WO2005047843A1

WO2005047843A1 - Method and system for leak detection

Info

Publication number: WO2005047843A1
Application number: PCT/AU2004/001585
Authority: WO
Inventors: Bryan Clarence Loft; John Zuccon
Original assignee: The Refrigerant Oil Company (Singapore) Pte Ltd
Priority date: 2003-11-17
Filing date: 2004-11-17
Publication date: 2005-05-26

Abstract

A method of detecting leakages in refrigeration systems and other apparatus containing a liquid oil, wherein a fluorescent dye composition and an N-alkylpyrrolidone solvent is incorporated into the liquid oil and subsequently an external surface of said apparatus is irradiated with a source of electromagnetic radiation in a frequency range selected to excite enhanced fluorescence in the fluorescent dye composition in the presence of the N-alkylpyrrolidone solvent, the location and/or extent of a leakage being indicated by a fluorescence response from leaked liquid oil on said external surface. A working fluid composition for an internally lubricated apparatus is provided wherein the working fluid composition includes a liquid oil selected from a refrigerant oil, engine oil, transmission fluid, power steering fluid, gear box fluid, hydraulic system fluid or the like.

Description

TITLE: "METHOD AND SYSTEM FOR LEAK DETECTION" FIELD OF THE INVENTION This invention is concerned with a method and system for detection of leakages in an apparatus containing a liquid oil. The invention is concerned particularly, although not exclusively with detection of leakages in refrigeration systems. BACKGROUND OF THE INVENTION Loss of working fluids, especially lubricants, from machinery or equipment through leaks can lead to loss of function of the machinery or equipment and/or to release of a toxic or environmentally deleterious substance into the environment particularly if the working fluid is under pressure. It is necessary to be able to detect the site of a leak before any repair can be made to seal the leak. Incorporation of dyes, particularly fluorescent dyes, into the working fluid provides enhanced leak detectability. The dye may be introduced into the system either as a dilute solution in the working fluid or one component of the working fluid before the system is filled for the first time or when the working fluid or the said component is renewed for any reason, or as a very small volume of concentrated solution added to a system full of working fluid. Alternatively, the dye may be added when servicing the system using a lesser volume of a solution of dye of intermediate concentration. In all cases there will be a threshold dye concentration in the working fluid needed for efficient leak detection. The use of dyestuffs for detection of leaks in refrigeration systems is well known. In early systems a dyestuff soluble in the refrigeration lubricating oil could be detected under daylight conditions to show the site of a leak. Typically, early dye systems were chosen from oil soluble azo and anthraquinone dyes but these exhibited stability problems at high temperatures. Other early dye systems included methyl violet, crystal violet, auramine B and rhodamine B but these too were found to be unstable at high temperatures and had a low solubility at low temperatures. United States Patent 4,758,366 taught the use of mineral oil soluble fluorescent dyes for detection of leaks in refrigeration systems by means of an ultraviolet light source. Suitable mineral oil soluble fluorescent dyes identified were naphthoxanthene, perylene, naphthalene and monocyclic aromatic compounds having an organometallic component. A claimed advantage of these leak detection dyes was that they were easily washable from surfaces with aliphatic non-toxic solvents whereas toxic aromatic or halogenated solvents were required to clean away daylight visible dyes. The advent of synthetic polyalkylene glycol (PAG) and polyolesters (POE) as refrigeration system lubricants however rendered the prior art mineral oil-soluble perylene fluorescent dyes as largely ineffective as many of the mineral oil-soluble dyes were only partially soluble in these newer refrigeration system lubricants. However, later HFC refrigerant compositions tended to operate at higher temperatures than CFC systems at which temperatures the perylene dyes exhibited thermal chemical instablility United States Patent 5,421 ,192 described the use of Naphthalimide dyes for use in more contemporary refrigeration systems utilizing HFC refrigerants and natural or refined mineral oil or synthetic refrigeration lubricants. This leak detection system exhibited green-blue to green-yellow fluorescence when irradiated with ultra-violet light having emission wavelength in the range 380 - 400 nm depending upon the nature of the refrigerant/lubrication oil combination. Of more recent times United States Patent 6,165,384 disclosed a fluorescent leak detection system for incorporation into working fluids such as automotive engine oils and refrigeration lubricants wherein a mixture of oil soluble perylene and naphthalimide dyes was employed to provide excitation peaks at 340 to 375 nm, 400 to 410 nm, and another peak at about 530 nm when a broad band UV lamp was employed. The relatively narrow emission peaks at 340 to 375nm and at about 530 nm are produced by perylene dyes whereas naphthalimide dyes emit a broad fluorescence response between

480 to 520 nm but with a markedly lesser intensity than the perylene dyes.

The fluorescent responses, coloured green-yellow for perylene dyes and green for naphthalimide dyes were said to be such that the two dyes complement each other in that the absence of a fluorescent response by one or a reduced response by one dye is supplemented by a response by the other in an environment where the working fluid itself or contaminants therein can mask a fluorescent response. At present, the most commonly used leak detection system for refrigeration systems is a dyestuff which fluoresces orange-yellow under the influence of UV radiation. While generally adequate for their intended purpose these prior art leak detector fluorescent dyestuffs are less discernable than those of the present invention which fluoresce a yellow or yellow-green colour which is chosen to fall within the wavelength range to which the human eye is most sensitive. In the field of crack detection or for inspecting surface flaws in objects, it is known to utilize fluorescent dyestuffs which may be trapped in a surface crack to indicate the presence and extent of that crack. United States Patents Re. 26,888 and 3,928,046 describe a crack detection system wherein a solution of a fluorescent tracer dye is applied to the surface of an article or the article is soaked in the tracer solution for a period of time. Excess tracer solution is flushed from the surface of the object and a developer composition is applied to the treated surface to absorb any entrapped tracer dye and to enhance its visibility. Such developers usually comprise fine powers or pigments in particulate form or a liquid suspension of particulate materials such as silica aerogel or a mixture of silica aerogel and talc, barytes clay, magnesium sulphate, magnesium oxide, diatomaceous earth, silica or combinations thereof combined with a low molecular weight pyrrolidone fluorescent brightener which reacts with the fluorescent dyestuff on contact to enhance its brightness. Re. 26,888 describes the additional use of fluorescent brightening agents in combination with a fluorescent dye to enhance fluorescence response or to shift a colour response in crack detection and the like. International Publication WO 91/07654 also describes processes for revealing cracks and flaws in metal parts utilizing either a post- emulsifiable system or a water washable system to remove excess penetrant from the surface of the system. This disclosure also relies upon a developer in the form of a dusted-on white pigment or a solution containing dissolved salts from which the solvent is evaporated to leave a tracer enhancing pigment residue. The use of fluorescence enhancing higher molecular weight pyrrolidones incorporated in the developer composition or the penetrant composition is described but in both cases a particulate pigment developer is required to permit visibility of the penetrant systems. The system utilizes a colour dye and a sensitizer dye in combination with a pyrrolidone brightness enhancer. While there are many fluorescent dyestuffs from which to choose, the use of such dyestuffs in, say, a hydraulic system, an engine or pump or other automotive working fluids, a refrigeration system of an automotive or building air conditioner, a refrigerator or the like must satisfy a broad range of criteria. Apart from exhibiting a strong fluorescence response under UV radiation, the dyestuff must be soluble in and compatible with a wide range of lubricant and refrigerant compositions and also must maintain solubility over a wide temperature range to avoid precipitation or separation from solution. In addition it must retain thermal stability at elevated temperatures and desirably it should not stain paint finishes and otherwise be easily removed from leak test sites by non aggressive, non toxic solvent washing systems. Most importantly, compounds employed in a leak detection system for working fluids such as lubricating oils and the like must be chemically compatable with a wide range of such lubricating oils, with or without additive packages and otherwise must not alter any physical properties of these fluids such as viscosity and lubricity over a wide range of operating temperatures and moreover must not adversely affect gaskets, seals, valve seats, valve bodies or other components of natural or synthetic materials in the apparatus incorporating the working fluid. The present invention relates to an oleaginous working fluid containing amongst other components at least one fluorescent dye and a solvent which interacts with the dye to enhance its visibility and optionally with one or more other solvents in which the solvent(s) stabilize the fluorescent dye so as to enhance the storage properties of the composition containing the dye, particularly when the dye or the composition is exposed to low temperatures. The present invention finds particular application as a dye composition or a working fluid composition containing the dye composition for use in detecting leaks in pressurised fluid systems, such as machine lubricating systems, hydraulic control or power systems, air conditioning systems or the like in which the solvent or solvents solublise the dye so as to form a stable composition that remains soluble over a wider range of temperatures particularly a wider range of low temperatures, during use and storage of the dye composition so as to reduce and/or eliminate the occurrence of solid material precipitating or otherwise coming out of solution during use and/or storage of the dye containing composition. Further, the present invention relates to a dye composition or working fluid or lubricating composition that is brighter or more fluorescent than existing compositions as well as being stable. The present applicants have surprisingly discovered that not only can pyrrolidone solvents be employed to solubilize selected types of fluorescent dyes in a wide range of natural or refined mineral oils or synthetic lubricants, they also exhibit a fluorescence enhancing effect in the selected fluorescent dyes whereby even very small leaks in a working fluid system are readily discernible under ultra-violet radiation. Even in extreme environments such as automotive engine compartments in the presence of a wide range of contaminants which normally might mask the fluorescence response of prior art fluorescent leak detection systems, the fluorescent dyestuff/solvent combinations according to the present invention have been found to exhibit a high level of visibility. The ease of observing such brighter fluorescent solutions results in leaks being quicker to find, the extent of the leak being more readily determined and smaller volume leaks being discernable owing to the improved brightness of the fluorescent solution. It is an aim of the present invention to permit the introduction of a fluorescent dye into a leak detecting system for a working fluid, said system comprising a fluorescent dye material in which the dye has increased stability over a wide range of temperatures by being maintained in solution for a longer period of time and in which the dye solution is brighter than normally obtainable from the particular dye alone. According to one aspect of the present invention there is provided a method of detecting leakages in an apparatus containing a liquid oil, said method comprising incorporating into said liquid oil a fluorescent dye composition and a pyrrolidone solvent and subsequently irradiating an external surface of said apparatus with a source of electromagnetic radiation in a frequency range selected to excite enhanced fluorescence in said fluorescent dye composition in the presence of said pyrrolidone solvent, the location and/or extent of a leakage being indicated by a fluorescence response from leaked liquid oil on said external surface. Suitably, said fluorescent dye composition is selected from fluorescent dye groups comprising coumarin dyes, phthalimide dyes, naphthalimide dyes, xanthene dyes, thioxanthene dyes, perylene dyes, naptholactam dyes, azlactone dyes, methine dyes, oxazine dyes, thiazine dyes or mixtures thereof. Preferably, said fluorescent dye composition comprises a coumarin dye selected from coumarin 1 , coumarin 2, coumarin 30 and the like, coum, dercoum, derPcoum, 2coum, 2dercoum, 2derPcoum, silylated coumarin dyes including derivatives thereof and precursors therefore or mixtures thereof. Alternatively, said fluorescent dye composition may comprise a phthalimide dye selected from alkoxynaphthalimides, 4- aminonaphthalimides, 1',8'-naphthoylenebenzimidazoles, imides of naphthalene-1 ,4,5,8-tetracarboxylic dianhydride, 1 ',8'- naphthoylenebenzimidazole perdicarboximides, bis-benzimidazole derivatives of naphthalene-1 ,4,5,8-tetracarboxylic acid, 1' ,8' - naphthoylenepyrazoles, azo- and azomethine naphthalimides, and perylene- 3, 4, 9, 10-tetracarboxydiimides. If required, said fluorescent dye composition may be present in said liquid oil in the range of from 0.001 gm/l to 100 gm/l. Suitably, said fluorescent dye composition is present in said liquid oil in the range of from 0.001 gm/l to 10 gm/l. Preferably, said fluorescent dye composition is present in the range of from 0.001 gm/l to 10 gm/l. The pyrrolidone solvent may be selected from N- alkylpyrrolidones. Suitably, said solvent is selected from N-Cβ-iβ alkylpyrrolidones or mixtures thereof. The solvent may be present in said liquid oil in the range of from 0.01 % to 5% by volume. Suitably, said solvent is present in said liquid oil in the range of from 0.05% to 3.0% by volume. The liquid oil may be selected from natural or refined mineral oils or synthetic oils including naphthenic or paraffinic oils, alkylated benzenes, silicones, polyalkylene glycols, polyalphaolefins, diesters or triesters of dicarboxcyclic or tricarboxcyclic acids, and polyalkylsilicate oils, polylesters including di-, tri-, tetra-, or polyfunctional pentaerythritol esters or mixtures of any two or more thereof. According to another aspect of the invention there is provided a working fluid composition for an internally lubricated apparatus, said composition comprising a base oil selected from natural or refined mineral oils, including naphthenic or paraffinic oils, alkylated benzenes, silicones, polyalkylene glycols, polyalphaolefins, diesters ortriesters of dicarboxcyclic or tricarboxcyciic acids, and polyalkylsilicate oils, or mixtures of any two or

more thereof; an N-alkylpyrrolidone solvent or mixtures thereof; and, a fluorescent dye composition, said liquid oil composition characterized in that the location and/or extent of liquid oil leakages are indicated by a fluorescence response from said fluorescent dye composition in leaked liquid oil on an external surface of said apparatus and wherein said fluorescence response is enhanced by said solvent. Suitably, said solvent is selected from N-Cβ-iβ alkylpyrrolidones or mixtures thereof.

Suitably, said fluorescent dye composition is selected from fluorescent dye groups comprising coumarin dyes, phthalimide dyes, naphthalimide dyes, xanthene dyes, thioxanthene dyes, perylene dyes, naptholactam dyes, azlactone dyes, methine dyes, oxazine dyes, thiazine dyes or mixtures thereof. Preferably, said fluorescent dye composition comprises a coumarin dye selected from coumarin 1 , coumarin 2, coumarin 30 and the like, coum, dercoum, derPcoum, 2coum, 2dercoum, 2derPcoum, silylated coumarin dyes including derivatives thereof and precursors therefore or mixtures thereof. Alternatively, said fluorescent dye composition is selected from alkoxynaphthalimides, 4-aminonaphthalimides, 1 ',8'- naphthoylenebenzimidazoles, imides of Naphthalene-1 ,4,5, 8-tetracarboxylic dianhydride, 1',8'-naphthoylenebenzimidazole perdicarboximides, bis- benzimidazole derivatives of naphthalene-1 ,4, 5, 8-tetracarboxylic acid, 1 ' ,8' -naphthoylenepyrazoles, azo- and azomethine naphthalimides, and perylene-3, 4, 9, 10-tetracarboxydiimides. Preferably, said fluorescent dye composition is selected from CI. Solvent Yellow 43 or CI. Solvent Yellow 160:1 or mixtures thereof. The solvent is present in said oil composition in the range of from 0.05% to 3.0% by volume. Suitably, said fluorescent dye composition is present in the range of from 0.02 gm/l to 5.0 gm/l. If required, said working fluid may comprise an additive package including antioxidants, anti-wear agents, antistatic agents, dispersants and stabilizing agents or any combination thereof. The working fluid composition may be a lubricating oil. Alternatively, the working fluid composition may be a hydraulic working fluid. According to yet another aspect of the invention there is provided a refrigeration working fluid comprising:- a refrigerant composition fluid; a lubricant oil composition; an N-alkylpyrrolidone solvent; and, a fluorescent dye composition, said refrigeration working fluid characterized in that the location and/or extent of working fluid leakages in a refrigeration system are indicated by a fluorescence response from said fluorescent dye composition in leaked lubricating oil on an external surface of said refrigeration system and wherein said fluorescence response is enhanced by said solvent. Suitably, said solvent is selected from N-Cs-iβ alkylpyrrolidones or mixtures thereof.

Suitably, said fluorescent dye composition is selected from fluorescent dye groups comprising coumarin dyes, phthalimide dyes, naphthalimide dyes, xanthene dyes, thioxanthene dyes, perylene dyes, naptholactam dyes, azlactone dyes, methine dyes, oxazine dyes, thiazine dyes or mixtures thereof. Preferably, said fluorescent dye composition comprises a coumarin dye selected from coumarin 1 , coumarin 2, coumarin 30 and the like, coum, dercoum, derPcoum, 2coum, 2dercoum, 2derPcoum, silylated coumarin dyes including derivatives thereof and precursors therefore or mixtures thereof.

Alternatively, said fluorescent dye composition may be selected from alkoxynaphthalimides, 4-aminonaphthalimides, 1 ',8 - naphthoylenebenzimidazoles, imides of naphthalene-1 ,4,5, 8-tetracarboxylic dianhydride, 1',8'-naphthoylenebenzimidazole perdicarboximides, bis- benzimidazole derivatives of naphthalene-1 , 4, 5, 8-tetracarboxylic acid, 1 ' ,8' -naphthoylenepyrazoles, azo- and azomethine naphthalimides, and perylene-3, 4, 9, 10-tetracarboxydiimides. Preferably, said fluorescent dye composition is selected from

C. I. Solvent Yellow 43, C. I. Solvent Yellow 160:1 or mixtures thereof. The solvent may be present in said oil composition in the range of from 0.05% to 3.0% by volume. If required, said fluorescent dye composition may be present in the range of from 0.02 gm/l to 5.0 gm/l.

In a refrigeration (heat pump) system the working fluid will contain both a refrigerant and a lubricant. Typically the following materials may be used as the refrigerant or are contained in the refrigerant composition. - Hydro-chloro-fluorocarbons (HCFC), Hydroflurocarbons (HFC), halogenated or ether derivatives of methane, hydrogen, halogenated, ether or cyclic derivatives of any of ethane, propane, butane, pentane; mixtures of HCFC, HFC, hydrocarbons, carbon dioxide and ammonia. It is to be noted that HCFC, HFC and hydrocarbon refrigerants are considered less damaging to the environment and have reduced ozone depletion potentials.

Further examples of the refrigerants include but are not limited to R22, R-123, R-124, R-142B, R-32, R-134, R-134A, R-152, R-152A, R- 143a, R-125, R-245CA, R-245FA and R-225CA R407A, R407C and R410A. The refrigerant compositions of the invention can be used alone or in combination with one or more refrigerants. Refrigerant R134a is the refrigerant gas most commonly used in conjunction with fluorescent dyes. Refrigerant R134a, is a HFC.

Any type of suitable ultraviolet light source may be used to illuminate the leak of fluorescent dye material. Preferably the wavelength of the UV light source is matched to the particular fluorescent dye used in the formulation or composition in accordance with the present invention. Although a broad spectrum light source may be used it is preferred that a narrower range of light be used.

When a UV emitting light source having a light emission output in the range of from 300 to 480 nanometers is directed at the outside of a pressurised system in the vicinity of a leak the fluorescent dye material is immediately observable as a colored area such as for example as a yellow or yellow green color appearing at the leak site.

Other wavelengths of the emitted ultraviolet light include wave lengths between about 540 to 580 nanometer. Some types of dye emit an intense, but narrow band, fluorescent response which has main intensity peak between about 520 and 550 nanometer and a smaller peak between about 560 to 580 nanometer. Particularly preferred colors for the fluorescent dye include yellow or green yellow or yellow green. It is to be noted that the human eye is most sensitive to low intensity light in the yellow green region of the spectrum at between about 540 to 570 nanometer. Therefore, it is preferred that the fluorescent dye emits in this region or at a wavelength range to which the human eye is most sensitive. Mixtures of dyes can be used to provide further enhanced detectability under a variety of illumination conditions and viewing circumstances, eg to counter the natural fluorescence of other substances which might be present on the outside of the equipment, such as the detection of leaks in an automotive air conditioning system in the presence of mineral oil from the engine.

It is to be noted that other additives may be added to the fluorescent dye formulations or compositions. Additive packages are frequently added to lubricant oils, particularly in automotive engines to increase the performance and other parameters of the working fluid. Typically such additives may include antioxidants, antistatic agents, dispersants and stabilising agents although such additives should be chosen so as not to interfere with the fluorescence of the composition or alternatively, the fluorescent dyes are chosen on the basis that there is no chemical or physical reaction between any of the ingredients of the additive package which might otherwise interfere with or hinder the fluorescence response of the dye under UV radiation.

The invention of the present application is particularly applicable to the detection of leaks in a sealed system containing a refrigerant such as for example in a refrigeration, heating, ventilation or air conditioning system. The refrigeration system may be a fixed system or a mobile system. One example of a mobile system is located within a motor vehicle or similar. For example, vehicle air-conditioning systems are prone to development of minor refrigerant leaks from small fatigue cracks and loose pipe connections brought about by the vibration sustained by the systems during use and owing to the inhospitable environment in which components of the refrigeration system such as pipes, connectors, seals, gaskets or the like are used.

Certain prior art concentrated dye containing formulations or compositions have tended to separate out from the remaining components of the formulation or composition or to precipitate out of solution when subjected to temperatures lower than ambient i.e. less than 10°C When the dye material separates from the remaining components the particles thus formed have a tendency to clog or block the various orifices through which the refrigerant composition must travel during use of the refrigeration or air conditioning system.

In accordance with the present invention the dye material is preferably added to the solvent or solvents prior to mixing with the lubricant or other components of the composition or mixture. In other embodiments the dye may be mixed with the lubricant prior to mixture with the solvent or solvents. It is to be noted that any combination of any two materials mixed in any order with the remaining components falls within the scope of the present invention.

The use of fluorescent dyes to detect leaks in air conditioning systems of motor vehicles allows leak of such fluids to be readily differentiated from the leaks of other fluids used in motor vehicles such as engine oil, transmission fluid, cooler fluid, or the like. The use of florescent dyes is advantageous as they are fairly visible in daylight and the dyes are non staining being easily removed by washing with readily available non toxic solvents.

Owing to the presence of the solvent or combination of solvents the fluorescent dye is held in solution to a greater extent over a wide temperature range particularly over temperature ranges towards the lower end of from -40 to 5°C The addition of the solvent or solvents not only provides better stability and/or solubility of the dye, but also provides the totally unexpected advantage that the fluorescent dyes are brighter or appear brighter than similar or corresponding formulations not containing the solvent or solvents both in visible light and when reactive to UV illumination. Thus, the compositions and formulations of the present invention have dual advantages.

The compositions and formulations of the present invention containing the fluorescent dye and the solvent or solvents can be used as a replacement for existing refrigeration working fluids or can be used to top up or replenish existing refrigeration working fluids. Further, it is to be noted that when the dye containing material is used as to top up or for replenishing existing refrigeration working fluids the concentration of the dye is greater than if the entire refrigeration working fluid is being replaced.

A particular attribute possessed by the refrigeration working fluid and/or dye formulation or composition is that the mixture or solution is non abrasive so as to not damage the various components of the refrigeration system.

The present invention will now be described by way of example with reference to the accompanying examples:

COMPARATIVE EXAMPLE

One gram of a powdered coumarin dye which is Elbaplast fluorescent brilliant yellow R (CI. Solvent Yellow 160:1) was added gradually to the surface of two liters of stirred polyalphaolefin (PAO) oil (Enersyn LPS P068 supplied by BP Australia) so that the powdered dye was drawn into the vortex created by the stirrer and dispersed uniformly throughout the liquid.

The thus formed mixture was heated to 87°C over one hour until most of the powdered dye dissolved in the oil to form a pale yellow solution with a few large floating particles of dye solids remaining. This mixture was filtered hot into a clear PET bottle so as to remove any remaining solid particles so as to produce a dye solution substantially free of solids. After overnight cooling a significant deposit of yellow acicular crystals had formed towards the base of the PET bottle demonstrating that a 0.5 gram per liter solution of fluorescent dye was not stable at room temperature and that even at this temperature the particles of dye were precipitating out from solution as the solution cooled. Thus, this formulation was not suitable for use in air conditioning systems subject to cool or cold temperatures.

EXAMPLE 1

100 ml of N-Octyl 2-pyrrolidone (Agsolex 8 provided by International Speciality Products) was added gradually to 10 litres of stirred polyalphaolefin (PAO) oil (Durasyn provided by BP Australia) at room temperature.

This solution included the solvent and lubricant. 10 grams of a powdered coumarin dye which is Elbaplast fluorescent brilliant yellow R was added gradually to the surface of the stirred liquid solution of oil and solvent so that the powder was drawn into the vortex created by the stirrer and dispersed uniformly throughout the liquid. This dispersion was then heated with stirring to 80°C to dissolve any remaining dye powder, so as to produce a clear bright yellow fluorescent oil. This solution was cooled to 3°C without loss of clarity or crystallization of the dye particles, thus demonstrating that a 1.0 gram per liter solution of the fluorescent dye in the mixed solvent is stable at room temperature and below.

EXAMPLE 2

100 ml of N-octyl-2-pyrrolidone (Agsolex-8 provided by International SpecialTY Products) was added gradually to 10 liters of stirred polyalphaolefin (PAO) oil (Durasyn provided by BP Australia) at room temperature to form a solution of solvent and lubricant. 4 grams of a powdered coumarin dye, Elbaplast Fluorescent Brilliant Yellow R (C I. Solvent Yellow 160:1), was added gradually to the surface of the stirred liquid so that the powder was drawn into the vortex created by the stirrer and dispersed uniformly throughout the liquid. This dispersion was then heated with stirring to 65°C to dissolve the dye and thus form a homogeneous solution of clear bright yellow fluorescent oil. This oil solution was cooled to 3°C without loosing clarity or crystallising.

Thus, from the results of example 1 and 2 it can be readily seen that the addition of the solvent, in this case the N-octyl-2-pyrrolidone stabilized the solution of fluorescent dye so that the solution remained homogeneous at low temperatures and that there was no formation of solid particles.

EXAMPLE 3 0.8 ml of N-docecyl 2-pyrrolidone (Agsolex-12 provided by International Speciality Products) was added to 80ml polyalphaolefin (PAO) oil (Enersyn LPS PO 68 provided by BP Australia) at room temperature to form a solution of solvent and lubricant. 10 milligram of powdered phthalimide dye being C I. Solvent Yellow 43 was added gradually to the surface of the stirred liquid so that the powder was dispersed uniformly throughout the liquid. This dispersion was then heated with stirring to 52°C to dissolve the dye and thus form a homogeneous solution of clear bright yellow fluorescent oil. The equivalent solution without the Agsolex-12 had a pale yellowish-blue fluorescence.

This Example shows that phthalimide dyes may be used in the compositions of the invention with the same results as the coumarin dyes.

EXAMPLE 4

20ml of N-Methyl-2-pyrrolidone (M-PYRROLE provided by International Speciality Products) was dispersed in 2 litre of vigorously stirred polyalphaolefin (PAO) oil (Enersyn LPS PO 68 provided by BP Australia Limited). 1 g of Elbaplast Fluorescent Brilliant Yellow dye (C I. Solvent Yellow 160:1 was added gradually to the vortex of the stirred dispersion. The subsequent mixture was heated 73 deg C to form a clear solution. This solution was cooled to room temperature when some dye crystallised. The clear supernatant liquid was a bright yellow-green colour. A thin film spread on steel was readily detectable with a UV-emitting torch.

EXAMPLE 5 As a first step, 7g of Elbaplast Brilliant Yellow (C I solvent Yellow 160: 1 ) was dissolved in 100 ml of N-(n-octyl)-2-pyrrolidone by stirring in the powered dye at room temperature to form a dye concentrate.

(a) 0.2ml of this dye concentrate was added to 50ml of polyalkyleneglycol

(PAG) lubricant (PAG II from Technical Chemical Company). A brilliant yellow-green fluorescence was seen. The colour was slightly darker than the same dye concentrate in Polyalphaolefin oil due to the blue dye in the PAG

A thin film spread on stainless steel was readily visible under a UV emitting LED torch.

(b) 0.2ml of this dye concentrate was added to 50ml of polyolester (POE) refrigeration oil (Castrol ICEMATIC SW 100). The resulting brilliant yellow- green fluorescence was equal to that from the same volume of concentrate in polyalphaolefin oil.

A thin film spread on stainless steel was readily visible under a UV-emitting LED torch. (c) 0.25ml of this dye concentrate was added to 100ml of solvent refined mineral oil (Fuchs Renolin B 68 hydraulic oil). The resulting brilliant yellow- green fluorescence was slightly duller than that from the same volume of concentrate in polyalphaolefin oil because of the yellow brown colour of the Renolin B.

(d) 0.4ml of this dye concentrate was added to 100ml of alkylbenzene refrigeration oil (Zerol 200TD). The original pale blue fluorescence of the Zerol changed to a brilliant yellow-green fluorescence equal to that from the same volume of concentrate in polyalphaolefin oil.

A thin film spread on stainless steel was readily visible under a UV-emitting LED torch.

EXAMPLE 6

A Delphi model 5465 automotive air conditioning compressor was filled with 220ml of the oil of this invention (Polyluminaa 68, a PAO oil supplied by Refrigerant Oil Company Pty Ltd) and the oil-filled compressor connected into an air conditioning system (supplied by Air International Pty Ltd) of the type fitted as original equipment to a model VY Holden Commodore motor car, which was mounted on an instrumented test bench. The system was evacuated for 30 minutes and then filled with R134a refrigerant gas using an Ariazone 4001 electronic refrigerant processor and charging system (supplied by Ariazone International of Thomastown, Victoria, Australia). Once the A/C system was fully charged with refrigerant, it was run for 3 hours at full load (eg ambient air temperature 19.3 °C; cooled air termperature 2.3 °C) and then inspected for leaks using a UV-emitting flashlight and yellow UV-filtering goggles.

A tiny leak from the receiver/dryer coupling was easily observable.

EXAMPLE 7

(a) 5 ml of N-(n-dodecyl)-2-pyrrolidone was mixed into 100ml of polyalphaolefin (PAO) oil (Synfluid 10 from CP Chemicals) and 20mg of dye powder (CI: Fluorescent Brightener 61 - Columbia Blue from DayGlo Corporation) was added with stirring and heated in a waterbath to dissolve the dye power.

(b) For comparison purposes 20mg of the same dye was added with stirring into 100ml of polyalphaolefin (PAO) oil (Synfluid 10 from CP Chemicals) and heated in a waterbath to dissolve the dye.

The dye powder in sample (a) dissolved much more readily than in sample (b) and gave a solution with a purplish-blue fluorescence. The solution of sample (b) had a barely detectable bluish fluorescence much inferior to that of the solution of sample (a). EXAMPLE 8

20mg of dye power (CI: Fluorescent Brightener 61 - Columbia Blue from DayGlo Corporation) was added to 5 ml of N-(n-dodecyl)-2-pyrrolidone) in a glass-stoppered test tube. The stopper was inserted and the liquid was shaken vigorously to dissolve the dye giving a bright blue fluorescing liquid. This solution was added to 100ml of polyalphaolefin (PAO) oil (Synfluid 10 from CP Chemicals) at room temperature to give a solution with a purplish- blue fluorescence comparable to that produced in Example 7(a).

EXAMPLE 9

The chemical stability of a lubricating oil composition containing 0.42g/l of CI Solvent Yellow 160:1, 0.6% v/v N-(n-octyl)-2-pyrrolidone in a polyalphaolefin oil of ISO Viscosity Grade 68 was tested in the presence of an equal volume of refrigerant by heating in a sealed tube for 14 days at 175 deg C in the presence of iron, copper and aluminium catalysts according to the method of ASHRAE Standard 97 "Sealed Glass Tube Method to Test the Chemical Stability of Material for use in Refrigeration Systems". Separate tests were performed using the refrigerants R134a, R407A, and R407C In all cases there was no change in the appearance or fluorescing ability of the oil as a result of this extreme test regime. MISCELLANEOUS

Additional tests were conducted to conform the stability of fluorescent dyes in other N-alkylpyrrollidones such as N-cyclohexyl-2-pyrrolidones thus suggesting that straight, branched or cyclic alkyl-moeities in the range C₁-C₁₈ may be employed with the invention.

Typically formulations in accordance with the present invention include the following:

A. Top-up Lubricant 1 % pyrrolidone solvent in the base oil 10OOppm dye in powdered form

B. Refrigeration working fluid 0.3% pyrrolidone solvent 49.6% base oil 50% R134a refrigerant 250ppm dye

C Fluorescent lubricating oil 1 % pyrrolidone solvent in the base oil 400ppm dye in powdered form plus conventional additives if desired. A particular advantage of the present invention that the dye/solvent combination exhibits enhanced solubility and/or stability over a wide range of temperatures, particularly at low temperatures in a wide range of natural and synthetic lubricants or oleaginous working fluids.

Another advantage is that the fluorescent dye/solvent combination is optically brighter so that it is more visible in difficult to observe situations.

A still further advantage of the present invention is that less fluorescent dye material can be incorporated into the formulation since it is more reactive to incident UV light. As the fluorescent dye materials are expensive, the system can be manufactured more cheaply.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

It will be understood to persons skilled in the art of the invention that many modifications may be made without departing from the spirit and scope of the invention.

Claims

CLAIMS:

1. A method of detecting leakages in an apparatus containing a liquid oil, said method comprising incorporating into said liquid oil a fluorescent dye composition and a pyrrolidone solvent and subsequently irradiating an external surface of said apparatus with a source of electromagnetic radiation in a frequency range selected to excite enhanced fluorescence in said fluorescent dye composition in the presence of said pyrrolidone solvent, the location and/or extent of a leakage being indicated by a fluorescence response from leaked liquid oil on said external surface.

2. A method as claimed in claim 1 wherein said fluorescent dye composition is selected from fluorescent dye groups comprising coumarin dyes, phthalimide dyes, naphthalimide dyes, xanthene dyes, thioxanthene dyes, perylene dyes, naptholactam dyes, azlactone dyes, methine dyes, oxazine dyes, thiazine dyes or mixtures thereof.

3. A method as claimed in claim 2 wherein said fluorescent dye composition comprises a coumarin dye selected from coumarin 1 , coumarin 2, coumarin 30 and the like, coum, dercoum, derPcoum, 2coum, 2dercoum, 2derPcoum, silylated coumarin dyes including derivatives thereof and precursors therefore or mixtures thereof.

4. A method as claimed in claim 2 wherein said fluorescent dye composition comprises from a phthalimide dye selected from alkoxynaphthalimides, 4-aminonaphthalimides, 1 ',8'- naphthoylenebenzimidazoles, imides of Naphthalene-1 , 4, 5, 8- tetracarboxylic dianhydride, 1',8'-naphthoylenebenzimidazole perdicarboximides, bis-benzimidazole derivatives of naphthalene-1 , 4, 5, 8- tetracarboxylic acid, 1 ',8'-naphthoylenepyrazoles, azo- and azomethine naphthalimides, and perylene-3, 4, 9, 10-tetracarboxydiimides.

5. A method as claimed in claim 1 wherein said fluorescent dye composition is present in said liquid oil in the range of from 0.001 gm/l to 100 gm/l.

6. A method as claimed in claim 5 wherein said fluorescent dye composition is present in said liquid oil in the range of from 0.001 gm/l to 10 gm/l.

7. A method as claimed in claim 5 wherein said fluorescent dye composition is present in the range of from 0.001 gm/l to 10 gm/l.

8. A method as claimed in claim 1 wherein said pyrrolidone solvent is selected from N- alkylpyrrolidones.

9. A method as claimed in claim 8 wherein said solvent is selected from N-C₅-ι₈ alkylpyrrolidones or mixtures thereof.

10. A method as claimed in claim 1 wherein said solvent is present in said liquid oil in the range of from 0.01% to 5% by volume.

11. A method as claimed in claim 10 wherein said solvent is present in said liquid oil in the range of from 0.05% to 3.0% by volume.

12. A method as claimed in claim 1 wherein said liquid oil is selected from natural or refined mineral oils, including naphthenic or paraffinic oils, alkylated benzenes, silicones, polyalkylene glycols, polyalphaolefins, diesters or triesters of dicarboxcyclic or tricarboxcyciic acids, and polyalkylsilicate oils, or mixtures of any two or more thereof.

13. A working fluid composition for an internally lubricated apparatus, said composition comprising a base oil selected from natural or refined mineral oils, including naphthenic or paraffinic oils, alkylated benzenes, silicones, polyalkylene glycols, polyalphaolefins, diesters or triesters of dicarboxcyclic or tricarboxcyciic acids, and polyalkylsilicate oils, or mixtures of any two or more thereof; an N- alkylpyrrolidone solvent or mixtures thereof; and, a fluorescent dye composition, said liquid oil composition characterized in that the location and/or extent of liquid oil leakages are indicated by a fluorescence response from said fluorescent dye composition in leaked liquid oil on an external surface of said apparatus and wherein said fluorescence response is enhanced by said solvent.

14. A working fluid composition as claimed in claim 13 wherein said solvent is selected from N-C₅-₁₈ alkylpyrrolidones or mixtures thereof.

15. A working fluid as claimed in claim 13 wherein said fluorescent dye composition is selected from fluorescent dye groups comprising coumarin dyes, phthalimide dyes, naphthalimide dyes, xanthene dyes, thioxanthene dyes, perylene dyes, naptholactam dyes, azlactone dyes, methine dyes, oxazine dyes, thiazine dyes or mixtures thereof.

16. A working fluid as claimed in claim 15 wherein said fluorescent dye composition comprises a coumarin dye selected from coumarin 1 , coumarin 2, coumarin 30 and the like, coum, dercoum, derPcoum, 2coum, 2dercoum, 2derPcoum, silylated coumarin dyes including derivatives thereof and precursors therefore or mixtures thereof.

17. A working fluid composition as claimed in claim 13 wherein said fluorescent dye composition is selected from alkoxynaphthalimides, 4- aminonaphthalimides, 1',8'-naphthoylenebenzimidazoles, imides of Naphthalene-1 ,4, 5, 8-tetracarboxylic dianhydride, 1',8'- naphthoylenebenzimidazole perdicarboximides, bis-benzimidazole derivatives of naphthalene-1 ,4, 5, 8-tetracarboxylicacid, 1 ',8'- naphthoylenepyrazoles, azo- and azomethine naphthalimides, and perylene- 3, 4, 9, 10-tetracarboxydiimides.

18. A working fluid composition as claimed in claim 15 wherein said fluorescent dye composition is selected from CI. Solvent Yellow 43 or CI. Solvent Yellow 160:1 or mixtures thereof.

19. A working fluid composition as claimed in claim 13 wherein said solvent is present in said oil composition in the range of from 0.05% to 3.0% by volume.

20. A working fluid composition as claimed in claim 13 wherein said fluorescent dye composition is present in the range of from 0.02 gm/l to 5.0 gm/l.

21. A working fluid composition as claimed in claim 13 including additives selected from antioxidants, antiwear agents, antistatic agents, dispersants and stabilizing agents.

22. A working fluid composition as claimed in claim 13 wherever used as a lubricating oil.

23. A working fluid composition as claimed in claim 13 wherever used as a hydraulic working fluid.

24. A refrigeration working fluid comprising:- a refrigerant; a lubricating composition; an N- alkylpyrrolidone solvent; and, a fluorescent dye composition, said refrigeration working fluid characterized in that the location and/or extent of working fluid leakages in a refrigeration system are indicated by a fluorescence response from said fluorescent dye composition in leaked lubricating oil on an external surface of said refrigeration system and when said fluorescence response is enhanced by said solvent.

25. A refrigeration working fluid as claimed in claim 24 wherein said solvent is selected from N-Cs-is alkylpyrrolidones or mixtures thereof.

26. A refrigeration working fluid as claimed in claim 24 where, said fluorescent dye composition is selected from fluorescent dye groups comprising coumarin dyes, phthalimide dyes, naphthalimide dyes, xanthene dyes, thioxanthene dyes, perylene dyes, naptholactam dyes, azlactone dyes, methine dyes, oxazine dyes, thiazine dyes or mixtures thereof.

27. A refrigeration working fluid as claimed in claim 25 wherein, said fluorescent dye composition comprises a coumarin dye selected from coumarin 1 , coumarin 2, coumarin 30 and the like, coum, dercoum, derPcoum, 2coum, 2dercoum, 2derPcoum, silylated coumarin dyes including derivatives thereof and precursors therefore or mixtures thereof.

28. A refrigeration working fluid as claimed in claim 25 wherein said fluorescent dye composition is selected from alkoxynaphthalimides, 4- aminonaphthalimides, 1',8'-naphthoylenebenzimidazoles, imides of Naphthalene-1 ,4, 5, 8-tetracarboxylic dianhydride, 1 ',8'- naphthoylenebenzimidazole perdicarboximides, bis-benzimidazole derivatives of naphthalene-1 ,4, 5, 8-tetracarboxylic acid, 1 ',8'- naphthoylenepyrazoles, azo- and azomethine naphthalimides, and perylene- 3, 4, 9, 10-tetracarboxydiimides.

29. A refrigeration working fluid as claimed in claim 25 wherein said fluorescent dye composition is selected from C I. Solvent Yellow 43, C I. Solvent Yellow 160:1 or mixtures thereof.

30. A refrigeration working fluid as claimed in claim 25 wherein said solvent is present in said oil composition in the range of from 0.05% to 3.0% by volume.

31. A refrigeration working fluid as claimed in claim 30 wherein said fluorescent dye composition is present in the range of from 0.02 gm/l to 5.0 gm/l.