Filson Hydro Screen

Supply Top Quality Hydro Screens To Customers Around The World

Filson provides standard hydro screens with slot opening sizes from 0.25mm to 2.5mm and flows rates up to 620m³/h. If you have more challenging filtration needs, do not hesitate to consult filson engineers. We also offer OEM services for your specific requirements.

Without moving parts or complicated connections, Filson hydro screens are cost-economical choices for you. It can help you remove rag and dry solids from wastewater sludge, to reduce blockages and increase downstream treatment efficiency.

Just contact us today at +86 157 3695 8886, alternatively email sales@filsonfilters.com!

Hydro Screen: The Ultimate FAQ Guide

I know probably, you’re looking for high quality and reliable hydro screen.

Or, you would like to learn more about hydro screen.

A reason this guide will answer all your question about this filtration system.

So, keep reading to learn more.

What Are The Advantages Of Hydro Screens?

1. They improve the coverage of water and its conservation by getting rid of blocked gates and nozzles.
2. By use of ditch diversions and existing checks, they eradicate debris, weed and moss from water sources.
3. They reduce operational costs by preventing blockage of gated pipes, pumps and nozzles thus improving efficiency.

What Is Hydro Screen?

This is a filtering robust structure usually made of stainless steel wedge wire that is used in the separation of liquids and solids and other water screening applications.

What Are The Different Types Of Mechanical Hydro Screens?

Through Flow Continuous Belt Screen

This design is wisely famous for serving two purposes at a go, that is, having a filtering and removal mechanism in the same machine.

The screenings are normally knocked off by a static or rotating brush.

 A Through Flow Continuous Screen

Materials are ordinarily offloaded by a spray wash.

Merits;

• It has a housing fully made of stainless-steel which makes it strong and corrosion-resistant.
• Maintains a very low profile with a small footprint
• It is very economical

Limitations;

• Its capture rate is not high
• Larger solids are hard to lift with this type of screen
• High water flows cannot be screened

Single Rake Bar Screen

A bar rack comprising of openings larger than 1“is the design feature of this Hydro Screen. The screen is affixed within a channel.

The screening materials are lifted up by a rake arm and removed out of the channel.

Merits;

• Large objects can easily be lifted out of very deep channels
• Its heavy duty frame made of steel carbon makes it rugged hence very reliable.

Limitations;

• Maintenance points are not easily accessible due high overhead heights
• They have a high probability of jamming

Single Rake Bar Screen

Multi-Rake Bar Screen

This is a design that has evolved from the single rake bar screen. The multiple rakes are contained in a structure made fully or partially with stainless steel.

Merits;

• It is very durable
• Maintenance can be easily achieved by accessing it from the top channel
• Rakes are more positively engaged into bars compared to other bar screens.
• Protection of the headworks coarse screening or the pump is guaranteed.

Limitations;

• It has a high possibility of jamming
• Maintenance points are not easily accessible due high overhead heights

Multi Rake Bar Screen

Step Screen

This type of mechanical Hydro Screen contains two step-shaped stainless-steel plates placed vertically against each other.

One of the plates rotates while the other one remains stationery.

The step screen surface is formed by the plates alternating across the channel opening’s width.

It is from this that the solids are elevated to the discharge point a step at a time.

Merits;

• It has a full stainless-body thus very strong and can withstand corrosion.
• Maintains a very low profile with a small footprint
• Very cost effective.

Limitations;

• It has a very low capture rate
• Has difficulties lifting bigger solids
• High flow cannot be screened using step screen

Spiral Screw Screen

The design consists of ¼” hole basket that is perforated together with a trough.

Rotating screws clean the screening which takes the solids into a compaction area.

Merits;

• A fully stainless-steel design
• Very cost effective

Limitations;

• It can only be used in small plants
• Its capture rate is low
• While cleaning the screening, rotating screws sometimes push them into the perforated basket
• Maintenance may be costly mostly if the water flow has grit

Spiral Screw Screen

Inclined Drum Screen

It was developed to carry out various tasks in a single unit, that is, screening, washing then handling. The static basket is replaced by a rotating drum screen which is inclined.

Solids are offloaded into a trough using spray bars. The troughs contain the rotating screws.

Merits;

• The use of perforated drums ensures a very efficient screening
• There is zero debris carryover
• The screening capture ratio is very high

Limitations;

• Its capacity is restricted and larger plants require numerous units
• There high risk of blinding and a very high head loss.

 Inclined Drum Screen

Center Flow Screen

The screen opening of this Hydro Screen is designed to elongate. This is a solution provided for the restrictions of the design of the drum screen.

This feature allows an increased flow of water into the screen. Its structure features an all stainless steel equipment.

Merits;

• It is very effective in wastewater applications
• Its screening capture ratio is very high
• The screen area is submerged in a comparatively slim channel
• Downstream receives zero debris carryover

Limitations;

• It is challenging to have an efficient seal with frame and panels.
• This is among the costliest screens

Center Flow Screen

How Does Through Flow Hydro Screen Compare To Weir Mounted Through Hydro Screen?

Weir mounted through Hydro Screens are used for flow conditioning before it passes on top of the weir crest.

In the process of conditioning and slowing the flow, the debris drops out of the stream of flow and gather behind the weir plate.

Through flow Hydro Screens a linked band made up of perforated stainless steel panels.

This system is very compact and can easily be integrated into current channels. Flexible hydraulic conditions can be achieved with through flow profile.

How Do Manually Cleaned Hydro Screens Compare To Mechanically Cleaned Hydro Screens?

Manually Cleaned Hydro Screens

• Are relatively cheap
• Require little or no maintenance equipment
• They experience regular flow surges with a very low solid capture efficiency when being cleaned manually
• It has high labor costs

Mechanically Cleaned Hydro Screens

• Flow conditions re improved with a high screen capture
• Labor costs are low with reduced nuisances
• Cost of equipment maintenance is very high
• Equipment cost is very high

What Are The Four Classifications Of Mechanically Cleaned Hydro Screens?

These Hydro Screens are designed to lower operational and maintenance cost and glitches therefore increasing the screens efficiency. They are classified into four major types:

Catenary Screen

A weight of chain holds the rake against the rack. These screens are cleaned from the front.

In the event that a heavy object gets blocked between the bars, the rakes simply pass over the jammed object instead of the debris jamming the screen further.

Catenary Screen

Chain Driven Screens

In this type of Hydro Screen, the screen is cleaned using an automatic chain.

Depending on the raking of the screen in the downstream or in the upstream, the chain driven screen is classified into back and front.

This classification also observes if the rakes yield to the bar screen bottom from the back or from the front.

Continuous Belt Screen

This is a self-cleaning screen that is continuous and it eliminates coarse and fine debris. The drive chain has a large number of rakes attached to it.

The channel depth of the screen determines the quantity of screening elements.

Reciprocating Rake/Climber Screen

For this type of Hydro Screen, the rake engages the bars by moving to the screen base.

It then pulls the debris or screenings up to the screens top where they are ejected.

Unlike other screens utilizing multiple rakes, this Hydro Screen uses just a single rake.

This results in a limitation of the handling capacity of heavy debris and screening loads.

What Are The General Classifications Of Hydro Screens?

Hydro Screens are normally categorized into three depending on their screening elements openings and their removal mechanism:

Coarse Screens

The openings of coarse screens are clear and they range between 6mm to 150mm. Their components include wire mesh, parallel bars and perforated plates with rectangular or circular shaped openings.

Coarse Screens are also called “bar rack”.

Large debris and coarse solids like rags are removed by coarse screens to prevent clogging that may lead to destruction of other accessories.

Coarse screens are divided into two based on based on their cleaning method:

• Hand cleaned screens
• Mechanically cleaned screens

Fine Screens

The openings of fine screens are clear and are less than 6mm. Their components include wire cloth, perforated plates and smaller openings wedge wire elements.

Their purpose is the removal of fine solids found in primary effluent. Fine screens can be divided into three categories;

• Static wedge wire screen – they have a 0.2 – 1.2mm clear opening with a design flow rate of 400 – 1200L/M² min.
• Rotary drum screen – a cylinder rotating in the flow channel has the screening medium mounted in it. Water flows into the top of the unit or into the drum end and out through the outlet of the screen with debris collected on the interior.
• Step type screen – consist of a fixed and movable thin vertical plates which are step shaped. They form one screen face by alternating across the channel width.

Debris collected on the screen face elevated to the fixed step landing and discharged to the outlet via the screen top.

Micro Screens

Their drum skins are rotary with a low variable speed of up to 4r/min operating under gravity flow environment with a continuous backwash.

Also, the openings ranges of the filtering fabric should be from 10 – 35 µm.

The fabric should be installed on the drums periphery.

Besides, the drum lined with fabric receives the influent. Backwashing collects all the retained solids and transports them for disposal.

Coarse Type Of Screens

How Does Static Wedge Wire Screen Compare To Rotary Drum Screen In The Fine Hydro Screens?

Wedge wire screens contain 0.2-1.2mm clear openings with a flow rate of 400-1200 L/m2 of the screen area.

They require large floor area for installation and should be cleaned once or twice a day.

Rotary drum screens have a rotating cylinder in the flow channel mounted with a straining medium.

Water flows into any drum end and out through the drum screens outlet and the debris is amassed on top of the unit.

What Are The Advantages Of Manual Coarse Hydro Screens?

• Have a very high capacity for waste discharge
• Have the ability to be maintained above the water level
• Their installation is quite easy and fast
• They require low investment and operational costs
• Efficiency of water treatment process is increased by eradicating potential pump damages and mechanical equipment loss.
• They are able to capture all sizes of waste and debris

What Are The Types Of Screening Media Used In Hydro Screens?

The four screening media most commonly used are;

Bars

The most commonly used Hydro Screen media is the bar, most often for trash racks and coarse screens.

The bars come in various shapes like trapezoidal, rounded, rectangular and teardrop.

Due to their low capture efficiency, rounded bars can only be used on bar racks with large opening.

Bars with a trapezoidal shape have progressively more wide openings.

This is to allow screenings that went through the narrowest opening in the front screen to pass without the bars trapping them.

Teardrop bars are a combination of trapezoidal bar benefits with improved hydrodynamic flow features. These help in reducing headloss occurring on the screen.

Wedge Wire

This is an improvement of trapezoidal bar screen and its application is in much finer screenings.

The similar narrow-to-wide opening profile prevents the solids from being trapped between the openings.

Much thinner media is as a result of the narrow openings of the wedge wire. That is the reason why they are called wires as opposed to bars.

Perforated Plates

They are more efficient than bars or wedge wires at netting debris when fine screening is needed e.g. hair removal.

The perforated plate technology is rapidly progressing with a current lower size limit of 1mm.

The decrease in effective opening area causes a higher headloss.

Other causes of increased head loss are an increased blinding and orifice losses compared to wedge wire and bar media.

Mesh

Due to the manufacturing restrictions of perforated plate media, the mesh is utilized for fine screens measuring 1mm or less.

Due to its fragile nature of mesh media, stapling of solids occurs within the media.

This hinders the release of netted solids by the mechanism removing them.

Water jet cleaning at very high pressure is recommended to prevent the mesh from clogging.

The side-to-side distance determines the opening sizes in the mesh media.

Figure 10- Mesh Used As A Screening Media

What Are The Design Considerations For Hydro Screens?

• The location of the Hydro Screen
• The climate and environment: heat should be provided to the Hydro screens in freezing environments and discharge chute and screen rake covered in extremely windy areas.
• Sufficient safety factors when peak screening quantities are determined.
• Access in the event of screen replacement
• Requirements for washing and compacting
• The coatings and construction material required for the overall unit
• Availability of spare parts
• Access to water for maintenance and cleaning
• The buildings ventilation requirements and hazardous classifications
• The height of the equipment and its footprint
• Establishment for bypass manual screen or redundant screen
• Provisions for screen removal during maintenance
• The discharge height that will accommodate the conveyed screenings or compactor tools.

What Is The Hydraulic Design And Fouling Of Hydro Screens?

Principle

The passage speed through the bars should be adequate enough to guarantee that matter is delivered against the screen.

This should not generate a very high head loss or bring about exhaustive bar fouling or let matter pass through with the water.

Approach Velocity

The approach velocity must not surpass 0.6 – 0.7 m/s when it is at peak all through the waters path in the delivery channel.

Deposits from the screen upstream will be inevitable because this velocity is low.

This will require a sequenced stirring system or a permanent one to be installed.

Passage Speed Between Bars

The passage speed is normally between 0.5 m/s and 1 m/s but at maximum throughput can reach 1 m/s to 1.2 m/s. Such speeds with a fouled screen only apply to the free passage unit.

Fouling

The water quality determines the suitable fouling level calculated as a percentage of the free wetted unit.

The waste clearing system also determines the same.

For automatic strainers and screens:

• Spacing > 10mm roughly 25%
• Spacing 5 – 10 mm roughly 50%
• Spacing ˂ 5 mm roughly 75%

What Are The Features Of A Chain Operated Bar Screen?

• Main drive
• Front cleaning design to ensure all-out efficiency of screening ensuring rake teeth do not slide over accumulated debris on the bar.
• The chain drive is rugged for sufficient head shaft
• The head shaft housing is totally enclosed
• The teeth are accurately formed to clean the bar’s front and sides
• The drive sprocket has a shear pin
• The chains and attachments are wear-resistant
• Guides guard the chain strand and support it on both runs
• Rake teeth
• Dead plate
• Head sprocket

What Is The Maximum Allowable Head Loss For A Manual Coarse Hydro Screen?

The maximum allowable head loss in relation to manual coarse screen is 150mm. However, it ranges from 150-600mm for mechanical screens.

What Are The Common Fabrics Used To Manufacture The Screen Of A Hydro Screen?

The three common fabrics use to manufacture screens are:

• Woven wire
• Perforated plate
• Wedge wire

The fabrics can be made from various materials including aluminum, synthetic materials like nylon, stainless steel or coated steel. Some considerations should be put before choosing fabrics that require protective coatings.

The possibility of abrasive flow causing wear and tear on the coating and the impact of debris and screen cleaning should be considered. Heavy gauge stainless steel wire is used to construct woven wire screens.

Aluminum plate or light gauge stainless steel wire is used to fabricate perforated plate screens. For wedge wire screens, stainless steel materials are generally used for their construction.

What Are The Factors To Consider When Choosing The Screen Of A Hydro Screen?

1. Availability of power at the site of installation
2. The head loss that the screen should cover
3. The depth water flow at the site
4. Channel velocity at installation site
5. Site constraints that can inhibit allowable footprint during installation
6. The type of debris at the site
7. Screen flow to channel flow average ratio

What Are The Benefits And Limitations Of Multi-rake Bar Hydro Screen??

Benefits

• Multi-rake bar is very durable
• Maintenance can be easily achieved by accessing it from the top channel
• Rakes are more positively engaged into bars compared to other bar screens.
• Protection of the headworks coarse screening or the pump is guaranteed.

Limitations

• It has a high possibility of jamming
• Maintenance points are not easily accessible due high overhead heights

What Are The Advantages Of Self-cleaning Hydro Screens?

• Reduced cost of labor
• They eliminate blockages
• Reduce operational costs
• They reduce the maintenance time
• No power or moving parts required
• They are simple and easy to install

What Are The Limitations Of Manually Cleaned Hydro Screens?

• They require regular raking to prevent clogging and high levels of backwater. This leads to a buildup of debris on the screen.
• The labor cost is increased by the increase in raking frequency
• Flow surges may occur due to the removal of the mat during cleaning thus reducing the efficiency of solid capture of the units downstream.

Other related products we offer include DSM screen, gravel pack screen, intake screen and sand screen amongst others.

Foe any questions or inquiry about hydro screens, contact us now.