CA1201788A - Air pulse failure detector - Google Patents
Air pulse failure detectorInfo
- Publication number
- CA1201788A CA1201788A CA000425852A CA425852A CA1201788A CA 1201788 A CA1201788 A CA 1201788A CA 000425852 A CA000425852 A CA 000425852A CA 425852 A CA425852 A CA 425852A CA 1201788 A CA1201788 A CA 1201788A
- Authority
- CA
- Canada
- Prior art keywords
- air
- pulse
- control circuit
- puff
- circuit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/02—Particle separators, e.g. dust precipitators, having hollow filters made of flexible material
- B01D46/04—Cleaning filters
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/0084—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours provided with safety means
- B01D46/0086—Filter condition indicators
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/42—Auxiliary equipment or operation thereof
- B01D46/4281—Venturi's or systems showing a venturi effect
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/66—Regeneration of the filtering material or filter elements inside the filter
- B01D46/70—Regeneration of the filtering material or filter elements inside the filter by acting counter-currently on the filtering surface, e.g. by flushing on the non-cake side of the filter
- B01D46/71—Regeneration of the filtering material or filter elements inside the filter by acting counter-currently on the filtering surface, e.g. by flushing on the non-cake side of the filter with pressurised gas, e.g. pulsed air
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Filtering Of Dispersed Particles In Gases (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention relates to a solid state pulse air flow sensor suitable for use in reverse air pulse dust collectors. A sequencing circuit causes air pulses to blow into filter bags at predetermined times. A sensor con-sisting of a thermistor and associated circuitry then detects the presence of the air pulse at the times determined by the sequencing circuit. If the air pulse is not present, at the predetermined time, an alarm circuit will be activated.
The present invention relates to a solid state pulse air flow sensor suitable for use in reverse air pulse dust collectors. A sequencing circuit causes air pulses to blow into filter bags at predetermined times. A sensor con-sisting of a thermistor and associated circuitry then detects the presence of the air pulse at the times determined by the sequencing circuit. If the air pulse is not present, at the predetermined time, an alarm circuit will be activated.
Description
AIR PULSE FAILURæ DETECTOR
The present invention relates to a solid state pulse air flow sensor suitable or use in reverse pulse air dust collectors.
Reverse pulse air dust collectors are used in a broad range of air pollution control and particulate recovery applications. In many industries, process gases laden with dust must be cleaned before being released to the atmosphere.
One method used to clean the gases is to pass them through filter bags. The bags trap the dust particles, and the dust particles accumulate on the outer surface of the bay~ Once a dust cake has been formed on the filter bags, the cake must be periodically removed in order to preserve the eficiency of the dust collector. A common method of removing the dust cake is by a controlled blast of compressed air.
When the controlled blast of compressed air is blown into the filter bag, the sudden release of energy into the filter bag causes it to instantly expand to its maximum size causing the dust to be thrown off the outside surface of the filter bag. When the cleaning energy from the air pulse is spent, the filter bag returns to its normal filtering position, while the dust precipitation from the filter bags falls to a collection hopper.
Should the air pulse not operate properly, serious problems can occur. The ilter b~gs can become so laden with dust that the process gases will no longer be able to flow.
. ~
As a resultt the process gases must be discharged directly into the atmosphere, resulting in pollution and eventually the shutdown of the operation to allow for repair of the system. Such problems would occur if the air pulser does not pulse, or if it is continuously discharging air into the filter bags.
The present invention relates to a solid state device which will detect if the air pulse has failed, or if there is an air leak resulting in continuous air flow In addition, the present invention is small enough in size to conveniently fit in the compressed air manifold of a reverse pulse air dust collector.
The sensor is capable of continuous operation, is easily installed and callibrated, and is sensitive to short air bursts in the order of 50 milliseconds to 250 milliseconds, occuring once every two seconds or at any other longer predetermined time interval.
secause dust collectors operate under a wide range of process conditions, the cleaning or pulsing parameters must also be variable. The cleanin~ air is normally under a pressure of between 60 PSIG to 130 PSIG. The high pressure air pulse duration is normally between 50 msec. to 250 msec.. The high pressure air pulsing rate is normally within the range of l pulse every two seconds to l pulse every 600 seconds. In addition, the temperature o~ -the pulsing air can vary between -20C to ~0C, depending on the application.
In the present invention, the sensor which will be used to detect the presence of an air pulse will be a thermistor, operating in the self heat mode, and having a mass such that its resistive change, caused by the cooling effect of moving air, will be no less than 2 to 1 in 50 msec.. A thermistor will be disposed near the outlet of a blower so that the air pulse will blow directly upon it. If the thermistor is placed in the path of the cleaning air pulse, it will be cooled by the air pulse, and accordingly, its resistance will change due to the temperature change. The resulting change in resistance creates a voltage change, which can be used to give an indication of the air pulse.
The supporting circuitry will use this voltage change to determine i~ there is no air pulse, or if there is continuous air flow, or if the timing of the air pulse is incorrect. The circuitry incorporatlng the thermistor sensor unit must attempt to maintain a constant level of current flowing through the sensor. Current flowing through the thermistor must also provide enough energy to heat the thermistor above ambient temperature, viz, the thermistor must be in the self heat mode. As the thermistor is internally heated, any small fluctuation in ambient temperature will not give a false indication of the desired air source.
In aeeordance with the present invention, there is provided an air pulse failure detector eomprising an air puffer, a sequencing circuit to activate the air puffer at predetermined times, sensor means responsive to the presence of an air puff, a control eircuit which receives information from the sequeneing eircuit and from the sensor to determine whether an air puff has not occurred at a predetermined time, and an alarm circuit receiving information from the control circuit and capable of causing an alarm to activate when an air puff has not occurred at a pre-determined time.
Thermistors have characteristic dissipa-tion constants and time constants. If the current flowing through the thermistor is known, the temperature oE the thermistor can be found using the mathematical relationship between these constants. In operation, once the thermistor has reached a stead~ state internal temperature, and a cleaning air pulse is introduced, the thermistor will cool. A sequencer circuit can activate a solenoid causing the air pulse blower to operate, while at the same time, sending a signal to a control circui-t which would cause a timer to start. The control Gircuit would then determine if a second signal were received as a result o~ the air puff acting upon the thermistor. If such an air puff is presentr a second signal will be received which can cause the timer to stop and reset.
Where the timer does not stop, the timer will time out and the control circuit will then send a signal to an alarm circuit.
If an air puff is present, no alarm signal will be sent out. However, if the air puff is not present, the timer will time out and the alarm circuit will be activated~ If there is an air leak such that the air puffer is continuous]y blowing air, the therm.istor will not be able to heat up and prepare itself for a sudden change of air flow. Accordingly, no signal would be sent back from the thermistor circuit to stop and reset the timer thus causing the timer to time out and an alarm to sound. In addition, if -the air puffer is not activated at predetermined times, determined by the sequencer which causes the timer -to startl the cooling and heating up of the thermistor will not be in synchronization with the sequencer circuit, and accordingly, the timer will not be stopped, causing -the alarm circuit to be activated.
Reference will now be made to the accompanying drawings.
Figure 1 shows a typical reverse pulse air dust collector in the filtering position.
Figure 2 shows the same reverse pulse air dust collector in the cleaning position.
Figure 3 is a block diagram of a preferred embodiment of the present invention.
Figure 4 shows a thermistor operating in the self heat mode.
Referring to the drawings, Figure 1 shows a typical reverse pulse air dust collector operating in the filtering position. Air to be filtered enters into the dust collector at 9 in the direction of the arrows. The dust laden air must pass through filter bag 5 which is supported by cage 6. The filtered air is passed up through venturi 3, outside secondary nozzle 2, and exits at 10. Filter bag 5 will eventually build up a cake of dust on its outside.
~0 Referring to Figure 2, in order to periodically clean Eilter bag 5~ an air blast is introd~lced at 8 in manifold 1 through pximary nozzle 4 into the interior of filter bag 5. The air blast causes ~ilter bag 5 to expand rapidly, thereby loosening the caked d~lst and causing it to fall in the direction indicated by arrows 7 to a hopper. When the cleaning air blast is ended, the filter bag 5 will return to its normal filtering position, and after the dust precipitation has settled in the hopper, the 7~
dust collector can again be operated in the filtering position.
Referring -to Figure 3, a sequencer circuit would be used to control the timing of the air pulses. The sequencer circuit could be adjusted to periodically send a signal to a solenoid which would activate the air pulser. This sequencer circuit would preferably be adjustable to send a signal from once every two seconds to once very 600 seconds. The signal sent would cause the air pu~fer to puff for a duration of between 50 msec. and 250 msec..
Located in the manifold 1 or primary nozzle 4 would be a thermistor and printed circuit boards containing a control circuit and timer circuit. The control circuit would maintain the self heat current in the thermistor, and detect -the sudden chan~e in resistance of the thermistor caused by an air puff~
The control circuit would also receive a signal from the sequencer circuit causing a timer to start when the air puff is supposed to have occurred. The signal received from the change of resistance of the thermistor would cause the timer to stop and reset. Where the timer stops and resets; the system is ready for the next air puff. However, if the timer is not stopped, it will time out and cause a si~nal to be sent to an alarm circuit.
Referring to Figure 4, thermistor 25 is shown in the self heat mode. Typical values are V=12 volts dc~ Rl-5.1 k ohms R2=110 o~ls, R3=230 ohms, and thermistor 25 = 1 x 1040hms. A
typical transistor T would ~e 2 N 4123.
The timîng portion of the control circuit would be a typical timer, and the control portion could be an AND gate or of any other known configuration. The alarm circuit could be a bell or light or other type of alarm.
The preferred embodiment of the present invention as shown in the drawings is by way of example only, and is not intended to limit the scope of the invention, which is defined in the claims.
The present invention relates to a solid state pulse air flow sensor suitable or use in reverse pulse air dust collectors.
Reverse pulse air dust collectors are used in a broad range of air pollution control and particulate recovery applications. In many industries, process gases laden with dust must be cleaned before being released to the atmosphere.
One method used to clean the gases is to pass them through filter bags. The bags trap the dust particles, and the dust particles accumulate on the outer surface of the bay~ Once a dust cake has been formed on the filter bags, the cake must be periodically removed in order to preserve the eficiency of the dust collector. A common method of removing the dust cake is by a controlled blast of compressed air.
When the controlled blast of compressed air is blown into the filter bag, the sudden release of energy into the filter bag causes it to instantly expand to its maximum size causing the dust to be thrown off the outside surface of the filter bag. When the cleaning energy from the air pulse is spent, the filter bag returns to its normal filtering position, while the dust precipitation from the filter bags falls to a collection hopper.
Should the air pulse not operate properly, serious problems can occur. The ilter b~gs can become so laden with dust that the process gases will no longer be able to flow.
. ~
As a resultt the process gases must be discharged directly into the atmosphere, resulting in pollution and eventually the shutdown of the operation to allow for repair of the system. Such problems would occur if the air pulser does not pulse, or if it is continuously discharging air into the filter bags.
The present invention relates to a solid state device which will detect if the air pulse has failed, or if there is an air leak resulting in continuous air flow In addition, the present invention is small enough in size to conveniently fit in the compressed air manifold of a reverse pulse air dust collector.
The sensor is capable of continuous operation, is easily installed and callibrated, and is sensitive to short air bursts in the order of 50 milliseconds to 250 milliseconds, occuring once every two seconds or at any other longer predetermined time interval.
secause dust collectors operate under a wide range of process conditions, the cleaning or pulsing parameters must also be variable. The cleanin~ air is normally under a pressure of between 60 PSIG to 130 PSIG. The high pressure air pulse duration is normally between 50 msec. to 250 msec.. The high pressure air pulsing rate is normally within the range of l pulse every two seconds to l pulse every 600 seconds. In addition, the temperature o~ -the pulsing air can vary between -20C to ~0C, depending on the application.
In the present invention, the sensor which will be used to detect the presence of an air pulse will be a thermistor, operating in the self heat mode, and having a mass such that its resistive change, caused by the cooling effect of moving air, will be no less than 2 to 1 in 50 msec.. A thermistor will be disposed near the outlet of a blower so that the air pulse will blow directly upon it. If the thermistor is placed in the path of the cleaning air pulse, it will be cooled by the air pulse, and accordingly, its resistance will change due to the temperature change. The resulting change in resistance creates a voltage change, which can be used to give an indication of the air pulse.
The supporting circuitry will use this voltage change to determine i~ there is no air pulse, or if there is continuous air flow, or if the timing of the air pulse is incorrect. The circuitry incorporatlng the thermistor sensor unit must attempt to maintain a constant level of current flowing through the sensor. Current flowing through the thermistor must also provide enough energy to heat the thermistor above ambient temperature, viz, the thermistor must be in the self heat mode. As the thermistor is internally heated, any small fluctuation in ambient temperature will not give a false indication of the desired air source.
In aeeordance with the present invention, there is provided an air pulse failure detector eomprising an air puffer, a sequencing circuit to activate the air puffer at predetermined times, sensor means responsive to the presence of an air puff, a control eircuit which receives information from the sequeneing eircuit and from the sensor to determine whether an air puff has not occurred at a predetermined time, and an alarm circuit receiving information from the control circuit and capable of causing an alarm to activate when an air puff has not occurred at a pre-determined time.
Thermistors have characteristic dissipa-tion constants and time constants. If the current flowing through the thermistor is known, the temperature oE the thermistor can be found using the mathematical relationship between these constants. In operation, once the thermistor has reached a stead~ state internal temperature, and a cleaning air pulse is introduced, the thermistor will cool. A sequencer circuit can activate a solenoid causing the air pulse blower to operate, while at the same time, sending a signal to a control circui-t which would cause a timer to start. The control Gircuit would then determine if a second signal were received as a result o~ the air puff acting upon the thermistor. If such an air puff is presentr a second signal will be received which can cause the timer to stop and reset.
Where the timer does not stop, the timer will time out and the control circuit will then send a signal to an alarm circuit.
If an air puff is present, no alarm signal will be sent out. However, if the air puff is not present, the timer will time out and the alarm circuit will be activated~ If there is an air leak such that the air puffer is continuous]y blowing air, the therm.istor will not be able to heat up and prepare itself for a sudden change of air flow. Accordingly, no signal would be sent back from the thermistor circuit to stop and reset the timer thus causing the timer to time out and an alarm to sound. In addition, if -the air puffer is not activated at predetermined times, determined by the sequencer which causes the timer -to startl the cooling and heating up of the thermistor will not be in synchronization with the sequencer circuit, and accordingly, the timer will not be stopped, causing -the alarm circuit to be activated.
Reference will now be made to the accompanying drawings.
Figure 1 shows a typical reverse pulse air dust collector in the filtering position.
Figure 2 shows the same reverse pulse air dust collector in the cleaning position.
Figure 3 is a block diagram of a preferred embodiment of the present invention.
Figure 4 shows a thermistor operating in the self heat mode.
Referring to the drawings, Figure 1 shows a typical reverse pulse air dust collector operating in the filtering position. Air to be filtered enters into the dust collector at 9 in the direction of the arrows. The dust laden air must pass through filter bag 5 which is supported by cage 6. The filtered air is passed up through venturi 3, outside secondary nozzle 2, and exits at 10. Filter bag 5 will eventually build up a cake of dust on its outside.
~0 Referring to Figure 2, in order to periodically clean Eilter bag 5~ an air blast is introd~lced at 8 in manifold 1 through pximary nozzle 4 into the interior of filter bag 5. The air blast causes ~ilter bag 5 to expand rapidly, thereby loosening the caked d~lst and causing it to fall in the direction indicated by arrows 7 to a hopper. When the cleaning air blast is ended, the filter bag 5 will return to its normal filtering position, and after the dust precipitation has settled in the hopper, the 7~
dust collector can again be operated in the filtering position.
Referring -to Figure 3, a sequencer circuit would be used to control the timing of the air pulses. The sequencer circuit could be adjusted to periodically send a signal to a solenoid which would activate the air pulser. This sequencer circuit would preferably be adjustable to send a signal from once every two seconds to once very 600 seconds. The signal sent would cause the air pu~fer to puff for a duration of between 50 msec. and 250 msec..
Located in the manifold 1 or primary nozzle 4 would be a thermistor and printed circuit boards containing a control circuit and timer circuit. The control circuit would maintain the self heat current in the thermistor, and detect -the sudden chan~e in resistance of the thermistor caused by an air puff~
The control circuit would also receive a signal from the sequencer circuit causing a timer to start when the air puff is supposed to have occurred. The signal received from the change of resistance of the thermistor would cause the timer to stop and reset. Where the timer stops and resets; the system is ready for the next air puff. However, if the timer is not stopped, it will time out and cause a si~nal to be sent to an alarm circuit.
Referring to Figure 4, thermistor 25 is shown in the self heat mode. Typical values are V=12 volts dc~ Rl-5.1 k ohms R2=110 o~ls, R3=230 ohms, and thermistor 25 = 1 x 1040hms. A
typical transistor T would ~e 2 N 4123.
The timîng portion of the control circuit would be a typical timer, and the control portion could be an AND gate or of any other known configuration. The alarm circuit could be a bell or light or other type of alarm.
The preferred embodiment of the present invention as shown in the drawings is by way of example only, and is not intended to limit the scope of the invention, which is defined in the claims.
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:-
1. An air pulse failure detector comprising an air puffer, sequencing circuit means to cause the air puffer to be activated at predetermined times, sensor means responsive to the presence of an air puff and physically located to receive an air puff, control circuit means receiving information from said sequencing means and from said sensor means, capable of determining whether an air puff has not occurred at a predetermined time, and alarm means receiving information from said control circuit means capable of causing an alarm to activate when an air puff has not occurred at a predetermined time.
2. In combination, a reverse pulse type dust collector having an air inlet for introducing gases to be filtered, at least one filter bag, an air outlet from which filtered air can exit, and blower means to blow an air pulse into the filter bag, detection means responsive to said blower means interposed between the blower means and the filter bag, a control circuit associated with the blower means and the detection means, said control circuit capable of causing an alarm to activate in the absence of an air pulse at predetermined intervals, and a sequencing circuit causing the blower means to operate at predetermined intervals.
3. An air pulse failure detector according to Claim 1 wherein said sensor means includes a thermistor operated in the self heat mode.
4. An air pulse failure detector according to Claim 1 wherein said control circuit means includes a timing circuit which is activated by said sequencing circuit means and deactivated by said sensor means.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000425852A CA1201788A (en) | 1983-04-14 | 1983-04-14 | Air pulse failure detector |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000425852A CA1201788A (en) | 1983-04-14 | 1983-04-14 | Air pulse failure detector |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1201788A true CA1201788A (en) | 1986-03-11 |
Family
ID=4125010
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000425852A Expired CA1201788A (en) | 1983-04-14 | 1983-04-14 | Air pulse failure detector |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1201788A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2937128A1 (en) * | 2014-04-25 | 2015-10-28 | Siemens VAI Metals Technologies GmbH | Monitoring of a pressurised gas based cleaning of a hose filter assembly |
| CN106669301A (en) * | 2016-09-13 | 2017-05-17 | 沈阳隆基电磁科技股份有限公司 | Vacuum dust removal equipment for single crystal growth furnace |
| WO2020088899A1 (en) * | 2018-10-31 | 2020-05-07 | Hengst Se | Filter arrangement and method |
-
1983
- 1983-04-14 CA CA000425852A patent/CA1201788A/en not_active Expired
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2937128A1 (en) * | 2014-04-25 | 2015-10-28 | Siemens VAI Metals Technologies GmbH | Monitoring of a pressurised gas based cleaning of a hose filter assembly |
| WO2015161968A1 (en) * | 2014-04-25 | 2015-10-29 | Primetals Technologies Austria GmbH | Monitoring of a pressurized gas-based cleaning process in a hose filter installation |
| CN106232203A (en) * | 2014-04-25 | 2016-12-14 | 首要金属科技奥地利有限责任公司 | Monitoring to the cleaning process based on gas-pressurized in hose filter equipment |
| US20170036154A1 (en) * | 2014-04-25 | 2017-02-09 | Primetals Technologies Austria GmbH | Monitoring of a pressurized gas-based cleaning process in a hose filter installation |
| JP2017513705A (en) * | 2014-04-25 | 2017-06-01 | プライメタルズ・テクノロジーズ・オーストリア・ゲーエムベーハー | Monitoring pressurized gas-based cleaning processes in hose filter equipment |
| CN106232203B (en) * | 2014-04-25 | 2019-09-17 | 首要金属科技奥地利有限责任公司 | Monitoring to the cleaning process based on gas-pressurized in hose filter equipment |
| CN106669301A (en) * | 2016-09-13 | 2017-05-17 | 沈阳隆基电磁科技股份有限公司 | Vacuum dust removal equipment for single crystal growth furnace |
| WO2020088899A1 (en) * | 2018-10-31 | 2020-05-07 | Hengst Se | Filter arrangement and method |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |