sewage screens

IS 6280: Scope - Key Specifications & Materials (Clause 3.1)

This standard covers materials for various parts of sewage screens. Below is a summary table of recommended materials and corresponding IS codes:

Note: Refer to the respective IS codes for detailed material properties, fabrication, and testing requirements.

Additional Info: Disposal of Screenings (Clause 7.1)

• Use rubber-tyred tippers (≥140 liters), trailers for large plants, or cleanable wheelbarrows for small plants.
• Disposal methods: sanitary landfill or incineration.

flowchart TD
    A[Sewage Screen Components] --> B[Civil Works: Concrete, Masonry]
    A --> C[Gates: Cast Iron, Steel]
    A --> D[Floats: Plastic]
    A --> E[Rake Arm & Frame: Structural Steel, Cast Iron]
    A --> F[Teeth: Cast Steel]
    A --> G[Shaft: Cold Finished Steel]
    A --> H[Electrical: Motors, Switches]
    A --> I[Structural: Flats,

IS 6280 - Definitions & Key Specifications

1. Definitions (Clause 2.0)

• Defines terms used in the standard for sewage screens.

2. Materials for Component Parts (Clause 3.1, Table 1)

3. Screen Opening Velocity (Clause 4.3)

• Max velocity through screen openings: ≤ 0.9 m/s at max flow.
• Effective area = vertical projected area from channel invert to flowline.

Notes:

• All materials must comply with respective IS standards.
• Rounding of test/analysis results per IS 2-1960.

flowchart TD
    A[Screen Components] --> B[Civil Works]
    A --> C[Gates]
    A --> D[Floats]
    A --> E[Rake Arm & Mechanism]
    A --> F[Teeth]
    A --> G[Shaft]
    A --> H[Electrical Parts]
    B --> I[Concrete, Brick, Stone]
    C --> J[Cast Iron, Steel]
    D --> K

IS 6280: Materials for Sewage Screens (Clause 3.1 & Table 1)

Notes:

• Concrete and masonry follow standard construction codes (IS 456 for concrete).
• Structural steel and castings adhere to IS 226 and IS 210 respectively.
• Electrical components like motors and switches comply with IS 325, IS 996, etc.
• Floats use corrosion-resistant plastics for durability.

This table guides material selection ensuring compliance with Indian Standards for sewage screen components.

IS 6280: Location and Installation Requirements for Screening Devices

Key Specifications:

• Separation & Ventilation (Clause 4.1.2):
  • Screening devices inside buildings must be separated by partitions.
  • Provide adequate ventilation to avoid accumulation of gases or odors.
  • Forced ventilation recommended with blowers at ground level and flexible ducts (Clause 5.1.6).
  • Lighting should be low-voltage or flame-proof type.

Materials for Construction (Clause 3.1, Table 1):

Disposal of Screenings (Clause 7.1):

• Use rubber-tyred tippers (≥140 litres) or wheelbarrows for small plants.
• Disposal methods: sanitary landfill or incineration.

Ventilation Setup Diagram (Conceptual):

flowchart LR
    A[Ground Level] -->|Blower| B[Flexible Ducting]
    B --> C[Screening Device Pit]
    C -->|Displace Air| D[Outside Air]
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IS 6280: Construction and Design Requirements - Key Specifications & Materials

1. Materials for Sewage Screen Components (Clause 3.1, Table 1):

2. Design Guidance (Clause 4.1):

• Mechanical screens are recommended when sewage flow > 400 m³/h.
• Mechanical medium screens must be preceded by manually cleaned coarse screens.
• No fixed standard design; designs should suit the overall sewage treatment scheme.

3. Disposal of Screenings (Clause 7.1):

• Use rubber-tyred tipper (≥140 liters capacity) or trailers/wheelbarrows.
• Disposal methods: sanitary landfill or incineration.

Summary Diagram: Material Selection Flow

flowchart TD
    A[Sewage Screen Components] --> B[Civil Works]
    A --> C[Gates]
    A --> D[Floats]
    A --> E[Rake Arm & Frame]
    A --> F[Teeth]
    A --> G[Shaft]
    A --> H[Motors & Switches]
    A --> I[

IS 6280: Manually Cleaned Screens – Key Points & Specifications

Key Specifications (Clause 5.1.2)

• Platform: Top of screen channel must have a perforated platform for operator access.
• Drainage: Platform should have suitable draining facilities to avoid water accumulation.
• Tools: Provide a hand rake for manual removal of screenings.

General Guidance (Clause 5.1 & 0.4)

• Manually cleaned screens are mainly coarse screens, used when flow < 400 m³/h.
• Mechanical screens are preferred above 400 m³/h, preceded by manual coarse screens.
• No fixed design criteria; design depends on sewage characteristics and treatment scheme.

Typical Dimensions & Design (based on engineering practice)

Recommended Formula for Screen Capacity:

[ Q = A \times v ]

• ( Q ) = flow rate (m³/s)
• ( A ) = effective screen area (m²)
• ( v ) = velocity through screen (typically 0.6–1.0 m/s)

flowchart LR
    Sewage_Flow --> Coarse_Manual_Screen
    Coarse_Manual_Screen --> Perforated_Platform
    Perforated_Platform --> Operator_Hand_Raking
    Operator_Hand_Raking --> Screenings_Removal

Summary: Manually cleaned screens in IS 6280 require a safe platform with drainage, hand rake provision, and are used primarily for flows <400 m³/h as coarse screens. Design depends on flow and sewage characteristics.

IS 6280: Mechanically Cleaned Screens – Key Points

• Definition (Clause 5.2.1):
  Mechanically cleaned screens consist of a screen with a mechanical raking device for automatic cleaning.

• Design Guidance (Clause 4.1 & 0.4.1):

  • No fixed standard design; design must suit overall sewage treatment.
  • Mechanical screens recommended if sewage flow > 400 m³/h.
  • Mechanical medium screens should be preceded by manually cleaned coarse screens.

Typical Design Considerations (from general practice):

Basic Formula for Flow Through Screen:

[ Q = A \times V ]

Where:

• (Q) = Flow rate (m³/s)
• (A) = Effective open area of screen (m²)
• (V) = Approach velocity (m/s)

flowchart LR
    Sewage_Flow --> Coarse_Manual_Screen
    Coarse_Manual_Screen --> Mechanical_Screen
    Mechanical_Screen --> Raking_Device
    Raking_Device --> Screen_Cleaning

Summary: Use mechanical screens for >400 m³/h flow, preceded by manual coarse screens. Design approach velocity ~0.6–1 m/s; screen openings depend on debris size. Mechanical raking ensures continuous cleaning.

IS 6280 - Painting & Corrosion Protection: Key Specifications

Clause 6.1 Painting System:

• Primer: One coat of Redroxide (zinc chromate) primer.
• Top Coats: At least 3 coats of bitumastic or other approved anti-corrosion paint.
• Application: Painting to be done after erection of steel components.
• Reference: IS 1477 (Part I & II) for painting workmanship and schedules.

Summary Table: Painting Layers

Additional Notes:

• Use fabricated structural steel as per IS 226 for frames and rake arms.
• Ensure surface preparation before painting for proper adhesion.
• Follow IS 1477 for detailed painting procedures and quality control.

flowchart TD
    A[Steel Surface] --> B[Apply 1 Coat Redroxide Primer]
    B --> C[Apply 3 Coats Bitumastic/Approved Paint]
    C --> D[Final Corrosion Protection]

This system ensures durable corrosion protection for steel components in sewage screens and allied structures.

IS 6280: Disposal of Screenings - Key Points

Disposal Equipment (Clause 7.1)

• Use rubber-tyred tipper with minimum capacity 140 litres for collection/disposal.
• For large plants, trailers are recommended.
• For small plants, use cleanable wheelbarrows.

Disposal Methods

• Sanitary landfill
• Incineration

Additional Guidance

• Mechanical screens recommended if sewage flow > 400 m³/h (Clause 0.4.1).
• Coarse manual screens should precede mechanical screens.

Summary Table: Screening Disposal Equipment

This ensures hygienic, efficient collection and disposal of screenings per IS 6280.