Rotary Rake Type Mechanical Screen Grille

Mechanical grille is a type of grille equipment that can automatically remove garbage attached to the grille.
Mechanical grille is one of the early purification equipment in water supply and drainage treatment technology. It greatly reduces the labor intensity of workers, protects their physical health, reduces the head loss of water inflow, and improves the efficiency of pump stations

Rotary Rake Type Mechanical Screen Grille

The Rotary Rake Type Mechanical Screen Grille is an automatic wastewater screening machine designed to remove coarse solids, floating debris, rags, plastics, fibers, paper, and other unwanted materials from wastewater streams. It is commonly installed as preliminary treatment equipment at municipal sewage treatment plants, industrial wastewater facilities, pumping stations, and other water treatment systems.

Screening is one of the first treatment operations in a wastewater treatment plant. Large solids and debris can interfere with treatment processes, clog pipelines, damage pumps, and increase maintenance requirements. Mechanical screening provides an efficient way to intercept these materials before they enter downstream treatment equipment. EPA guidance identifies screening as a preliminary treatment process used to remove materials such as rags, paper, plastics, and metals that could cause damage or clogging downstream.

Rotary Rake Mechanical Screening Principle

The machine consists of a fixed screen grille, rotary rake mechanism, drive system, guide structure, frame, motor, control system, and screenings discharge section.

When wastewater flows through the grille, solids larger than the selected screen opening are retained on the bars. The rotary rake moves through the screen area and engages the accumulated solids. As the rake travels upward, it lifts the captured material away from the wastewater flow and transfers it toward the discharge section.

The screening cycle can be continuous or intermittent depending on the equipment design and control strategy. Mechanically cleaned bar screens can use electrically driven rake mechanisms to remove retained material continuously or periodically.

After the solids reach the upper discharge area, they can be released into a collection hopper, chute, screw conveyor, belt conveyor, or screenings compactor.

Efficient Coarse Solids Removal

The rotary rake screen grille is designed for effective removal of coarse materials from wastewater.

Typical materials that can be intercepted include:

Rags and textiles
Plastic bags and packaging
Paper and cardboard
Fibrous materials
Hair and string-like debris
Leaves and organic waste
Food processing residues
Wood fragments
Floating garbage
Large suspended solids

The appropriate screen opening depends on wastewater characteristics, hydraulic conditions, solids loading, and downstream process requirements. Mechanically cleaned bar screens are commonly used for coarse screening, with the exact opening selected according to the treatment application.

Protect Downstream Equipment

A major advantage of the mechanical screen grille is its ability to protect equipment installed further along the treatment process.

Large debris entering pumps or pipelines can cause blockages, while fibrous materials can wrap around rotating components. Plastics, rags, and other solids can also interfere with biological treatment, filtration, and sludge-handling systems.

Installing a rotary rake screen at the inlet helps reduce these risks by intercepting coarse solids before they reach downstream equipment.

The screen can be installed before:

Wastewater pumps
Grit removal systems
Primary clarifiers
DAF systems
MBBR treatment systems
MBR systems
Biological treatment tanks
Sludge treatment equipment
Filtration systems

EPA wastewater guidance specifically notes that screening removes objects that could damage or clog downstream equipment, piping, and associated components.

Automatic Rake Cleaning

Unlike manually cleaned grilles, the rotary rake type mechanical screen automatically cleans the screen surface.

As debris accumulates, the rake mechanism engages the material and carries it upward. This automatic cleaning cycle helps maintain the open area of the screen and reduces the amount of manual labor required.

Automatic operation can be configured using:

Timer control
Water-level differential control
Level sensors
PLC control
Automatic start/stop sequences
Central wastewater plant control systems

The exact control method can be selected according to the treatment plant requirements.

Mechanically cleaned screens are particularly useful where wastewater flow is continuous and manual cleaning would create excessive labor requirements or operational difficulties.

Rotary Rake and Screen Grille Design

The rake teeth are designed to pass through the openings between the screen bars and collect the solids retained on the grille.

The screen frame and rake mechanism can be configured according to channel width, channel depth, installation angle, flow rate, screening opening, and discharge height.

For mechanically cleaned bar screens, design considerations include hydraulic conditions, screen opening, approach velocity, solids handling, head loss, and available installation space.

This allows the equipment to be adapted for different wastewater treatment projects rather than relying on a single standard configuration.

Municipal Wastewater Applications

The rotary rake mechanical screen can be installed at the headworks of municipal sewage treatment plants.

Incoming sewage often contains rags, plastics, paper, sanitary materials, fibers, and other debris. Removing these materials during preliminary treatment helps protect downstream pumps, pipes, biological treatment units, and clarification equipment.

For larger wastewater plants, the screening machine can also be combined with screenings washing, conveying, dewatering, and compacting equipment to create an automated solids-handling process.

Industrial Wastewater Applications

The machine is also suitable for industrial wastewater containing coarse or fibrous materials.

Potential applications include:

Food Processing Wastewater
Slaughterhouse Wastewater
Textile Wastewater
Paper Mill Wastewater
Printing and Dyeing Wastewater
Chemical Industry Wastewater
Agricultural Wastewater
Beverage Production Wastewater
Industrial Sewage Treatment

The final screen opening and equipment configuration should be selected according to the actual wastewater characteristics and required treatment performance.

Pumping Station Screening

Rotary rake mechanical screens can also be installed at wastewater pumping stations.

Screening before pumps helps prevent large debris from entering pump chambers and impellers. This can reduce the risk of blockage and simplify pump maintenance.

For pumping stations with variable flow, automatic control can allow the rake system to operate according to wastewater level or a preset cleaning cycle.

Durable Construction

Wastewater treatment equipment operates in wet and potentially corrosive environments. Depending on the project, the mechanical screen grille can be manufactured from stainless steel, coated carbon steel, or other suitable materials.

Stainless steel options are particularly useful when enhanced corrosion resistance is required.

Key components that require routine inspection include the screen bars, rake teeth, drive motor, transmission mechanism, guide system, fasteners, electrical controls, and screenings discharge area.

Proper lubrication, adjustment, cleaning, and preventive maintenance can help maintain reliable operation. EPA training materials recommend keeping mechanically cleaned screens properly lubricated and adjusted and following the equipment manufacturer's maintenance recommendations.

Flexible Wastewater Treatment Integration

The rotary rake type mechanical screen can function as an independent preliminary screening machine or as part of a complete wastewater treatment system.

A typical treatment sequence may include:

Inlet → Rotary Rake Mechanical Screen → Grit Removal → Equalization → DAF/Sedimentation → Biological Treatment → Filtration → Disinfection

The exact process depends on wastewater quality, required effluent standards, treatment capacity, and project objectives.

Why Choose Us
Automatic rotary rake mechanism for efficient screening
Designed for continuous wastewater pretreatment
Effective removal of rags, plastics, fibers, and coarse solids
Helps protect downstream pumps and treatment equipment
Suitable for municipal and industrial wastewater
Multiple screen openings and configurations available
Automatic timer or level-based control options
Flexible channel width, depth, angle, and discharge design
Compatible with conveyors and screenings compactors
Suitable for integration into complete wastewater treatment plants
FAQ
1. What is a rotary rake type mechanical screen?

It is an automatic screening machine that uses a rotating or traveling rake mechanism to remove solids retained on a fixed wastewater screen grille.

2. What does a rotary rake screen remove?

It can remove rags, plastics, paper, fibers, hair, leaves, food residues, packaging materials, and other coarse solids.

3. Why is a mechanical screen installed in wastewater treatment?

It provides preliminary solids removal and helps prevent large debris from clogging or damaging downstream pumps, pipes, and treatment equipment.

4. How does the rake mechanism work?

The rake teeth pass through the screen openings, engage retained solids, lift them upward, and discharge them at the top or designated collection area.

5. Can the machine operate automatically?

Yes. The screen can be controlled by timers, differential water levels, sensors, PLC systems, or other automatic control methods.

6. Can the screen opening be customized?

Yes. Screen opening, channel dimensions, installation angle, rake configuration, discharge height, and other parameters can be selected according to the project.

7. Is the machine suitable for industrial wastewater?

Yes. It can be used for food, slaughterhouse, textile, paper, chemical, agricultural, printing, dyeing, and other industrial wastewater applications.

8. Can the screen be installed before a wastewater pump?

Yes. Installing a mechanical screen upstream of a pump can help intercept large debris and reduce the risk of pump blockage.

9. Can screenings be transported automatically?

Yes. The discharge section can be connected to a screw conveyor, belt conveyor, screenings compactor, hopper, or collection container.

10. What materials can be used to manufacture the screen?

Depending on wastewater conditions, stainless steel, coated carbon steel, and other suitable materials may be selected for different components.

11. Does the rotary rake screen require maintenance?

Yes. Regular inspection of the rake, screen bars, drive system, guides, motor, fasteners, and discharge system is recommended.

12. Can it be integrated with other wastewater treatment equipment?

Yes. It can be used upstream of grit removal, DAF, sedimentation, MBBR, MBR, biological treatment, filtration, disinfection, and sludge treatment systems.

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