Note: Descriptions are shown in the official language in which they were submitted.
CA 02469966 2004-06-04
COMPOSITION AND METHODS FOR INJECTION OF SEALANTS INTO AIR
CONDITIONING AND REFRIGERATION SYSTEMS
FIELD OF THE :INVENTION
The general field of the invention is the injection of sealant into
refrigeration and air
conditioning systems by means of suitable selection of sealant, mixtures,
equipment and
procedures to seal small leaks that develop in the system
BACKGROUND OF THE INVENTION
Organosilanes have been marketed successfully as automotive air conditioning
(A/C) system
sealants for several years. Their ise is targeted at small pinhole leaks that
develop over time,
allowing escape of refrigerant. Leaks lead to loss of efficiency for the a/c
system as well as
undesirable release of refrigerant gas to the environment. The application of
these sealants to
hermetically sealed systems used in non-automotive a/c systems and in
refrigeration systems has
been less widespread. In these applications, sealant injection often leads to
compressor
shutdown due to bearing seizure. At least one sealant manufacturer recommends
the use of a
"hard-start kit" apparently to overcome this issue.
It is desirable to develop alternative products and methods for the
introduction of sealant into air
conditioning and refrigeration systems.
SUMMARY OF THE INVENTION
In a first aspect the invention provides a method for injecting sealant into
an air conditioning or
refrigeration system having a compressor, a high pressure side ("high side"),
and a low pressure
side ("low side"). The method includes injecting the sealant in a quantity to
provide sufficient
lubrication to maintain proper operation of the compressor when the sealant is
fully distributed in
the system, and injecting the sealant so as to maintain proper operation of
the compressor before
the sealant is fully distributed in the system.
The sealant maybe injected at the high side of the system so as to maintain
proper operation of
the compressor before the sealant is fully distributed by distributing the
sealant starting at the
high side. The injected sealant may be injected at a rate of less than 6% per
minute of lubricant
within the system.
The sealant may be injected at a controlled rate so as to maintain proper
operation of the
compressor before the sealant is fully distributed in the system.
The sealant may be injected into a non-operating system under vacuum, and
other system
contents, including refrigerant, are later injected into the system causing
distribution of the
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previously injected sealant. Approximately 60% of total system refrigerant may
be injected after
the sealant.
The sealant may be injected as a part of a fluid mixture, and the mixture
further comprises one or
more of lubricant, drying agent, corrosion/rust inhibitor, antiwear agent,
fluorescent or
phosphorescent dye.
The sealant may be an organosilane. The organosilane may be a monomer capable
of forming a
solid polymer with itself or other chosen organosilanes in the presence of
moisture, and is stable
in the absence of moisture, and does not substantially interfere with the
normal operation of other
contents of the system in selected quantities.
The sealant may be part of a fluid mixture further comprising a lubricant. The
lubricant may be
an oil, the compressor may have a sump containing oil, and the minimum
viscosity of the
injected fluid mixture may be ?ij as determined by:
exp(xinj.ln ?inj + xsu np.ln ?sump + C) = Fr. ?sump
where,
In is the natural logarithm and exp is the exponential,
xiõ j, is mole fraction of injected material in final sump mixture,
xsõmp is mole fraction of original sump oil in final sump mixture,
?inj, ?sump are viscosities of the injected material and original sump oil
respectively, and
Fr is a desired fraction of original sump oil viscosity to be maintained.
Fr may be equal to approximately 0.9 or more.
The viscosity of the mixture may be not less than 7 CST @ 40 C.
In a second aspect the invention provides a method of introducing sealant into
an air
conditioning or refrigeration system having a compressor and evaporator. The
method includes
connecting a vessel containing a sealant mixture comprising an organosilane
between the
compressor and the evaporator, and while the system is running, allowing the
sealant mixture to
enter the system at a rate to prevent liquid slugging and to maintain
sufficient concentrations of
lubricant for proper operation of the compressor during the injection process,
allowing the
sealant to enter the system in an amount to maintain sufficient compressor
lubricant viscosity for
continued proper operation of the compressor, and allowing the sealant to
enter in an amount that
will allow continued proper operation of the air conditioning or refrigeration
system.
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In either aspect the sealant may be one or more of an organosilane and a
polymeric latex
consisting of one or more of a vinyl acetate, methacrylate, nitrile, epoxide
and styrene polymer.
The mixture may also include one or more of an accelerant and a catalyst.
The sealant mixture may be allowed to enter the system by pressurizing the
sealant mixture
sufficiently above system low side operating pressure to cause the sealant
mixture to enter the
system from the vessel when the system is running. Pressurizing the sealant
mixture may include
using the system pressure of the system in a non-running state to pressurize
the sealant mixture
in the vessel.
The method may also include allowing the sealant mixture to cool to near
ambient temperature
after the vessel is pressurized and while the vessel is fluidly connected to
the system in the non-
running state. The method may also include fluidly disconnecting the
pressurized vessel from
the system after cooling, running the system until low side pressure drops,
and fluidly connecting
the vessel to the low side of the system and allowing the sealant to enter the
system as provided
above.
In a third aspect the invention provides a method of introducing sealant into
an air conditioning
or refrigeration system having a compressor and an evaporator. The method
includes turning off
the system; allowing system pressure to equalize; connecting a vessel
containing a sealant
mixture comprising an organosilane between the compressor and the evaporator,
and while the
system is running, allowing the sealant mixture to enter the system at a rate
to prevent liquid
slugging and to maintain sufficient concentrations of lubricant for proper
operation of the
compressor. The organosilane is a monomer capable of forming a solid polymer
with itself or
other chosen organosilanes in the presence of moisture, and is stable in the
absence of moisture
in the system, and does not substantially interfere with the normal operation
of contents of the
system in selected quantities.
The step of connecting the vessel may include providing fluid connection
between the vessel and
the system, and the method may further include allowing sufficient time for
the sealant mixture
to achieve ambient temperature before running the system after fluid
connection.
The method may further include turning off the system when a selected amount
of sealant
mixture has entered the system for a period of time to allow system pressure
to equalize, and
repeatedly allowing the sealant mixture to enter the system as specified above
and turning off the
system to allow pressure to equalize as set out above, until a total selected
amount of sealant has
entered the system. The method may include equilibrating the system after
injecting the
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approximately 60% of the refrigerant then turning on the system and adding
remaining
refrigerant.
The sealant mixture may have a viscosity above 7 cst. when measured at 40 C.
The flow rate of
injection may be 6 cc/sec or less.
The viscosity for a particular lubricant/sealant mixture may be l1inj or
greater where 11inj is
determined by:
exp(xinj.ln ilinj + xsump.In rIsump + C) ? Fr . rlsump
where,
In is the natural logarithm and exp is the exponential,
xij, is mole fraction of injected material in final sump mixture,
Xsump is mole fraction of original sump oil in final sump mixture,
71ini, flsump are viscosities of the injected mixture and original sump oil
respectively,
and
Fr is a desired fraction of original sump oil viscosity to be maintained.
r
Fr may be equal to 0.9 or more. Where the calculated viscosity may be less
than 7 cst., then the
minimum viscosity may be set at 7 cst.
The step of allowing the sealant to enter the system may further include
allowing the sealant to
enter through an orifice having an opening within a range of from 0.020-0.06
inches diameter.
The step of connecting the vessel to the system may include connecting a hose
assembly between
the vessel and a low pressure side service port of the system. The hose
assembly may include a
first fitting for connection to the vessel and a second fitting for connection
to the port.
The step of providing fluid connection between the vessel and the system, and
the step of
allowing sealant mixture to enter the system, may include opening a valve in
the second fitting.
The vessel may be a sealed canister, and the step of providing a fluid
connection between the
canister and the system may include tapping the canister before opening the
valve in the second
fitting.
The second fitting may be a can-tapper. The method may also include
substantially evacuating
the hose assembly prior to connection to the system.
In a fourth aspect the invention provides a device for introducing sealant
into a hermetically
sealed air conditioning or refrigeration system. The device includes a sealed
vessel including an
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organosilane mixture of an organosilane and a miscible material, the mixture
having a viscosity
above 7 cst. when measured at 40 C. In this aspect the organosilane is a
monomer or oligomer
capable of forming a solid polymer with itself or other chosen organosilanes
in the presence of
moisture, and is stable in the absence of moisture in the system, and does not
substantially
interference with the normal operation of contents of the system in selected
quantities.
The device may include a metering device for fluid connection with the sealed
vessel, and for
controlling fluid flow from the sealed vessel. The metering device may be an
orifice having an
opening within a range of from 0.020-0.06 inches.
The device may further include a fitting for sealed fluid connection to a low
side port of the
system, and the fluid flowing through the metering device also flows through
the fitting. The
device may also include a hose assembly with a first fitting for sealed fluid
connection to a low
side port of the system, and a sealed fluid connection to the sealed vessel.
The device may also include a metering device for controlling fluid flow from
the sealed vessel
through the hose assembly.
The fluid connection to the sealed vessel may be a second fitting. The second
fitting may include
a manually operable valve for providing fluid connection between the hose
assembly and the
sealed vessel. The second fitting may include a can-tapper for opening the
sealed vessel.
The device may include a filter is placed between the fitting connecting to
the system and the
orifice. The orifice may have a diameter of 0.06 inches or less. The sealed
vessel may be a
sealed canister.
The organosilane or components of the sealant mixture may include components
that can be
represented as (Ri)(R2)Si(R3)(R4)
where,
R1 =is an alkyl radical of 1-4 carbon atoms or vinyl or -OH
R2 is R1 or -OR1 or -NH(R1) or -N(R1)2 or -R1NHR1NH2,
R3 is R1 or -OR1 or -NH(R1) or -N(R1)2 or -R1NHR1NH2, and
R4 is R1 or -OR1 or -NH(R1) or -N(R1)2 or -R1NHR1NH2.
A component of the sealant mixture may include components that can be
represented as
(R5)(R6)(R7)Si-O-Si(R5)(R6)(R7)
R5, R6 or R7 are each any one of R1,R2,R3 or R4 where,
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R1 =is an alkyl radical of 1-4 carbon atoms or vinyl or -OH,
R2 is R1 or -OR1 or -NH(Ri) or -N(RI)2 or -R1NHR1NH2,
R3 is R1 or -OR1 or -NH(RI) or -N(RI)2 or -R1NHRINH2, and
R4 is R1 or -ORI or -NH(R1) or -N(RI)2 or -R1NHR1NH2.
The sealant mixture may also include a lubricant miscible with the
organosilane and refrigerant
for use in the system. The miscible mixture may include a lubricant selected
from one or more
of a polyol ester, polyalkylene glycol, mineral oil, polyalphaolefin and
alkylbenzene. The
miscible mixture may include a lubricant further comprising additives to
enhance and refresh the
performance of lubricant in the compressor.
The preferred embodiment of these and other aspects of the invention will be
described later
herein.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention and to show more clearly
how it may be
carried into effect, reference will now be made, by way of example, to the
accompanying
drawings which show the preferred embodiment of the present invention and in
which:
FIG. 1 is a graphic representation of a sealant injection assembly in
accordance with a preferred
embodiment of the present invention in use with an air conditioning or
refrigeration system 1,
FIG. 2 is a partially exploded perspective view of the assembly of FIG. 1,
FIG. 3 is an end view of a fitting and orifice used in the assembly of FIG. 2,
and
FIG. 4 is a cutaway view of a typical single cylinder hermetic compressor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, a typical hermetically sealed air conditioning or
refrigeration system 1 has
an evaporator 3, compressor 5, condenser 7 and expansion device 9. The system
1 has a "low
side" 10 consisting of the part of the system 1 between the expansion device 9
(for example, an
orifice 9) and the suction line to the compressor 5. The compressor 5 draws in
low pressure, low
temperature refrigerant in a gaseous state from the "low side" 10. The
compressor 5 compresses
the gaseous refrigerant to a high pressure, high temperature gaseous state
that flows to the
condenser 7. The refrigerant passes through the condenser 7 and is cooled to a
liquid state. The
liquid refrigerant passes through the expansion valve 9, which causes the
refrigerant to expand to
a low pressure, low pressure temperature gas. The evaporator 3 absorbs heat
from outside the
system 1, and relatively low temperature, low pressure gas is reintroduced to
the compressor 5.
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For the test environment, the low side pressure is 77 psig at the compressor
5, and pressure on
the high pressure side of the compressor (the discharge 11) is 256 psig. The
temperature at the
evaporator 3 is 45 F and at the condenser 126 F. The ambient temperature is 90
F. The
temperature of the gas between the valve 9 and evaporator 3 is 55 F. The
temperature at the
compressor 5 discharge 11 is 171 F. The valve 9 in the test environment had a
diameter of 0.059
inches. The gas flow rate in the low side between the evaporator 3 and the
compressor 5 is 1596
ft/min. The diameter of pipe in the low side is nominal 3/4 inch, while the
inside diameter of pipe
at the discharge is 3/8 inches. This is for a single phase 2 ton compressor 5.
These are typical characteristics for an air conditioning system 1 or the
environment about an air
conditioning system 1. For larger and smaller systems 1, the particular
specifications may
change. This a design choice. The particular parameters under which sealant is
introduced into
the system may vary accordingly.
In order to seal small leaks in the system 1 it is desirable to introduce
organosilanes or other
sealants into the system 1. Organosilanes cure when in the presence of
moisture, such as would
occur at the situs of a leak.
The use of organosilanes in non-hermetically sealed air conditioning or
refrigeration systems 1 is
previously known, see for example, U.S. Patent No. 4,237,172 issued 2 December
1980 to Packo
et al under title Sealing Leaks by Polymerization of Volatilized Aminosilane
Monomers; United
States Patent No. 4,304,805 issued 8 December 1981 to Packo et al under title
Sealing Leaks by
Polymerization of Volatilized Aminosilane Monomers; U.S. Patent No. 4,331,722
issued 25 May
1982 to Packo et al under title Sealing Leaks by Polymerization of Volatilized
Organosilane
Monomers; and U.S. Patent No. 5,417,873 issued 23 May 1995 to Packo under
title Sealant
Containing Partially Hydrolized Tetraalkoxy Silane, for Air Conditioning and
Refrigeration
Circuits that describe mixtures for this purpose. As previously mentioned, the
simple injection
of an organosilane or mixture of organosilanes into a hermetically sealed
system 1 will typically
cause compressor 5 failure.
Referring to FIG. 2, an injection assembly 12 has a vessel 15 containing an
organosilane mixture.
In the preferred embodiment the vessel 15 is a canister 15. The mixture is
selected for
miscibility with the contents of the system 1. It is to be recognized that, in
addition to
refrigerant, the system 1 contains a miscible lubricant for lubrication of the
compressor 5. The
system 1 may also have other contents, such as a fluorescent dye for leak
detection. It may also
contain a chemical dryer to remove moisture from the system 1.
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The inventors have recognized that, in addition to liquid slugging, the
introduction of greater
concentrations of organosilanes remove lubricants from the compressor 5,
resulting in
compressor 5 failure. The organosilane should be introduced in sufficiently
low concentrations
and be miscible with the system I lubricant to avoid liquid slugging and to
maintain sufficient
lubricant for proper operation of the compressor 5. The organosilane is
introduced from vessel
to a low side port 17 between the evaporator 3 and compressor 5.
The organosilane is introduced at a rate that allows the concentration of the
organosilane to be
diluted sufficiently by the other system I contents to prevent liquid slugging
and to maintain
sufficient concentration of lubricant for proper operation of the compressor
5.
10 Referring to Fig. 4, controlled injection of the organosilane combined with
the miscible lubricant
is critical when injected at the low side port 17 because of the close
proximity between the low
side charging port 17 and compressor 5. After the organosilanehaiscible
lubricant mixture enters
the compressor 5 along with cool refrigerant vapor it has to first pass by
outboard shaft bearing
18. This aids in replacing oil to the outboard bearing which may have been
stripped by passing
15 refrigerant. The mixture continues on flow path 19a rushing over motor
windings (stator 19b,
rotor 19c) removing heat from the electric motor. The flow of refrigerant
vapor /mixture is then
drawn over oil reservoir (sump) 19d into compressor pump l9e where it is
compressed into a hot
vapor and discharged. During this flow path the importance of maintaining a
suitable viscosity is
important for a continued oil barrier between metal internals.
Many refrigeration and air conditioning systems use semi-hermetic or open seal
(external drive)
compressors and the type of compressor may be reciprocating (piston-cylinder),
rotary, scroll,
screw or centrifugal. While compressor geometry is critical to the hermetic
systems as explained
above, general engineering considerations also require control of flow rate,
quantity and
viscosity of the injected material for the other drives to ensure continued
good operation and
acceptable compressor life.
The organosilane can be introduced by many different methods. For example, it
can be injected
at a very slow rate while the compressor 5 is running continuously. This
requires fine control
over the injection rate. In order to allow increased rate of introduction, the
organosilanes (or a
portion thereof) can be injected into a running system 1, followed by a period
of time during
which the system 1 is stopped. The initial use of a running system 1 allows
the organosilane to
be distributed through the system 1. Stopping the system 1 allows the
distributed organosilanes
to further mix with the system 1 contents, without forcing areas of high
organosilane
concentration to flow through the compressor 5 repeatedly. This process can be
repeated until all
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of the organosilane is introduced. Although this may allow for greater rates
of introduction, the
process would still be slow, and fine control is still required.
An alternative method of introducing the organosilane is to form an
organosilane mixture by pre-
diluting the organosilane in a material miscible with the system 1 contents
and with the
organosilane. This mixture is then introduced into the system 1 using one of
the methods
discussed above.
In the preferred embodiment, the organosilane is mixed with a lubricant to
form the organosilane
mixture. This has an additional benefit of maintaining lubricant in close
proximity to the
organosilane at all times. For increased flow control the viscosity of the
organosilane mixture
can be maintained within a selected range. Organosilane on its own has a very
low viscosity (for
example <1 est. at 40 C). This in part results in difficulty in controlling
the flow of
organosilane.
An additional method of injection would include the use of a fluid injector
that can inject the
mixture into the working low side system of the unit in small increments, an
example include a
Revolver TM sold by Cliplight Manufacturing Company of Toronto, Canada. The
Cliplight device
allows for approximately 0.04 of an ounce to be measured in at any one time.
Additional
amounts of the mixture depending on the system size could be accurately added.
This would be
an acceptable method of injection allowing only small amounts of the mixture
into the suction
gas path and thus preventing possible liquid slugging to the compressor 5.
Also, there are other modifications that could be made to an injection device.
For example, a
filter 16A could be added, as shown in FIG. 1, to the hose apparatus 16 to
filter out any particles
injected from the system 1 when charging the canister 15.
Further details of the preferred embodiment will be described.
Referring to the FIGS., the use of sealants based' on organosilanes for
refrigeration and air
conditioning systems 1 is made possible by control of the rate of introduction
and viscosity of the
sealant mixture within certain ranges. An appropriate choice of organosilane
sealant is made to
allow effective sealing of small pinhole size leaks in the air conditioning or
refrigeration system
1.
Preferably, the organosilane is chosen with several criteria in mind. The
organosilane is miscible
in the lubricant fluid; it is typically a monomer, but may contain oligomers,
capable of forming a
solid polymer with itself or other chosen organosilanes in the presence of
moisture under the
conditions of the particular application. The reaction rate of the
organosilane or mixture of
organosilanes is sufficient to form an effective seal at the situs of the
leak. The polymeric seal is
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chosen to be sufficiently strong to maintain an effective barrier to prevent
further leakage of
refrigerant from the system 1. Also, the organosilanes are chosen to be stable
in the absence of
moisture, be non-corrosive and otherwise inactive to the components of system
1 and be
generally environmentally acceptable. Further, the nature and injected
quantity of the
organosilanes is chosen, to the extent that it would interefere with the
refrigerant and/or
lubricant, so that such interference remains consistent with the normal
operation of the
refrigerant fluid e.g. vaporization and liquefaction characteristics.
The organosilane is combined with a miscible lubricant at particular ratios to
provide the proper
mixture viscosity for injection to the refrigerant system 1 to prevent bearing
seizure. Specific
orifice 20 (see FIG. 3) sizes are selected for an apparatus to ensure that the
mixture is injected at
flow rates required to prevent liquid slugging and subsequent compressor 5
shutdown or failure.
In addition, certain procedures are performed for effective introduction of
the mixture. Injection
procedures are also described that reduce risk of temporary or catastrophic
equipment shutdown.
These include allowing the sealant mixture to cool to ambient temperatures
before injection.
Cooling permits better control over the flow rate of the organosilane
component of the mixture.
Preferred components and compositions for the organosilane include those
described in U.S.
Patent No. 4,237,172 issued 2 December 1980 to Packo et al under title Sealing
Leaks by
Polmerization of Volatilized Aminosilane Monomers; United States Patent No.
4,304,805 issued
8 December 1981 to Packo et al under title Sealing Leaks by Polmerization of
Volatilized
Aminosilane Monomers; U.S. Patent No. 4,331,722 issued 25 May 1982 to Packo et
al under
title Sealing Leaks by Polymerization of Volatilized Organosilane Monomers ;
and U.S. Patent
No. 5,417,873 issued 23 May 1995 to Packo under title Sealant Containing
Partially Hydrolized
Tetraalkoxy Silane, for Air Conditioning and Refrigeration Circuits.
Particular compositions for the organosilane are dependent on the selected
criteria from those set
out above. However the general nature of the organosilane can be represented
as
(Ri)(R2)Si(R3)(R4) where the preferred nature of the radicals is that
R1 is an alkyl radical of 1-4 carbon atoms or vinyl or -OH
R2 is R1 or-ORI or NH(R1) or N(RI)2 or -RINHRINH2
R3 is RI or -OR1 or NH(R1) or N(R1)2 or -R1NHR1NH2, and
R4 is R1 or -OR1 or -NH(R1) or N(R1)2 or -R1NHR1NH2
Other components which can be included are oligomers of the monomeric silanes
described.
One such example are the siloxanes:
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(R5)(R6)(R7)S-O-Si(Rs)(R6)(R7)
Where R5,R6 or R7 may be R1,R2,R3 or R4
This composition was present at about 10% in the organosilane mixture used for
experimental
purposes where R5 and R6 were -OCH3 and R7 was either -CH3 or vinyl.
These compositions are illustrative only as indicated by the patents cited for
Packo et al. It is
also recognized that not all silanes or combinations will meet each or all of
the criteria set out of
above.
The lubricant is preferably chosen to be miscible with the organosilane
mixture at ambient
temperatures to provide proper control of the flow. Preferred lubricants would
include those
based on fluids such as polyolesters. Lubricants based on other fluids might
be used. Those
known to be miscible with o:rganosilanes include, for example, mineral oils,
alkyl benzenes and
polyalkylene glycols.
Other fluids as alternatives to the lubricant or in combination with the
lubricant may also be used
provided that they result in an appropriate viscosity for the mixture and are
compatible with
contents of the system 1. In those other systems where the refrigerant is not
a carrier for the
lubricant, i.e. systems with separate refrigerant and lubrication circuits,
these other fluids may
also be added. The restrictions outlined elsewhere herein for high-side
injection to a 6 vol % max
per minute based on oil capacity also apply. These other fluids include, for
example, drying
agents, elastomer and metal conditioners, antioxidants, corrosion and rust
inhibitors, antiwear
agents, metal deactivators, acid and base neutralizers, detergents,
fluorescent and phosphorescent
dyes and such Drying agents include, for example, mono- and polyhydric
alcohols, including
glycols, preferentially mono-, di and trihydric alcohols, organosilanes, or so-
called
orthoformates. Conditioners include, for example, :methylene chloride and
cyclohexanone.
Antioxidants include those based on phenolic and aminic derivatives. Corrosion
and rust
inhibitors include, for example, esters of derivatives from succinic acid.
Antiwear agents
include, for example, sulphur and phosphorus derivatives. Metal deactivators
include, for
example, triazole derivatives. Acid and base neutralizers include, for
example, buffering agents.
Detergent additives include, for example, nor-ionic detergents.
Other sealants, alternative to or in combination with organosilanes, may also
be used. These
sealants may consist ofpolymeric latexes, vinyl acetates,
acrylonitriles,epoxide or methacrylates
or some combination thereof The sealant may include alkylene glycol. The
sealant may
contain a catalyst or accelerator. The catalyst may contain a copper or cobalt
compound. The
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catalyst or accelerator may contain a solubilizer. The sealant may contain a
filler. The filler may
be graphite, carbon powder or a polytetrafluoroethylene.
Preferred compositions of the lubricant/organosilane mixture are those
providing viscosities
above a viscosity of 7 est. when measured at 40 C. The choice of this
viscosity minimum was
determined by experiment as illustrated below in examples 4 to 7. The 40 C
measurement point
is used simply because this is the temperature at which compressor lubricants
are typically
characterized for viscosity.
The quantity of organosilane to be added depends on the size of the
refrigeration or air
conditioning system. This is not due to the size or number leaks in the system
For small leaks,
say less than 1/16" in diameter, and a sealant plug 1/16" long, several
hundred seals would easily
require only an ounce of organosilane. The rapidity with which a leak will
seal depends on
delivering an effective quantity of the sealant to the situs of the leak. This
latter consideration,
experience in automotive applications, and general practical considerations
such as the size of
the injection apparatus, suggest that injections of between 1/8 and 1 oz. of
organosilanes are
sufficient for most applications, with larger systems requiring the larger
amount. In addition, it
has been found that injections up to a maximum of 10% of the lubricant
quantity in the system
are recommended due to concerns with injection of liquid into the low side in
proximity to the
compressor.
In the preferred embodiment, organosilane is combined with a miscible
lubricant. The quantity
of lubricant mixed with the organosilane is determined by considerations of
first, providing
adequate lubrication as the fluid enters the compressor as has been previously
described and
second, of producing limited effect on the final lubricant viscosity,
preferably no more than 10%
reduction, once the organosilane has been distributed throughout the system.
The desired viscosity of the lubricant/organosilane mixture can be achieved by
varying the ratio
of the two or by adjusting the viscosity of the lubricant. Organosilanes of
interest generally have
very low viscosities (<1 est. @ 40 C) while lubricants of interest are much
higher in viscosity
(10 to 220 cst. or more @ 40 C). The effect of the injected mixture on the
final lubricant mixture
depends on the injected viscosity as well as both the viscosity and quantity
of oil in the system.
Table 2 provides information on the range of characteristics of typical
refrigeration and air
conditioning systems. As described previously, the systems in Table 2 cover
the range of
compressor drives and types. The methods and considerations outlined in herein
apply to all
such systems.
TABLE 2
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CA 02469966 2004-06-04
CHARACTERISTICS OF TYPICAL REFRIGERATION AND AIR CONDITIONING
SYSTEMS
SYSTEM TYPICAL SUMP CAPACITY OIL VISCOSITY
CAPACITY APPLICATION (OZ) RECOMMENDATION
(TON/HR.)* (CST. @ 40 C)
300 - 18,000 BTU/hr Residential 10 - 30 10 - 32
Commercial
refrigeration, air
conditioning
18,000 Residential 30 - 65 32, 46
- 60,000 BTU/hr Commercial
refrigeration, air
conditioning
60,000 BTU/hr Commercial, 65- 512 32,46, 68
(5 ton) - 25 industrial
refrigeration an air
conditioning
25 + Industrial 65 - 900 and greater 46, 68 up to 220
applications
*1 ton represents approximately 12,000BTU
Given the wide range of possibilities represented in Table 2, it was found to
be convenient to
evaluate the effect of various injected lubricant viscosities,
lubricant/organosilane ratios, oil
sump size and oil sump viscosity by calculation of these factors,. This
process guides selection of
the preferred viscosity and quantity of the injected mixture. The following
serves to illustrate the
process only.
The viscosity of a binary mixture of similar materials is often related to the
viscosity of the
components by the relation:
In ? mix = xi.ln ? i + x2.ln ? 2 + C (Equation 1)
where: In is the natural logarithm
?,,,ix is the viscosity of the mixture
? 1, ?2 are the viscosities of components I and 2 and
xi and x2 are the corresponding mole fractions
C is a constant dependent on. the nature of the components.
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CA 02469966 2004-06-04
This equation has been found to predict the viscosity of organosilane /
lubricant mixtures quite
well for the current application. A similar relationship can be written for
multicomponent
mixtures as well as for calculation of densities.
With component 1 taken as the injected material and component 2 as the
original sump oil,
Equation I can be rearranged to give the final viscosity of the mixture as:
?final = exp(ainj.ln ?inj + xsump.ln ?sump + C) (Equation 2)
where ?final is the final viscosity of the sump mixture after injection of the
sealant mixture
In is the natural logarithm and exp is the exponential
xinj, is the mole fraction of injected material in the final sump mixture
xuump is the mole fraction of the original sump oil in the final sump mixture
?inj, ?sump are the viscosities of the injected material and original sump oil
respectively
and C is a constant dependent on the nature of the components.
With the limit that the final sump viscosity should not be lowered more than
10% compared to
the original sump viscosity, then based on Equation 2, this amounts to a
requirement that:
exp(xinj.ln ?inj xsump=ln ?sump + C) = 0.9 ?sump (Equation 3)
Since the mole fraction of any component depends on the weight percent present
for that
component, then Equation 3 provides a basis for determining the desired
viscosity and quantity
limits on the injected material.
Of course, Equation 3 can be adjusted based on any selected limit on final
viscosity other than
the 90% of original sump viscosity used here.
exp(xinj=ln ?inj + xsump=ln ?sump + C) = Fr. ?sump (Equation 4)
where Fr is the desired fraction of the original sump oil viscosity to be
maintained.
Examples of these predicted effects using Equation 2 are shown for various
situations in Table 3.
TABLE 3
VISCOSITY EFFECTS OF LUBRICANT /ORGANOSILANE MIXTURES ON
REFRIGERATION SYSTEMS
1 2 3 4 5 6 7 8
Lubricant Lubricant System Volume Viscosity of - Weight % Weight % Final Oil
Viscosity Viscosity Oil Injected Lube/Organosilane Lubricant Organosilane Sump
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CA 02469966 2004-06-04
in system injected Capacity (oz.) Injected Injected Injected Viscosity
(est. @ 40 (est. @ 40 (oz.) (est. @ 40 C) (est. @ 40
C) C) C)
1 32 - 10 1 0.6 0 100 18.7
2 10 32 10 1 10 76 24 9.9
3 32 32 10 1 15.6 87.5 12.5 29.9
4 32 32 30 1 10 79 21 30.7
32 32 30 1 7 71 29 30.2
8 32 32 50 1 10 79 21 31.2
9 32 32 50 2 10 79 21 30.4
32 32 50 3 10 79 21 29.7
11 46 32 65 3 10 79 21 42.2
12 68 32 512 3 10 79 21 66.9
As seen in row 1 of Table 3, the injection of 1 oz. of these particular
organosilanes causes a drop
in viscosity in a 10 oz. sump from 32 to below 19 est. (all viscosities will
refer to 40 Q. A
maximum drop in sump viscosity of about 10% is generally acceptable,
corresponding to 29 est.
5 limit for units designed for 32 est. viscosity oils. In such small systems,
our testing indicates
that this low viscosity material would cause bearing seizure. Rows 2 and 3 of
Table 3 show that
injection of organosilane blends with a 32 viscosity lubricant can provide
satisfactory results. In
row 2, it is indicated that 1 ounce of a mixture containing about 1/4 ounce of
an organosilane
mixture and 3/4 ounce of a POE lubricant having a viscosity of 32: cst. at 40
C combine to form a
10 mixed viscosity of 10 est. When this is injected into a system containing
10 ounces of a
lubricant having a viscosity of 10 est. at 40 C, the resultant sump viscosity
of the mixture is
expected to be just below 10 est., at about 9.9 est. at 40 C. This result is
due to the effect of the
molar fraction term in equation 1. Line 3 similarly shows that injecting 1/8
of an ounce of
organosilane in 1 ounce of the lubricant/organosilane mix into such a system
using a 32 est.
lubricant rather than a 10 est. would produce a sump viscosity of 29.9 est.
This is above the
suggested 29 est. limit for this lubricant and would be an acceptable
formulation Rows 4 and 5
show information for systems using a 32 est. lubricant and having a sump
capacity of 30 ounces.
Up to about 1/ 5 of an ounce of organosilane can be injected while still
maintaining an injected
viscosity of at least 7 est. Rows 8, 9, and 10 indicate the diminishing effect
of larger sump size
with various injections compared to the previous rows, allowing up to 3/5 of
an ounce of
organosilane to be injected while still maintaining final viscosity above 29
est.. Rows 11 and 12
give information for systems using 46 or 68 cst. lubricants in the sump.
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CA 02469966 2004-06-04
An example of the use of this computational technique is the determination of
the best
combination of lubricant and organosilane to be injected by consideration of
the system
characteristics exhibited in Table 2. For example if a small unit with a 10
oz. sump contains 32
cst. lubricant, what should be the composition of the injected material using
a 32 cst. lubricant
and an organosilane mix? With 1 ounce injected, the maximum amount of
organosilanes used
here is calculated to be 0.175 of an ounce with the injected mixture having a
viscosity of 12 est.
and the system lubricant having a final viscosity of 29 est. At the minimum
injected viscosity of
7 est., then 0.6 ounces of a mixture containing 28.7% organosilanes could be
added to the 29
est. final viscosity, representing 0.17 2 ounces which is slightly lower.
Table 4 gives examples of situations where the viscosity limit of lubricant
(32 cst)/organosilane
mix needs to be controlled above the minimum viscosity requirement of 7 est.
dependent on the
total amount injected. For exampie, to maintain a 10 oz. system containing 32
est. lubricant
above 29 est. after addition of 1 oz. of mixture, then the
lubricant/organosilane mixture should be
at a minimum viscosity of 12 est. at 40 C which correspond to less than 0.175
oz. of organosilane
in the 1 oz. of material injected. In the case of injecting 3 ounces of this
lubricant/organosilane
mix into a system containing 30 oz. of 32 est. lubricant, then a similar
minimum viscosity holds.
The minimum viscosity for a larger system with 65 oz. of 46 est. oil is
limited to a maximum of
0.81 oz organosilanes when the total charge is 3 oz. in order to keep final
viscosity above 41.4
cst. With the 65 oz. sump size, a unit using 68 est. oil would be limited to a
minimum viscosity
injected of 17 est. corresponding to just over %2 oz of silane in a 3 oz.
total charge to maintain
final viscosity above 61.2 est.. Dropping the injected charge to 2 oz.
actually yields little benefit
in organosilane injected in this case and also has a much lower injected
viscosity for the injected
material at the minimum injected viscosity.
TABLE 4
DEPENDENCY OF INJECTED VISCOSITY ON REFRIGERATION AND AIR
CONDITIONING SYSTEMS
Sump size (oz.) Lubricant Grade Injected Amount Minimum Maximum
in Sump oz * Viscosity organosilane
In'eccted' * injected (oz)
est. at 40 C)
10 32 1 12 0.175
32 3 12 0.525
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CA 02469966 2004-06-04
65 46 3 8.2 0.81
65 68 3 17 0.51
65 68 2 7.6 0.6
lubricant of 32 est. at 40 C combined with organosilanes
** to 90% viscosity limit in sump viscosity
It is not required that the viscosity of the injected lubricant be the same as
the lubricating oils in
the system, only that there be effective injection of the sealant and non-
deleterious longer term
effects. The effect of increasing the viscosity of the injected mixture using
higher lubricant
viscosity, however, is relatively small as seen in Table 5 which shows the
effect of introducing
an organosilane/POE lubricant mix into a unit designed to operate with a
lubricant at 32 est.
TABLE 5
EFFECT OF VARYING LUBRICANT VISCOSITY OF INJECTED ORGANOSILANE
MIXTURE INTO SYSTEM USING 32 CST. POE LUBRICANT
Injected Wt.% POE Wt. % Viscosity Final System
Viscosity Organosilane Injected Viscosity
(cst@40 C) (cst@40 C) (est. @ 40 C)
1 32 79 21 10 28.5
2 46 79 21 13 29.0
3 68 79
21 17 29.6
*10 oz. sump capacity, 1 oz. injected ff
The application of Equations 1-4 allows calculation of the most desirable
mixture of lubricant
and organosilane to be used for any specific situation in terms of the size of
the unit (oil
capacity) and viscosity of the sump oil. The minimum ratio of lubricant to
organosilane is
predetermined by the minimum allowable injected viscosity and the individual
viscosities of the
lubricant and organosilane in the injected mixture. The viscosity of mixtures
relate exponentially
to component viscosities and in ratios dependent on mole fractions rather than
simple weight
fractions. In addition, it is recognized that the molecular nature of the
lubricant affects the
relation between viscosity and molecular weight so that the examples presented
here are not to
be taken as representing the only possible trends.
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CA 02469966 2004-06-04
These examples demonstrate that the application of the techniques described
herein is not limited
to fluids of a particular viscosity except as related to effective injection
and longer term
operation of the system particularly as related to the compressor.
Some systems operate with a lubricating sub system that is independent of the
refrigerant. In this
case, organosilanes alone are injected into the refrigerant circuit.
It is also possible to inject organosilanes alone in systems where the
lubricant is carried by a
miscible refrigerant. In this case, the organosilane alone, or in a mix with
lubricant, can be
injected into the high side of a refrigeration system while the unit is
operating up to a maximum
of 6% per minute of the systems total oil content. For example, a system with
a 50 oz oil
capacity could be injected up to a rate of 3 oz/ min. of organosilanes. The
quantity injected
remains limited by the foregoing based on limits to reduction in sump
viscosity. After 6% is
exceeded, there will be a decreased level of compressor performance due to
higher discharge
temperature resulting in possible decreased oil return to the low side of
compressor eventually
damaging the shaft bearings. Injecting at a rate above 8% per minute of the
total oil system's
content will likely result in loss of effective heat transfer, decreased
bearing lubrication and
possible catastrophic compressor failure. It is recognized that the 6% and 8%
amounts are for
typical systems and there are likely systems that can exceed these thresholds
while falling within
the principles described herein.
The sealant could also be injected into the high side of the unit while it is
out of service and in a
vacuum state with all refrigerants removed. Once injected into the high side,
the system is
recharged using refrigerant gas or liquid into the high- side up to at least
60% of the systems full
charge. This is carried out while the unit is turned off. The system is then
allowed to completely
equilize before turning the unit on and topping off the required system's
charge.
These methods can be utilized regardless of the class of compressor.
In the preferred embodiment, injection of the lubricant/organosilane mixture
is accomplished
through the use of a sealed canister 15 and a coupling hose assembly 16 that
is first fitted to the
canister 15 and then to the inactive refrigeration system 1 through an
injection port 17 on the
low-pressure side of the compressor 5.
The canister 15 can be pressurized before the canister 15 is sealed. The
pressure in the canister
15 causes the sealant mixture to enter the system 1 when the canister is
opened, there is fluid
connection to the system 1, and the system I is running to cause "low side" 10
pressures to drop.
In test environment the canister 15 was not pre-pressurized as will be
explained below;, however,
a charged pressure of 100 psig was found to be acceptable for allowing the
sealant mixture to
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CA 02469966 2009-05-12
enter the system 1 in the test environment, where the low side pressure was 77
psig as mentioned
previously.
Alternatively, the sealed canister 15 can have a pressure near, at or below
ambient. The canister
15 can be charged (pressurized) using the system 1 pressure. First the system
1 is turned off and
pressure within the system 1 is allowed to equalize. In the test environment,
this results in an
overall system 1 pressure of approximately 100 psig. The canister 15 is then
placed in fluid
connection with the system 1. This causes the canister 15 to be pressurized to
approximately 100
prig. The system 1 can then be run. This causes the pressure in the low side
10 to drop. The
higher pressure within the canister 15 causes the sealant mixture to enter the
system 1.
Using a non-pressurized canister 15 as described above is preferred as such
containers are less
hazardous. This means, for example, that they are transportable without having
to comply with
the, strict transportation regulations applicable to pressurized containers.
More details of a preferred method used in the test environment will now be
described. Before
use, the canister 15 is at a pressure of about 20 inches of mercury vacuum.
The vacuum is a
result of packaging processes that ensure much of the air is removed from the
canister 15 before
it is sealed. Hose assembly 16 is evacuated and then the canister 15 seal is
broken using a can-
tapper 21 that is built into the hose assembly 16 in such a way that
refrigerant mix from the
system 1 is allowed into the canister 15 until pressures are stabilized, and
the canister 15 is
charged. The can-tapper 21 has a manually operated valve (see valve handle 25
below) for fluid
connection (open) and fluid disconnection (closed) of the canister 15 from the
system 1. It also
has a tapping pin (operation described below) for unsealing the canister 15
(which is also
required for fluid connection when the canister 15 is sealed). The can-tapper
21 is also a fitting
for sealed fluid connection to the canister 15, typically by way of compatible
threads in the can-
tapper and on the canister 15, and corresponding seals, such as a rubber
gasket or an o-ring.
The addition of canister 15 contents to the refrigerant system 1 is controlled
to a maximum flow
rate of about 6 cc/sec, which in the preferred embodiment is obtained through
the use of orifice
20 having a maximum diameter of about 0.06 in. One such arrangement is shown
in Figure 2.
Although there is no minimum flow rate required, the minimum orifice size
should be about 0.02
inches in diameter to avoid orifice plugging due to contamination from
particles from system 1
as the canister 15 is charged. The minimum restriction could be removed by the
inclusion of a
filter, such as filter 16A of FIG. 1, in the injection hose between the
fitting 22 and the injection
port 17.
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CA 02469966 2004-06-04
The orifice 20 is located within fitting 22 of FIG. 2.. In the test
environment an orifice of 0.0292
inches diameter was successful. The hose assembly 16 has a hose 23 between the
can-tapper 21
and the fitting 22.
Surprisingly, it has been found that the action of filling the canister 15
with refrigerant upon
tapping the canister 15 and opening a valve in the tapper 21 causes the
canister 15 and its
contents to heat to temperatures well above ambient. Temperatures of 135 F
were encountered
in tests. This may affect the flow rate of the organosilane as it enters the
system 1. In the
preferred embodiment, the canister 15 is fluidly disconnected after charging
and the system 1 is
run. Then the canister 15 is again fluidly connected to the system 1. This
allows the system 1 to
achieve full low side 10 pressure that will best allow the sealant mixture to
enter the system 1.
As there is a period of time between disconnecting and re-connecting the
canister 15, the canister
should be allowed to cool to at or near ambient temperature while still
fluidly connected to
the non-running system 1. If not, then charge in the canister 15 may be lost
as pressure will drop
with the temperature in a closed canister 15.
15 Also, the contents of the canister 15 should enter the cooler suction gas
stream with as close to
ambient temperature of the system 1 as possible so as not to effect the volume
of the cooler gas
going to the compressor 5. A compressor 5 generally requires at least a four
percent return of oil
to maintain adequate lubrication on metal-to-metal surfaces. In practical
terms, a residential
system I operating at a suction pressure of 70 psig will typically have a
corresponding
evaporator 3 saturation temperature of 41 degrees F. If the system 1 is
operating satisfactorily
then the actual suction line 10 temperature should be approximately 51 degrees
F. This is due to
an extra 10 degrees of superheat picked up during the expansion. Elevating
this temperature
momentarily could cause an erratic expansion of gas followed by contraction
resulting in a
cavitation effect on the compressor 5. Experiments show a fluctuation in low
side and high side
pressures when the product has not been sufficiently cooled. Rapid changes of
pressure can
damage compressor valves and discharge excess oil from the compressor sump
into the high side
line. This excess oil will begin to log and affect downstream conditions such
as temporary high
discharge pressures accompanied by temporary low- side pressure. The
percentage of required
oil to be carried back could lower to the point of not supplying adequate
lubrication to metal-to-
metal contact causing damage to the compressor 5.
These and other steps in the procedure of the preferred embodiment are
described in Table 1.
TABLE 1
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CA 02469966 2004-06-04
1. Turn off A/C system 1 and allow enough time for refrigerant to equalize in
system
1.
2. Confirm that can-tapper 21 piercing pin is fully retracted below seating
washer.
(Turn valve handle 25 counter clockwise, opening the valve in the tapper 21)
3. Thread canister 15 onto can-tapper 21 by turning clockwise. Be careful not
to
cross thread or over tighten.
4. Thread female fitting 22 onto vacuum pump, not shown, and draw vacuum for
approximately 1 minute to eliminate air in tap hose 5.
5. Remove female fitting 22 from vacuum pump while it is running to maintain
vacuum in tap hose 5. After disconnecting shut down vacuum. pump.
6. Thread female fitting 22 onto low side service port 17 immediately after
removing
from vacuum pump.
7. Turn can-tapper 21 piercing handle 25 clockwise until it stops. (This
action
pierces the can, and closes the valve in the can-tapper 21.)
8. Hold canister 15 upside down and above the low side service port 17. Turn
handle
counter-clockwise (open the can-tapper valve and provided fluid connection
between the canister 15 and the system 1) slowly allowing the system 1
refrigerant to fully charge canister 15. The canister 15 will become warm once
the refrigerant mixes with its contents. Allow the canister 15 to dissipate
the
20 additional heat of charging which should take between 5 to 10 minutes
depending
on system 1 charge and ambient air conditions. When the can's temperature has
equalized with ambient air conditions then proceed with next step. Be sure to
check that all connections from canister 15 to system 1 are secure and that
there is
no leakage occurring.
25 The primary reason for inverting the canister is to simplify the procedure
for the
technician. If the technician forgets to invert the canister before injection
into the
air-conditioning unit (see 10. below) then the transfer of the mixture would
not be
successful because of the gas on top and the heavier liquid residing on the
bottom
of the can. The connection to the low-side charging port is made with the
canister
inverted for charging and injection as one-step. This also limits stressing
the hose
assembly by changing position while under pressure. Having the gas first pass
through the mixture also helps to mix the contents of the mixture if possible
stratification occurred between the organosilane and the miscible lubricant.
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CA 02469966 2004-06-04
9. Turn handle 25 clockwise until it stops, isolating charged canister 15 from
A/C or
R system 1.
10. While holding the canister 15 upside down turn on A/C system 1. Slowly
turn
handle 25 counter-clockwise gradually releasing sealant into the system 1.
This
should take approximately 3 to 5 minutes.
Releasing sealant too quickly could result in liquid slugging. Shake canister
15 gently
to determine when empty. if all of the contents in canister 15 are not emptied
after 5
minutes then turn canister 15 tapper 21 piercing handle 25 clockwise until it
stops.
Turn of A/C or R system 1 and repeat steps 8, 9 and 10.
11. Once canister 1.5 is empty remove female fitting 22 from low side service
port 17,
then shut down A/C system 1. Allow system 1 pressure to equalize. The A/C or R
system 1 should be left off for approx. 5 minutes. This procedure allows
product
to mix with systems 1 oil and when the system 1 is restarted will allow for
equal
distribution throughout system 1.
In typical experiments performed during the course of the current development,
a canister
was used with approximate dimensions of 5 cm. diameter and 10 cm height and
this
contained about 89 cc (3 oz.) of a lubricant/organosilane mix. With the
canister 15 filled
with refrigerant and inverted at ambient conditions, this would produce a
lower column
of liquid about 4.5 cm. high covered with a gaseous column of refrigerant 5.5
cm. in
height. The pressure exerted by the refrigerant was around 120 psi and this
was then
injected into a system operating at 66 psi. Thus the driving force for
injection of the
liquid phase into the system was about 54 psi.
In an ideal situation the equation
Q = Cd x A x (2 x ?P/ ?) (Equation 5)
could be applied where
Q is flow rate
Cd is the coefficient of discharge
?P is the differential pressure, and
? is the fluid density.
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CA 02469966 2009-05-12
Experiments in transparent glass vessels showed the expected result that the
liquid
actually contained bubbles of refrigerant. Nevertheless, considering the ideal
one-phase
flow situation, equation 5 can be applied to obtain at least a model of the
injection
process. For an orifice of 0.029 inches in diameter, the canister was found to
empty in
about 90 sec. This corresponds to a coefficient of discharge of 0.37.
Experiments
showed that satisfactory injections could be made using orifice sizes up to
about 0.060
inches. This corresponds to an initial flow rate of 6 cc/sec and a final flow
rate of 4
cc/sec for the last fraction of the liquid.
Considerations of system size relate to the effect on viscosity of the
lubricant in the system
which tends to increase with the size of the system itself. System size is
typically measured in
tons - a measure if the cooling capacity of the system 1 (1 ton is equivalent
to the delivery of
12,000 BTU cooling capacity per hour). General consideration of these factors
provide "rules of
thumb" to guide quantities of organosilane mixture to be added. For example,
one scenario
suggests for units above 5 tons capacity, a mixture about 7-8 est. @ 40 C is
appropriate and
about 10 est. for smaller units. The actual total quantity of lubricant/silane
mix is dependent on
ensuring effective delivery of sealant material to the situs of the leak.
Typically, units below 1
ton should require about 1/8 - 1/4oz. of organosilane and larger units'/2 -1
oz. The total
quantities of the mixture will also depend on the practicality of the details
of the injection system
being used. The viscosity of the mixture and the quantity of organosilane can
be adjusted within
these general guidelines.
EXAMPLES
The principles described herein are further illustrated in the following
examples, but the scope is
not limited by these examples.
Test Methods
The general test apparatus is shown schematically in Figure 2 and represents
the basic
components of a typical refrigeration system 1. A refrigerant gas (R-22 was
used in the test
environment; however, R134a and other refrigerants could also be used) is
circulated by means
of a hermetically sealed electric motor and compressor 5. The gas is cooled to
liquid by means
of a condenser 7; the liquid passes through valve 9 and then through an
evaporator 3 where the
liquid is regenerated to a gas accompanied by the desired cooling effect. The
gas then returns to
the compressor 5 for repeating cycles of the process.
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CA 02469966 2009-05-12
Sealant and mixtures were added by the procedure represented in Table 1 to the
low pressure
(suction) side of the compressor 5.
Sealant
In the base case, simple injection of the organosilane sealant in the low side
port 17 was shown
not to be appropriate for hermetically sealed refrigerant compressor 5 systems
1.
Example 1
In a laboratory test, a 2 ton vertical hermetic single phase refrigeration
system 1 with a full
refrigerant load was loaded to simulate an ambient temperature above 32 C. An
organosilane
mixture was injected into the circuit and the compressor 5 failed after only
one further hour of
operation due to bearing seizure.
Example 2
In another set of tests, two 2 ton single phase piston type systems 1 were
injected with a mixture
of commercial organosilane and immiscible lubricating oil. Failure occurred in
one system 1
after 10 minutes and after 1 hour in the second case.
Exam lpe3
Two small 10,000 BTU packaged refrigerant systems 1 were tested. Both failed
within 10 hours.
Subsequent examination of these systems 1 showed that failure was due to lack
of oil to the
upper sleeve bearing, referred to as the compressor-5 outboard bearing.
Sealant Viscosity
The effect of sealant viscosity was investigated by varying the ratios of
organosilane and
lubricating oil in the sealant mixture.
Example 4
Mixtures of organosilane sealant (viscosity < 1 cst@40 C) and immiscible
compressor 5 oil
(viscosity 68cst. @ 40 C) caused bearing seizure in all five cases in Examples
1,2, and 3.
Example 5
Use of straight organosilane mixture caused compressor 5 bearing seizure
within one hour in a
test with the 2 ton system 1.
Example 6
A test was performed using a 0.029 in. orifice 20 to inject a 3 fl. oz.
mixture consisting of 3 parts
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CA 02469966 2009-05-12
of a commercial polyolester refrigeration compressor 5 oil and 1 part of an
organosilane sealant
such that the mixture had a viscosity of 8 cst. @ 40 C. The oil capacity of
the single phase
hermetically sealed 2 ton system 1 was 55 oz. The system 1 was injected with
the
organosilane/oil mixture with no change in amperage of the motor, indicating
no liquid slugging.
The system 1 was run successfully for 12 days until shut down deliberately.
Example 7
A test was performed similar to that described in Example 6 except that the
mixture injected
consisted of 2 parts of the commercial polyolester refrigeration compressor 5
oil and 1 part of
the organosilane sealant to give a mixture viscosity of 11 cst. @ 40 C.
A start/stop test was run with 60 start/stops over a 3 V2 hr. period. This is
a severe test due to the
surge of electricity required to start the spinning of the rotor of the motor
and also due to some
initial loss of oil from the inboard bearing at each start. The test was
successful with no change
in operating variables and the system 1 ran for an additional 13 days with
excellent operation
until it was deliberately shut down.
Rate of Injection
Controlled rate of introduction of the organosilane/oil mix was investigated
as a variable. The
hose assembly shown in Figure 2 was used to introduce mixtures into a 2 ton
refrigeration
system 1 fitted with an oversized 2 'V2 ton condenser 7. The can-tapper 21 at
one end of the hose
seals and punctures a canister 15 containing the sealant. The fitting 22 at
the other end is
attached to the refrigeration system 1 and low-side port 17 is opened to allow
the sealant mixture
to enter the refrigeration system 1 through an orifice 20. The size of this
orifice 20 affects the
injection rate of the sealant.
Example 8
Using an orifice 20 size of 0.094 in., it was found that the rate of addition
of the sealant/oil
mixture caused fluctuations in suction and discharge pressure of the system 1.
As previously
mentioned this upset condition can cause the compressor to momentarily
discharge from the
sump into the discharge line causing logging possibly affecting oil return to
the suction side of
the compressor and eventual bearing failure. Any needle valve associated with
the orifice 20
would not allow sufficient additional fine control to overcome this problem.
Example 9
A capillary tube was used to control introduction of the sealant. An orifice
20 size of
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CA 02469966 2004-06-04
0.055 in. was found to allow successful introduction of the sealant into the
above refrigeration
system 1. The system 1 ran for 18 days with no change in operating variables
before it was
deliberately shut down.
Example 10
Inserting an orifice 20 size of 0.029 in. into the system 1 described in
Example 8 was tested and
found to give successful injection of organosilane/oil mixes.
Quantity of injection
Smaller systems are of the greatest concern for susceptibility to the rate and
quantity of injection
The two examples below were inj ected with a mixture consisting of /4 oz of
polyolester
lubricating oil and 1/4 oz of a silane mixture having a total viscosity of 9.8
est. at 40 C using the
injection technique outlined in Table 1. In each case, the sump originally
contained 10 oz. of
polyalkylene glycol lubricant having a viscosity of 32 est. at 40 C. Examples
11 and 12 below
support an injection limit of up to 10 vol% of sealant mixture, bases on sump
oil charge, can be
injected into refrigeration or air conditioning systems. In addition, it is
apparent in these
examples that the refrigerant charges are extremely small (3.70 and 1.69 oz)
but that the
additional 10 vol% liquid has had no effect on the thermal efficiencies of the
units.
Example 11
DANBY Model DCR433W
Refrigerant - 134A
Charge - 105g
AMPS - 1.1
Procedure: Bullet piercing valve installed
Conditions: Base of compressor - 101 F to 104 F
.87 AMPS
Suction temp - 72 F
Discharge temp - 101F
Inside panel, freezer 0 to 2F (Temperature glide effect)
Allow 3 min to fill can
5 min cool down
Allow 5 min run then switch to off
After stop time, put in operation
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CA 02469966 2004-06-04
After 90 days, the system continued[ to run successfully.
Example 12
Unit : GE with Matsushita SB30C50GAU6 compressor
Refrigerant 134A
Charge 1.59 ounces
Procedure : Bullet piercing valve installed
Conditions : Base of compressor - 90 F
.88 AMPS
Suction temp - 70F
Discharge temp - 102F
Inside - panel - freezer - 4F to 5F
Allow 3 min to fill
5 min cool down
Allow 5 min run then switch off
After stop time, put in operation
After 90 days, the system continued to run successfully
Injection Procedures
As outlined in Table 1, the typical procedure used to inject mixtures into the
refrigeration system
1 involves opening the canister 15 containing the oil/organosilan.e mixture to
a low pressure port
17 just prior to the non-operating compressor 5. The mixture is at a pressure
near 20 inches of
mercury vacuum before opening to the refrigerant system I which is typically
near 100 prig.
The entry of the refrigerant into the mixture in the canister 15 causes a
heating effect and raises
the canister 15 and contents to about 25 C above ambient. Single phase systems
1 are
particularly susceptible to this effect since entry of the hot mixture into
the refrigeration system 1
would cause momentary heating of the suction vapor and a decrease in the
vapor's density. This
in turn affects the ability of the vapor to cool the motor and other
mechanical parts.
Therefore as part of the procedure to inject the mixture from the canister 15,
it is important to
allow the refrigerant/ sealant mixture to cool before introduction into the
refrigeration system 1.
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Variations and modifications can be made without departing from the spirit of
this invention. It
should be understood that the form of the invention described above, including
the Figures and
Tables, is illustrative only and is not intended to limit the scope of the
present invention.
It will be understood by those skilled in the art that this description is
made with reference to the
preferred embodiment and that it is possible to make other embodiments
employing the
principles of the invention which fall within its spirit and scope as defined
by the following
claims.
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