تصميم وتصنيع وتركيب وحدات الفصل الميكانيكى الناعم والخشن لمخلفات الصرف الصناعى لمصانع الاغذية

Gent. / Iti-company
Reffered to /eng. Eman badr
Date /27/6/2011

According your request:-

Mechanical fine & coarse bar screen

Inclined type, stainless steel 304 material of construction with 15mm bar spacing and screen inclination 55º
2 M Width X 3 M Length X 2.8 M Height
It consists of the tank itself (in polyester reinforced with fiberglass) and the coarse or fine filter should be in stainless steel
.
It is made up of the following parts
:
Feed box: in the upper where liquid to be treated enters
Filter grate: in the central part where the solid – liquid separation takes place.
Termination tank: in the back part of the tank, receive the filter residue

The technical-offer

Bar Screens

Bar screens are typically at the head works (entrance) of a wastewater treatment plant (WWTP), bar screens are used to remove large objects such as rags, plastics bottles, bricks, solids, and toy action figures from the waste stream entering the treatment plant. Bar screens are vital to the successful operation of a plant, they reduce the damage of valves, pumps, and other appurtenances.

Floatables are also removed at the entrance to a treatment plant, these are objects that "float" on the surface of the water and if aren't removed end up in the primaries or aeration tanks. It is not uncommon to see floatables hanging over the weirs of some clarifiers. Though they don't diminish the function of those processes, floatables are rather unsightly.

Chain Bar Screens Another place where floatables can become are problem is at combined sewer overflow (CSO) outfalls, which is also where trash racks and bars screens are used. During wet weather events when a treatment plants capacity is overloaded flow may be diverted to an outfall where raw sewage and rain water are discharged to a body of water. Both trash racks and bar screens may be installed at an upstream location of the outfall, in some instances they are installed in tandem.

The trash rack is installed upstream of the bar screen to prevent damage to the unit. Even though the bar screens are very durable, they are not designed to withstand the impact of some of the debris that enter a combined sewer. In many cases screening is the only treatment the combined sewer flow will see prior to being discharged.

Coarse bar screens (or bar screens) are distinguished from fine screens by the space opening. Coarse screens usually have a spacing of 6 mm (or 0.25 in [metric system conversion]). and larger, whereas fine screens spacing is usually between 1.5 mm (or 0.059 in) through 6 mm (or 0.25 in [metric to inches]). Fine screens are installed at some wastewater treatment plants that do not have primary treatment to minimized clogging of downstream liquid and solid processes. Fine screens have been used for "effluent polishing" which increases secondary effluent to tertiary effluent quality.

They also are installed upstream of the trickling filters to minimize clogging and fouling of distributor nozzles.

Typically bar screens fall under two classification, mechanical bar screens and manual bar screens (trash racks can either be manually cleaned or mechanically cleaned). Both manual and mechanical screens contain equally spaced vertical or inclined bars that span the width of a channel. Design considerations for both mechanical and manual screens include: bar spacing, bar size, geometry of bar, channel width, angle of screen and approach velocity.

Mechanical bar screens ( or mechanical screens )

Chain Bar ScreensThe standby bar screen will be brought online when the mechanical bar screen is inoperable or down for routine maintenance. At larger treatment facilities there may be more than two mechanical bar screens, having two or more duty as well as standby units. Stop logs should be installed to allow each channel to be isolated, so that the channel can be dewatered and the bar screens maintained.

The clear bar spacing for mechanically cleaned bar screens is usually between 6 mm to 38 mm (or 1/2 to 1 1/2 inches [metric system conversion]). The amount of debris removed from the bar screen can be directly linked to the bar space opening. The bar screen should be positioned at a 45 to 90 degree angle from the horizontal, with 60 degree being the most common configuration.

This will increase the screening surface area, which in turn will expedite cleaning and eliminate clogging. This configuration will augment screening surface area up to 100%, it will also facilitate cleaning and eliminate escalating head from matting on the bar screen.

When designing any wastewater treatment process at a wastewater treatment facility, head loss calculations should be performed. To obtain the head loss through the bar screen the follow equations is used:

h = 1 ((V2 - v2)/2g)
0.7
where: h = head loss, m (ft)
v = approach velocity, m/s (ft/sec)
V = velocity through bar opening, m/s (ft/sec)
g = acceleration from gravity
0.7 = head loss coefficient

This equation assumes that bar are completely free of rags or other stringy material, as experience teaches us, this is usually not the case. As the mechanical bar screen traps solids and debris, the bar screens starts to become matted. Mechanical bar screens are supplied with some type of cleaning mechanism. Once solids accumulate on the bar screen, the cleaning mechanism is initiated.

The mechanical device that cleans the bar screen is activated by a manual start-stop switch, a timer, a overload switch, a actuator which senses pressure differential between points upstream and downstream of the bar screen, and a float that turns on when head across the bar screen is greater than some predetermined elevation. In wastewater treatment process combustible gases such as methane are emitted. To avoid catastrophic failure, all motors and controls are to be explosion proof.

In addition to head loss considerations, velocity must also be optimized to ensure successful operation of the mechanical bar screen. The flow should be uniformly distributed across the bar screen, this is done by provided an straight approach channel this is several feet ( about 6 in) length.

This approach should be used for both manual and mechanical cleaned bar screens. To reduce grit deposition, the minimum approach velocity in the channel should be no less than 0.40 m/s (or 1.25 ft/sec). The velocity through the bar screen should not exceed 0.62 m/s (or 2 ft/sec) at average flow. To reduce break through at peak flow, the velocity through the bar screen should not exceed 0.9 m/s (or 3 ft/sec).

Mechanical bar screens offers several advantages over the trash rack or manual bar screen. With mechanical bar screens labor cost from maintenance are usually alot lower, screenings capture is more efficient, and larger debris are removed with less hastle.

These are a few ways mechanical bar screens show improvement over manual bar screens. More recent bar screens are using more robust materials such as stainless steel to stand up against resist corrosion.

Mechanical Bar screen

purpose

the mechanical bar screen is installed for the purpose of removing bulky material which would be objectionable and cause trouble in the later processes in the sewage treatment plant. It is continous and automatic cleaning mechanism requiring a minimum of care and attention.

design

this machine is capable of handling large flow rates.
the machine is a sturdy mechanism is fully automatic
the operation is grit removal mechanism is fully automatic
the mechanism will operate only when there is a per determined liquid head developed between upstream and down stream side of the screen.

the hydraulic level difference is a result of choking of the screen caused when solids particles accumulate on the screen surface.

the operation of grit removal mechanism is intermittent during normal season resulting in considerable power saving. It can be put to continuos operation during monsoon when large quantum of grit is expected.

this machine required minimum spares as it is not in operation continuously.
the machine is designed in modular construction to suit installation at a greater depth of waste channel below the ground.

the speed of the machine for removal of grit in designed to consume low power.
1 hp motor is normally recommended for the operation of the machine
since all components except screen and grit removal rake guide are above liquid level, there is very little corrosion of components.

all under water parts are sand blasted and epoxy painted.

construction

description of the carious parts are as follow:

screen is made a flat bars spaced as required and given a special shape to suit easy grit removal.

screen is installed at a particular degree in the channel and grit carrying trays are also installed in the same angle so that the grit doesn't;t fall back into the channel during removal.

rake guide is made of high quality case steel to withstand wear and tear. It is designed to remove all the grit that accumulates on the screen.

drive unit consists of motor and reducer directly coupled to drum shaft on which drums are installed.

drive shaft is supported on drum shaft bearing enclosed in a plumber block.
rake guide is connected to the drum by means of steel wire ropes. Movement is controlled by high level and low level toggle type limit switches.

the limit switches are installed at suitable points on the housing depending on the lift required.

the housing is de singed such that the removed grit falls through the hopper directly into the trolley which can be carried away.

entire mechanism is controlled by floats installed in separate chambers on upstream and down stream sides.

the screen is designed to operate upto 600 mm loss across the screen
.
Bar Screen

Heavy-duty construction

Designed to handle most wastewater and raw water applications including severe service applications
No mechanical components, such as bearings or sprockets, permanently located
underwater

All routine maintenance can be performed from operating floor level
3/8-inch thick, 34-inch wide side frames (minimum)
0.24-inch to 3 inch + bar spacings available
90 degree to 45 degree setting angles available (80 to 85 degree is the most popular setting angle range)

Submersible electric or submersible hydraulic drives are available
2-
speed drives are available for deep channels
Dead plate and discharge chute can be heat traced and insulated for outdoor

applications

Electrical Controls

Each control panel we provide is designed and manufactured by our in-house electrical shop to meet the specifications for each particular project. Our panels are UL listed and can be labeled UL 508A or UL 913. Panels can be installed as free standing, wall mounted or screen mounted. Controls can also be installed into existing MCC buckets when clearance issues prevent the installation of a new control panel.

Drive System Options

Submersible electric and submersible hydraulic drive systems are available for deep channel applications.

A two-speed drive system is an option for all electric and hydraulic drives to provide a faster cleaning rate (during first flush events). As needed, the system increases the rake speed to clear debris rapidly during periods of higher screenings volume.

For wider screens, a dual synchronized drive system adds the power and reliability of two drives to the rake arm assembly.

Rake speeds available from 20 fpm to 40 fpm. Please contact Vulcan if faster speeds are deemed necessary.

Course Bar Screen

An innovative raking type deep-water coarse screen for sewage pumping stations and water intake structure.

Application:

screen mechanically raked deep water coarse screens designed specially for screening out medium to large floating wastes like plastic bags, cloths, rags logs etc. coming along with domestic sewage.

coarse screens are also ideal for screening out weeds, grass and other floating wastes that come along with the water from river or reservoirs to intake wells of water treatment plants.

Working:

screens are installed at inclination of 75 degrees where screens operate automatically based on differential level between up stream and down stream. Up on receiving the signals the rake starts from its resting home position and moves downwards.

During this movement the rake remains away from the bars. Upon reaching the lower most position, rake swings towards the bars curved at the bottom portion in the digging manner and get engaged with the bars.

This ensures efficient lifting of all the waste from the bottom most ends. After engagement, the rake starts moving upward carrying the waste along with it. Once the rake reaches the discharge point a scraper sweeps across the rake and discharges the waste on to the chute. The waste coming out through the chute can either be collected on a trolley or allowed to be drop on the belt of the conveyor.

Bar Spacing: 10 mm to 75 mm. For sewage pumping stations bar spacing 30 to 40 mm is recommended.

Material Of Construction for coarse screens are completely made from stainless steel to prevent from corrosion and to provide longer life. As a standard they are made of stainless steel AISI 304 grade. Other grades of stainless steels are also available up on request.

Advantages:

Due to Inclination better embrace of rake with the bars-More effective screening.
Teardrop profile bars- privation of hard material getting struck between the bars, minimum resistance to the flow and turbulence free passage of water.

Replaceable special plastic comb-Prevention from galling, long life of the bars.
Built in scraper and discharge chute- Very effective scraping of the waste, no falling back of the waste.

Generally un-submerged cogwheels and chains- Long life of chains and cogwheels and lower breakdowns.

On built over torque protection-protection to the screen.

Factory assembled and movement tested- Ensures affectivity of movements.

Mechanical Fine Bar Screen (Rotoclean-W)

An innovative, drum type fine bar screen for sewage and effluent treatment plants.

Application: Rotoclean-W is the most advanced fine rotary drum screen now available in India. Rotoclean-W screens are highly recommended as primary screening equipment in municipal sewage treatment plant and effluent treatment plants of various industries like Food processing, Rayon and textiles, Paper and pulp, Pharmaceuticals, Tanneries, Slaughter houses and so on.

Working:

Rotoclean-W is installed at an inclination of 35° with the horizontal in to the channel of treatment plant. The wastewater flows in to the open end of the wedge wire drum.

While the filtered wastewater comes out from the sides of the drum passing though the wedge wire, the solids of the size more than the bar spacing are retained on the surface of the drum itself.

Owing to the blockage by the retained solids, the water level increases on the up stream of the screen.

When the water level reaches to the pre-determined level, by virtue of the signal transmitted to the drive, the raking arm mounted on the drive shaft starts rotating.

The comb mounted on the raking arm sweeps the drum and deposits the solids on to the collection trough at the center of the drum. The high-pressure water jet assists the deposition.

From the trough the solids are conveyed to the washing and compaction zone where high-pressure water jet washes the solids and removes the soluble component.

The water used for washing containing soluble components is sent back to the wastewater stream though the pipe.

The washed solids free of faeces are dewatered by squeezing in the compaction zone before the solids are finally discharged in the container or on to the belt conveyor from the discharge point.

Materials Of Construction: To prevent from corrosion and to provide longer life “Rotoclean-W fine screens are completely made from stainless steel AISI 304 grade as standard. Other grades of stainless steels are available up on request
.
Advantages:

Rugged mechanical construction – Very long life.
Compact design-Low space requirement.
Inclined at 35 Deg- Increased operational efficiency.
Completely made of stainless steel- Very long life.
Higher capture rate - Ability to handle diverse waste.
Self cleaning- No entrapment of solids.
Minimum moving parts-Lower wear and tear, minimum maintenance, Long life.
Simple installation and operation.

The financial offer

Mechanical fine & coarse bar screen

Inclined type, stainless steel 304 material of construction with 15mm bar spacing and screen inclination 55º
2 M Width X 3 M Length X 2.8 M Height
It consists of the tank itself (in polyester reinforced with fiberglass) and the coarse or fine filter should be in stainless steel
.
Fine bar screen(roto clean) = 500000 egyptain pounds
Course bar screen = 750000 egyptain pounds
The prices unincluding the trade-taxes

Delivery-time = 3 months
Origin = egyptain + europian
Payment term = 75% advanced payment
25% after delivery,erection,testing
Validity =30 days

Thx for regarding
Colonel.dr
Bahaa badr
Waste water treatment consultant
Technolab el-bahaa group

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