Extraction system with product accumulation sensor / s

Abstract

The invention relates to an extraction system (1) with product accumulation sensor / s. The system comprises: • a) one or more extraction inlets X from which dust and air is extracted from a work place, • b) a duct or ducts (2) leading from each extraction duct inlet to an extraction duct outlet Z, • c) an extraction fan to extract air and dust from the extraction duct outlet, • d) an air velocity sensor (10) in the duct or ducts (2) to detect build up of product in the duct / s, said air velocity sensor (10) using a pair of pressure sensors (11A,11B), one measuring pressure upstream of a venturi and the other measuring pressure through the restriction of the venture or downstream of the venturi, and • e) a pair of pressure sensors (13A,13B) spaced either side of the air velocity sensor (10) in the duct or ducts to detect build up of product in the duct / s, in use said air velocity and / or pressure sensor / s causing the fan to increase its extraction power upon build-up of product to cause said build up of product in ducts to be extracted until said sensor / s no longer sense build-up of product.

Description

[0001] Extraction System with Product Accumulation Sensor / s

[0002] The present invention relates to an extraction system with product accumulation sensor / s.

[0003] Product extraction systems (such as dust, fume and kitchen extraction systems) are well known to extract dust and fumes from workplace environments. Such extraction systems designed for dust extraction, such as woodworking buildings or particulate material handling premises, are often required to run their extraction fans at excessively high speeds so that product (dust / particulate) does not accumulate in the extraction ducts in the first place. Air speeds through pipes of 16 to 22 m / s are quite common. This leads to unnecessarily high energy costs, driving the fan at high speeds. In many cases these high speeds are “regulation speeds” and do not take into account whether in fact product build up is a problem.

[0004] The invention seeks to provide a solution to this problem by creating a system which can extract product from ducts by increasing extraction fan speeds only when product build up is present to reduce energy costs.

[0005] According to an aspect of the present invention, there is provided an extraction system, comprising: a) one or more extraction inlets from which dust and air is extracted from a work place, b) a duct or ducts leading from each extraction duct inlet to an extraction duct outlet, c) an extraction fan to extract air and dust from the extraction duct outlet, d) an air velocity sensor in the duct or ducts, e) a pair of pressure sensors spaced either side of the air velocity sensor in the duct or ducts to detect build up of product in the duct / s, and f) a controller for controlling the extraction fan in dependence on the output of the air velocity sensor and / or the pair of pressure sensors.

[0006] The extraction fan may be located either upstream or downstream or between the pressure sensors, and / or of the extraction duct outlet.

[0007] In use, said air velocity and / or pressure sensor / s cause the fan to increase its extraction power upon build-up of product to cause said build up of product in ducts to be extracted until said sensor / s no longer sense build-up of product.

[0008] The air velocity sensor may comprise a pair of pressure sensors, one measuring pressure upstream of a venturi or through the restriction of the venturi and the other measuring pressure through the restriction of the venturi or downstream of the venturi.

[0009] Said air velocity and / or pressure sensor / s may cause the fan to increase its extraction power for a pre-determined period of time when the fan extraction power is then decreased, and then the sensor / s only increase the fan’s extraction if product continues to be sensed.

[0010] The pressure sensors either side of the air velocity sensor may compare a pressure increase or flow rate increase either side of the air velocity sensor with a pressure and flow rate value determined when a duct is known to be clear of product and at different flow rates. The system may comprise a sensor including an infra-red transmitter and an infra-red receiver , and changes in infra-red waves received by the receiver due to product build up in the pipe may be compared to when the pipe is clear of product senses the build-up of product in the duct.

[0011] According to another aspect of the invention there is provided an extraction method, comprising the steps of: extracting air and dust from an extraction duct outlet in fluid communication, via a duct or ducts, with one or more extraction inlets from which dust and air is to be extracted from a work place, sensing an air velocity at a predetermined position in the duct or ducts, sensing air pressure to either side of the predetermined position, and controlling the extraction in dependence on the sensed air velocity and / or the sensed air pressure.

[0012] According to another aspect of the present invention there is provided an extraction system with product accumulation sensor / s comprising: a) one or more extraction inlets from which dust and air is extracted from a work place, b) a duct or ducts leading from each extraction duct inlet to an extraction duct outlet, c) an extraction fan to extract air and dust from the extraction duct outlet, and d) an air velocity sensor in the duct or ducts to detect build up of product in the duct / s, said air velocity sensor using a pair of pressure sensors, one measuring pressure upstream of a venturi or through the restriction of the venturi and the other measuring pressure through the restriction of the venture or downstream of the venturi, and e) a pair of spaced pressure sensors spaced either side of the air velocity sensor in the duct or ducts to detect build up of product in the duct / s, in use said air velocity and / or pressure sensor / s causing the fan to increase its extraction power upon build-up of product to cause said build up of product in ducts to be extracted until said sensor / s no longer sense build-up of product.

[0013] Preferably said air velocity and / or pressure sensor / s cause the fan to increase its extraction power for a pre-determined period of time when the fan extraction power is then decreased, and then the sensor / s only increase the fan’s extraction if product continues to be sensed.

[0014] Preferably the pressure sensors either side of the air velocity sensor compare a pressure increase or flow rate increase either side of the air velocity sensor with a pressure and flow rate value determined when a duct is known to be clear of product and at different flow rates.

[0015] Preferably the sensor includes an infra-red transmitter and an infra-red receiver, and changes in infra-red waves received by the receiver due to product build up in the pipe are compared to when the pipe is clear of product senses the build-up of product in the duct.

[0016] According to another aspect of the present invention, there is provided an extraction system, comprising: a) one or more extraction inlets disposed at a location from which gases and / or dust or other particulates are to be extracted, b) a duct or ducts leading from each extraction duct inlet to an extraction duct outlet, c) an extraction fan to draw the gases and / or dust or other particulates through the duct from the extraction inlet to the extraction duct outlet, d) an air velocity sensor in the duct or ducts to detect a velocity of air passing through the duct, e) a pair of pressure sensors disposed in the duct or ducts to detect a pressure drop along the duct / s, and f) a controller for controlling the extraction fan in dependence on the output of the air velocity sensor and / or the pair of pressure sensors.

[0017] The output of the air velocity sensor and the pair of pressure sensors may be used to detect or determine a build up of product within the duct, for example (and as described herein) based on a deviation of the sensed air velocity and pressure drop with respect to calibrated values, or based on a deviation of a metric derived from the sensed air velocity and pressure drop from a calibrated value of the metric.

[0018] In response to a detection of the build up, the controller may control the extraction fan to increase its speed. The increased speed may continue for a predetermined period of time, or until the build up is determined to have been cleared (based on further measurements of air velocity and pressure drops). An embodiment of the invention will now be described with reference to the accompany drawings in which:

[0019] Figure 1 shows a flow rate and pressure drop sensor, and

[0020] Figure 2 shows an infra red transmitter / receiver mounted on a window in a duct.

[0021] Referring now to Figure 1, there is shown part of a product extraction system 1. System 1 has a duct 2 (only small part shown) connected at one end to one or more extraction inlets X from which product and air is extracted from a work place. The other end leads to an extraction duct outlet Y. An extraction fan (not shown but well known in the art) extracts air and product from the extraction duct outlet into ambient air. Over a period of time product can accumulate in the duct 2, reducing airflow rate and increasing pressure in the duct 2.

[0022] A venturi type air velocity sensor 10 (or an ultrasonic receiver / transmitter air velocity measurer) is provided in the wall of the duct 2 to measure the airflow velocity in the duct 2. Ideally the measurer 10 measures to an accuracy of + / - 2%. Air velocity sensor 10 in the duct or ducts to detect build up of product in the duct / s. Air velocity sensor 10 has a pair of pressure sensors / spigots 11 A, 1 IB, sensor 11 A measuring pressure upstream of a venturi 12 as shown (or through the restriction of the venturi not shown) and the other 1 IB measuring pressure (through the restriction of the venturi 12 not shown) or downstream of the venturi 12 as shown. In some implementations, the spigots may be around 200mm apart, or slightly less.

[0023] In an alternative implementation, ultrasonic velocity sensors are used to measure the speed of sound waves traveling through the pipe instead of the above arrangement. Depending on the sensor type, they may either use the Doppler effect (measuring frequency shifts from reflections off particles in the fluid) or the time-of-flight method (comparing the travel time of ultrasonic pulses sent upstream and downstream) to determine the velocity of the airflow.

[0024] These are non-contact devices, allowing measurement without disrupting the flow or damaging the sensors.

[0025] The pressure sensors / spigots 13A,13B, are shown spaced either side of the air velocity sensor in the duct or ducts, and these detect build up of product in the duct / s. These are generally further apart from each other than the air velocity sensor spigots, and may be as far apart as possible within a given section of pipework.

[0026] The venturi may be in the shape half of an extended teardrop with a widened leading edge and a tapering trailing edge. The base may be curved to conform to the inner circumferential shape of the duct 2. The venturi 12 may be of the type described in our co-pending patent application no GB2413725.9 relating to an air velocity sensor, the contents of which are hereby incorporated by this reference. In such a case, the sensor spigot 1 IB could pass through tear drop venturi or substantially in the area of the cross section of the pipe passing through of the venturi as described in the co-pending patent application.

[0027] The pressure across a section of duct 2 of the same (constant) diameter may be measured with static pressure spigots 11 A,1 IB, fitted flush to the pipe, using high accuracy, low pressure sensors. In practice a non-constant diameter duct could also be used if compensated for in the modelling. The pressure across the duct section 2 will be calibrated when clean, at a known air velocity, via an automatic ‘calibration routine’. This will generally be carried out when the system is commissioned, following installation. It could also be carried out subsequently after the ducts have been cleaned or replaced. The calibration data will then be used to model the pressure / velocity characteristics (across the design range) for the ‘clean’ pipe section. The data will be checked against an empirical model for pipe friction based on friction factor for the particular type of duct and the air velocity change due to reduced flow area. During operation the actual airflow / pressure characteristics will be measured and compared against the model to confirm if a product deposit is occurring. That is, a deviation of the airflow / pressure characteristics from the model is indicative of the presence of a buildup of product within the duct.

[0028] Considering the modelling in more detail, during calibration the fan speed is varied (for example ramped up over time, continuously or in discrete steps), and a pair of air velocity and pressure drop values is measured using the sensors described above. Each pairing of measured air velocity and measured pressure drop can then be combined using any suitable formula (for example by multiplying or dividing the measured values by each other) into a single value indicative of a resistance factor of the duct.

[0029] Then, during operation, the air velocity and pressure drop are monitored, and the resistance factor can be similarly computed and monitored. If the resistance factor increases (or reduces, depending how computed) beyond a threshold deviation (for example 2% or 5%) Alternatively, instead of using a resistance factor, the air velocities and pressure drops measured during calibration may define a lookup table, or derived expression (mapping) between measured air velocity and measured pressure drop. Then, during operation the measured air speed can be used as a lookup (or input to the equation) and the output (the expected pressure drop) compared with the newly measured pressure drop. A deviation between the expected and actual pressure drop representing an indication of deposit build up within the duct. This may then trigger an increase in fan speed to clear the deposited material from the duct, as discussed elsewhere.

[0030] If product is established, then additional airflow can be passed through the duct 2 such as by increasing the speed of the fan and / or drawing more air in from the extraction inlets (for example using a booster fan - not shown), as controlled by a controller 12.

[0031] Generally the duct 2 will be the largest section of duct within a multi-branch extraction system to be measured and should have the same diameter across the whole section. Generally this will be the section immediately upstream of the main extract fan or filtration / abatement unit.

[0032] The velocity and pressure sensors 10 and 13A,13B may suit instances where a large amount of product may be present.

[0033] In addition, the sensor may include three infra-red transmitters and infra-red receivers 14A,14B,14C, and changes in infra-red waves received by the receiver due to product build up in the pipe compared to when the pipe is clear of product senses the build-up of product in the duct. Infra-red transmitters and infra-red receivers 14A,14B,14C may more usually be used in ducts with lower amounts of product build up. However, since these sensors typically only sense a build up within a small spatial area (single point) of the duct, build ups elsewhere will not be identified, at which point the velocity and pressure sensors as described above are required to detect build up indirectly.

[0034] As shown in Figure 2, the three infrared transmitters / receivers are each mounted onto a clear polycarbonate or other plastic curved window 20 the duct 2 wall, and product build up on the window changes the output of the sensors. If product is established, then additional airflow can be passed through the duct 2 such as by increasing the speed of the fan and / or more air in from the extraction inlets, as controlled by a controller 15. In particular, in some applications there can be booster fan mounted in the individual branch ducts, or if the fan is operating very inefficiently (for example in stall mode), just by opening additional branches / or energy harvester, this may increase the duct velocity sufficiently (without increasing main fan speed). The infra-red transmitters / receivers ideally can detects levels of dust / product >50 microns.

[0035] If desired the infra-red transmitters and infra-red receivers 14A,14B,14C could be mounted downstream of the sensors 10 and 11 A, 11 IB rather than opposite.

[0036] In another alternative implementation, long range (guided wave) ultrasonic sensors could be used to detect deposition on the pipe walls in place of the IR sensor technology, but this would still be used in combination with the pressure / velocity measurements and deposition algorithm described above. In use the system of the invention prevents the need to run extraction fans continuously at high speeds to create a high velocity airflow through an extraction system to prevent theoretical build-up of product. The fan can be run a lower speeds so saving energy, and the fan can then be increased in speed only where a build-up of product actually occurs. The new product deposition technology of the invention will eradicate the need for unnecessary assumptions, enabling lower airflows and significant energy savings, often over 50%, depending upon the utilisation of any multi-branch or single branch ventilation system, this is compared to running the fan at a set speed or duct transport velocity.

[0037] Adaptive learning can be used to improve product deposition detection over time for each sensor / system type. This may also apply to different product types being transported in the ventilation system.

[0038] For cohesive products and liquid aerosols, an LEV system will use the sensor to self-optimise; determining the minimum transport velocity required to limit the build-up to an acceptable rate. For dry non-cohesive products, the sensor will determine when the duct needs to be cleaned and will ramp up the air velocity to re-suspend and remove the accumulation as required.

[0039] In conjunction with other controls, the system can also ensure that any individual branch airflows in the extraction system are maintained to ensure control of the ‘hazardous’ atmosphere at source.

[0040] The invention may take a form different to that specifically described above. Further modifications will be apparent to those skilled in the art without departing from the scope of the present invention.

Claims

CLAIMS1. An extraction system, comprising: a) one or more extraction inlets from which dust and air is extracted from a work place, b) a duct or ducts leading from each extraction duct inlet to an extraction duct outlet, c) an extraction fan to extract air and dust from the extraction duct outlet, d) an air velocity sensor in the duct or ducts , and e) a pair of pressure sensors spaced either side of the air velocity sensor in the duct or ducts to detect build up of product in the duct / s, f) a controller for controlling the extraction fan in dependence on the output of the air velocity sensor and / or the pair of pressure sensors.

2. An extraction system according to claim 1, wherein in use said air velocity and / or pressure sensor / s causing the fan to increase its extraction power upon build-up of product to cause said build up of product in ducts to be extracted until said sensor / s no longer sense buildup of product.

3. An extraction system according to claim 1 or claim 2, wherein the air velocity sensor comprises a pair of pressure sensors, one measuring pressure upstream of a venturi or through the restriction of the venturi and the other measuring pressure through the restriction of the venturi or downstream of the venturi.

4. An extraction system according to any preceding claim, wherein said air velocity and / or pressure sensor / s cause the fan to increase its extraction power for a pre-determined period of time when the fan extraction power is then decreased, and then the sensor / s only increase the fan’s extraction if product continues to be sensed.

5. An extraction system according to any preceding claim, wherein the pressure sensors either side of the air velocity sensor compare a pressure increase or flow rate increase either side of the air velocity sensor with a pressure and flow rate value determined when a duct is known to be clear of product and at different flow rates.

6. An extraction system according to any preceding claim, wherein the system comprises a secondary sensor for directly sensing a build-up of product in the duct, wherein the controller controls the extraction fan in dependence on the sensed build-up.

7. An extraction system according to claim 6, wherein the second sensor comprises an infra-red transmitter and an infra-red receiver , and changes in infra-red waves received by the receiver due to product build up in the pipe compared to when the pipe is clear of product senses the build-up of product in the duct.

8. An extraction method, comprising the steps of: extracting air and dust from an extraction duct outlet in fluid communication, via a duct or ducts, with one or more extraction inlets from which dust and air is to be extracted from a work place,sensing an air velocity at a predetermined position in the duct or ducts, sensing air pressure to either side of the predetermined position, and controlling the extraction in dependence on the sensed air velocity and / or the sensed air pressure.

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