Note: Descriptions are shown in the official language in which they were submitted.
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COMPOSITION AND METHOD FOR DETECTING LEAKS IN HERMETIC REFRIGERANT SYSTEMS
The present invention relates to the detection of leaks in
refrigeratiomsystems, and to an
improved leak detection composition and to a refrigerant composition
incorporating
same. The invention also relates to a method of formulating such compositions.
The invention is generally applicable to the detection of leaks from a
hermetic refrigerant
system, such as refrigeration, heating, ventilation and air-conditioning
systems, wherein a
fluorescent dye or other visible indicator composition is combined with a
suitable
refrigerant system lubricant and a material suitable to function as a heat
transfer agent or
refrigerant in a hermetic system.
The invention is especially directed towards locating refrigerant leaks from
refrigerant
systems using refrigerant substances other than chlorofluorocarbons (CFC) that
have been
banned under the Montreal Protocol.
Refrigerants that are devoid of the chlorine atom and therefore considered
environmentally friendly to the earth's ozone layer have been developed and
continue to
be developed to replace CFC and HCFC materials that are the circulating heat
transfer
media in many hermetic systems. Many chemical companies have developed
products
that alone or in combination are suitable to function as heat transfer agents
or refrigerants
in a hermetic system such as, but not limited to, hydro-chloro-fluorocarbons
(HCFC),
hydrofluorocarbons (HFC) and hydrogen, 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.
These
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foregoing HCFC, HFC and hydrocarbon refrigerants are considered less damaging
to the
environment and have ozone depletion potentials which range from zero to a
fraction of
one, while the ozone depletion potential of a CFC refrigerant, such as CFC-12,
is one.
The use of these new alternative refrigerants has required the use of new
kinds of
refrigeration system lubricants such as synthetic polyalkylene glycols (PAG)
and
polyolesters (POE) and has rendered prior leak detection chemicals employing
materials
such as those described in U.S. Pat. Nos. 4,758,366 and 5,149,453, issued on
Jul.19,1988
and Sep. 26,1992, respectively, as largely ineffective. These patents teach
the use of
perylene yellow fluorescent dyes formulated with mineral oils. Mineral oil is
a
hydrocarbon. Hydrocarbons such as synthetic hydrocarbons (SHC), alkylbenzene
(AB),
and polyalphaolefins (PAO) may only be partially soluble in polyalklene glycol
and in
polyolester lubricants such as those used in the new HFC refrigerant-
containing systems.
Leaks in refrigeration systems have up until the present invention been
located by various
methods, including the injection of a suitable dye material into the system
and the
detection of the residues of dye left on the surface of the system. For
example, vehicle
air-conditioning systems are prone to developing minor refrigerant leaks from
small
fatigue cracks and loose pipe connections brought about by the vibration that
the systems
are subjected to in use. The detection and location of the leaks is rendered
difficult
because the refrigerants in question are normally odourless and colourless.
Thus, it has become commonplace for diagnostic compositions containing dyes
which
fluoresce under the influence of ultra-violet radiation to be used to make the
leaks
obvious. Hitherto, it has been usual when servicing a leaky system to charge
the system
with a small quantity of the dye-containing composition, then if no gas was
left in the
system to add gas as well. Then, run the system to cause leakage of the
composition with
the gas and then detect the leak by detecting the residues of dye left on the
surface of the
system components at the site of the leak. See U.S. Pat. No. 5,421,192 re-
issued under
Re. 35,370 on 5 November 1996.
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This type of procedure is a laborious, lengthy procedure requiring the use of
special
injection equipment. It has also been disadvantageous for the service provider
in that
there is always the possibility of either under-dosing or over-dosing the
system, or the
accidental spillage of the diagnostic composition causing discoloration of the
customer's
vehicle and service equipment requiring elaborate clean up procedures. This
can
contribute significantly to servicing costs.
Attempts have been made to incorporate the dye material into the refrigerant
in its
pressurised storage cylinder as a pemnanent means of visual identification of
refrigerant
leakage from the gassed or regassed refrigeration system but previous attempts
have been
unsuccessful due primarily to chemical instability or insolubility.
Some new HFC systems reach higher operating temperatures and pressures than
the old
CFC systems because of different thermodynamic properties. Such higher
temperatures
and pressures can adversely affect the thermal stability of the dyes in the
new HFC-
containing systems.
In practice, the dyes have tended to separate out, or to precipitate out of
solution. For
example, it was found that although it is possible to mix powdered
naphthalimide dyes
with a wide range of solvents, it was difficult to maintain the dye in
solution when the
solvent and dye mixture was further mixed with a refrigerant gas while in its
liquid phase,
often resulting in the formation of a precipitate when mixed with the liquid
gas, having a
similar appearance to snow, causing clogging of the valves of the storage
cylinder and
making the product unfit for sale or use.
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It is an object of the present invention to provide an improved refrigerant
leak detection
system which goes at least some way towards overcoming or at least minimising
the prioi
art problems or limitations outlined above.
It is also an object of the present invention to provide an improved leak
detection
composition that incorporates a fluorescent dye or other visible dye suitable
for
permanent or long-term inclusion in a hermetic refrigeration system.
It is another object of the present invention to provide an improved
refrigerant
composition which incorporates a fluorescent dye or other visible indicator
composition
as an essential permanent component thereof.
It is a further object of the present invention to provide a method of
manufacturing such
compositions.
It is yet another object of the present invention to provide a method of
detecting leaks in a
refrigeration system utilising the above referenced compositions.
These and other objects of the invention will become more apparent from the
following
description.
pI~I;~OS RE OF THE INVEN~LQN
The present invention is based on the discovery that small but effective
quantities of
known fluorescent dyes or other diagnostic compositions may remain permanently
in
suspension or solution in the liquid refrigerant when stored in pressurised
storage vessels
(e.g. cylinders) long term. The pre-mixture of the dye or other diagnostic
composition in
solution, with or without the refrigerant and the refrigeration lubricant
allows for
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simplified introduction of the dye or other diagnostic composition into the
hermetic
refrigeration system.
According to one aspect of the invention, there is provided a leak detection
composition
for a refrigeration system comprising a fluorescent dye or other visible
diagnostic
composition dissolved in or in suspension or emulsion in a solvent for said
dye or
diagnostic composition together with a refrigeration system lubricant.
According to another aspect of the invention, there is provided a refrigerant
composition
comprising essentially an admixture of a liquid refrigerant with a fluorescent
dye or other
visible diagnostic composition dissolved in or in suspension or emulsion in a
solvent for
the dye or diagnostic composition, and a refrigeration system lubricant. This
mixture,
when pressurised, provides a refrigerant gas composition including a permanent
dye
component or other visible indicator.
According to a further aspect of the invention, there is provided a method of
detecting
leaks in a refrigeration system that uses in combination a refrigerant, a
refrigerant system
lubricant and a fluorescent dye or other visible diagnostic composition
permanently
entrained therein, the method comprising the steps of:
preparing a solution of the fluorescent dye or other visible diagnostic
composition
in a solvent suitable therefor
- adding a predetermined amount of the solution from the preceding step to a
combination of liquid refrigerant and refrigeration system lubricant to form a
stable
refrigerant composition having the dye or other visible diagnostic composition
dissolved
or solubilized therein
charging the hemnetic refrigeration system with a predetermined amount of the
refrigerant composition from the preceding step
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- operating the charged system as and when required and determining the
presence
of a leak site by the presence of a coloured fluorescence or other visible
coloration
detectable by visual observation or with the aid of a lamp that produces light
having an
emission wavelength from 300 to 480 nanometers, directed at said refrigeration
system.
t~FTAl1 FD DESCRIPTION OF THE PREFERRED EMBODIMENTS AND BEST
MOD OF CARRYING OUT THE INVENTION
The present invention is directed to the detection of leaks in refrigeration
systems
employing the new alternative HFC environmentally friendly refrigerants where
said
refrigeration system is suitable for cooling, freezing, heating, ventilating
and air
conditioning and where said refrigeration system employs alone or in
combination, any
material, suitable to function as a heat transfer agent or refrigerant in a
hermetic system
such as, but not limited to, chlorofluorocarbons (CFC),
hydrochlorofluorocarbons
(HCFC), hydrofluorocarbons (HFC) and any hydrogen, halogenated or ether
derivatives
of methane, hydrogen, halogenated, ether or cyclic derivatives either ethane,
propane,
butane, pentane, mixtures of HCFC, HFC, hydrocarbons, carbon dioxide and
ammonia.
Examples of the refrigerants include but are not limited to CFC-11, CFC-12,
HCFC-22,
HCFC-123, HCFC-124, HCFC-142b, HFC-32, HFC-134, HFC-134a, HFC-152, HFC-
152a, HFC-143a, HFC-125, HFC-245ca, HFC-245fa and HFC-225ca.
The refrigeration systems can use alone or in combination, refrigeration
system lubricants
including, but not limited to, hydrocarbons such as natural or refined mineral
oils,
synthetic hydrocarbons (SHC), alkylbenzenes (AB), polyalphaolefins (PAO) and
synthetic polyalkylene glycols that are terminated as mono- or diethers or as
esters, and
the general class of polyolester lubricants that are either di-, tri-, tetra-
or polyfunctional
pentaerythritol esters.
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The mixture of refrigerants and refrigeration system lubricants can be
composed of the
aforementioned materials having at least 0.001 grams of general naphthalimide
dye
(including structures that incorporate any nitrogen alkyl derivatives and any
functionalized ring chemistry, both carbocyclic and heterocyclic, with either
nitrogen,
sulfur, carbon or oxygen) dissolved per 100 grams of refrigeration working
fluid.
The choice of dye for inclusion in the refrigerant gas composition is from any
suitable
known dye which can be dissolved in a solvent and is compatible with the
combination of
refrigerant and refrigeration system lubricant, and is not precipitated from
solution. The
preferred dyes are naphthalimide and perylene fluorescent dyes, but are not
limited
thereto. The dye is incorporated into the solvent generally in the range of
about 1 to S%
by weight of the solution, and then entrained into the refrigerant composition
in the range
of about 0.001 to about 0.1% by weight based on the weight of the dye
substance per 100
grams of refrigerant working solution.
The refrigerant composition including the dye entrained therein is circulated
throughout
the entire hermetic refrigeration system, and in time the system will be
inspected for leaks
with a light excitation source having emission wavelengths in the range from
300 to 480
nanometers.
The preferred compositions disclosed herein are invisible or of a lesser
intensity in
ordinary light. When a lamp having a light emission output in the range from
300 to 480
nanometers is directed at the lubricant and naphthalimide dye mixture, a
striking
fluorescence, for example with the colour yellow to yellow green, is
immediately
noticeable at the leak site.
Conventionally, refrigerant is supplied by refrigerant wholesalers to service
persons and
refrigeration equipment manufacturers in pressure vessels able to withstand
the vapour
pressure of the refrigerant at normal ambient temperatures. Those pressure
vessels are
commonly referred to simply as "gas cylinders", notwithstanding that a
normally full said
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gas cylinder is very nearly full of liquid refrigerant in equilibrium with
only a relatively
small ullage volume of refrigerant vapour. Each said gas cylinder is fitted
with a
manually operable outlet valve including a standardised hose connector,
whereby the
cylinder may be connected to standardised manually operable inlet valves, also
furnished
with standardised hose connectors, for the admission of refrigerant into both
the liquid
filled high pressure and vapour filled low pressure parts of a refrigeration
or air-
conditioning system.
The present invention contemplates that a wholesaler or manufacturer may
incorporate an
effective amount of dye stuff into the refrigerant while filling the said gas
cylinders for
delivery to the system manufacturer or service provider, to enable the latter
persons to
charge the system with refrigerant in a normal manner, to thereafter render it
unnecessary
for a service provider to add the dye composition separately when placing gas
in a system
or adopt special procedures to detect leaks.
In experiments leading to the present invention it was found that if a
conventional
diagnostic composition is injected into an already filled cylinder the dye is
likely to form
a precipitate which will not thereafter re-mix with the liquid refrigerant;
but that this
could be overcome by injecting a dye containing composition into the liquid
refrigerant at
a slow and controlled rate as it is piped into the gas cylinder or back to
bulk storage by
the wholesaler or other filler thereof. It is thought that this is effective
because it limits
the localised concentration of dye composition in the liquid refrigerant at
any one time.
Thus, the invention further consists in a method of filling a gas cylinder
with an
admixture of liquid refrigerant and an effective amount of a diagnostic dye,
comprising
the step of continuously injecting a minor flow of a dye into a filler pipe
through which a
major flow of liquid refrigerant is being fed into a cylinder being filled.
They dye may be
metered into the filler pipe by any form of positive displacement pump or
similiar system
running at an appropriate speed to deliver the dye against the pumping and
vapour
pressure of the refrigerant at the temperature in the pipe.
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The above described method of the invention is applicable to the filling of
present day
gas cylinders. In a less preferred alternative using a special gas cylinder
with an auxiliary
filling valve the dye may be injected directly into the liquid pool in the
cylinder
simultaneously with the input of refrigerant through the conventional valve.
As a general rule, the pigments in dyes that are currently used as diagnostic
agents are
essentially solids made available as powders. Before they can be readily
pumped they
require to be dissolved in an appropriate liquid solvent. Indeed they are
currently
marketed as solutions containing about 2% by weight of pigment in a liquid
solvent.
Therefore the term "dye" as used herein includes within its ambit liquid
solutions of the
pigment material.
Furthermore, in preferred embodiments the dye is preferably delivered in a dye
composition comprising such liquid solutions of pigment, preferably a pigment
that
fluoresces under the influence of ultra-violet radiation, in admixture with
one or more of
the following - mineral oils - vegetable oils - surfactants - synthetic oils -
esters - or other
suitable solvents therefor.
Thus a preferred composition for inclusion in the liquid refrigerant may
comprise dye
solution containing about 2% by weight of pigment dissolved in an admixture of
a
combination of the chemicals described above. Those chemicals have been found
to
reduce or stop the forming of the precipitate previously mentioned.
In a preferred form of the invention a napthalimide dye was solubilized into a
refrigerant
composition by first dissolving the dye in a solvent mixture comprising:
50% Fatty Acid Ethoxylate
30% Alcohol Ethoxylate
18% Polyolester Oil
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2% Naphthalimide Dye
An example of the Fatty Acid Ethoxylate is an Ethylene Oxide Ester based on
Oleic Acid.
It has six mots of Ethylene Oxide per mol of Oleic Acid.
An example of the Alcohol Ethoxylate is Cetyl Oleyl Alcohol Ethoxylate, which
has two
mots of Ethylene Oxide per mol of Cetyl Oleyl Ethoxylate.
Polyolester Oil is a lubricant used in air conditioning systems. Particularly
those using
HFC refrigerants. This chemical could be replaced by any of the lubricants
used in
refrigeration and air conditioning systems.
Napthalimide dyes are recognised for their suitability for fluorescing when
exposed to
light between 300 - 480 nm.
R134a is the gas most commonly used in conjunction with this dye mixture.
R134a, is an
HFC (hydrofluorcarbon) however suitability is not limited to that gas. It is
also suitable
for use with but not limited to, HCFC's (hydrochlorofluorocarbons) and
hydrogen,
halogenated, ether or cyclic derivatives of ethane, propane, butane, pentane,
mixtures of
HCFC, HFC, hydrocarbons, carbon dioxide and ammonia. The dyes able to be used
are
not limited to Naphalimide dye. It is also suitable for use with Perylene dye
and other
dyes used for their ability to fluoresce when exposed to Light between 300 -
480 nm. The
above exemplified dye in solvent solution is then mixed with the liquid
refrigerant in a
ratio of one part per one hundred.
It was found that although it was not difficult to mix powdered Napthalimide
dye with a
wide range of solvents, there was considerable difficulty making the powder
stay in
solution when the solvent and powder mixture were mixed with a refrigerant gas
while in
its liquid phase. Unless a suitable solvent or mixture of solvents was used
this mixture
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would form a precipitate when mixed with the liquid gas. This precipitate had
a similar
appearance to snow and rendered the product unfit for sale or use.
The above described mixture produces acceptable results but other mixtures and
chemicals can be used to achieve a similar outcome. These include but are not
limited to
mineral based oils and synthetic Hydrocarbon (SHG~ oil, Polyalkylene glycols
and other
chemicals used for lubrication of air conditioning and refrigeration systems,
fatty acids
such as Oleic Acid and other "vegetable oils", esters and surfactants
including but not
limited to fatty acid Ethoxylates and other Ethoxylates.
In respect of the present invention, the inventor has speculated that the
chemical
composition of the dye's solvents must be such that those chemicals used are
not
completely soluble in the refrigerant gas. If solvents such as (but not
limited to) oils,
intended for use with a certain refrigerant are used to carry the dye in
solution it was
found that when the dye and solvent are mixed with the liquid refrigerant, the
solvent and
refrigerant become bonded and the dye is released from the solvent and then
will appear
as a solid precipitate in the refrigerant gas.
Only those chemicals, which are not fully soluble with the chosen refrigerant,
can be used
to carry the dye without forming a precipitate. However the solvent must be
soluble to a
limited extent or a situation in such as with oil and water will occur.
Although an exemplary embodiment of the present invention has been described,
it will
be apparent to those having ordinary skill in the art that a number of
changes,
modifications or alterations to the invention described herein may be made,
none of
which depart from the spirit of the present invention. All such changes,
modifications
and alterations should therefore be seen as being within the scope of the
present
invention.
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It should be appreciated that the present invention provides a substantial
advance in the
detection of refrigeration system leaks, providing all of the herein-described
advantages
without incurring any relative disadvantages.
