The range of reverse jet filter units are designed to cater for more specialist dust that cannot be handled by the standard shaker type filter systems.
Reverse jet/reverse pulse units are normally required where a constant air volume is needed without possibility of the equipment being shut off for cleaning. To achieve this maintenance of the designed air volume at pre-determined intervals a burst of compressed air is released from the reservoir on the unit inducing a shock wave and short back flow of air into the cartridges or bags. This breaks free the dust cake formed on the outer surface of the cartridge or bag, allowing this to then freely fall into the hopper at the base of the unit. This is all controlled automatically with an electrical panel mounted on the unit.
To cater for the wide variation of air volumes encountered in these types of systems we are able to offer a variety of fan options, which can be mounted either directly on the units or at floor level adjacent to the units. Alternatively, the units may be provided without fans for incorporation into either existing systems or fitting with free issue fans. Our engineers are at hand to select the correct fan for your particular requirement when necessary, or at anytime for advice.
The filtration of the air is achieved by passing it through either a cloth tube supported by an internal wire cage, or alternatively, utilising circular multi-pleat cartridges. The standard tubular units are supplied with bags manufactured in polyester felt fabric, whilst the standard cartridge unit utilises polypropylene material. All other forms of medias are available for different applications including felts with surface treatments or membranes, or alternatively, manufactured utilising epitropic fibres to give antistatic properties. Automatic cleaning in the normal operation of the filtration system allows the air to pass through either the cartridge or the filter tube passing up the centre void and out into the top plenum of the unit before being discharged out to atmosphere.
The collected dust is entrained on the surface of the filter media forming a semi-rigid cake. At pre-set intervals solenoid valves on the control system open allowing diaphragm valves within the air circuit to vent to atmosphere. When the air from the diaphragm valve is vented this allows the compressed air held within the reservoir on the unit to pass into the pulse bars arranged above the filter tubes/cartridges. A series of jets sited immediately above the orifice of the tube or cartridge allows the air to be discharged into a venturi mounted on top of the bag/cartridge. Passage of the high-pressure air through the venturi induces local air to be drawn into the neck of the orifice causing a momentary reverse flow of air. The high-pressure pulse also pneumatically shocks the bag/cartridge allowing the accumulated dust cake to break and be dislodged from the surface of the media.
This is repeated on each of the diaphragm valves progressively moving along the filter unit to clean all of the cartridges/bags. The interval between cleaning and the period for which the solenoid and consequently, diaphragm remain open are variable set by dials within the control panel. An air saver option is available utilising a pressure differential switch monitoring the pressure across the filter media. This ensures that the cleaning of the filter media only occurs when required.
ENERGY EFFICIENT FANS
Our standard range of fans from 0.7Kw up to 18.5Kw is designed to give high-energy efficiency for the volume being handled whilst still delivering sufficient external pressure to cover most of the range of commonly encountered problems. The fan impellors are of backward inclined plate mounted type and are mounted directly onto the motor shaft.
These fans are mounted on top or side of the units giving easy access for wiring and services and in the event of fire ensures that the motor is outside of the airstream. On larger systems we are able to supply floor-mounted fans of any size to exhaust from the units. These would still normally be of a backward inclined system, however should there be specialist requirements for alternative pressures or volumes, other forms of impellor might be employed.
SPECIALIST FILTER MEDIA
Standard fabric units are supplied with tubular bags manufactured in felt fabric, however, other medias are available for greater efficiency. These include plain polyester and polypropylene Needlefelt fabrics, felts with either surface treatments or membranes, or alternatively felts manufactured incorporating epitropic fibres to give antistatic properties.
The casing of all of our units is robustly constructed from heavy gauge zinc coated sheet in a welded panel form with stiffening where required. Access doors wherever provided are fitted with either cam lock mechanisms or of a quick release type to allow easy access.
On the standard range of units the hoppers and structures are supported on preformed section legs, however on larger units these would be manufactured from a combination of channel and angle sections.
SIMPLE DUST DISPOSAL
The units are manufactured with a valley type hopper to channel the discharged dust into round collection bin(s). Each of these has a quick release system allowing easy removal and for them to be taken away for emptying at predetermined intervals. Dampers are provided on the discharge points into the bins to allow the bins to be removed whilst the equipment is on line and bin liners may be provided with pressure balance pipes as an option.
All of the components are designed for minimal tool usage when carrying out maintenance, including removal of the pulse bars, cages, fans, motors and reverse jet cleaning equipment. The standard units are designed for clean side bag removal where the cages or cartridges are withdrawn upwards from the casing, however dirty side change can be made available as an alternative option.
HARD WEARING FINISHES
The units are all manufactured from zintec mild steel, which is then primed and top coated finishing in a BS18E53 Blue as standard. Alternative colour finishes or paint application systems are available.
- Silencers are offered as an extra item if required for areas where noise must be kept to a minimum.
- Flange mounting units are also offered for mounting on alternative equipment. Explosion relief features including antispark fans, earth filter elements, reinforced construction and blast release doors are available for hazardous conditions.
- Manometers are available to provide visual indication of the pressure drop across the filters.
- Air saving devices including pressure switches and connection to the control panels can be fitted to reduce compressed air usage.
- Secondary and absolute filters may be fitted where a higher degree of filtration than normal filter is required on the outlet of the unit.
- Alternative hopper discharges are available via either flap or rotary valve, screw conveyors and/or alternative bin discharges.
- Unit may be manufactured in alternative materials to suit special requirements or climatic conditions.
- After sales spare and/or maintenance contracts are available to ensure that the equipment continues to work effectively in line with current Health and Safety Regulations.
Case Study 1
Portable reverse jet cartridge filter for on site dust control where customer is surface blasting to remove existing coatings prior to recoating. The unit was moved by vehicle…
Portable reverse jet cartridge filter for on site dust control where customer is surface blasting to remove existing coatings prior to recoating. The unit can be moved by vehicle to site then located either with fork truck or overhead crane to the working area. Only requirement then was an incoming mains electrical supply for the fan and cleaning controller and compressed air supply for the pulse cleaning system. This was the second of two supplied for the same client. Used in highly sensitive areas such a petrochemical and nuclear industries where their hard wearing coatings were specifically suited.
Case Study 2
These reverse jet filter plants were installed at William Cooks in Sheffield in recent years to exhaust from the foundry and welding applications. The foundry ventilation…
These reverse jet filter plants were installed at William Cooks in Sheffield in recent years to exhaust from the foundry and welding applications. The foundry ventilation system utilised a tubular type reverse jet filter having a total of 560 tubular bags fitted within two fabricated housings. Both exhausted by a common floor mounted fan discharging directly to atmosphere.
The welding application utilises a cartridge type filter compressing a larger surface area of filter media into a smaller footprint. As it was possible that not all of the booths within the building would be utilised at any one time the system was fitted with two exhaust fans allowing 50% of the system to be operated if required. Backdraft dampers on the inlet prevented recirculation of the air.