JPH025244B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a β-ray transmission type dust meter, and more specifically, the gas flow path to be measured is formed flat, and
By installing the material at an angle from one wall in the thickness direction of the channel to the opposite wall, the distance between the β-ray source and the β-ray detector is shortened, which significantly improves measurement accuracy. Concerning an improved dust meter.

Conventionally, the method of measuring the concentration of dust in the atmosphere using β-rays involves passing the air through a tape-shaped paper and collecting the dust in the atmosphere on the surface of the paper. There is a method of measuring the degree of attenuation and calculating the dust concentration from this. In other words, this method uses the following equation (1) between the transmitted β-ray intensity and the thickness of the collected dust.
This is an application of the fact that the relationship holds true.

I = I ₀ exp (-μX) ...... (1) where I: β-ray intensity transmitted through paper and dust I ₀ : β-ray intensity transmitted only through paper μ: Mass absorption coefficient (cm ² /g) X: Dust amount (g/cm ² ) Further, the dust concentration in the atmosphere is expressed by equation (2).

C=A/μQt1nI ₀ /I (2) where A: Collection area (cm ² ) Q: Passing flow rate (cm ³ /min) t: Collection time (min) C: Dust concentration (g/ cm ³ ) Therefore, by actually measuring the transmitted β-ray intensities I ₀ and I before and after dust collection, the dust concentration in the atmosphere can be determined from equation (2). It is possible to carry out continuous measurement, that is, the collection of dust and the measurement of the amount of dust by β-ray transmission can be carried out simultaneously in parallel, and the flow path of the gas to be measured is formed in a straight line, that is, the flow path of the gas to be measured is linear. If there are bends in the flow path, dust will settle there and cause measurement errors, so the structure should avoid bends in the flow path, and the distance between the β-ray source and the detector should be short. This means that β reaching the detector
Increasing the dose to reduce statistical errors in measurements or allowing the use of sources with small beta doses, having fewer moving parts, i.e. in collecting dust, measuring transmitted beta doses, etc. In order to improve measurement accuracy, it is desirable to perform these operations without moving the material, the β-ray source, and the detector, and to prevent measurement errors caused by these movements.

However, in conventional dust meters, these ~
There is no one that can satisfy all of the conditions, and each has its advantages and disadvantages. That is, FIGS. 1 to 4 respectively show conventional dust meters. Among these dust meters, in the dust meter shown in FIG. The paper a is then irradiated with the β rays emitted from the β ray source e, and the transmitted β ray intensity
I ₀ is measured by the β-ray detector f and stored. Next, the paper a is rewound, and the portion of the paper that has been irradiated with the β-rays and whose transmitted β-ray intensity I ₀ has been measured is attached to the cover c. Thereafter, the suction pump is activated, and atmospheric air is sucked downward (in the direction of arrow P in the figure) through the suction pipe g, whereby dust in the atmosphere is separated by the paper a. Next, the paper is fed out again, and after the excess portion is moved to the measurement section d, the β-ray intensity I that has passed through the paper and the deposited dust layer is measured, and the thus determined I ₀ and I, the dust concentration C is calculated using equation (2). In addition, h is a pinch roller, i
is a capstan and j is a take-up roll.

In the case of the dust meter shown in Fig. 2, paper a is unwound from roll paper b, and after the transmitted β-ray intensity I ₀ of paper a is measured in measuring section d, it is sent to passing section c. This is where the atmosphere passes. Then,
The measuring part d is rotated 180 degrees around the axis of the suction tube g, and the measuring part d is moved to the position shown by the two-dot chain line in the figure, and the paper a is also moved, and the paper a and the dust are removed at the position shown by the chain line. β transmitted through the layer
Linear intensity I is measured, and dust concentration C is calculated from I ₀ and I obtained in this way using equation (2).

In both of the above-mentioned dust meters, moving the same part (over part) of paper a to measuring part d and over part c with good reproducibility is a necessary condition for accurately measuring the amount of dust. On the other hand, it is quite difficult to do so, and there is a problem in that the deviation between the above-mentioned measurement positions and the suction position that occurs when the paper is moved directly causes measurement errors.

A dust meter shown in FIG. 3 or 4 is known as a device that solves the above problem. In the dust meter shown in Fig. 3, atmospheric air is sucked by a pump k and flows into a suction pipe g, and after dust is separated by a paper a, it passes through a β-ray irradiation path l, and is further passed through a discharge pipe m. is discharged from the system through. The dust n separated in this way and deposited on the upper surface of the paper a is irradiated with β-rays emitted from the β-ray source installed at the bottom of the irradiation path, and the transmitted β-ray intensity I is the same as that of the β-ray source e. The dust concentration is detected by the detector f disposed above, but if the transmitted β-ray intensity I ₀ for only paper a is measured in advance before operating the pump k, the dust concentration will be equal to the above I ₀ and It can be calculated from I, and in this case
Since there is no movement of the paper during the measurement of I _{0 and} I, it is unlikely that a measurement error would occur due to a shift in the measurement position of the paper caused by movement of the paper, as in the former two dust meters. However, in the case of this dust meter, air is supplied into the irradiation path 1 from the side of the irradiation path 1 almost parallel to the paper a and passes through the paper a, so that a dust layer n is not formed on the paper a. Easy to deposit evenly.
Moreover, since the atmosphere is supplied from the side of the irradiation path l, the distance between the β-ray source e and the detector f becomes large. For this reason, there is a problem that measurement accuracy is reduced, and since the structure is such that the atmosphere is discharged to the outside through the irradiation path 1, the irradiation path is easily contaminated by fine dust. Therefore, it is necessary to periodically clean this dirt, but this is a complicated process, and furthermore, cleaning is difficult to perform simply due to its structure.

Furthermore, the dust meter shown in Figure 4 has almost the same structure as the dust meter shown in Figure 3, except that it has a β-ray source e' for comparison, and therefore has the same problems as the dust meter shown in Figure 3. It has points. In addition, o in Fig. 4 is β
Ray-transparent metal thin film, p is amplifier, q is recorder, r
is a particle sizer.

The present invention was developed in view of the above circumstances, and addresses the mutually contradictory structural requirements of performing measurements without moving the material and shortening the distance between the β-ray source and the detector. It is an object of the present invention to provide a dust meter with high measurement accuracy, which is solved by forming a gas flow path to be measured flat and installing a material in the flow path inclined in the flow direction.

An embodiment of the present invention will be described below with reference to FIGS. 5 to 7.

1 in Figure 5 is a material wound into a roll,
The material 1a unwound from the roll-shaped material 1 is supplied to a detection section 2 disposed forward in the direction of movement (direction of arrow A in FIG. 5). This detection part 2 is formed using a rectangular parallelepiped-shaped metal block main body 3, and this block main body 3 is cut obliquely from the lower part of one side wall to the upper part of the opposite side wall. It can be separated into an upper block 3a and a lower block 3b.

Further, as shown in FIGS. 6 and 7, in the block main body 3, there is a measured gas flow path 4 having a rectangular cross section that passes through the block main body 3 from the center of one side wall to the center of the opposite side wall. The flow path 4 is formed with the width direction being horizontal, and inside the block main body 3, this flow path 4 intersects with the cut surface on which the blocks 3a and 3b were formed. One end of a sampling pipe 5 is connected to the flow path 4 at one side wall of the block main body 3, and the other end (not shown) of the pipe 5 is arranged at a sampling location of the gas to be measured. Furthermore, one end of a suction pipe 6 is connected to the flow path 4 on the other side wall of the block main body 3, and the other end of the suction pipe 6 is connected to a suction portion of a suction pump 7. Note that 8 is a discharge pipe connected to the discharge section of the suction pump 7.

The block main body 3 has a large diameter β-ray source holder insertion hole 9 and a detector insertion hole 10 perforated along the vertical direction from the center of its upper and lower surfaces, respectively. The bottom wall 9a and the top wall 10a are formed thin. Further, a through hole is formed in the center of the bottom wall 9a and the top wall 10a of both the insertion holes 9, 10 along the vertical direction, thereby forming a β-ray irradiation path 11. The β-ray irradiation path 11 further intersects the intersection of the flow path 4 and the joint surface of the upper and lower blocks 3a, 3b.

A β-ray source holder 13 having a β-ray source 12 attached to its lower end surface is inserted into the insertion hole 9,
The β-rays emitted from the β-ray source 12 pass through the irradiation path 11.
irradiated inside.

Further, a β-ray detector 14 is inserted into the detector insertion hole 10 with its detection surface 15 facing the β-ray source 12.
The β-ray intensity emitted from the radiation source 12 and reaching the detector 14 through the β-ray irradiation path 11 is measured, converted into an electrical signal corresponding to the β-ray intensity, and sent to the electrical section 16.

The material 1a supplied to the detection section 2 having the above structure
The block main body 3 has an upper block 3a and a lower block 3b along the direction from the lower part of one side wall to the upper part of the other side wall.
The flow path 4 is covered by this. When moving the material 1a, the blocks 3a and 3b are opened vertically, the material 1a is moved, and then the space between the blocks 3a and 3b is closed. In this case, the flow path 4
In order to maintain airtightness, known means such as using rubber packing are employed.

Next, the material 1a passes between the pinch roller 17 and the capstan 18 and is wound onto the take-up roll 19, and the movement of the material 1a is performed by the pinch roller 17 driven under the control of the electric section 16. It will be done. Note that 20 is a display unit connected to the electrical unit 16, on which measurement results and the like are displayed.

Next, to explain the case of continuously measuring the dust concentration in the atmosphere using the above-mentioned dust meter, first, with the other end of the sampling pipe 5 installed at the air sampling location to be measured, the β-ray source 12 β is emitted from the beam, passes through the material 1a, and reaches the detector 14.
The line intensity is measured and this measured value I ₀ is temporarily stored in the electrical section 16 . Thereafter, the suction pump 7 is activated and atmospheric sampling is started. That is, the air sucked from the other end of the sampling pipe 5 flows into the flow path 4 formed in the block main body 3 from one side wall of the block main body 3, and moves inside the flow path 4 toward the other side wall. At this time, the material 1 is stretched in the flow path 4 with an upward slope along the flow direction of the atmosphere inside the flow path 4.
a, dust in the atmosphere is separated and a deposited dust layer 21 is formed on the upper surface of the material 1a, but in this case, since the material 1a is stretched with an upward slope, the deposited layer is approximately square. is formed. Next, the atmosphere from which the dust has been separated by the material 1a is
It further moves through the flow path 4, flows into the suction pipe 6, passes through the pump 7, and is discharged to the outside from the discharge pipe 8. When the pump 7 operates for a predetermined period of time and a predetermined amount of air is sucked in, the pump 7 is stopped and the air sampling is stopped, but the air sampling continues continuously from the time the air sampling starts to the time it stops. The β-ray intensity I from the β-ray source 12 that passes through the material 1a and the dust deposit layer 21 and reaches the detector 14 is measured and continues to be stored in the electrical section 16, and the obtained measurement value I is sent to the electrical section 16, where the measured value is stored in advance.
The dust concentration is calculated by the above formula (2) using I ₀ ,
It is displayed continuously on the display unit 20. Thereafter, the blocks 3a and 3b are moved up and down to separate them from each other, and the pinch roller 17 is driven.
Material 1a is forward in the direction of travel (direction of arrow A in Figure 5)
move a predetermined distance. As a result, the deposited layer 21 is moved outside the channel 4, and a new part of the material on which no dust is deposited is supplied into the channel 4, and in this state, the gap between the blocks 3a and 3b is closed. Return to initial state. Thereafter, similar operations are repeated to continue measuring the dust concentration, but all these operations are automatically performed according to instructions from the electrical section 16.

In the dust meter of this embodiment, the cross-sectional shape of the gas flow path 4 to be measured is formed into a flat rectangular shape, so that the distance between the β-ray source 12 and the detection surface 15 of the detector 14 can be shortened. The β-ray intensity (corresponding to the number of counts per unit time, etc.) reaching 15 is significantly increased, which reduces statistical errors during measurement and significantly improves measurement accuracy. Furthermore, since the material 1a is stretched upwardly from the lower wall surface to the upper wall surface of the flow channel 4, the excess area is wider than when the material is stretched perpendicularly to the flow channel. Therefore, fluctuations in suction pressure due to dust deposition are less likely to occur. For this reason, the amount of air suction does not vary significantly between the start and end of suction, and the amount of air suction can be always constant. This can be prevented and measurement accuracy can be improved. Furthermore, in the detection unit 2 of this dust meter, the flow path 4 is formed in a straight line and is not bent, so there is no accident such as dust depositing on the bends in the flow path, and dust is not deposited in the flow path. move material 1 uniformly.
A uniform deposited layer 21 is formed on the surface. Therefore,
The β-ray intensity measured by passing through the uniform deposited layer 21 accurately corresponds to the amount of deposited, and therefore the amount of dust can be measured with high accuracy.

Although the channel 4 is formed to have a rectangular cross section in this embodiment, it can also be formed to have various flat cross-sectional shapes such as an elliptical or elliptical cross section. In the irradiation path 11, the opening end of the irradiation path 11 may be closed with a β-ray transparent thin film to prevent dust and the like from entering the irradiation path 11.

In addition, the β-ray source 12 is attached to the upper block 3a and the detector 14 is attached to the lower block 3b to irradiate downward with β-rays; however, the β-ray source 12 can be attached to the lower block 3b. , and detector 1
4 may be attached to the upper block 3a, and furthermore, although the channel 4 and the irradiation channel 11 are arranged to intersect at right angles, the present invention is not limited to this. Although the transmitted β-ray intensity is measured while suctioning and the amount of deposited from moment to moment is continuously measured, it is also possible to measure after the completion of dust deposition or at predetermined time intervals. Various modifications may be made without departing from the gist.

Therefore, the present invention includes a β-ray source, an irradiation path for β-rays emitted from the β-ray source, a material supplied to the irradiation path, and a detector for detecting the amount of β-rays transmitted through the material. , an electric part that processes and outputs the signal detected by the detector, and a gas flow path to be measured that intersects the material, and the gas to be measured flowing through the gas flow path through the material is passed through the gas flow path. Collecting suspended dust in the gas to be measured, and detecting the amount of attenuation of material-transmitting β rays due to the collected dust with the detector,
In a β-ray transmission dust meter that determines the amount of suspended dust in the gas to be measured by processing and outputting this detection signal in an electric section, the flow path for the gas to be measured is formed flat, and the flow path is A material is stretched in an inclined manner from one wall in the thickness direction to the other wall opposite to it so as to block the flow path, and the irradiation path is made to intersect with the flow path at the stretched portion of the material to increase the thickness of the flow path. Since it is connected to both walls in both directions, the distance between the β-ray source and the detector can be shortened, and since the material is inclined with respect to the direction of the flow path, the overarea is expanded and the influence of pressure fluctuations due to the deposited layer is reduced. Can be minimized. Therefore, the measurement accuracy of the dust concentration meter of the present invention is significantly improved.

[Brief explanation of drawings]

1 to 4 are explanatory front views showing a conventional dust meter, respectively. FIG. 5 is a front view showing an embodiment of the present invention. FIG. FIG. 7 is an enlarged side view of the detection section. 1a... Material, 4... Gas flow path to be measured, 7...
Suction pump, 11...β-ray irradiation path, 12...β-ray source, 14...detector, 15...detection surface, 16...
Electrical part, 21...Deposition layer.

Claims (1)

[Claims] 1. A β-ray source, an irradiation path for β-rays emitted from the β-ray source, a material supplied to the irradiation path, and a detector for detecting the amount of β-rays transmitted through the material. , an electric part that processes and outputs the signal detected by the detector, and a gas flow path to be measured that intersects the material, and the gas to be measured flowing through the gas flow path through the material is passed through the gas flow path. At the same time as collecting suspended dust in the gas to be measured, the detector detects the amount of attenuation of β-rays passing through the material due to the collected dust, and this detection signal is processed by the electric section and output. In a β-ray transmission type dust meter that determines the amount of suspended dust in a gas, the flow path of the gas to be measured is formed flat, and the flow path is blocked from one wall in the thickness direction of the flow path to the other wall opposite to this. The β-ray irradiation path and the β-ray detection path intersect with the flow path and are connected to both walls in the thickness direction of the flow path at the stretched portion of the material. β-ray transmission type dust meter. 2. The dust meter according to claim 1, wherein the cross-sectional shape of the gas flow path to be measured is rectangular, oval, or elliptical.