Joint Components (Clause 6.2.1)

• Joint consists of:
  • Central collar
  • Two rubber rings
  • Two cast iron flanges
  • Required bolts & nuts

2. Assembly Specification (Clause 6.2.4)

• Leave a 5 mm gap between pipe ends before jointing.
• This gap allows for deflection and thermal expansion after assembly.

3. Deflection & Radius of Curvature (Clause 6.4 & Table 1)

• Note: Deflection must be applied after joint completion.
• Radius of curvature is calculated based on successive deflections.

4. Thrust Blocks (Clause 7.1)

• Required to transfer hydraulic thrust to soil.
• Size depends on pipe diameter and soil bearing capacity.

Summary Diagram of Joint Assembly:

graph LR
    A[Pipe End 1] -->|Rubber Ring| B[Central Collar]
    C[Pipe End 2] -->|Rubber Ring| B
   

IS 6530: Anchorage and Thrust Blocks – Key Points

Thrust Blocks (Clause 7.1, 7.3)

• Purpose: Transfer hydraulic thrust from fittings/pipes to larger soil bearing area.
• Design Factors: Pipe size, water pressure, fitting type, gravity on slopes, soil type.
• Location: As per Fig. 8 (typically at bends, tees, end caps).

Anchorage (Clause 8.3, 8.3.1)

• Material: Concrete (cast-in-situ) or masonry with cement mortar.
• Extension: Into firm soil on trench sides.
• Shape: Full trench width, extending vertically ~15 cm over the fitting.
• Bearing Area: Proportional to thrust and soil bearing capacity.

Deflection & Radius of Curvature (Table 1, Clause 6.4)

Summary Diagram of Thrust Block Concept

flowchart LR
    PipeEnd -->|Hydraulic Thrust| ThrustBlock[Thrust Block]
    ThrustBlock -->|Load Transfer| SoilBearingArea[Soil Bearing Area]
    SoilBearingArea -->|Resists Thrust| Ground

Note: Always verify soil bearing capacity and hydraulic thrust calculations before finalizing thrust block dimensions.

IS 6530: Anchorage Details Summary

Key Specifications (Clause 8.3.1)

• Anchorage must be concrete cast-in-situ or masonry in cement mortar.
• Anchors extend to firm soil at trench sides.
• Anchors spread full trench width and extend vertically ~15 cm over specials.
• Bearing area on trench sides proportional to thrust force and soil bearing capacity.

Purpose (Clause 8.3)

• Prevent pipe/special ends from slipping out under working/test pressure.
• Essential for blank end caps, bends, tees.
• Anchorage resists hydraulic thrust.

Thrust Block Design (Clause 7.1)

• Transfers hydraulic thrust to larger soil bearing area.
• Size depends on thrust magnitude and soil bearing capacity.

Typical Anchorage Design Formula (based on thrust force):

[ A = \frac{T}{q} ]

Where:

• ( A ) = Required bearing area of thrust block (m²)
• ( T ) = Thrust force from pipe fitting (N)
• ( q ) = Allowable soil bearing pressure (N/m²)

Additional Notes:

• Anchorage shape depends on specials used.
• Vertical extension (~15 cm) ensures load transfer over specials.
• Proper anchorage prevents pipe joint failure due to thrust.

flowchart TD
    A[Pipe Fitting] -->|Hydraulic Thrust| B[Anchor Block]
    B --> C{Soil Bearing Capacity}
    C -->|Adequate| D[Stable Anchorage]
    C -->|Inadequate| E[Increase Anchor Size]

For detailed thrust values and soil capacity, refer to site-specific geotechnical data and IS 6530 Clause 7 tables.

IS 6530: Service Connections Key Points

1. Size of Hole Drilled in Pipe (Clause 9.2, Table 2)

• Holes for service connections must not exceed these sizes to maintain pipe integrity.

2. Service Connection Method (Clause 9.1)

• Connections to distribution house services are made via saddle pieces.
• Avoid vertical GI connections over the saddle.
• Use GI pipe lengths about 1000 to 1250 mm for connections.
• Backfill with fine earth or sand for protection.

3. Anchorage & Backfilling (Clause 8.3.1)

• Anchorage must be concrete or masonry, extending to firm soil.
• Anchors spread full trench width, carry vertically about 15 cm over specials.
• Bearing area proportional to thrust and soil bearing capacity.

Visual Summary of Service Connection Setup

flowchart LR
    AC_Pipe[AC Pressure Pipe] -->|Drill Hole (Max size per Table 2)| Saddle[Saddle Piece]
    Saddle --> GI_Pipe[GI Pipe (1000-1250 mm)]
    GI_Pipe --> House[Service Connection to House]
    Soil[Soft Soil] -->|Backfill with Fine Earth or Sand| AC_Pipe
    Rock[Rock Side] -->|Trench Boundary| Soil

This ensures safe, leak-proof service connections without compromising pipe strength.

IS 6530: Backfilling and Tamping Key Points

• Initial Backfill Material (Clause 10.3):

  • Free from large stones & dry lumps.
  • In stony areas, use shaved trench sides material.
  • Avoid vegetable matter (bogs/marshes); use gravel/crushed stone instead.

• Layer Thickness & Consolidation (Clause 10.4):

  • Place initial backfill in ~100 mm layers.
  • Each layer must be properly tamped/consolidated.
  • Continue until a minimum 300 mm cushion covers the pipe.

• Tamping Method (Clause 10.2):

  • Use tamping bars or water to consolidate soil under pipe and coupling for firm, continuous support.

• Balance Backfill (Clause 10.6):

  • Less stringent material selection allowed.
  • Avoid large stones that can damage the pipe.

Typical Backfill Layering & Tamping Procedure

flowchart TD
    A[Excavation] --> B[Initial Backfill (100 mm)]
    B --> C[Tamping (bars or water)]
    C --> D{Cushion thickness ≥ 300 mm?}
    D -- No --> B
    D -- Yes --> E[Balance Backfill]
    E --> F[Final Compaction]

Summary: Proper backfilling per IS 6530 ensures pipe support and protection by using fine, tamped layers up to 300 mm, then completing with less selective fill while avoiding large stones.

Field Testing of Pipeline as per IS 6530 (Clause 11)

Key Specifications & Formulas:

• Test Pressure (P_test):
  [ P_{test} = 1.5 \times P_{operating} ]
  But shall not exceed limits in Table 3.

Table 3: Maximum Field Test Pressure (kgf/cm²)

Testing Procedure Highlights:

• Backfill: Adequate backfill must be placed to resist upward thrust (Clause 11.3).
• Thrust Blocks: Must be fully cured; no temporary bracing allowed.
• Filling: Pipeline section filled with water manually or by low-pressure pump (Clause 11.6).
• Air Venting: All air must be vented at high points to avoid pressure build-up errors.
• Test Duration: Sufficient to carefully check the pipeline section (Clause 11.9).

flowchart LR
    A[Prepare pipeline section] --> B[Place backfill & cured thrust blocks]
    B --> C[Fill pipeline with water]
    C --> D[Vent air from high points]
    D --> E[Apply test pressure (≤ Table 3 max)]
    E --> F[Observe & check for leaks/damage]

This ensures integrity and workmanship quality post-installation and transit.

IS 6530 - Disinfection of Pipeline Before Commissioning (Clause 12)

• Applicability: Pipelines carrying potable water must be disinfected before commissioning.
• Reference Codes: Use guidelines from
  • IS 3114-1965 (Cast iron pipes)
  • IS 5822-1970 (Welded steel pipes for water supply)

Key Points for Disinfection:

• Disinfection is done after pressure testing and filling the pipeline with water.
• Follow procedures in referenced IS codes for chlorine dosage, contact time, and flushing.
• Typical chlorine concentration for disinfection: 50 mg/L (ppm) for a contact time of at least 24 hours.
• After disinfection, flush the pipeline thoroughly with potable water to remove residual chlorine.

Typical Disinfection Procedure:

Additional Notes:

• Allow water absorption for asbestos cement pipes as per Clause 11.7 before testing and disinfection.
• Ensure proper venting of air to avoid pressure test issues.

flowchart TD
    A[Fill pipeline with water] --> B[Add chlorine solution (50 mg/L)]
    B --> C[Maintain contact time (≥24 hrs)]
    C --> D[Flush pipeline with potable water]
    D --> E[Pipeline ready for commissioning]

This ensures safe potable water supply free from microbial contamination.

IS 6530 Safety Precautions - Key Points & Tables

Safety Provisions (Clause 4.2.6.1 & 4.2.8)

• Barricades, signs, red lanterns, and guards must be installed and maintained during construction to protect people and property.
• Follow local safety regulations and Indian Standards.
• For deep trenches or loose soil, provide proper shoring to prevent collapse and ensure worker safety.

Thrust Blocks (Clause 7.1)

• Thrust blocks transfer hydraulic thrust from pipe fittings to soil.
• Must be designed to bear loads safely on soil.

Deflection & Radius of Curvature (Table 1, Clause 6.4 & Fig. 6)

Summary:

• Use adequate barricades and shoring for safety.
• Design thrust blocks to safely transfer loads.
• Use deflection and radius of curvature data to ensure pipe alignment and avoid undue stress.

flowchart LR
    A[Excavation] --> B{Soil Condition}
    B -->|Loose or Deep Trench| C[Provide Shoring]
    B -->|Stable| D[

IS 6530: Maintenance and Inspection Key Points

1. Thrust Blocks (Clause 7.1)

• Transfer hydraulic thrust from fittings/pipes to a larger soil bearing area.
• Essential for stability at bends, tees, and valves.

2. Deflection & Radius of Curvature (Clause 6.4, Table 1)

Use this for allowable pipe deflections during installation and inspection.

3. Testing & Disinfection (Clauses 11.9 & 12.1)

• Test duration: Sufficient to ensure pipeline integrity.
• Disinfection: Follow IS 3114-1965 or IS 5822-1970 before commissioning potable water pipelines.

Summary for Maintenance & Inspection:

• Inspect thrust blocks for soil bearing and stability.
• Check pipe deflections against Table 1 limits.
• Conduct pressure tests for adequate duration.
• Disinfect potable water pipelines as per referenced IS codes.

flowchart LR
    A[Inspection] --> B[Check Thrust Blocks]
    A --> C[Measure Pipe Deflection]
    A --> D[Pressure Testing]
    D --> E{Test Duration Sufficient?}
    E -->|Yes| F[Disinfection]
    E -->|No| D
    F --> G[Commission Pipeline]
``

IS 6530: Key Annexures, Tables & Figures Summary

1. Thrust Blocks (Clause 7.1)

• Purpose: Transfer hydraulic thrust from pipe/fitting to soil.
• Design ensures load bearing soil section supports thrust.

2. Table 1: Deflection and Radius of Curvature (Clause 6.4 & Fig. 6)

• Usage: For calculating pipe deflection and bending radius during installation.

3. Figures

• Fig. 6: Illustrates deflection and radius of curvature by successive pipe deflections.
• Fig. 7: Link diagram for changeover from Cast Iron to Asbestos Cement Pressure Pipe.
• Fig. 2C: Bedding detail ensuring uniform pipe support (Clause 4.2.9).

4. Important Specifications

• Trench Bedding (Clause 4.2.9): Trench bed must be excavated to pipe grade with even bedding for full pipe length support.
• Handling & Laying: Pipes must be handled and laid carefully to avoid damage.
• Rounding Off (IS:2-1960): Final values must be rounded off per IS rules.

flowchart LR
    A[Hydraulic Thrust] --> B