Coarse Screening · Headworks

Rotary Bar Screen (Multi-Rake Type)

A chain-driven rotary bar screen built for the first job that has to be done right at the headworks: pulling rags, wipes, wood and plastics out of the flow before they reach your pumps. Multiple rakes on a continuous loop clean the bar rack every few seconds — so peak storm flow does not normally outrun the screen.

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Loway rotary bar screen (multi-rake type) for wastewater headworks

Where It Fits

Where a rotary bar screen is the right screen

A rotary bar screen — also called a multi-rake bar screen, a chain-driven bar screen or a mechanical bar screen — is the coarse, high-load machine at the head of a treatment train. It earns its place in deep channels and at sites with a heavy, variable debris load.

It is recommended for deep channels and a heavy, variable debris load. Where the channel is shallow and the load is light, or where the site has no disposal route for screenings, a step screen or a grinder usually runs with less to maintain. Set against a static bar rack, a multi-rake rotary bar screen keeps a continuous cleaning cycle running across the full channel width, so head loss stays steady through the day instead of spiking between rake passes. That matters most where the screen protects rotating equipment downstream — a rag that slips past the headworks is a pump rebuild, a heat-exchanger blockage, or a plant bypass waiting to happen.

Continuous cleaning, not batch cleaning

On a rotary bar screen, multiple rake teeth travel the bar rack on the same chain loop, so the rack is swept roughly every few seconds rather than once per cycle. Debris does not sit long enough to blind the bars.

Built for deep channels and high loads

Heavy-duty frames and a rigid bar rack are why a rotary bar screen suits deep headworks channels and high solid loads, which is where light-duty screens start to deflect, jam or wear through their guides.

Working Principle

How a multi-rake bar screen works

A rotary bar screen is a stationary bar rack plus a moving cleaning mechanism: a set of rake teeth mounted on a heavy-duty drive chain that runs the length of the rack and back. Water passes through the rack at an approach velocity of roughly 0.6–1.2 m/s, fast enough to carry solids to the bars without driving them through the gaps.

Rotary bar screen installed in a wastewater channel during operation — A rotary bar screen unit on the Loway factory floor before dispatch.

Interception

Wastewater flows through the stationary bar rack. Solids coarser than the bar gap — branches, bottles, wipes, rags — are held on the upstream face of the bars.

Raking

The rake teeth ride the chain down the rack face and comb the captured solids upward, penetrating between the bars so nothing is left lodged in the gap.

Discharge

At the top of the travel the rakes strip the screenings onto a discharge chute, belt or container. The chain returns down the back of the frame for the next pass.

Design Detail

Built for continuous duty in the channel

Four machine-level details decide whether a rotary bar screen survives the years at the headworks or becomes a maintenance line item.

Overload protection on the drive

An electromechanical overload device watches motor current. If a heavy object jams the rake, the drive stops and reverses instead of stalling the gearbox or shearing the chain; a shear pin backs it up. The alarm signal goes to your control panel.

Teardrop-profiled bars

Bar section sets the energy loss more than bar count. A teardrop profile has a shape factor of about 0.76 against roughly 2.42 for a sharp rectangular bar, so the same opening carries more flow for less head loss — and the leading edge sheds debris instead of trapping it.

Heavy-duty roller chain

The chain-driven rake assembly runs on high-tensile roller chain specified for wet, abrasive and mildly corrosive service, with a take-up adjustment that keeps chain tension stable and cuts re-tensioning visits.

Optional full enclosure

The above-water section can be fully enclosed in stainless steel for odour control and operator safety — standard practice on covered or indoor headworks.

Manufacturing

How Loway builds the rotary bar screen

Loway has manufactured solid-liquid separation equipment since 2017. Every rotary bar screen is welded, machined and tested in our own workshop before it is crated.

01 Precision laser cutting

Frame components and rake teeth are laser-cut so rake-to-bar clearance is consistent. Uniform clearance is what prevents tooth skipping and premature chain wear.

02 Full-penetration welding

The load-bearing frame is welded with full penetration so it holds its geometry under hydraulic load and long-term immersion rather than distorting at the joints.

03 Pickling & passivation

After welding, stainless parts pass through acid pickling and passivation to restore the passive oxide layer and remove weld discolouration — the usual starting point for corrosion.

04 Dry-run acceptance test

No unit ships without a dry run on our floor, where chain tension, motor current and running noise are checked and recorded before crating.

Loway workshop fabricating a rotary bar screen frame — Frame fabrication and assembly in the Loway workshop.

Rotary bar screen manufacturing process at the Loway factory — Frame fabrication and assembly in the Loway workshop.

Engineering Data

Rotary bar screen specifications

Every rotary bar screen is built to the channel, so the table below sets the working envelope rather than a fixed catalogue number. Standard channel width is 500 – 3,000 mm; wider channels up to 4,000 mm are built to order.

Parameter	Specification
Model series	LW-RBS (rotary bar screen, multi-rake)
Bar gap	5 / 10 / 20 / 30 / 50 mm standard; intermediate sizes built to order
Channel width (W)	500 – 3,000 mm standard; up to 4,000 mm on request
Discharge height (H)	800 – 10,000 mm, suited to deep headworks channels
Installation angle	60° – 85° (75° standard)
Frame & bar material	SS304 standard; SS316L or Duplex 2205 for chloride service
Rake teeth	Wear-resistant alloy, replaceable
Drive	Chain-driven rake assembly, geared motor with overload protection; IP67
Control	PLC panel with level-differential and timer control modes; panel IP55, IP65 for outdoor mounting
Side sealing	Replaceable EPDM / neoprene seals against the channel wall

Gap size sets what the screen captures; channel width and depth set the model. Send us the channel drawing and design flow and we will return a general arrangement (GA) drawing with the sizing worked through.

Where It Runs

Bar screen applications: pump stations, stormwater and industrial intakes

The rotary bar screen is the coarse stage of the treatment train. What changes between projects is the channel, the debris load and how the screenings leave — not the machine.

Deep headworks channels

Inlet channels three to six metres deep, where the rotary bar screen rake travels a long way and the frame has to stay rigid under load. Discharge height is matched to your operating platform, up to 10,000 mm. This is the classic setting at a municipal sewage works.

Sewage pump stations and lift stations

Where a rotary bar screen sits inside a wet well or a small chamber and protects the pumps directly. A compact frame and a low discharge height keep the station footprint small. Where there is no room to store screenings at all, a channel grinder replaces the screen.

Stormwater and combined sewer overflow

Peak flow arrives in minutes and brings a debris surge with it. On a rotary bar screen, the continuous multi-rake cleaning cycle is what keeps the rack clear through the first flush, and the channel is laid out with a bypass or overflow weir so flow is not blocked while the screen is serviced.

Industrial intake and process water

River, lake and cooling-water intakes on mine sites and power plants, where the opening is set by what must not reach the downstream process and the wetted material is upgraded to SS316L or Duplex 2205 for chloride service.

Pulp and paper mills

Coarse plastic rejects and tramp wire lifted out ahead of finer screening, with the fiber fraction downstream recovered rather than sent to landfill.

Selection

Multi-rake bar screen vs climber screen

Both clean a bar rack. On a rotary bar screen the difference is how often the rack is cleaned — and that difference shows up on the worst day of the year, not the average one.

Criteria	Multi-Rake (this unit)	Single-Rake Climber
Rakes per pass	Several rakes on one chain loop	One rake arm
Cleaning frequency	Continuous — seconds	Once per full travel cycle
Peak storm flow	Keeps pace with rising debris load	Can be overwhelmed between passes
Best fit	Headworks, pump stations, deep channels	Small channels, low and steady flow
Head loss behaviour	Stable through the day	Rises between rake cycles

Sizing

What we need to size your bar screen

A rotary bar screen is built to the channel, so these are the inputs that set the model, the gap and the discharge arrangement.

Channel width and channel depth
Design flow and peak flow (m³/h or m³/s)
Upstream water level, including the highest flood level
Required bar gap and the solids you expect to screen out
Discharge height and how screenings will be conveyed away
Installation angle and available headroom above the channel
Water chemistry — chlorides decide SS304 vs SS316L or Duplex
Odour control — whether the above-water section must be enclosed

Share a channel cross-section and we will work through the hydraulics with you. For the wider selection logic across mechanical bar screens, drum screens and grinders, see our mechanical screening equipment range overview.

Technical FAQ

Rotary bar screen questions, answered

The questions engineers actually ask us during selection. If yours is not here, send it with your channel drawing.

Q1. What bar gap should I specify for a bar screen?

Match the gap to what the screen has to protect, not to the smallest number available. 20 mm is the usual municipal headworks setting — it holds wipes and rags out while keeping the screenings volume manageable. 5–10 mm is used where a downstream pump or process needs finer protection, and the price is a higher screenings load and more compaction duty. Below about 1 mm you are into micro-screening, which is a drum screen, not a bar rack.

Q2. What head loss does a rotary bar screen add to the channel?

Design for the blinded case, not the clean rack. On a clean rack the head loss is small; as debris builds, the open area falls and the head loss rises several-fold, so the channel is normally laid out for a loaded-screen design head loss under 0.15 m. The bar profile matters here: a teardrop section has a shape factor around 0.76 against roughly 2.42 for a sharp rectangular bar, which lowers energy loss and keeps the design figure predictable. We confirm the number against your full flow range when we size the unit.

Q3. What is the advantage of a multi-rake screen over a single-rake climber screen?

Speed and head-loss stability. A climber screen has one rake arm that travels down and back up, so the rack is only cleaned once per cycle. A multi-rake rotary bar screen carries several rakes on the same chain loop and cleans the rack continuously, which is what keeps the screen ahead of the debris load during storm flow.

Q4. How does the automatic control logic work?

The PLC panel normally runs on a level-differential sensor. As debris builds on the rack the upstream level rises; when the difference between upstream and downstream reaches a set point (commonly around 100 mm) the screen starts. Once the rack is clean and the differential falls, the screen returns to standby. Timer and manual modes are available as alternatives. The panel is IP55 as standard, with IP65 for outdoor mounting.

Q5. What happens if a large object jams the rake?

There are two layers of protection. The electronic torque limit on the drive monitors motor current and, on a spike, stops and reverses the chain to clear the obstruction. If that fails, a mechanical shear pin releases to disconnect the drive and protect the gearbox from damage.

Q6. Can the screen be pivoted out of the channel for maintenance?

Yes. The frame can be supplied with pivot supports at the operating-floor level so the whole unit tips out of the channel. Underwater chain guides and bearings can then be inspected at floor level instead of by confined-space entry.

Q7. Does the equipment need a recess cut into the concrete channel?

A small recess lets the frame sit flush with the channel walls, which is the cleanest arrangement on a new build. On an existing channel without a recess, we supply flow-guide baffles to smooth the approach flow and avoid turbulence at the frame.

Q8. How do you stop waste bypassing the screen at the channel walls?

The frame carries heavy-duty EPDM or neoprene side seals that press against the channel walls. The seals are replaceable wear items, so the flow is kept passing through the bar rack rather than around it, and they can be renewed without removing the screen.

Q9. Can you build the screen in SS316L for a seawater or coastal intake?

Yes. For desalination plants, coastal power stations and chloride-bearing process water we build the unit in SS316L or Duplex 2205, and can add sacrificial anodes for cathodic protection where required.

Q10. What is the lead time for a custom-sized unit?

Because the screen is built to the channel, production typically runs four to six weeks after drawing approval. The general arrangement drawing is issued within a few business days of order so civil works can proceed in parallel.

Still deciding? Our engineering team can review your channel data and recommend the right screen type — see who you will be working with on the engineering team page.

Next Step

Send us your channel dimensions and flow rate

Our engineers will size the rotary bar screen to your channel and return a general arrangement drawing with a quotation. Tell us the channel width, depth and design flow and we will take it from there.

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Rotary Bar Screen

Rotary Bar Screen (Multi-Rake Type)