Measuring and testing – Specific gravity or density of liquid or solid
Patent
1982-10-15
1985-03-26
Ruehl, Charles A.
Measuring and testing
Specific gravity or density of liquid or solid
7386102, 250308, 2503581, G01N 924
Patent
active
045065411
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the determination of the combined bulk density of material being in the form of either a gas, a vapour, an aerosol, or particulate solids suspended in a gas (for example; dust). The term combined bulk density refers to the density of the material when viewed as a whole. For example, in the case of suspended solids in a gas, cognizance is taken of the volume between the particles of material as if it were part of the composition.
The invention was devised primarily to monitor the combined bulk density of powdered coal in flow streams of coal entrained with air and/or other gases. Thus, the invention is described primarily with reference to that application but it will be appreciated that it is applicable to the measurement of the combined bulk density of other materials generally in the aforementioned form.
Hitherto, one technique for determining the combined bulk density of such material, has been to beam beta radiation from an isotope source through a predetermined thickness of the material to a radiation detector.
The extent to which the beam of radiation is attenuated by the material is determined by the detector which detects the residual radiation of the beam which is related to the bulk density of the material. In any particular application the calibration of the apparatus is either: density (often zero); has been determined by more fundamental but less convenient measurement.
The maximum sensitivity of such an apparatus is obtained using the aforementioned classical relationship. This is only true, however, if a collimator is used on either the source and/or detector to minimise the amount of scattered radiation being detected. Sensitivity varies according to the quality of the collimator and rarely could the classical equation be used without modification by a more practical method of calibration. In addition, because of the inevitable inefficiency of collimators, some of the residual radiation that would otherwise follow the classical attenuation relationship is absorbed by the collimator and thus is not detected. This in turn reduces the precision with which the determination of combined bulk density could be made within a certain time period according to the theory of radiation detecting statistics and assuming all other aspects of the apparatus remain unchanged.
The foregoing technique suffers from the fact that the narrow beam of radiation intersects only a small sample of the material and thus is liable to error if that sample is not representative of the material as a whole.
The present invention seeks to overcome the above indicated disadvantages by very simple means.
According to the invention a bulk density measuring apparatus is provided comprising uncollimated radiation source means, uncollimated radiation detector means spaced from said source means to measure radiation received therefrom, containment means for the material of which the density is to be determined such that a charge of the material within said containment means occupies the space between the source means and detector means, and a radiation opaque shield positioned to prevent direct radiation from the source means reaching the detector means.
Thus instead of detecting the intensity of the original radiation less the attenuated radiation, the detector of apparatus in accordance with the invention detects only scattered radiation and, due to the diffuse scatter path, the radiation reaching the detector has been affected by a much larger volume of the material than is the case in prior art apparatus.
Once again the apparatus is calibrated before use against samples of a material of predetermined bulk density.
In preferred embodiments of the invention the radiation source and detector are mounted externally of the containment means and the radiation travels from one to the other through radiation transparent windows in the wall or walls of the containment means.
In some instances, the containment means may be a duct through which a stream of the material is caused to flow and in such instances the
REFERENCES:
patent: 2925007 (1960-02-01), Silver
patent: 3300640 (1967-01-01), Eubank
patent: 3654109 (1972-04-01), Hohl
patent: 4053229 (1977-10-01), McCluney
patent: 4072421 (1978-02-01), Coyne
patent: 4178103 (1979-12-01), Wallace
patent: 4210809 (1980-07-01), Pelavin
patent: 4282433 (1981-08-01), Loffel
Kovalick Vincent P.
Mount ISA Mines Limited
Ruehl Charles A.
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