WO1995027431A1

WO1995027431A1 - Components for and methods of operation of bag house filter/cartridge cleaning systems

Info

Publication number: WO1995027431A1
Application number: PCT/AU1995/000172
Authority: WO
Inventors: Jeff Elliott
Original assignee: Goyen Controls Co. Pty. Ltd.
Priority date: 1994-04-11
Filing date: 1995-03-27
Publication date: 1995-10-19
Also published as: EP0755215A1; CA2187875A1; EP0755215A4

Abstract

The present invention relates to a method of controlling a filter bag and cartridge cleaner cleaning system, whereby the opening of valves to allow passage of cleaning air into the filter bags or cartridges is dependent upon the attainment of a predetermined pressure existing in the header rather than the normal on/off timer control. There is also disclosed a control panel, components and a flow control device for use with a cleaning system.

Description

COMPONENTS FOR AND METHODS OF OPERATION OF

BAG HOUSE FILTER /CARTRIDGE CLEANING SYSTEMS

FIELD OF THE INVENTION

The present invention relates to filter cartridge and filter bag house cleaning systems, and more particularly to the components and structures which cooperate with the filter bags or cartridges in such cleaning systems; and methods of controlling said systems.

Throughout the specification and claims, the term "Filter Bag" includes a reference to filter cartridges which are generally formed of folded paper filter elements, as well as conventional filter bags which are usually formed of a wire frame work and a filter material covering the frame work.

BACKGROUND ART

Filtering systems can be housed in a structure called a Bag House in the case of filter bags. The term Bag House can also used to describe a filter system made up of a collection of filter cartridges. Bag Houses commonly comprise a particle collection chamber into which air containing particles is directed in order to remove the particles therefrom. Normally provided in a bag house are a plurality of Filter Bags extending into the particle collection chamber, each surrounding a clean air outlet, and are supported therein by suitable supports or support cages. Air passes through the Filter Bags to the clean air outlets which make connection with a clean air discharge chamber. The Filter Bags may be arranged in any desired array but are normally located in straight line distributions within the particle collection chamber.

For filtering systems to work efficiently, it is necessary to repeatedly remove particle build up on the outside of Filter Bags, with the particles thus removed being collected and removed from a base zone of the particle collection chamber. One known arrangement for removing the aforesaid particle build up is to direct a reverse pulse of pressurised air which passes from discharge holes in a blow tube located within the clean air discharge chamber into the mouth of each Filter Bag. The reverse air pulse, in the case of filter bags, rapidly expands the bag to dislodge the particle build up. The reverse pulse, in the case of a filter cartridge produces a reversal of the air flow without the rapid expansion of the filter material. To increase the air flow in the reverse pulse it has also been proposed to use various forms of venturi arrangements on or adjacent to the mouth of the Filter Bag. In known arrangements of this kind, the venturi provided can extend into or out of the top section of the Filter Bag.

Such Venturis and alternative forms of inlets to the Filter Bag are generally of a circular/cylindrical nature. During servicing of the cleaning system, these Venturis can cause difficulty by presenting an obstacle around which operators and maintenance staff have to walk. They also present another difficulty in that to gain access to some of the Venturis and Filter Bags, a maintenance operator will place a plank across the Venturis to walk over them. Because of the shape and placement of the Venturis the plank may not be properly supported.

For the type of venturi designed for placement inside the Filter Bag, there need not be any formation which projects above the level of the support for the Filter Bag, because the venturi extends downwardly. A sealing arrangement around the open end of each bag separates the clean air from the dirty air sections of the cleaning system, and any disruption to this sealing arrangement caused by persons walking or stepping thereon may provide a direct passage for dirty air to find its way into the clean air section of the cleaning system thus bypassing the Filter Bag assembly.

When the Venturis are located inside the Filter Bag, a maintenance worker is presented with a series of holes on the support plate, which will render the process of walking over the support plate quite difficult, as no firm foot hold is available.

Another difficulty with bag house systems is that the reverse pulse jet which is ejected from the blow tube and into the Filter Bag strikes the top portions of the Filter Bag in an area known as the impact zone. The impact zone generally wears out faster than the rest of the filter material on the Filter Bag due to the receipt of the impact when the force it is at its greatest. The fact that the impact zone receives such a blast can create over cleaning of the top portion of the Filter Bag whereas the lower portions may not be effectively cleaned. Over cleaning of the top portion to the neglect of portions lower down can lead to a more rapid deterioration of the filtering capacity of the Filter Bag than if the Filter Bag has been properly and evenly cleaned, and may shorten Filter Bag life. Prior art bag house cleaning systems generally operate by a timer controller which times the length of time that a pulse of compressed air is allowed to exit from a blow tube and into a Filter Bag for cleaning purposes. The same timer unit also determines the length of time between pulses. The off time of the system needs to be dependent upon the provision of sufficient time for the header tube or pressure of the reservoir to build up to operating pressure before the next time a reverse pulse is activated.

Prior art control panels for Filter Bag cleaning systems are generally very simple control panels (normally a simple timer with on/off adjustment only) which provide an operator very little information and control of the functioning characteristics of those cleaning systems. The information is generally represented in an ad-hoc fashion and the use of them is reliant on extensive training and abstract correlation of the information displayed with the real functioning of the system. This can lead to incorrect controlling by inexperienced operators.

SUMMARY OF THE INVENTION

The invention provides, a component for a Filter Bag cleaning system, said component having at least one substantially planar portion and an aperture there through for the passage of air, said component being adapted to be positioned over a Filter Bag port through which air can pass into and out of said Filter Bag.

Preferably the aperture has associated with it a flow control formation, such as a venturi or like formation. It is also preferable that the member is a load bearing member and that the member maintains a relatively low profile even when a flow control formation is provided.

The flow control formation can be integrally formed in the member, or formed separately and attached thereto.

Preferably the member is substantially planar and most preferably it is a disc. If the member is an elongated member it is most preferably a U-shaped member, or a H- shaped member. If it is a U-shaped member or channel it can be positioned with the legs extending downwardly or upwardly.

The member can be attached to the upper structure of a Filter Bag, or it can be adapted to stand over, either in contact with or not in contact with, the top end of a Filter Bag or its support arrangement. If it is adapted to stand over the Filter Bag support arrangement it can do so by feet or a wall depending from the member.

The component can be of any desired shape but a rounded shape provides the best balance between minimum amount of material used and the removal of sharp corners such as would exist with square or triangular shapes, which can be a hazard to persons walking over same.

The member provides the advantage of providing a safe foot placement over each of the Filter Bags and between them, and also provides an unobtrusive flow control formation. If required, the channel member provides a safe and stable platform upon which to place a walking platform without damage to the seal between the Filter Bag and the filter support. To prevent damage to sealing means between the Filter Bag and the filter support, the channel member can be spaced above the Filter Bag support arrangement by a foot member interposed between said channel and said filter support. The foot may be placed between adjacent Filter Bag openings. The invention further provides Filter Bag component, said component being open ended and substantially cylindrical and adapted to be placed in the open end of a Filter Bag, said component extending downwardly from said open end a distance which is sufficient to receive the impact of a reverse pulse, said member having only two holes, namely the open ends.

The invention also further provides a filter bag support cage for a bag house cleaning system, said filter bag support cage comprising a first end containing an aperture for the exit of cleaned air from a bag to be associated with said cage, as well as the entry of a reverse pulse of air for the purposes of cleaning said bag, said filter bag support cage also including a support structure for the filter bag depending from said first end, characterised in that said first end is constructed of a sheet material having means to support said end in a filter bag support and whereby said sheet material extends downwardly from said support a distance which includes at least the impact zone of a reverse pulse of air injected into said filter bag. Preferably sheet metal will extend into the bag some 150 to 350 mm, depending upon location of the impact zone.

The advantage which flows from a bag having such a protective device built therein, or added as a further component at a later time is that the filter medium is not over cleaned and is not damaged by the over cleaning due to the effect of the reverse pulse of air impacting the impact zone.

The invention still further provides a method of controlling a reverse pulse cleaning system for a filter cartridge or a Filter Bag house, said system comprising a supply of compressed air and a flow control means to control movement of compressed air from said supply to outlets to clean filter material, said flow control means adapted to allow said movement of compressed air for a predetermined period and terminate said movement until such time as said movement is required again, characterised in that a sensing means senses when said supply is of a desired pressure said sensing means interacting with said flow control means to thereby permit said movement of compressed air, when said desired pressure is reached.

It is preferable that the desired pressure can be varied according to system conditions which may exist from time to time.

The inventive feature of sensing the compressed air pressure allows the control system to operate immediately upon pressure being reached. A further advantage is that a comprehensive control monitoring system can utilise the sensed information which can determine where faults exist and the performance of the system. The invention also still further provides a method of operating a reverse pulse bag house cleaning system having at least a supply of compressed air, communicable passage between said supply and outlets which eject compressed air into a Filter Bag, flow control means to control passage of compressed air from said supply to said outlets, said method comprising the steps of:

1. Raising the pressure available from said supply to a first predetermined level.

2. Opening said flow control means to emit a pulse of air for a predetermined or modifiable time limit.

3. Closing said flow control means until said cleaning is again required.

4. Sensing the pressure attained by said supply after closing of said flow control means.

5. Communicating the attainment of a second predetermined pressure level in said supply to said flow control means.

6. Permitting said flow control means to open passage between said supply and said outlets simultaneously with or once said second predetermined pressure level is sensed.

"Permitting" is taken to mean the ability to operate whether or not such operation takes place.

A seventh step can be added, whereby the desired pressure level and the second desired pressure level can be varied according to system conditions which may exist from time to time.

The inventive feature of this invention, that is the sensing of the pressure of the air and utilising the air once it has attained a desired pressure allows the user of a bag house to reduce the time between the shutting off of supply and the opening of supply. This will lead to a more interactive "cleaning on demand system" which in the prior art has been limited by the use of on-off timers.

The present invention further provides a control panel for a filter cleaning system, said panel including thereon:

(a) gauges or displays to indicate system characteristics;

(b) a graphical representation of the system characteristics; the displays being located at or linked to the graphical representation of each respective characteristic. It is further preferable that there are control means to vary system characteristics and that those control means are located at or linked to the graphical representation of each characteristic.

The present invention also further provides a control panel for a filter cleaning system, said panel including thereon:

(a) control means to vary system characteristics;

(b) a graphical representation of the system characteristics; the control means being located at or linked to the graphical representation of each respective characteristic. The advantage which follows from the immediately preceding two inventive features is that a user utilising the control panel can readily identify which characteristic needs to be changed and by what control means this can be done.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic view of a prior art Filter Bag cleaning system assembly;

Figure 2 is a front view in part section of the top portion of a bag house arrangement;

Figure 3 is a plan view of the U shaped members of figure 2 in situ, side by side;

Figure 4 is a schematic side elevation in partial section of an alternative filter bag component for protecting the impact zone.

Figure 5 is a side elevation in partial section of an apparatus of another embodiment similar to figure 3;

Figure 6 is a side elevation in partial section of another arrangement similar to figure 5;

Figure 7 is a perspective view of one of the components of figure 6;. Figure 8 is a side elevation in partial section of another arrangement similar to figure 5;

Figure 9 is a perspective view of one of the components of figure 8;

Figure 10 is a schematic view of a filter bag cleaning system assembly and control panel in diagrammatic form for use in a method aspect of the present invention;

Figure 11 is a plan view of a preferred internal control panel; Figure 12 is a plan view of a preferred external control panel; and

Figure 13 is a plan view of a simplified control panel. DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates a prior art arrangement Filter Bag cleaning system having a header 2, and a cleaning valve 4. The cleaning valve 4 connects to a blow tube 6, which passes through the wall of a bag house 8. The blow tube 6 has nozzles 10, but these are not always present in the prior art. On top of filter bags 12 is a venturi 14 which is of a tapered cylindrical construction.

Figure 2 illustrates an embodiment of an inventive filter bag assembly 16. The assembly 16 comprises a standard filter bag cage 18 which has a wire frame work 44 and a skeletal flange portion 20 around which a filter material 22 is placed. The end 76 (as illustrated in Figure 4) is closed whilst the open end 24 allows for the exit of clean air out of the filter bag assembly 16 in the direction of arrow 26, and the entry of reverse pulse air in the direction of arrow 28 into the filter bag assembly 16.

The filter material 22 has at its terminus a sealing means 30 to seal the filter bag 16 relative to a filter bag support plate 32. The filter bag support plate 32 has a series of ports through which other filter bag assemblies similar to filter bag assembly 16 are situated. The seal 30 ensures no air passes between the clean side 34 and dirty side 36 of the bag house system.

The filter bag arrangement 16 also has a generally cylindrical can 38 which has a flange 40 at one end thereof. The can 38 is of a diameter and height to fit into the filter bag cage 18, and allows communicable passage from the open end 24 into the internal portions of the filter bag assembly 16. The can 38 can be used with any other flow control devices which may be inserted at the open end 24 of the filter bag assembly. Here it is illustrated with a flow control device 42 of a particular construction.

The length of the can 38 is determined by the height of the impact zone. The impact zone height is a characteristic of the height 46 of blow tube from the open ends 24 and the flow control device 42. A reverse pulse of air out of a nozzle 10 will generally keep to the path defined by phantom lines 48, pass through the flow control device 42, and impact in the circumferential region 50, it being noted that this is a generally cylindrical filter bag. The circumferential region 50 can be broadly described as the impact zone as it is the first point of contact of the compressed air from nozzle 10 as it hits the filter material 22. The use of the can 38 will protect the bag material 22 in the impact zone 50 and produce an improved cleaning of the bag. The length of the can 38 will determine the type of flow that exits the lower most point of the can 38. When air passes through the can 52 of the filter bag assembly 54, a velocity profile 56 of this air at a length 58 down the can 52, is produced. By the time length 60 has been attained, the velocity profile 62 is changed considerably and is more uniform across the width of the can 52. This uniform velocity profile provides an improved cleaning effectiveness. An alternative embodiment of a filter bag construction is illustrated in Figure 4 where the can 38 is constructed the same as the top portion of the filter bag cage 18. From the lower edge 64 of can 38 a wire frame work 44, similar to filter bag cage 18, is connected thereto and depends downwardly therefrom. This will provide an improved positive flow characteristic of the reverse pulse of air entering the filter bag system.

Because a can 38 is utilised, a complicated sealing means 30 as in figure 2 is not required, nor is the flange portion 20 of the cage. As shown in figure 4, an O ring 30 depending from the under surface of flange 40 of can 38 could be utilised to effect a seal with filter bag support plate 32. Alternatively a flat cylindrical seal member (not illustrated) could be used.

The apparatus illustrated in Figures 2 and 3 shows a flow control device 42 which is a generally U shaped channel member 66. The flow control device 42 has two sides 68 which depend from a central portion 70. Spaced at substantially equal intervals along the U shaped channel 66 are a series of apertures 72 which are formed in the central portion 70 to allow passage of air in the system in the direction of arrows 28 and 26. The rim 74 of aperture 72 is curved so that the rim 74 is at least approximately at a tangent to the phantom lines 48 or parallel thereto.

The diameter of the aperture 72 is selected to prevent the air encapsulated between phantom line 48 from being directed outwardly from the opening provided by aperture 72. In the present instance, the tangent to the rim 74 as illustrated in Figure 2 forms an angle of approximately 10° to the vertical. However, depending upon the system to which the U shaped member 66 is applied, a different angle might need to be selected for rim 74.

The ends 78 of sides 68 are doubled over in order to provide reinforcing, however this is an optional feature. The spacing between the end of the nozzle 10 and the ends 78 will allow the ends 78 to carry removable a plank or walking platform (not illustrated) which in turn allows a maintenance personnel to walk upon the plank or walking platform placed over the system in any desired direction with the plank being properly supported. This will allow easy repair and visual monitoring of filter bags and replacement thereof without the risk of an improperly supported plank or walking platform which would normally increase the risk of accidents and personal injury.

The apertures 72 can be formed in central portion 70 by a combined punching and drawing process in order to achieve the desired shape.

Illustrated in Figure 3 is a plan view of the apparatus of Figure 2 with the blow tubes 6 removed. The U shaped channel 66 can be secured to the filter bag support plate 32 at convenient intervals by the securing means 80, which can be bolts or TEK (registered trade mark) screws or the like. At similar intervals, a spacer block 82 illustrated in ghost or phantom outline can be utilised to maintain the underneath surface 84 of central portion 70 a distance 86 above the filter bag support plate 32 (see Figure 2). By the use of spacer blocks 82 no weight is placed upon flange 20 of the filter bag cage 18 or flange 40 of can 38. In this way no forces are transmitted which might break the seal and thus allow communicable passage between the clean side 34 and dirty side 36. Different shaped spacers 82 can be utilised and they may be provided at other intervals than that indicated in Figure 2.

Illustrated in figure 5 is an arrangement showing another filter bag assembly 88, and a nozzle arrangement 90, associated with a blow tube 6 through which a reverse pulse of air is emitted, for the purpose of cleaning the filter bag assembly 88.

The filter bag assembly 88 comprises a filter support plate 92 through which a filter bag cage 94 is assembled. In this instance, the filter bag cage 94 includes a can 96 at the top portion of the filter bag support structure, having a surface which makes a seal via seal member 98 with the filter support plate 92. The can 96 has a flanged end 102 with turned down portions 100 at the top of the filter bag cage 94 to engage the filter support plate 92. This arrangement supports the weight of the filter bag cage 94, filter material and the collected particles.

In contact with the flanged end 102 of can 96 is a disc 104 which has a flow control formation 106 integrally formed therein. The flow control formation 106 can be formed in the disc 104 by a combined piercing and extruding process in order to achieve the desired shape of flow control formation. Alternatively a hole without an extruded rim can be pierced through the disc and a shaped rim attached to the hole rim to provide a flow control formation 106.

The flow control formation 106 has a rim 108 curved so that it is tangential to the outer edge of a conical air stream 110, which is represented by phantom lines. The diameter of the flow control formation 106 is selected to be greater than the conical air stream 110 as it reaches the flow control formation 106. In a preferred arrangement, a tangent to the extremity of the rim 108 forms an angle of approximately 20 degrees to the vertical. However, depending upon the system in which the disc 104 may be used, a different conical angle might be present and thus a different tangential angle would be selected.

The flow control formation 106 illustrated in the drawings is round, to suit to a cylindrical shaped filter bag or cartridge. Any appropriately shaped flow control formation can be used. Other shapes such as elongated holes, square holes, elliptical holes, slots and slits can be utilised, depending upon the result to be obtained and the cross sectional shape of the filter element being cleaned. Disc 104 can be connected to the can 96 by any convenient means such as screws, welded, or turned down over the turned down portions 100 and secured thereto or to support plate 92. The filter bag can be manufactured and sold with a disc 104 integrally connected thereto, although disc 104 may be retrofitted to existing installations where suitable. A similar arrangement to disc 104 is illustrated in figures 6 and 7. It is constructed for use with existing systems which utilise a more delicate sealing mechanism than the seal member 98 used in figure 5. In this embodiment disc 104 has sufficient strength, or is suitably rigid so that, when load is placed on it, it does not deflect to contact filter bag cage 94 or support flange 102. This can be controlled by the height of the legs 112. Legs 112 rest upon and may be attached to support plate 92, thereby controlling the height that disc 104 sits above the filter bag cage 94.

Another variation is illustrated in figures 8 and 9 and is similar to the embodiment of figure 6. However legs 112 are replaced with a cylindrical wall 114 having a height which serves the same functional purpose as the height of the legs 112. In the case of both variations illustrated in figures 7 and 9, it is preferable that they are constructed in a nestable format. Such a nesting feature will potentially reduce the amount of inventory space and transport costs of such items.

If desired, and if different flow control characteristics are required, the flow control formation 106 can be formed in reverse fashion, that is the rim 108 of the flow control formation 106 can be formed so that it projects in a downward direction relative to the disc 104 (not illustrated), rather than upwardly as shown in figures 7 and 9, for example.

An alternative (not illustrated) which may be utilised is to provide a disc 104 with a flat aperture and utilise a separate flow control formation which is mounted in association with the support flange 102 for instance. In this example the flow control formation is associated with the disc and cooperates therewith, but is not attached thereto.

Illustrated in figure 10 is a filter bag cleaning system 116 which includes a header tank 118 to which is connected a pressure transducer 120 and air solenoid valves 122. The air solenoid valves 122 control the passing of air into blow tubes 124. The blow tubes 124 may have a nozzle arrangement (not illustrated) to clean the filter bags 126 located in the dust collector vessel 128. A differential pressure monitor/sensor 130 connects the clean air side 34 and the dirty air side 36 of the dust collector vessel 128 and sends a signal to a control unit 132 at a remote location from the dust collector vessel 128. The pressure transducer 120 is connected to the control unit 132 to provide system information to the control unit 132 and the air solenoid valve 122 is like wise connected to receive control signals. The pressure transducer 120 and the pressure monitor/sensor 130 can be replaced by fittings to pipe air from the system to the control panel 132. In this case pressure transducer 120 and the pressure sensor 130 are located inside the control unit 132 with pneumatic tubing connections to the system 116. On the clean air side 34 of the dust collector vessel 128 is a fan blower motor 134 which is connected to a fan blower switch 136. The fan blower switch 136 also connects into the control unit 132 and can be controlled thereby. Downstream from the fan blower motor 134 is a filtered exhaust air outlet 138 with which is associated an emission monitoring probe 140. At the base of the dust collector vessel 128 is an unfiltered air inlet port 142. Below the unfiltered air inlet port 142 is a hopper level sensing probe 144 in the base of the dust collector vessel 128. In figure 10 a waste product 146 is illustrated which is approaching the level of the hopper level sensing probe 144. The hopper level sensing probe 144 is also connected back into the control unit 132. Once the waste product 146 reaches the level of the probe 144 this will trip an indicator on the control panel 132. If the hopper or base of the dust collector vessel 128 is full, it needs to be emptied, which can be done by manual or automatic means (not illustrated). A header tank drain valve 148 is also provided to drain the header tank 118 if required during servicing.

Illustrated in figure 11 is an internal control panel 132 which has a Differential Pressure gauge 150 which indicates the difference in pressure between the clean air side 34 and dirty air side 36 of the dust collector vessel 128. Indicator lines 152 and 154 are used to set lower and upper (respectively) trip points of the system. Pointer 156 displays the actual differential pressure.

A Header Pressure User Preset Value display 158 is also provided to display the design pressure of the system. The Design Pressure is that pressure required to provide effective cleaning. The Design Pressure can be set to any desired or predetermined value into the control system associated with control panel 132. Once the Design Pressure has been set by the operator, the display 158 will indicate that value, and once that pressure is reached (if the system is in HR DEMAND mode-see later discussion) the air solenoid valve 122 will open to allow passage of air from the header 118 into the blow tube 124.

When required, and by the closing (or opening) of a switch 204, the display 158 can indicate the pressure which is the lower trip point of the system. This is known as the Valley Pressure.

A Header Pressure OK indicator 160 is a green LED which, when lit, indicates that the Design Pressure has been reached in the header 118. A Header Pressure Low indicator 162 is a red LED which indicates that the pressure in the header 118 is lower than the design pressure. This could occur either because the header pressure has not yet reached the design pressure or a valve 122 has successfully opened causing the header pressure to fall. If the valve 122 is indicated as having successfully opened, then if the pressure remains low a fault in the valve 122, preventing it from closing, may be the reason.

An Off Timer Active indicator 164 is an LED indicator that indicates the control panel 132 is still functioning during long valve off times. Generally this is only used in DEMAND and CONTINUOUS modes. DEMAND mode uses a differential pressure and ignores the header pressure feed back in its normal operating cycle. DEMAND mode of operation may be useful when isolating part of the system during normal maintenance procedures, without shutting down the complete system. Contrasted with this is the CONTINUOUS mode which ignores the differential pressure and header pressure feedback in its normal operating cycle. The CONTINUOUS mode of operation may be useful when isolating part of the system during normal maintenance procedures, without shutting down the complete system.

A User Error indicator 166 is also provided and is an LED. User Error occurs where the user is attempting to enter invalid data or an invalid command into the control system. If this is attempted the indicator 166 will illuminate. A Valley Pressure OK indicator 168 is provided and is a yellow LED which indicates that the programmed Valley Pressure is being achieved during operation of the system 116.

A Pulses To Clean Per Cycle read out 170 displays how many times valves have opened during the current or last cleaning cycle. Associated with this characteristic is a trip point being a predetermined number of pulses to clean which is initialised into the control panel 132 by the operator. The trip point set by the operator works in conjunction with a Too Many Pulses To Clean Per Cycle indicator 176. The indicator 176 IS an LED and alarm which will illuminate if the number of pulses to clean previously initialised by the operator, has been exceeded.

A Time Between Cleaning Cycles readout 172 displays in minutes and seconds the time between cleaning cycles. Associated with this readout 172 is a trip point which is set into the control panel 132 by the operator. This trip point works in conjunction with a Too Short time between cleaning cycles indicator 178. Indicator 178 is an alarm LED which illuminates if the time, between cleaning cycles set by the operator has not been reached before the next cycle starts. A Header Recovery Time read out 174 displays in seconds, the time that is taken between valve openings for the header pressure to reach the Designed Pressure indicated in indicator 158. An operator can input into the control system the desired header recovery time, which time can act as a trip point for a Too Long header recovery time indicator 180. The indicator 180 is an alarm LED which illuminates if the operator set time for the header recovery, has been exceeded. The trip points in respect of indicators 176, 178 and 180 may be predicted by the operator or the system 116 designer, based on the system parameters and characteristics. Whilst the control panel 132 can be initialised with such trip points, those trip points can be re-set according to the actual operation and functioning of the system 116

An Emission Level read-out 182 is provided when the emission monitor probe 140 is installed. The Emission Level read-out 182 is a bar graph which is used to display the current emission level and to set the alarm trip point for excessive emissions. When the alarm trip point is reached an Emission Trip indicator 188 which is an LED, will light up to indicate when the user preset emission level has been reached. An Emission Alarm indicator 192 which is an LED will be triggered if this LED has been illuminated for more than the user preset time delay period.

A Last Valve To Operate display 184 is a read-out which will show the last valve 122 instructed to open by the control panel 132.

A Last Valve To Malfunction display 186 is provided to display the identification number of the last valve 122 which was instructed to open by the control panel 132, for which the valley pressure did not fall below the operator initialised value.

A Last Valve To Malfunction indicator 190 is an LED that indicates the identification number of the last valve instructed by the control system 132 which malfunctioned. This can be read in association with the Last Valve To Malfunction read out 186.

A Trip Level Control knob 194 is provided for use in association with the emission level monitor system mentioned above. The Trip Level Control knob 194 is used in conjunction with a Set button 196 to set the point at which the Emission Trip Indicator 188 will trip out.

A hopper alarm 198 is provided as an optional feature if a hopper level monitor 144 is installed. A liquid crystal display 200 is provided to guide the user, and allow them to view the data entered by a key pad 202 as well as to display any particular error messages that might be installed on the system.

A Read VP (Valley Pressure) button 204 is used in conjunction with Valley Pressure knob

206 to set the valley pressure on the Header Pressure User Preset Value display 158. When a valve 122 is successfully fired the header pressure will fall. So that the control panel 132 can register the valve 122 as having fired successfully, the valley pressure must be set within reach of the pressure drop which is typically 60% to 80% of the Design Pressure.

A Design Pressure knob 208 is a knob which is used to set the design pressure on the Header Pressure User Preset Value display 158. In order for a valve 122 to fire successfully, the header tank 118 will need to reach the design pressure for the system.

A control key pad 210 is provided to allow the control panel 132 to be controlled from within the cabinet rather than on the front door of the operator panel which overlies the whole system. The control key pad includes a HR (Header Recovery )-DEM AND key; a SHUT DOWN key; a Clear key; a Stop key; a DEMAND key and a CONT (Continuous) key. These keys determine which mode of operation by which the system 116 will be operated. The HR-DEMAND key, the SHUT DOWN key, the Stop key and Clear key on the internal control panel 132 have their counterparts on the external control panel 236.

In figure 12 is an external control panel 236 which is generally mounted on a door (not illustrated) which covers the internal control panel 132. The door also has window or see- through panels so that all the indicators, read outs and displays of the internal control panel 132, are visible.

The control panel 236 has three segments- manual mode panel 238, alarm control panel 240 and mode select panel 242. Before the SHUT DOWN button 244 or the HR- DEMAND button 246 will operate the Manual indicator 248 has to be illuminated. The MANUAL mode of operation is generally used during maintenance and testing, to override the normally selected FAN SW mode which is indicated by Fan SW indicator 250. The button 246 is pushed to start the cleaning cycle in MANUAL mode. The cleaning cycle will continue until the SHUT DOWN button 244 or the Stop button 252 are depressed. The buttons 244, 246 and 252 have their counterparts on the internal control panel 132 in the key pad 210.

The Shut Down button 244 when depressed will engage a SHUT DOWN function when the cleaning cycle is complete. The cleaning cycle will continue cleaning until the selected number of valves 122 previously initialised by the operator have opened. The fan blower 134 is usually switched off prior to starting the shut down procedure. The Stop button 252 can be pushed at any time to stop the system 116.

The alarm control panel 240 is used to manually control an external alarm system. When the control system is commissioned, the Clear button 254 is internally preset to enable or disable. If preset to enable, the Clear button 254 will clear all alarm LED, all internal LCD displays and the main alarm. The Clear button 254 will not function unless the stop button 252 has been depressed first. If preset to disable the external alarm system will be disabled when the Clear button 254 is pressed. The Snooze button 256 when activated will begin a SNOOZE function which will temporarily suspend the main external alarm to provide uninterrupted time by removing distractive noise while determining the source of the alarm. The duration of the suspension is preset when the system is commissioned. The Trip indicator 258 when illuminated indicates an alarm condition. When it is not illuminated there is either no alarm condition or the SNOOZE function is active.

The Active indicator 260 when flashing indicates that the SNOOZE function is active. The Trip Indicator 258 will extinguish if the Active indicator 260 is flashing. If the Active indicator 260 is not flashing, the SNOOZE function is not active. The mode select panel 242 is used to select and indicate the mode of operation of the control system. Using the Select button 262 will toggle between MANUAL mode (indicated by indicator 248) and FAN SW mode (indicated by indicator 250). MANUAL mode will enable the use of the HR-DEMAND and SHUT DOWN functions on panel 238. The FAN SW mode will operate the control system automatically when a signal is received from the fan blower switch 136. The signal will first start a delay timer which will allow time for the fan blower 134 to run up or down before the cleaning cycle or shutdown procedure will commence. While in FAN SW mode the HR-DEMAND and SHUT DOWN functions are disabled. On this panel is a FAN ON indicator 264 which when illuminated indicates that the blower 134 is switched on. The Fan Delay indicator 266 indicates that the blower 134 is either running up or running down.

By the interaction of the control panel 132 and the system 116, an operator need only switch the main fan blower 134 on and the control panel 132 will automatically start the cleaning cycle after the blower 134 has run up to speed. When the blower 134 is switched off, the control panel 132 will wait for the blower 134 to wind down and then the control panel 132 will go into a SHUT DOWN mode which will continue to purge the filter bags 126 for the number of cycles set at commissioning. The control panel 132 and system 116 will then be ready for operation at the next start up.

The system 116 in co-operation with control panel 132 allows the header pressure user preset value which is displayed in display 158 to be set by a knob 208 at any design pressure desired. For economical reasons users can attempt to keep the design pressure 208 at the lowest pressure possible and still obtain proper cleaning of filter bag 126. A lower pressure generally means a more economical system operation cost. By the control panel 132 and design pressure knob 208 the design pressure can be incrementally increased until the operator is certain that the design pressure selected will produce adequate cleaning across all the bags 126 in the dust collector vessel 128. The air source pressure may fall or reduce (below the Design Pressure) because of external reasons such as need for compressed air by other parties or faults such as may occur when a valve 122 remains in an open condition. This will reduce the pressure available in the header tank 118. If the valley pressure and other controls of the control panel 132 are set according to the Design Pressure (as it existed before the reduction in pressure available), the system will not properly function because the header pressure has not reached the design pressure. In a situation such as this, the operator can reduce the Design Pressure (as displayed on Header Pressure User Pre-Set Value display 158) by which the system operates, by means of the Design Pressure knob 208, to a pressure which is below that available from the compressor or air source. Generally operators will set the Design Pressure to below the level of pressure available from the compressor in order to be given a trouble free operation of the system 116.

In this way, the system can continue to operate until such time as a maintenance person or other person has a chance to check the operation of the faulty air solenoid valve 122. The system will indicate the air solenoid valve 122 which has malfunctioned on the display 186 and the indicator 190.

As shown in figure 11, the control panel 132 has graphically indicated thereon the features of the system. It will be noted that the header pressure graph line 212 begins at the Header Pressure OK indicator 160. The Design Pressure graph line 214 runs across the graph 212 and down to the Design Pressure knob 208. By running across the graph in this way it represents the desired pressure. The Valley Pressure graph 216 also runs across graph 212 and down to the valley pressure control knob 206. The displays 170, 172 and 174 are located at those portions of header pressure graph 212, so that the information which is displayed on displays 170, 172 and 174 corresponds to that location. These graphs 212, 214 and 216 and the interactive co-operation with which both displays 170, 172 and 174 and control knobs 206 and 208 has therewith, renders the system more user friendly and easier to learn and ultimately control the system 116.

The key pad 210 is utilised to determine the mode of operation of the control panel 132. The HR DEMAND key is pressed to have the system operate in header recovery mode. Header recovery mode will utilise the differential pressure and header pressure feedback in its normal operating cycle. This is the preferred mode of operation of the control panel 132. The DEMAND button engages demand mode whilst the CONT button engages the continuous mode. The characteristics of these modes of operation have been described previously. Being able to provide these various modes of operation in the one control panel, gives the control system improved versatility when compared to prior art units. A unit 218 can also be provided in order to input stored information into the system, to make a back up memory disc for the installed settings and to print out information on the operation of the system 116 and the control panel 132. The control panel 132 gives the user a greater deal of valuable information on the operation of the system and allows users to more accurately and optimally control the system 116.

Illustrated in Figure 13 is a less elaborate control panel 220 having a row of green lights 222, and red lights 224 to indicate whether valve operation has been successful or not on each of the valves which are connected to the one header tube A. Other indicators include an indicator of the header pressure 226, the number of pulses in the last cleaning cycle 228, pressure recovery time 230, off time 232 and dust emission level 234.

Generally speaking, the control system of a bag house cleaning system operates on the differential pressure between the clean side 34 and dirty side 36 in a bag house system such that when the differential pressure has increased to a high set point the controller identifies this and activates the cleaning pulse mechanism. There are set pressure set points on the differential pressure unit such that when the differential pressure rises above the highest of the two set points, the timer is activated and pulsing commences with pulse length and pulse interval set according to the setting on the timer card. When a differential pressure falls below the lower of the set points, the timer is deactivated and pulsing ceases.

The number of pulses which is taken to bring the differential pressure down from the higher set point to the lower set point is indicated in window 228 of the timer control panel 220. The timer recognises which valve was last activated and when the timer is activated it is the next valve in the sequence which is then pulsed.

By running an air line from the header to the control panel and incorporating a pressure transducer on that air line in the control cabinet the pulsing of the next valve can be made once the header pressure has recovered sufficiently.

Another feature is a reduced pressure operation capacity. The indicator 236 lights up in response to enablement of the system (by flicking of a switch) to operate when the pressure in the header attains 85% of the normal operating pressure. This feature will allow the reverse pulse cleaning system to operate if there is a fault such as with a valve, which will tend to reduce the pressure available in the header.

Other information can be utilised by the readings from the pressure transducer. Such information will indicate whether the header pressure has dropped sufficiently during a single pulse which is required to drop approximately 30% for the cleaning system to be operated correctly providing also the design of the system has been done correctly. Normally the time interval between pulses is a constant and is provided so that there is sufficient time for the header pressure to return to operational pressure. If there are any faults in the valves which prevent the pressure returning to operation, the prior art systems will use the lower pressure and thus ineffective cleaning air will be pulsed through the system.

If header pressure does not fully recover after a pulse then the operator will know that a particular valve is not closing properly or is being forced to remain open. A slow header recovery can indicate either a damaged valve if it stays open or that there is interference to the header supply or there is in fact a compressor problem. Whereas if the pressure does not drop enough, either the valve did not open or it did not open sufficiently indicating that a valve part or the valve itself might require changing. It is important to note that there is one control panel per header and each header may have typically eight valves to control movement of air from the header into the blow tube and thus into the bags.

The pressure recovery time is indicated by read out 230 and this displays the time for the pressure in the header to return to operating pressure after the header has been discharged, causing the pressure to drop therein. By coupling the timer signal with the pressure transducer signal, it is possible to give a green light to each valve to indicate that it has operated correctly on signal from the timer or a red light if there is a malfunction which is indicated by the fact that the header pressure has not dropped by the correct amount.

The red light for valve operation and the header pressure can have an associated audible signal to indicate the malfunction in the system. Such an alarm can be given a five minute bypass in order to enable the problem to be rectified in silence without the annoying alarms affecting the performance of the operator. The red light can also have a reset button so that the operator can re-check for any indicated malfunction. Other optional alarms and/or indicators can be provided from sensors including tribo-electric units and point level probes from the hoppers collecting dust. The point level probes will indicate when a hopper needs all the dust removed for the efficient operation of the bag house system.

The off time indicator 232 , displays a reading of the time it takes for the differential pressure to move from the lower set point to an upper set point. Generally it will display and hold the last off time measurement. The time between cleaning cycles is generally of the order of five minutes but may vary according to the system. The indicator 232 showing readings of less than the known time between cycles may indicate the system tending to operate out of control. Should the time drop to zero or almost zero, then the system is indicated as definitely out of control and in need of substantial maintenance .

From information such as the number of pulses in the last cleaning cycle an operator can determine whether or not filter material in the filter bags of a string of blow tube outlets under the control of one valve are being cleaned effectively and if not being cleaned effectively this may be a result of the condition of one or more bags, which may indicate replacement is required.

Other pressure sensing means can be utilised such as strain gauges and the like. The pressure transducer can be located on the header, so that only an electrical connection between the header and control panel need be made.

Modifications by those skilled in the art can be made hereto without departing form the scope of the present invention. Whilst the above description has been in respect of a bag house cleaning system, it will be understood that the present invention is applicable to cartridge systems, which may have some constructional features different to bag house systems.

Claims

1. A component for a Filter Bag cleaning system, said component having at least one substantially planar portion and an aperture therethrough for the passage of air, said component being adapted to be positioned over a Filter Bag port through which air can pass into and out of said Filter Bag.

2. A component as claimed in claim 1 whereby the aperture has associated with it a flow control formation. ^~

3. A component as claimed in claim 2 wherein said flow control formation is a round edged orifice.

4. A component as claimed in any one of claims lor 2 or 3 wherein said component is a load bearing member.

5. A component as claimed in claim 1, 2, 3 or 4 whereby the component maintains a relatively low profile even when said flow control formation is provided.

6. A component as claimed in any one of claims 1 to 5 wherein the flow control formation can be integrally formed in the component, or attached thereto.

7. A component as claimed in any one of claims 1 to 5 wherein the flow control formation is not attached to the component, but cooperates therewith.

8. A component as claimed in any of the preceding claims wherein the component is a substantially planar.

9. A component as claimed in any of the preceding claims wherein the component is a disc, round, annular or cylindrical in shape.

10. A component as claimed in any one of claims 1 to 5 where in said component is an elongated member.

11. A component as claimed in claim 10 wherein said elongated member is a U-shaped member, or an H-shaped member.

12. A component as claimed in any one of the preceding claims, wherein the component is adapted to be attached to the upper structure of a Filter Bag.

13. A component as claimed in any one of claims 1 to 11, where in the component is adapted to stand over, either in contact with or not in contact with, the top end of a Filter

Bag or its support arrangement.

14. A component as claimed in claim 13 whereby the component is adapted to stand over the Filter Bag support arrangement by feet or a wall depending from the component.

15. A Filter Bag cleaning system utilising a component as claimed in any one of the preceding claims.

16. A Filter Bag component, said component being open ended and substantially cylindrical and adapted to be placed in the open end of a Filter Bag, said component extending downwardly from said open end a distance which is sufficient to receive the impact of a reverse pulse, said member having only two holes, namely the open ends.

17. A Filter Bag support cage for a filter cleaning system, said Filter Bag support cage comprising a first end containing an aperture for the exit of cleaned air from a bag to be associated with said cage, as well as the entry of a reverse pulse of air for the purposes of cleaning said bag, said Filter Bag support cage also including a support structure for the Filter Bag depending from said first end, characterised in that said first end is constructed of a sheet material having means to support said end in a Filter Bag support and whereby said sheet material extends downwardly from said support a distance which includes at least an impact zone of a reverse pulse of air injected into said Filter Bag.

18. A Filter Bag support cage for a filter cleaning system as claimed in claim 17, being further characterised in that said sheet material will extend into the bag some 150 to 350 mm.

19. A method of controlling a Filter Bag reverse pulse cleaning system, said system comprising a supply of compressed air and a flow control means to control movement of compressed air from said supply to outlets which eject compressed air in order to clean filter material, said flow control means being adapted to allow said movement of compressed air for a predetermined period and terminate said movement until such time as said movement is required again, characterised in that a sensing means senses when said supply is of a desired pressure said sensing means interacting with said flow control means to thereby permit allowance of said movement of compressed air, when said desired pressure is reached.

20. A method as claimed in claim 19 characterised in that the desired pressure can be varied according to system conditions which may exist from time to time.

21. A method of operating a Filter Bag cleaning system having at least a supply of compressed air, communicable passage between said supply and outlets which eject compressed air into a Filter Bag, flow control means to control passage of compressed air from said supply to said outlets, said method comprising the steps of:

1. Raising the pressure available from said supply to a first predetermined level. 2. Opening said flow control means to emit a pulse of air for a predetermined or modifiable time .

3. Closing said flow control means until said cleaning is again required.

6. Permitting said flow control means to open passage between said supply and said outlets simultaneously with or after said second predetermined pressure level is sensed, but before the first predetermined pressure level is reached.

22. A method as claimed in claim 21 being further characterised by a seventh step being the variation of the first predetermined pressure level and the predetermined desired pressure level according to system conditions which may exist from time to time.

23. A control panel for a Filter Bag cleaning system, said panel including thereon: (a) gauges or displays to indicate system characteristics;

(b) a graphical representation of the system characteristics; the displays being located at or linked to the graphical representation of each respective characteristic.

24. A control panel for a Filter Bag cleaning system as claimed in claim 23 being further characterised by including control means to vary system characteristics.

25. A control panel for a Filter Bag cleaning system as claimed in claim 24 being further characterised by the control means being located at or linked to the graphical representation of each characteristic.

26. A control panel for a Filter Bag cleaning system, said panel including thereon: (a) control means to vary system characteristics;

(b) a graphical representation of the system characteristics; the control means being located at or linked to the graphical representation of each respective characteristic.