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Mechanical Bar & Step Screens

Automatic Mechanical Bar Screen for Wastewater Pretreatment

Automatic mechanical bar screen for municipal and industrial wastewater pretreatment. Review working principle, screen spacing, capacity selection, control options and sizing data.

Automatic Screening for Wastewater Pretreatment

An automatic mechanical bar screen removes coarse solids and debris from wastewater before pumps and downstream treatment equipment. It is commonly installed at the inlet of municipal and industrial wastewater treatment systems where continuous or automatic screenings removal is required.
Correct screen selection depends on more than design flow alone. Channel dimensions, peak flow, required screen opening, solids characteristics, operating water level and downstream process requirements should all be considered before the final equipment size is confirmed.


How the Mechanical Bar Screen Works

Wastewater passes through the screen while larger solids are retained by the screening elements. A rake or tooth-chain mechanism continuously lifts the retained material from the channel and discharges it at the upper section of the unit.
The cleaning mechanism removes screenings from the rake elements during operation. The drive system can be equipped with overload protection to reduce the risk of mechanical damage when abnormal loading occurs.
For projects requiring automatic operation, PLC control and integration with the plant control system can be configured according to project requirements.


Screen Opening and Capacity Selection

The required screen opening should be selected according to the type and size of solids that need to be removed and the protection requirements of downstream equipment.
A smaller opening is not automatically better. Finer screening can increase captured solids, hydraulic resistance and cleaning frequency. The appropriate opening should therefore be selected together with the wastewater characteristics and downstream process requirements.
Rated capacity should not be selected from a catalogue table alone. Actual hydraulic capacity can be affected by:
  • Channel width
  • Operating water level
  • Peak flow
  • Screen opening
  • Solids loading
  • Allowable headloss
  • Installation angle
  • Upstream and downstream hydraulic conditions

HLCF Series Technical Data

📊 Technical Parameters (HLCF Series)

(Note: Data based on a standard Flow Depth H3 = 1.0m and Flow Velocity V = 0.8 m/s)
Flow Rate Capacity Q (m³/s) Based on Grid Spacing (b):
Grid Spacing (b) mm
HLCF-500
HLCF-600
HLCF-700
HLCF-800
HLCF-900
HLCF-1000
HLCF-1100
1 mm
0.03
0.04
0.05
0.06
0.07
0.08
0.08
3 mm
0.07
0.09
0.10
0.12
0.14
0.16
0.18
5 mm
0.09
0.11
0.14
0.16
0.18
0.21
0.23
10 mm
0.11
0.14
0.17
0.21
0.24
0.27
0.30
15 mm
0.13
0.16
0.20
0.24
0.27
0.31
0.34
20 mm
0.14
0.17
0.21
0.25
0.29
0.33
0.37
25 mm
0.14
0.18
0.22
0.27
0.31
0.35
0.39
30 mm
0.15
0.19
0.23
0.27
0.32
0.36
0.40
40 mm
0.15
0.20
0.24
0.29
0.33
0.38
0.42
50 mm
0.16
0.20
0.25
0.29
0.34
0.39
0.43


Information Required for Preliminary Selection

For preliminary mechanical bar screen selection, please provide the following project information:
  • Design flow
  • Peak flow
  • Channel width
  • Channel depth
  • Normal operating water level
  • Required screen opening, if already specified
  • Wastewater source
  • Main solids or debris characteristics
  • Upstream and downstream treatment process
  • Installation angle, if already determined
  • Available civil drawing, if applicable
  • Power supply
  • PLC or SCADA requirements
Final equipment dimensions should be confirmed after reviewing the actual hydraulic and civil conditions.


Drive and Control Options

Mechanical bar screens can be configured according to different operating and automation requirements.
Available configurations may include:
  • Automatic continuous or intermittent operation
  • Drive overload protection
  • Local control panel
  • PLC control
  • Level-based operation
  • Integration with SCADA or plant control systems
The final control configuration should be confirmed according to the project specification.


Typical Applications

Automatic mechanical bar screens are commonly used for:
  • Municipal wastewater inlet screening
  • Industrial wastewater pretreatment
  • Pumping station protection
  • Removal of coarse debris before downstream treatment
  • Pretreatment before biological treatment
  • Pretreatment before solid-liquid separation systems
  • Wastewater treatment plant inlet channels
The screen is primarily intended for coarse solids and debris removal. It should not be selected as a replacement for downstream fine solids separation or biological treatment.


Civil Works and Installation

Mechanical bar screen sizing is closely related to inlet channel design.
Channel width, channel depth, operating water level, installation angle and equipment width should be reviewed together before final equipment confirmation.
For projects where the civil works have not yet been finalized, HydroNovus can review the available channel dimensions and installation conditions before equipment sizing.
For detailed channel sizing, B1–B4 dimension relationships, installation angle and civil works requirements, see:
Mechanical Bar Screen Civil Works Sizing & Installation


Mechanical Bar Screen Selection FAQ

What information is required to size a mechanical bar screen?

Design flow, peak flow, channel dimensions, required screen opening, solids characteristics, operating water level and installation conditions are normally required for preliminary selection.

How should the screen opening be selected?

The opening should be selected according to the size of solids that need to be retained and the protection requirements of downstream equipment. Smaller openings capture more material but can also increase hydraulic resistance and screenings load.

Can the mechanical bar screen be integrated with PLC or SCADA?

Yes. Control configuration can be selected according to the project requirements and the existing plant automation system.

Can HydroNovus review an existing civil drawing?

Yes. If channel drawings or civil dimensions are already available, they can be reviewed together with the design flow and screening requirements before preliminary equipment sizing.


Request Mechanical Bar Screen Selection

Planning a new wastewater pretreatment system or upgrading an existing inlet screen?
Send us your:
  • Design and peak flow
  • Channel dimensions
  • Required screen opening
  • Wastewater application
  • Available civil drawing
HydroNovus can review the preliminary equipment size, screening configuration and installation requirements for your project.

Request Engineering Selection