CN1207172A

CN1207172A - Device for measuring the concentration of airborne fibers

Info

Publication number: CN1207172A
Application number: CN 97191571
Authority: CN
Inventors: 布雷恩M·恩斯
Original assignee: Certainteed LLC
Current assignee: Certainteed LLC
Priority date: 1996-11-04
Filing date: 1997-11-03
Publication date: 1999-02-03

Abstract

Devices (100) and methods for measuring the concentration of airbone fibers are provided. The devices include flow means (5 and 6) for providing laminar flow to a portion of the fibers (20) in an air sample and a light source (9) for generating a light beam (12) directed to the laminarly flowing fibers (20) to produce a scattered light. The device further includes a sensor (14) for sensing a portion of this scattered light and producing an output from which a respirable fiber concentration estimate can be measured.

Description

The measurement mechanism of suspension fiber concentration in the air

The application is that to be called " measurement mechanism of suspension fiber size in the air " (Device For Measuring The Dimension Of A Airborne Fiber) sequence number be No.08/743 for the name submitted on November 4th, 1996, the sequence number that 554 U.S. Patent application and on November 4th, 1996 submit to is No.08/743, the application that continues of 555 U.S. Patent application, these two parts of applications have transferred this assignee equally, are hereby incorporated by.

The present invention relates to be used for predicting the method and apparatus of air suspension fiber concentration, and be particularly related to differentiate and breathe the device that fiber and non-fibrous particle maybe can not be breathed fiber.

At present, the method that has suspension fiber concentration in two kinds of basic monitoring air.In first method, suspension fiber in the air is collected in the filtrator.By microtechnic or chemical method this filtrator is analyzed, with the kind of determining existing fiber and the concentration of estimating suspension fiber in the air.There is following shortcoming in the method: information acquisition lags behind, and it is consuming time to require great effort, inconvenience, and the cost height of each sample, and lack precision.And the identification of its fiber is generally undertaken by range estimation, thereby has increased the uncertainty that suspension fiber is measured in the air of Special Category.

In the second approach, the real-time concentration of suspension fiber is to adopt optical technology to determine in the air, wherein to analyzing via the light of decaying by the other fiber of light source.Yet most of this type of device can not be distinguished suspension fiber in different types of air, and potential accurate measurement of breathing the particularly little glass fibre of fiber especially can not be provided.

Because the fibrous asbestos that suspends in the air causes serious health problem, the suspension fiber monitor generally lays particular emphasis on the fibrous asbestos concentration in the air sample of determining to contain asbestos and other fiber selectively in the recent real-time air.Because fibrous asbestos presents the paramagnetic characteristic, so some existing devices preferably adopt for example time dependent electric quadrupole field, mix electric field/magnetic field, or dual-purpose both fibrous asbestos is aimed at and vibration.The vibration that this kind brings out can produce the characteristic that makes the incident light scattering, promptly is asbestos thereby identify the vibration fiber.Also can adopt electrostatic technique.The example that is used to measure this apparatus and method of airblrne particulates concentration can be referring to the U.S. Patent No. 3 that is entitled as " devices of analyzing suspended particles " (Apparatus for Analyzing SuspendedParticles) of following document: Chubb, 692,412 (1972), the U.S. Patent No. 4 that is entitled as " method and apparatus of monitoring asbestos in real time " (Method and Apparatus for Real-timeAsbestos Monitoring) of Lillienfeld, 940,327 (1990), and the U.S. Patent No. 5 of being entitled as of Lillienfeld " determine and delivery air in the system and method for suspended particles concentration " (System andMethod for Determining and outputting Airborne Particle Concentration), 319,575 (1994).Also referring to MIE company (Billerica, FM-7400 type MIE fiber monitor user manual MA) (MIE Fiber Monitor ModelFM-7400 User ' s Manual).

Yet, because comprise such as potential harmful fibers breathed such as glass fibre and do not have the paramagnetic characteristic usually, so these class methods are not suitable for.Thereby, needing the measurement mechanism of suspension fiber concentration in a kind of air, it can accurately determine the fibre concentration breathed that suspends in the air sample in real time, and need not the parts of static, magnetic or hybrid electromagnetic.

In addition, Lillienfeld device more complicated only can be surveyed the fiber of small percentage in the given sample, and if in the sample fibre concentration lower or can not reflect and fibre concentration in the airflow then can produce measuring error.Therefore need a kind ofly in total fiber, carry out the greater amount sampling and the accurate fibre concentration measurement mechanism of reading when low concentration.

The invention provides a kind of apparatus and method that are used for measuring suspension fiber concentration in the air of fibrous air sample.Its preferred embodiment comprises the flow device that is used for providing to air sample at least a portion fiber laminar flow.So available light source is shone these laminar flow fibers to produce scattered light.Then a part of scattered light is surveyed,, measured fibre concentration numerical value according to this output to produce an output.In addition, can adopt the tripping device preliminary election to go out to have the fiber of specific dimensions, can breathe fiber so that for example only measure.The invention provides the inexpensive method of the fiber breathed in a kind of surveying work environment in for example glass interlayer or glass mat manufacturing works.

In more detailed embodiment of the present invention, provide a kind of be used for analyzing having can breathe fiber and can not breathe fiber or non-fibrous particle, the device of the air that perhaps haves both at the same time.This device comprises tripping device, is used for removing selectively and can breathing fiber from breathing fiber, contains the filtered air sample of arranging the good fiber breathed with generation.Then these fibers of arranging are thrown light on to produce scattered light, this scattered light is produced electricity output by the photo-detector collection.This device comprises that also the output that is used for according to photo-detector provides the treating apparatus that can breathe the fibre concentration estimation.

Accompanying drawing this place reference and that constitute this instructions part shows the preferred embodiment of apparatus of the present invention, and with instructions, is used to explain principle of the present invention.

Fig. 1 is the synoptic diagram of suspension fiber apparatus for measuring concentration in the air of the present invention.

Fig. 2 is a preferred embodiment synoptic diagram of detector of the present invention.

Fig. 3 is another preferred embodiment synoptic diagram of detector of the present invention.

Fig. 1 shows an embodiment of suspension fiber apparatus for measuring concentration 100 in the air in accordance with the principles of the present invention.Device 100 comprises the detector 1 that is used for surveying fiber and is used for from breathing fiber or the non-fibrous particle material is isolated the tripping device that can breathe fiber, for example virtual impactor 2.Term used herein " can be breathed fiber " and be meant the fiber of diameter less than about 3 μ M, refers in particular to those aspect ratios at least about 5: 1 (length: fiber diameter).In addition, term " light " had both referred to that electromagnetic visual also refers to invisible electromagnetic wave, comprised X ray and infrared ray.

The technician can find that virtual impactor 2 can adopt known technology can breathe particle and can not breathe particle separation, and therefore, the technician can adopt other tripping device can breathe fiber and separate from breathing the fiber.Fig. 1 shows an illustrative virtual impactor 2, has known that it is suitable for.This device is drawn fibrous surrounding air, and a Venturi nozzle is from the side discharged the less fiber breathed 21.Greater than the big fiber 41 of about 3 μ m, be inhaled into the central pipeline of virtual impactor 2.

Usually, the air that enters this device can have and can breathe fiber, can not breathe fiber and other particle object of sneaking into.Detector 1 is preferably surveyed the fiber breathed of airborne adjusted direction, but insensitive substantially to other non-fibrous particle object.The fiber breathed 20 that may contain in the air in operation, is evacuated to detector 1 from virtual impactor 2 by the flexible pipe 3 that connects empty knocker 2.Air is evacuated to the outlet 4 of low stream pipe 6 by system by a small vacuum pump 22.Air mass flow, higher and low stream are managed 5,6 length and diameter, are preferably the laminar flow that makes it possible to produce by managing 5,6.This lamina air flow is easy to make in the air in the

pipe

5,6 fiber 20 basic consistent with airflow direction, thereby consistent with the longitudinal axis 30 directions of managing 5,6.

Stream pipe

5,6 preferably separates a little gap 7 in detector 1.Perhaps, also can adopt single pipeline with a pair of notch that passes sidewall perpendicular to it.Gap 7 preferably is set to axle 8 symmetries along detector 1.

Stream pipe

5,6 and gap 7 constitute " flow channel " of this embodiment of the present invention.

A light source 9 is arranged in detector 1, and light source 9 can be coherent source, for example diode laser.Light source 9 can produce light beam 12, preferably has previously selected cross section along light path.Light source 9 preferably produces collimated light beam, and comparatively ideal is to have oval cross section at photo-detector 14 places.Photo-detector 14 is preferably photodetector.Light beam 12 can be aimed at along the axle 8 of detector 1, and the main shaft of elliptical beam is preferably substantially parallel with the gap 7 of managing between 5,6.The width of light beam 12 needn't be equally wide with the diameter of

stream pipe

5,6.

The suitable light source of this embodiment can be LPM03 (670-5) the type laser diode of for example being made by the PowerTechnology company of Arkansas State Little Rock.The same photodetector that is suitable for can be the Devar Model 509-1 of for example Connecticut State Bridgeport.Those skilled in the art can adopt other light source and photo-detector of being fit to, to provide and to survey indication and can breathe the light signal that fiber exists.

Fig. 2 shows the sectional view of preferred detector 1, and this detector is traditionally arranged to be perpendicular to airflow.After passing through gap 7, light beam 12 is incident to an optical lens group 10.Lens combination 10 can be for example a pair of convergent lens.This lens combination credit union has short focal length, makes the rear surface 24 of a part 23 directives second lens 25 of light beam 12.Can adopt light intercepting member 11 and light beam 23 can not be surveyed by photodetector 14 so that block collimated light beam 23 basically.Light intercepting member 11 preferably is positioned at concealment place with respect to photodetector 14, makes light intercepting member 11 to be covered the light beam that light is not indicated the fiber existence of being surveyed by photodetector 14.

As shown in Figure 2, along with the light beam 12 between the fiber 20

logical flow tubes

5,6, part fiber 20 can make beam divergence.When the light beam vertical incidence is for example shone the glass fibre cylinder, this right cylinder generally in flow channel with this light beam of predetermined direction scattering, promptly along in-plane scatter perpendicular to cylinder.Because fiber 20 has been adjusted direction by lamina air flow, so these fibers 20 are all along the direction orientation perpendicular to light beam 12.Therefore, light beam 12 meetings are along a substantially parallel in-plane scatter in plane that constitutes with the end of

stream pipe

5,6, thus the gap 7 that allows scattered light 26 to lead between the

flow tubes

5,6.

For laminar flow of the present invention, it is generally acknowledged and to satisfy two conditions.These two conditions are, Reynolds number should be less than about 2000, and must have the abundant distance that makes air-flow become laminar flow.In the situation of claimed device, the air-flow of the fibre diameter of about 4 liters/minute and 0.44 inch (1.1cm) has constituted about 500 Reynolds number, and this air-flow can enter laminar condition well.Stream length of tube before fiber arrives the laser beam place is about 5-50 inch (12.7-127cm), is preferably about 10 inches (25.4cm), and this is more than 22 times of fibre diameter.Because laminar flow should be set up in 10 diameter ranges of stream tube inlet, so the air-flow in this device should have the enough time to set up laminar flow condition.

Can carry out visual definite for the adjustment direction of transition period fiber between turbulent flow and the laminar flow.Can see: be at glass fibre under the situation of turbulence state, the diffraction laser beam is separated into the separation hot spot along any direction; And be at glass fibre under the situation of laminar condition, the diffraction laser beam is roughly assembled along a direction (zone), thereby shows that fiber is along the direction aligning that is basically parallel to air-flow.

Light beam along working direction 13 scatterings can gather and focus on the photodetector 14 by lens combination 10.Because this light beam is general not collimation when it enters lens combination 10, thus can on the point of a distance after the lens combination 10, focus on, thus walked around light intercepting member 11.Therefore, when light beam 12 and scattered light 26 were incident to lens combination 10, light beam 12 was generally blocked, and can not be incident upon on the photodetector 14, and scattered light 26 overwhelming majority focuses on the photodetector 14.Generally speaking, have only sub-fraction scattered light 26 to be blocked by light intercepting member 11.

Photodetector 14 preferably has the sensitizing range of finite width, and its width is enough to receiving scattered light 26.In this width, photodetector 14 in response to by the axle a distance, 30 both sides that is positioned at

stream pipe

5,6 with and the light of preceding and thereafter 20 scatterings of fiber.Therefore, fiber 20 need not single-row by light beam 12 or aim at closely with axle 30.When light beam 12 during by fiber 20 scatterings, this light beam scioptics group 10 focuses on also and is incident on the photodetector 14, thereby produces main electronic impulse by it.The amplitude of this pulse is preferably the light quantity that is proportional to by fibre scattering usually.The pulse that is produced can be sent to suitable electronic measurement circuit 31, and this circuit is noted pulse.Utilize other quantitative signal, for example pass through the air mass flow of detector 1, and the speed of definite received pulse, the concentration that can breathe fiber in the air can be measured.

Detector 1 is preferably insensitive to the non-fibrous particle object substantially.The preferred embodiments of the present invention are finished this selection by the optics difference of analyzing for example general column and can breathing between the particle object of fiber and other shape.That is to say, if sucked spherical or erose dust granules in the detector 1, the also light of scattered beam 12 of this particle object then.Yet this kind particle can be along spherical space with beam divergence.Most of this kind scattered light with the tube wall of

directive stream pipe

5,6 and by absorption.

Usually, have only sub-fraction can lead to gap 7 between the

flow tube

5,6 by the light beam of these particle scatterings.This very small amount of scattered light only can produce a weak signal in photodetector 14.Circuit 31 from photodetector 14 received pulses can be designed to ignore the pulse by a narrow margin that causes by the particle object.Therefore, can make device 100 only in response to can breathing fiber, and ignore other non-fibrous particle object that may exist.The device that is different from prior art, the present invention need not to adopt static or electromagnetic component to make levitated object generation motion in the air, so that determine whether this object is to breathe fiber.

In fact, device 100 is distinguished the ability that can breathe fiber and other particle and can be selected to utilize following principle.At first, before air enters detector 1, be that virtual impactor 2 is removed the fiber that can not breathe from air-flow by tripping device.The second, residual fiber can be consistent with stream tubular axis 30 directions by the lamina air flow of logical flow tube 5,6.The 3rd, light beam 12 is oriented to the optical axis perpendicular to stream

pipe

5,6 usually.The 4th, tend to along the in-plane scatter between the end of

logical flow tube

5,6 by the light of fiber 20 scatterings, and a part of scattered light focuses on the photodetector 14.The 5th, tend to than by the situation of cylinder scattering non-directional more by the light of other particle scattering.This kind of overwhelming majority light is absorbed by the tube wall of

stream pipe

5,6, only has sub-fraction light still to focus on the photodetector 14.The 6th, by distinguishing the amplitude of the signal that is received by photodetector 14, device 100 can be distinguished fiber and other particle.

In Fig. 1 and 2, lens combination 10 is shown as and light beam 12 almost coaxials or relative with photodetector 14.Consider instruction of the present invention, the technician can find that lens combination 10 and photodetector 14 can place any place of the axle 30 that encloses by-

pass

5,6, as long as they are still in the beam plane of 20 scatterings of fiber.Though the light quantity that lens combination 10 is assembled depends on the position of lens combination 10, detector 1 still can be distinguished by these alternative structure can breathe fiber and other particle.

For example, in Fig. 3, except lens combination 10 and photodetector 14 along the 90 degree directions rotations, basic identical among the parts of device 100 and Fig. 1 and 2.Also be in Fig. 3, the light intercepting member 11 shown in Fig. 1 and 2 has been removed, because light path 12 is no longer coaxial or relative with photodetector 14.

All publications of mentioning in this instructions are all represented those skilled in the art in the invention's technical merit.All these publications are hereby incorporated by to a certain extent, need incorporated by reference especially individually but its degree is equivalent to each single publication.

Implement specific embodiment of the present invention though describe in detail, one skilled in the art will appreciate that prompting, can make multiple change and alternative these details according to the whole instruction of this instructions.In fact, the technician can find, although the present invention is described with regard to the fibre concentration breathed that suspends in determining air, the apparatus and method of Xiang Ximiaoshuing can be used to survey, discern and manifest the particle that other has certain optical properties herein.Therefore, the special arrangement of disclosed method and apparatus is just illustrative, not delimit the scope of the invention, and its scope is provided by the whole extension of claims and whole embodiment thereof.

Claims

1. device 100 that is used for measuring in the suspension fiber the breathed concentration of the air sample that contains fiber is characterized in that described device 100 comprises:

A. flow device is used for providing laminar flow to described air sample at least a portion fiber;

B. flow channel 5,6, are used to receive a large amount of laminar flow fibers 20;

C. light source 9, are used to produce light beam 12, and the described a large amount of laminar flow fibers 20 of directive are to produce scattered light; With

D. photo-detector 14, are used to survey a part of described scattered light and produce an output, measure the numerical value of the fibre concentration breathed in the described air sample according to this output.

2. device as claimed in claim 1 wherein also contains in the sampled air and can not breathe fiber and non-fibrous particle object.

3. device as claimed in claim 1, wherein said device have a slit opening, for the described photo-detector of scattered light directive provides passage.

4. device as claimed in claim 1, wherein said light source comprises collimator apparatus, is used to provide the light beam that has predetermined cross-sectional along light path.

5. device as claimed in claim 4, wherein said flow channel has the longitudinal axis of the light path of being basically perpendicular to.

6. device as claimed in claim 3, wherein said slit opening is set to shield the scattered light that does not have towards the predetermined direction of photo-detector.

7. device as claimed in claim 6 also comprises an optical lens, is used to receive a part of scattered light with predetermined direction and with this scattered light direct light detector of at least a portion.

8. device as claimed in claim 7 also comprises a light intercepting member, is arranged in the light path of described light beam, and setting plays the concealment effect to described light intercepting member to photo-detector, and this light intercepting member blocks light beam substantially and enters photo-detector.

9. device as claimed in claim 1, wherein said photo-detector comprises the device that is used to produce first light pulse and second light pulse, wherein first light pulse has first amplitude that representative can be breathed fiber, second light pulse has non-second amplitude of breathing the particle of fiber of representative, described device can be distinguished and describedly breathe first amplitude of fiber and second amplitude of described particle, and provides a representative can breathe the signal of fibre concentration.

10. device as claimed in claim 9, wherein said particle is for can not breathe fiber.

11. a measurement contains the method for suspension fiber concentration in the fibre-bearing air sample that can breathe and can not breathe fiber, it is characterized in that:

A. at least a portion fiber provides laminar flow in described air sample, contains in the described part can breathe and can not breathe fiber;

What b. light beam is directed to described laminar flow breathes and can not breathe fiber to produce scattered light; And

C. survey a part of described scattered light and produce an output, draw the numerical value that to breathe fibre concentration according to this output.

12. method as claimed in claim 11, wherein said detection steps comprises, provide respectively corresponding to detecting from first and second pulse signals that can breathe and can not breathe the light beam of fiber, described first and second pulse signals have first and second amplitudes, and described method also comprises distinguishes described first and second amplitudes so that the signal of a fibre concentration breathed in the described air sample of representative to be provided.