Measuring and testing – With fluid pressure – Leakage
Reexamination Certificate
1998-06-11
2001-12-11
Williams, Hezron (Department: 2856)
Measuring and testing
With fluid pressure
Leakage
C073S04050A, C252S301190
Reexamination Certificate
active
06327897
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention is related to a method of introducing an in situant into a vapor compression system, as well as to a method for detecting leaks in the system components and an apparatus and composition useful for leak detection. “In situants” are defined as compounds which are the same or substantially similar to compounds already present in oils or lubricants, and which exhibit fluorescence and/or daylight visible qualities.
Daylight visible and ultraviolet fluorescent dyes have been used to detect leaks in refrigeration systems utilizing fluorocarbon refrigerants and refrigerant oils. Typically, these dyes are introduced into the refrigeration system, and at the site of the leak, the leaking refrigerant, oil and dye are detected under normal or UV light. The term “dye” in the context of leak detection generally refers to a compound that is distinctively different or unintentionally similar to components in the host fluid, having the specific purpose of generating a detectable color from a fluid. Typical dyes used by the industry up to present include blue anilino-anthraquinones, xanthenes, perylenes, and naphthalimides.
More specifically, a leak-detecting trace fluid, which is generally a fluorescence (powdered) dye material dissolved in an oil or petroleum fraction carrier, is introduced into the refrigeration system. The fluorescent dye material is carried throughout the system, and at the location of a leak, the refrigerant, oil, and fluorescent dye material leak into the atmosphere. The refrigerant is subsequently vaporized, leaving an oil residue containing the fluorescent dye material. Application of a UV light to this area results in the illumination of the oil/fluorescent dye material. The primary factors in selecting these dyes for use in leak detection is that the dyes are soluble in the host fluid, and that the dyes are used in such low concentrations that their presence does not alter the intended normal function of the host fluid.
U.S. Pat. No. 1,915,965 discloses a leak detector method for a compression refrigeration system. Daylight visible compounds, such as methyl violet, crystal violet, auramine B, rhodamine E, etc. are added to such systems as leak detectors.
U.S. Pat. No. 4,249,412 discloses a UV fluorescent dye composition comprising water, a nonionic surfactant, a 1.0 wt. % sodium fluorescein and a semi-synthetic thickening agent. This fluorescent dye composition is sprayed on the external surfaces of a system where the bubbles formed by the leak fluoresce under UV light.
Other references include U.S. Pat. No. 4,369,120, which discloses anilino anthraquinone blue dyes (methyl-ethylanilino, dimethylanilino, and trimethylanilino anthraquinones) for use as visual leak detectors of refrigerants, refrigerant oils, and mixtures thereof; U.S. Pat. No. 4,758,366, which discloses a UV fluorescent dye composition comprising a polyhalogenated hydrocarbon refrigerant, a refrigeration oil, or a mixture thereof, with a fluorescent dye such as naphthoxanthenes, perylenes, or naphthalene; U.S. Pat. No. 5,149,453, which discloses a fluorescent dye composition comprising an effective amount of a fluorescent, alkyl substituted perylene dye combined with a refrigerant oil and a polyhalogenated hydrocarbon refrigerant; U.S. Pat. No. 5,357,782, which discloses a UV fluorescent dye composition comprising an optical naphthalimide brightener mixed with either mineral oil, polyalkylene glycol or polyol ester refrigeration lubricant; U.S. Pat. No. 5,167,140, which discloses a method of adding a fluorescent dye solution into a system with an atomizing mist infuser, wherein four different formulas for the fluorescent dye solution are disclosed, wherein the dye solution is a fluorescent dye mixed with an appropriate refrigerant oil; WO 92/07249, which discloses a method and a sensor system for detecting hydrocarbon-containing fluids by fluorescent detection, wherein additives typically used in hydrocarbon-based fluids, such as gasoline, heating oils and motor oils, can fluoresce, and can be used to detect and locate the source of ground water contamination from gasoline and oil storage tanks using a fluorescent sensor which detects the presence of fluorescing materials such as Coumarin 153. The use of Coumarin 153 in ppm concentrations for this purpose does not degrade the performance properties of the particular hydrocarbon or oil. Moreover, coumarin compounds are related in structure and derivation to anthraquinones, which are sometimes used to improve oxidation stability.
Furthermore, U.S. Pat. No. 5,440,919, discloses a method of introducing a UV fluorescent dye additive into a closed refrigeration system by placing the fluorescent dye on a swatch of material installed in a desiccant bag which is placed in a dehydrator or filter (i.e. filter-dryer) of the refrigeration system. The swatch is capable of releasing as well as adsorbing the dye. The refrigerant and system lubricant flow through the dehydrator and are then mixed with the fluorescent dye, thereby allowing the fluorescent dye to be carried throughout the system. Although this system allows the introduction of the fluorescent dye into the system without requiring the use of a carrier oil, it also requires that the dehydrator or filter-dryer of the system be changed in order to introduce the dye into the system.
U.S. Pat. No. 3,386,920 teaches the composition of a fluorescent and daylight visible dye dissolved in solvents such as alcohols and oils to detect surface defects by applying the solution to a surface containing the defect, wiping excess solution off of the surface, and allowing the solutions to exude from the defect for detection. This reference does not teach the advantages of using a carrier fluid or solvent which is compatible or soluble in the fluid used in the process for which the defect is located, nor is there any preference for using dyes which are in situants to the fluid located on either side of the wall wherein the defect is located. The compounds suggested for use by this reference include coumarins, dibenzothiophene, azole dyes, perylene dyes, and pyridotriazoles.
U.S. Pat. No. 4,201,683 teaches an anti-friction solution comprised of anti-friction compounds and C5-C50 alkanols added to equipment having moving parts operating under boundary lubricating conditions. This reference does not teach the method of introducing the solution to a system under pressure nor does it teach that these compounds could be selected from in situants in the system's oil or lubricant. This reference also does not teach that certain performance improving compounds exhibit fluorescent qualities which when added to the system can be used to detect leaks.
U.S. Pat. Nos. 4,157,970, 4,179,386, and 4,320,018 all teach compositions containing polyhydroxy anthraquinones for improving oxidation stability in lubricating fluids. Thus, polyhydroxy anthraquinones would be considered an in situant.
U.S. Pat. No. 4,641,518 teaches a method to detect surface defects by applying a solution comprised by one embodiment of 7-diethylamino-4-methylcoumarin in isopropanol, wiping away excess solution, and applying a developer solution to absorb the fluorescent dyes from the surface defect. This reference does not require or prefer any specific fluorescent dyes which are in situants to the system which is being analyzed for surface defects, nor are oils taught as the carrier fluid. A method to inject the fluorescent or dye solution into a pressurized system is also not taught. This patent also appears to be for finding defects on static surfaces in ambient by spreading the solution over large areas and then observing where the fluorescence emanates from. This is in contrast to the current invention whereby the in situant chemicals are used to detect leaks in flowing systems, as in the case of vapor compression refrigeration, and the outer surface at which the leak is detected does not need to be prepared or coated in any form prior to detecting for leaks.
U.S. Pat. No. 5,605,650 teaches a com
Back Dwight D.
Grzyll Lawrence R.
Mayer Joseph
Meyer John A.
Scaringe Robert Peter
Crowell & Moring LLP
Cygan Michael
Mainstream Engineering Corporation
Williams Hezron
LandOfFree
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