Apparatus and method for detecting a corrosive substance leak in a chemical composition analyzer

An apparatus includes a detection element having a detection element property that changes when exposed to a corrosive substance, a testing device coupled to the detection element, the testing device configrued to measure the detection element property, and a processor in communication with the testing device, the processor configured to indicate the presence of the corrosive substance using the detection element property. In an embodiment, the detection element is metal and the detection element property is resistivity. In another embodiment, the apparatus further includes a comparison element coupled to the testing device and shielded from the corrosive substance, the comparison element having a comparison element property, and wherein the processor is configured to compare the detection element property to the comparison element property to determine whether the detection element property is within a predetermined range of the comparison element property. A method of detecting the corrosive substance is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

BACKGROUND

A chemical composition analyzer is a device that analyzes a material to determine the composition of the material. One common type of chemical composition analyzer is a gas chromatograph, which comprises a chromatography tube and a chromatograph detector. The chromatography tube is a long, thin tube that is typically coiled within the gas chromatograph. An inert gas carries a sample of the material along the chromatography tube, where the sample breaks up into different molecules. The molecules have different molecular weights and pass through the chromatography tube at various rates, such that the lighter molecules exit the chromatography tube before the heavier molecules. As the molecules exit the chromatography tube, they are analyzed by the chromatograph detector to determine the abundance and molecular weight of each type of molecule. The chromatograph detector, known to one skilled in the art, is connected to a data output device, such as a monitor, printer or computer, that displays the results of the sample analysis. The results of the sample analysis are generally in the form of a chromatogram, which is a chart that has time on the X-axis, the abundance (typically measured in millivolts) on the Y-axis, and a variable-height line with one or more peaks graphed on the two axes. Scientists and engineers can determine the chemical composition of the sample based on the data in the chromatogram. Alternatively, the gas chromatograph can be configured to automatically determine the chemical composition of the sample based on the data in the chromatogram.

Oftentimes, chemical composition analyzers, such as a gas chromatograph, are used to determine the composition of corrosive substances. The corrosive substances are generally kept within the internal plumbing of the gas chromatograph, such as the chromatography tube, chromatograph detector, and various valves and tubes. However, the corrosive substance will occasionally leak from the internal plumbing and corrode the internal components of the gas chromatograph, such as the circuits and control mechanisms. Although it may take days or even weeks for the corrosive substance to permanently damage the internal components of the gas chromatograph, when a corrosive substance leak occurs, it is rarely detected before the internal components are damaged. Corrosive substance leaks are rarely detected before the internal components are damaged because the gas chromatograph is examined or serviced infrequently, such as when one of the internal components fails or requires maintenance. The infrequency of service is due to the complex nature of the gas chromatograph and the necessity of maintaining an air-tight housing for some gas chromatographs. If there were a device that detected the corrosive substance leak, particularly during operation of the gas chromatograph, then the leak could be repaired and the corrosive substance removed from the chemical composition analyzer such that failure of the internal components could be avoided. Consequently, a need exists for an apparatus for detecting a corrosive substance leak in a chemical composition analyzer, particularly while the chemical composition analyzer is fully operational.

DETAILED DESCRIPTION

FIG. 1is a block diagram of one embodiment of a chemical composition analyzer, specifically a gas chromatograph, incorporating the invention. As with a traditional gas chromatograph, the gas chromatograph100of the present invention comprises a chromatography tube102and a chromatograph detector104. However, the gas chromatograph100shown inFIG. 1has been modified to include the present invention, which includes a detector106. The detector106detects the presence of a corrosive substance (not shown) in the interior of the gas chromatograph100and uses a data output line124to indicate the presence of the corrosive substance so that remedial action can be taken. Of course, persons of ordinary skill in the art will appreciate that the present invention includes chemical composition analyzers other than those specifically described herein and that the present invention should not be limited to the chemical composition analyzers described herein.

FIG. 2Ais a schematic section view of one embodiment of the detector106of the present invention. The detector106shown inFIG. 2Acomprises a testing device110, a detection element112, a comparison or control element114, a processor116, the data output line124, and a memory118. The memory118comprises a detector evaluation program200and optionally a history120. As explained in further detail below, the detection element112has a detection element property that can be measured by the testing device110. The detection element property changes when the detection element112is exposed to the corrosive substance (not shown). Similarly, the control element114has a control element property that can also be measured by the testing device110. However, the control element property does not change when the control element114is exposed to the corrosive substance. As explained in further detail below, the detector106shown inFIG. 2Auses the differences between the detection element property and the comparison element property to determine whether the corrosive substance exists in the gas chromatograph100.

FIG. 2Bis a schematic section view of an alternative embodiment of the detector106of the present invention. Similar to the embodiment of the detector106shown inFIG. 2A, the detector106shown inFIG. 2Bcomprises the testing device110, detection element112, processor116, data output line124, and memory118comprising the detector evaluation program200and optionally the history120. However, unlike the embodiment shown inFIG. 2A, the embodiment shown inFIG. 2Bcontains a comparison data122and does not contain the comparison element. Thus, the detector106shown inFIG. 2Bdoes not use the difference between the detection element property and the comparison element property to determine whether a corrosive substance exists within the gas chromatograph100. Instead, as explained in further detail below, the embodiment of the detector106shown inFIG. 2Bcompares the detection element property to the comparison data122to determine whether a corrosive substance exists in the gas chromatograph100. Of course, persons of ordinary skill in the art will appreciate that the present invention includes detectors other than those specifically described herein and that the present invention should not be limited to the detectors described herein.

The detection element112detects the presence of the corrosive substance in the gas chromatograph100. The detection element112is exposed to the interior of the gas chromatograph100such that the detection element112reacts with the corrosive substance if the corrosive substance exists within the interior of the gas chromatograph100. Preferably, the corrosive substance reacts with the detection element112prior to and/or at a faster rate than the other internal components of the gas chromatograph100, such as the chromatography tube102, chromatograph detector104, circuits (not shown), controllers (not shown), and the other elements of the detector106. In an embodiment, the detection element112may be made of a highly reactive metal material, such as copper or aluminum. In another embodiment, the detection element112may be made of a material that changes color when it reacts with the corrosive substance, such as litmus paper or other types of chemical indicators. Further in the alternative, the detection element112may be made of a material that changes optical properties when it reacts with the corrosive substance, such as a fiber optic. Of course, persons of ordinary skill in the art will appreciate that the present invention includes detection elements other than those specifically described herein and that the present invention should not be limited to the detection elements described herein.

The detection element112has a detection element property that changes when the detection element112reacts with the corrosive substance. The detection element property may be a physical property, such as mass, volume, density, temperature, color, tensile strength, or any other physical property. Alternatively, the detection element property may be an electrical property, such as resistivity, impedance, capacitance, or any other electrical property. If the detection element property is an electrical property, it may be an alternating current (AC) electrical property or a direct current (DC) electrical property. Further in the alternative, the detection element property may be an optical property, such as luminance, optical clarity, percent transmission, reflectivity, refractive index, or any other optical properties. Preferably, the detection element112is metal and the detection element property is resistivity. However, persons of ordinary skill in the art will appreciate that the present invention includes detection element properties other than those specifically described herein and that the present invention should not be limited to the detection element properties described herein.

The comparison element114comprises a material that does not react with the corrosive substance but is similar to the detection element112. In an embodiment, the comparison element114may be identical to the detection element112, with the exception that the comparison element114is shielded from the corrosive substance. The shielding may be a protective coating applied to the exterior of the comparison element114, such as paint, epoxy, or polymers. Alternatively, a shielding apparatus may separate the comparison element114from the remainder of the interior of the gas chromatograph100such that the comparison element114does not come into contact with the corrosive substance when the corrosive substance is present in the interior of the gas chromatograph100. Of course, persons of ordinary skill in the art will appreciate that the present invention includes comparison elements other than those specifically described herein and that the present invention should not be limited to the comparison elements described herein.

The comparison element114has a comparison element property that does not substantially change when the comparison element114is exposed to the corrosive substance. As explained above, the comparison element114may be shielded from the corrosive substance by a coating or shielding apparatus. However, even though the comparison element property is not substantially affected by the corrosive substance, the comparison element property may not be necessarily constant. Rather, the comparison element property may change as a result of variations in any of the environmental conditions within the gas chromatograph100, such as temperature, pressure, humidity, air composition, luminance, or other environmental conditions. In the preferred embodiment where the detection element112and the comparison element114are constructed of substantially identical materials, the detection element property and the comparison element property may be substantially identically affected by any changes in the environmental conditions within the gas chromatograph100. For example, if the temperature within the gas chromatograph100increases and changes the resistivity of a metal detection element112, the temperature increase also changes the resistivity of a metal comparison element114substantially the same amount as the change in resistivity of the metal detection element112. Consequently, the comparison element property may be used to account for changes in the detection element property due to factors other than the presence of the corrosive substance. Of course, persons of ordinary skill in the art will appreciate that the present invention includes comparison elements other than those specifically described herein and that the present invention should not be limited to the comparison elements described herein.

The testing device110is an apparatus that measures the detection element property and the comparison element property. As explained below, the processor116uses the testing device110to measure the detection element property and the comparison element property so that the processor116may compare the detection element property to the comparison element property and determine whether a corrosive substance exists within the gas chromatograph100. In an embodiment of the invention in which the detection element property and the comparison element property may be the mass of the detection element112and the comparison element114, respectively, the testing device110may be a device that measures the mass of the detection element112and the comparison element114, such as a scale. In the embodiment of the invention in which the detection element112and the comparison element114are metal and the detection element property and the comparison element property are resistivity, the testing device110may be an apparatus that measures resistivity, such as a galvanometer, ammeter, or voltmeter. Alternatively, in the embodiment of the invention in which the detection element112and the comparison element114are made of a material that changes color when it reacts with the corrosive substance, the testing device110may be an apparatus that measures the color of the detection element112and the comparison element114. Further in the alternative, in the embodiment of the invention in which the detection element112and the comparison element114are made of a material that changes optical properties when it reacts with the corrosive substance, the testing device110may be an apparatus that measures the optical properties of the detection element112and the comparison element114. In embodiments of the invention in which there is no comparison element114, the testing device may measure the detection element property and optionally the environmental conditions within the gas chromatograph100. Of course, persons of ordinary skill in the art will appreciate that the present invention includes testing devices other than those specifically described herein and that the present invention should not be limited to the testing devices described herein.

In the embodiment shown inFIG. 2B, the detector106comprises the comparison data122in lieu of the comparison element114. The comparison data122may be a compilation of data regarding the detection element112, specifically the detector evaluation program200. In one embodiment, the comparison data122may be a single value, such as the resistivity of the detection element112. Such an embodiment of the comparison data122is advantageous when the storage space in memory118is limited. In alternative embodiments, the comparison data122comprises different values for different sets of environmental conditions within the gas chromatograph100. For example, the comparison data122may comprise the resistivity of detection element112for numerous combinations of environmental conditions within the gas chromatograph100. Such an embodiment is beneficial because it accounts for changes in the detection element property due to changes in the environmental conditions within the gas chromatograph100while removing the need for the comparison element114. Of course, persons of ordinary skill in the art will appreciate that the present invention includes comparison data other than those specifically described herein and that the present invention should not be limited to the comparison data described herein.

In an alternative embodiment, the memory118further comprises the history120. The history120may be a record of the detection element property over time. If the detector106contains a comparison element114, the history120may optionally comprise the comparison element property over time. The value of the detection element property and optional comparison element property may be stored on a continual basis, or may be stored on an incremental basis, such as every second, minute, hour, day, week, or an integral value of any of the aforementioned time increments, such as 2, 3, or 5 second intervals. Of course, persons of ordinary skill in the art will appreciate that the present invention includes history other than those specifically described herein and that the present invention should not be limited to the history described herein.

Referring toFIGS. 2A and 2B, the processor116and memory118will now be described in greater detail. The processor116may be any logic performing circuitry that can interface with the memory118and a data output device (not shown) via the data output124. The memory118may be any type of storage media suitable for storing the comparison data122, the history120, and the detector evaluation program200described herein. The data output124allows the processor116to upload or download data from the memory118to an external device (not shown), such as a computer. The data that the processor116can upload or download includes the comparison data122, the history120, the detector evaluation program200, or any other data stored in the memory118. Persons of ordinary skill in the art are aware of several types of processors116and memory118that are suitable for the invention described herein.

The processor116and memory118may be stand alone components or may be integrated with the testing device110. In one embodiment, the processor116and memory118are stand alone components that may be individually added to or removed from the gas chromatograph100. In another embodiment, the processor116and memory118may be integrated with the processor and memory (not shown) used by the testing device110or the chromatograph detector104. Integrating the processor116, the memory118, and the testing device110together is advantageous because it allows the present invention to be easily added to existing gas chromatographs. When the processor116, the memory118, and the testing device110are integrated together, they contain the data output124such as a plug that can be connected to the other circuitry within the gas chromatograph100or to a data output device (not shown). Of course, persons of ordinary skill in the art will appreciate that the present invention includes processors and memory other than those specifically described herein and that the present invention should not be limited to the processors and memory described herein.

Another piece of data that may be stored in the memory118is the detector evaluation program200. The detector evaluation program200is a program executed by the processor116that compares the detection element property to the comparison element property to determine whether a corrosive substance leak exists within the interior of the gas chromatograph100.FIG. 3is an example of a flow sheet of the logic of the detector evaluation program200. The detector evaluation program200starts at202when the gas chromatograph100is operating. At204, the detector evaluation program200instructs the testing device110to measure the detection element property and the comparison element property. The detection element property and the comparison element property may be stored in the memory118for permanent storage as history120, but may also be stored in memory118temporarily until the detection element property is compared to the comparison element property by the detector evaluation program200.

In the alternative embodiment of the invention illustrated inFIG. 2B, the detector evaluation program200does not instruct the testing device100to measure the comparison element property because no comparison element exists. Instead, the detector evaluation program200accesses the comparison data122in the memory118and uses the comparison data122in lieu of the comparison element property for the processing steps described herein.

At206, the detector evaluation program200compares the detection element property to the comparison element property to determine the extent to which the detection element property deviates from the comparison element property. Minor deviations of the detection element property from the comparison element property do not necessarily indicate the presence of the corrosive substance leak. Persons of ordinary skill in the art will appreciate that the detection element property may vary from the comparison element property when a corrosive substance is not present within the gas chromatograph100because the comparison element114differs from the detection element112in that the comparison element114is coated or otherwise shielded from the corrosive substance. Thus, the detector evaluation program200is configured to compare the detection element property to the comparison element property and determine whether the detection element property falls outside of a predetermined range of deviation from the comparison element property. Persons of ordinary skill in the art know how to configure the predetermined range of deviation between the detection element property and the comparison element property. However, for the purposes of explanation and not to be construed in a limiting sense, the predetermined range may be any one of a 1, 2, 5, 10, 20, or 50 percent deviation from the comparison element property.

At208, the detector evaluation program200then determines whether the detection element property is within the predetermined range of the comparison element property. If the detector evaluation program200determines that the detection element property is within the predetermined range of the comparison element property, then the detector evaluation program200proceeds to212. If the detector evaluation program200determines that the detection element property is not within the predetermined range of the comparison element property, then the detector evaluation program200proceeds to210.

At210, the detector evaluation program200indicates the presence of the corrosive substance leak. The detector evaluation program200may indicate the presence of the corrosive substance leak by sending a signal to a data output device (not shown) via the data output124(shown inFIGS. 2A and 2B). Examples of data output devices that may be used to indicate the presence of the corrosive substance leak are lights, buzzers, klaxons, monitors, printers, diagnostic programs, telecommunication devices, and other output devices not specifically listed herein. Of course, persons of ordinary skill in the art will appreciate that the aforementioned list of data output devices is not exclusive and that the present invention should not be limited to the data output devices described herein. Once the detector evaluation program200has indicated the presence of the corrosive substance leak, the detector evaluation program200proceeds to212where the detector evaluation program200determines whether the detector evaluation program200should end. The detector evaluation program200should end when the gas chromatograph100(shown inFIG. 1) is shut down or otherwise in a sleeping or non-active state. If the detector evaluation program200determines that the detector evaluation program200should not end, then detector evaluation program200returns to204. If the detector evaluation program200determines that the detector evaluation program200should end, the detector evaluation program200ends at214.

Although the present invention is described in conjunction with a gas chromatograph, persons of ordinary skill in the art will appreciate that the present invention may be implemented on other types of chemical composition analyzers. More specifically, the present invention is useful for any type of testing apparatus in which detecting the presence of a corrosive substance within the interior of the testing apparatus is an important feature of the apparatus. Persons of ordinary skill in the art will appreciate that the present invention may be used in a variety of other applications.

While a number of preferred embodiments of the invention have been shown and described herein, modifications thereof may be made by one skilled in the art without departing from the spirit and the teachings of the invention. The embodiments described herein are exemplary only and are not intended to be limiting. Many variations, combinations, and modifications of the invention disclosed herein are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited by the description set out above, but is defined by the claims which follow, that scope including all equivalents of the subject matter of the claims.