Technical Design Requirements for Bar Screens

1. Installation Requirements

• Bar screens must be installed in wastewater treatment systems or upstream of pumps.

2. Clear Spacing Between Bars

• Coarse bar screens:

Mechanically cleaned: 16–25 mm (preferred)

Manually cleaned: 25–40 mm(preferred), up to 100 mm in special cases.

• Fine bar screens: 1.5–10 mm (preferred).
• Before pumps:Spacing should be determined based on pump requirements.

3. Flow Velocity and Installation Angle

• Wastewater flow velocity through the screen: 0.6–1.0 m/s (recommended).
• Mechanically cleaned screens (except drum-type screens): Installation angle of 60°–90°.
• Manuallycleaned screens: Installation angle of 30°–60°

4. Clearance for Screen Cleaners

• For wire rope-operated cleaners or mobile hoist grab-type cleaners: Minimum 1.5 m from the well wall.
• For chain-driven scraper cleaners or rotary solid-liquid separators: Minimum 1.0 m from the well wall.

5. Working Platform Requirements

• Mustbeinstalled above the screen, at least 0.5 m higher than the maximum design water level.
• afety and washing facilities must be provided on the platform.

6. Platform Walkway Dimensions

• Side walkways: 0.7–1.0 m (recommended).
• Front walkway:

Mechanically cleaned: ≥1.5 m.

Manually cleaned: ≥1.2 m.

7. Screenings Conveyance

• Coarse screenings: Preferably transported by belt conveyor.
• Fine screenings: Preferably transported by screw conveyor.

8. Sealing and Odor Control

• Inlets and outlets of bar screen cleaners, conveyors, and Dewatering Presses should be sealed.
• Odor control systems may be installed depending on environmental conditions.

9. Ventilation and Safety

• Mechanical ventilation (e.g., axial exhaust fans) must be provided.
• If toxic gases are present, gas detection and alarm systems must be installed.
• Large and medium-sized screen chambers should have hoisting equipment for maintenance and screenings removal.

10. Number of Screens

• Large/medium wastewater plants: Two-stage screening—

First stage (coarse screen): 10–40 mm spacing.

Second stage (fine screen): 3–10 mm spacing.

• Small wastewater plants: One screen with 3–15 mm spacing is sufficient

11. Material Selection

• Rake teeth and chain links, which aresubmerged for long periods, should be made of high-strength plastic or stainless steel to prevent corrosion.
• Chain shafts should also be stainless steel.