Measuring and testing – With fluid pressure – Leakage
Reexamination Certificate
1998-04-10
2001-01-09
Wu, Shean C. (Department: 1756)
Measuring and testing
With fluid pressure
Leakage
C073S04050A, C073S592000, C252S067000, C252S964000, C436S003000
Reexamination Certificate
active
06170320
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention is related to a method of introducing an additive into a fluid system, as well as to a method for detecting leaks and an apparatus and composition useful for leak detection.
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.
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.
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 introduced into 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 prior art examples include U.S. Pat. No. 4,369,120, which discloses anthraquinone blue dyes 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; U.S. Pat. No. 5,149,453, which discloses a UV 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 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 introducing 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 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.
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.
Generally speaking, the standard industry method of introducing daylight visible or fluorescent dyes into a refrigerant oil, has been to dissolve the dye in the refrigeration oil and to introduce this mixture into the system. There are however currently several different types of oils that are used in refrigeration systems. For example, polyalkylene glycol (PAG), polyol ester (POE), alkylbenzene (AB) and mineral oils are all used in current systems and some of these oils (or their additives) are incompatible with one another in concentrations as low as 1%. This means that a service technician must carry an inventory of all different types of fluorescent dye mixtures, i.e. one for each oil type.
An even greater problem with the conventional approach is that the technician must first determine which type of oil is used in the system which is being checked for leaks, as often, the technician is called upon to repair a leak in a system which has not been previously serviced and in which the oil used is unknown. This presents a significant problem. We have recognized that a more universal fluorescent leak check solution which is compatible with all potential lubricants and delivery method is needed to simplify leak detection in refrigeration systems.
The type of daylight visible or fluorescent material used for leak detection is also critical because the additives used in oils can interact with the material or the material could directly and negatively affect the properties of the oil or refrigerant. Although the quantity of material used for fluorescent leak detection is generally small, on the order of a few percent by weight of oil or less, a material can adversely affect the properties or performance of the oil or refrigerant to which it is added. In addition, conventional fluorescent materials have not always maximized visible light emission from UV excitation with respect to the amount of fluorescent material added.
Another drawback to current leak detection techniques is that conventional fluorescence leak detectors have used a very bright mercury vapor lamp with a UV filter. Commercial UV fluorescent leak detection devices also use halogen light sources. Other suitable UV light sources are disclosed Skoog, et al.,
Principles of Instrumental Analysis,
Saunders College, 1980, Figure 5-2, p. 116, which lists components and materials for spectroscopic instruments and lists several light sources, including a xenon lamp, as a source of visible light.
Flashing UV light has been used for various applications in the past. Typically these applications use excited xenon in a light tube to provide continuous light or to provide UV energy for chemical curing reactions, such as in dental reconstruction. Up until our present invention, however, flashing UV light has not been recognized as beneficial for leak detection.
For example, U.S. Pat. No. 4,279,254 discloses a UV light used on medical patients to radiate the skin. The UV electrical light circuit, which is not battery operated, counts pulse flashes in order to automatically shut off and avoid over-exposure as a safety measure; U.S. Pat. No. 4,112,335 discloses a rapid pulse UV light apparatus in which a UV light source is fed as a high frequency pulse into a high pressure (3 atmosphere) xenon light tube to cure epoxy resin tooth caps; U.S. Pat. No. 4,550,275 discloses a high efficiency pulse light source as a xenon light source to excite lasers; U.S. Pat. No. 5,185,552 discloses a vacuum UV light source which provides a high output UV light source using low pressure hydrogen or deuterium in a hollow tube at wave lengths below 180 mm; U.S. Pat. No. 4,229,658 discloses a dental xenon light apparatus which supplies UV and visible light and is used to cure tooth restoration materials by focusing the light on a small area of a tooth; and U.S. Pat. No. 5,043,634 discloses a pulsed light source using a pulsed xenon light tube coupled with a phosphorus coating which emits different colors of visible
Back Dwight D.
Grzyll Lawrence R.
Mayer Joseph
Scaringe Robert P.
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Mainstream Engineering Corporation
Wu Shean C.
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