|i~-'~'1r|«-.i«i.ii 1]irlIl\\1 hm i1i.iIi«-i1.rl in l:i.m..r ”.i[II|1|Hli. I []<l.i\. I
`
`. ]>]nI.I] \ ll. 1!-in
`
`SAE TECHNICAL
`PAPER SERIES
`
`932904
`
`Polyalkylene Glycol Refrigeration Lubricants -
`Current Status and Retrofit Applications
`
`William L. Brown
`
`Union Carbide Corp.
`
`Q‘ E me Engineering Society
`w For Advanging Mobility
`Land Sea Air and Space”
`’N T E 3 N A T ’ 0 N A L
`
`Worldwide Passenger Car
`Conference and Exposition
`pea.-bum, Michigan
`October25-27,1993
`
`400 Com monweaith Drive, Warrendale, PA 1 5096-0001 U.S.A. Tel: (412)776-4841 Fax:(412)776-5760
`
`Page 1 of 11
`
`Arkema Exhibit 1119
`
`Arkema Exhibit 1119
`
`

`
`Downloaded from SAE International by Bianca Hamilton, Friday, February 12, 2016
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`Page 2 of 11
`
`

`
`Dim IllU:l(ll‘(l l'rnm S \l-I lrilt-r‘mrtiur1:il It} Blalllfil Hamilton. l“ri(l;i} . ll-ltrtI:ir‘\ ll. 20]!»
`
`Polyalkylene Glycol Refrigeration Lubricants -
`Current Status and Retrofit Applications
`
`William L. Brown
`Union Carbide Corp.
`
`932904
`
`ABSTRACT
`
`also be addressed.
`
`lubricants have been
`(PAG)
`Polyalkylene glycol
`chosen for use with refrigerant I-IFC-l34a by the mobile air
`conditioning industry. As this industry gears up to use PAG
`lubricants, several issues have surfaced regarding the handling
`of these products. Information will be presented regarding the
`hygroscopicity and elastomer compatibility of PAG lubricants.
`Polyalkylene glycols are being evaluated by the
`automotive industry as retrofit
`lubricants. PAG lubricants
`exhibit good stability in the presence of residual CFC-l2.
`Data from retrofit tests performed on compressor test stands
`will be summarized. This paper will also describe the retrofit-
`ting of CFC-12 vehicles to HFC-l34a and PAG lubricants.
`
`INTRODUCTION
`
`In I987 the Montreal Protocol initiated a program to
`phase out
`the production and use of chlorofluorocarbons
`(CFCs) because of their adverse effect on the earth‘: ozone
`layer. A major use of CFC-12 is as a refrigerant in mobile air
`conditioning systems. This industry has chosen refrigerant
`HFC-l34a as a nonozone depleting replacement for CFC-12.
`ln mobile air conditioning units,
`the compressor
`lubricant travels through the system with the refrigerant.
`In
`order to ensure adequate return to the compressor, the lubri-
`cant must be sufficiently soluble in the refrigerant. The
`mineral oils which are currently used as lubricants with CFC-
`12 are insoluble in refrigerant HFC—l34a. Polyalkylene glycol
`(PAG) lubricants show good solubility in refrigerant lIFC-
`134a.
`Because of their good solubility and lubricating
`characteristics, polyalkylenc glycol
`lubricants have been
`chosen by the automotive industry for use in Hi-‘C-134a air
`conditioning systems.
`The first part
`This paper consists of two parts.
`reviews what polyalkylenc glycols are and describes some of
`the physical properties that have led to their use as refrigera-
`tion lubricants. These properties include their lubricity, elasto-
`mer compatibility, and solubility and stability in refrigerant
`HFC-l34a. The hygroscopicity of polyalkylenc glycols will
`
`Page 3 of 11
`
`The second part of this paper addresses the use of
`polyalkylenc glycols as retrofit lubricants. Data showing good
`stability in the presence of residual CFC-I2 will be presented,
`as will the results of retrofit trials perfomied on compressor
`test stands and in fleet vehicles.
`
`THE CURRENT STATUS OF PAG REFRIGERATION
`LUBRICANTS
`
`HISTORY - Polyalkylene glycols were invented in the
`early 1940's during a joint development program between
`Union Carbide Corporation and the Mellon Research Institute.
`One of their first commercial applications was as a thickener
`for the fire resistant hydraulic fluids that were used by the
`U.S. Navy during World War II. Since then, polyalkylenc
`glycols have found use in a wide variety of applications
`including gear, compressor, and food grade lubricants,
`metalworking fluids,
`textile fiber lubricants, mold release
`agents, and cosmetic additives (1).
`STRUCTURE AND PHYSICAL PROPERTIES —
`
`Polyalkylene glycols are synthetic polymers made from the
`monomers ethylene oxide (E0) and propylene oxide (PO).
`Other monomers such as butylene oxide can be used, but
`practically all commercially available polyalkylenc glycols are
`made using various ratios of ethylene oxide and propylene
`oxide. The polymer is made by reacting the oxide monomers
`with a starter, usually an alcohol, in the presence of a catalyst
`(Fig. 1).
`
`One of the unique aspects of polyalkylenc glycols is
`that their physical properties can be tailored to fit the needs of
`a specific application. The PAG‘s properties can be altered by
`changing the molecular weight, the starter, the proportions of
`the different oxide monomers used, the monomer sequencing,
`and the end groups.
`Polyalkylene glycols have a number of physical
`properties which have led to their use as lubricants with
`refrigerant HI-‘C-134a. These properties include low pour
`points, good stability, and low volatility. Of particular
`importance in refrigeration applications is the high viscosity
`
`

`
`I):-\\ IIl||'.l(l(‘(l from \ \l{ IIllt‘l'Il:llltill:Il hi ltiuimi llumillun. I-'ri(l;i_\. I51-hr1I;ir_\ I2. ltllti
`
`indices of polyalkylene glycols, typically ranging from 180 to
`over 250. Polyalkylene glycol refrigeration lubricants thus
`show significantly less change in viscosity with temperature
`than do mineral oils whose viscosity indices are typically less
`than 100. This means that when compared to mineral oil
`lubricants, PAGS are more fluid at low evaporator temperatures
`and still provide better lubricity in the hot compressor.
`
`FIGURE]
`
`
`POYALKYLENE GLYCOLS
`MONOMERS:
`
`
`
`
`
`
`
`
`Ethylene Oxide (E0)
`
`and
`
`
`
`H2
`
`2
`
`Propylene Oxide (PO)
`
`t..,
`POLYALKYLENE GLYCOL POLYMER:
`
`
`
`
`layers are not pure refrigerant and pure lubricant, but instead
`a lubricant-rich phase and a refrigerant-rich phase.
`The
`composition of the two phases that form in the high tempera-
`ture insolubility region can be determined from the intersection
`of the horizontal temperature tie line with the PAG's solubility
`curve. To demonstrate this, a 15 weight percent mixture of a
`PAG lubricant in refrigerant l-IFC-l34a was heated to 50°C
`and the phases were allowed to separate. The lubricant-rich
`phase was found to contain 38 weight percent lubricant. The
`refrigerant-rich phase contained 3 weight percent lubricant.
`Within experimental error, these points fall on the solubility
`curve of the polyalkylene glycol lubricant used in this exper-
`iment (Fig. 3).
`
`FIGURE}
`
`PAG PHASE CONCENTRATIONS
`IN H rc-134. SOLUTIONS
`
`
`
`to
`do
`‘lo PAG in HFC-l34a
`- 660 SUS PAG -0- Phase Coneentntiana
`
`The excellent low temperature miscibility of poly-
`alkylene glycols and refrigerant HFC-134a, as well as their
`mutual solubility at elevated temperatures, allow the circula-
`tion of the PAG lubricant
`through the AC system,
`thus
`ensuring good compressor lubrication.
`PAG STABILITY IN I-IFC-l34a - While it is critical
`
`that the lubricant shows good solubility in the refrigerant, it is
`also important that the refrigerant/lubricant pair is chemically
`and thermally stable. Polyalkylene glycol lubricants exhibit
`excellent stability in refrigerant HFC-134a.
`Sealed tube
`stability tests run at 131°C for 12 days in the presence of steel,
`aluminum, and copper coupons show the PAG/I-IFC-l34a
`combination to be at least as stable as mineral oils run under
`
`the same conditions in the presence of CFC-l2 (Table l)(2).
`Tests run at higher temperatures (l7S°C for 2 weeks and
`200°C for l 1.8 days) also show no signs of reactivity between
`the PAG lubricant, the HFC-134a, and the metal coupons
`(3,5).
`
`PAG LUBRICITY - Polyalkylene glycols are excel-
`lent lubricants.
`Pin & V-block wear tests run under one
`
`atmosphere of refrigerant show that PAG lubricants run in an
`HFC-134a atmosphere have higher failure loads than mineral
`oils that are saturated with CFC-l2 (Table 2)(S). Four ball
`wear tests show similar results. PAG lubricants saturated in
`HFC-134a have lower wear scars and lower coefficients of
`
`friction than do mineral oils of the same viscosity run in the
`presence of CFC-I2 (Table 3)(S).
`The good lubricity demonstrated by polyalkylene
`
`
`
`
`
`‘PH:
`
`catyl.
`
`ROH + E0 + P0 —> R0-(Cllz CH2—O)x—(CI*l CH;-O);H
`
`
`
`
`PAG SOLUBILITY IN HFC-134a - While poly-
`alkylene glycols have a number of physical properties which
`make them good refrigeration lubricant candidates, it is their
`good solubility in refrigerant HFC-134a that has led to their
`use in mobile air conditioning systems.
`The solubility curves of polyalkylene glycol lubricants
`in refrigerant HFC-l34a are well documented (2-4). Figure 2
`shows the solubility curves of four PAG lubricants of different
`viscosities. All four lubricants show excellent low temperature
`solubility. All four also exhibit a high temperature insolubility
`region at low PAG concentrations.
`In general, the lower the
`viscosity ofthe polyalkylene glycol, the smaller the insolubili-
`ty region. The solubility of polyalkylene glycols in refrigerant
`HFC-134a can also be affected by the PAG's starter, choice
`and ratio of oxide monomers, and end groups.
`
`FIGURE 2
`
`PAG SOLUBILITY IN HFC-134a
`
`0e288E#
`
`-
`
`- 650 SUS PAG V SOOSUS PAG I 180 SUS PAG A160 SUS PAG
`
`100
`W
`60
`40
`Wt“/o PAG In PAG/IIFC-13-la Mixture
`
`In the high temperature insolubility region, the two
`
`Page 4 of 11
`
`

`
`l)u\\ I]lU:l(ll‘(I from S,\l-I llilernziliunul Ii} liiauim Hamilton. I-‘ritluy . I51-liru:uj\ ll, 20]!»
`
`ELASTOMER COMPATIBILITY WITH HFC-134a
`
`AND PAG LUBRICANTS - In general, the polyalkylene
`glycols are compatible with most common elastomers.
`However, it is important to consider the effect of the refrig-
`erant HFC-l34a in cases where both refrigerant and lubricant
`are present. Table 4 shows the compatibility of a number of
`common elastomers with polyalkylene glycols, HFC-l 34a, and
`refrigerantl lubricant combinations (6). The compatibility tests
`were run at 25°C and 80°C for 27 days. Compatibility ratings
`were then determined.
`
`
`TAIIJO
`ELASl'mflEl.CClAPKl'lBlLfl'Y [MINE
`WITH HI-‘Glide ANUQ PAG LUBRICANT
`
`
`
`glycols in bench tests led to extensive testing on compressor
`test stands and in fleet vehicles. Polyalkylene glycol lubri-
`cants have performed very well with refrigerant HFC-l34a in
`a wide variety of AC systems employing a number of different
`compressor types. This success has led to the selection of
`polyalkylene glycol
`lubricants for use in HFC-l34a AC
`systems by all major automotive manufacturers.
`
`‘IA IL! I
`
`SB\l.£D TUBE STABILTTY TBTS
`PAG LUBE 0 HFC-1340 (IJI C. ll I DAYS)
`
`\-
`Ad e0
`
`lliléliliill
`
`Bu I Rubber
`H ,. . lane 4:
`Natural Rubba
`
`NordelO Rubber
`
`ThilltolO FA
`VitonO A
`
`llllllllllliaa
`lllllllllllilllllfllllllfiglllllllllllfiz
`
`
`
`
`
`lfiu: 0 (no change) - I (unaccaptdlo I‘lIIl'O)
`' No HFC- I14: decomposed
`
`TABLE I
`
`LUBRICITY OF PAG LUBBS
`USING PIN & V-BLOCK TEST
`
`REFRIGERANT oas
`(I am)
`
`LUBNCANT
`
`’°°~°*°s
`300 SUS PAG
`
`I-‘All. LOAD‘ roaoua AT
`(lbs)
`FAIL (in-lbs)
`
`"’° i
`
`~---~a1|n=|||IaIII
`won
`wmmkmtlliflllllilll
`cwaz
`‘ The larger the number. the better the lubricant.
`
`TAIL! J
`
`LU8 RICITY OF PAG LUBES
`USING FOUR BALL WEAR TEST
`
`llllillllillillllllllililfifili
`Ilaaaaaliiaaaaallssllllzaln
`IllfiiillllflflflfiillHIIIIHHII
`Illsaaalllaaaaaallarul
`Illaaaallllaaasrllsrll
`‘ The smaller the number, the better the lubricuit.
`
`Page 5 of 11
`
`E oonelmael - $(aevI!c.\IIcceptahlcdur¢e)
`
`
`
`The data in Table 4 show that at 25°C there are a
`
`number of elastomers that are compatible with PAG lubricants
`and HFC-l34a/PAG mixtures. At 80°C the choices are more
`limited. Because of the variations that can exist between
`
`elastomers in the same generic family, it is important to test
`the compatibility of specific elastomers that are to be used in
`critical applications.
`WATER AND POLYALKYLENE GLYCOLS - One
`
`of the major differences between polyalkylene glycols and
`mineral oils is their affinity for water. Polyalkylene glycols
`are hygroscopic relative to mineral oils. Polyalkylene glycol
`refrigeration lubricants usually have a maximum water
`specification of l00O ppm and normally range between 400
`and 800 ppm.
`Polyalkylene glycols are hygroscopic and
`will pick up water when exposed to humid air. They will
`continue to pick up water until an equilibrium or "saturation"
`level is achieved. Typical equilibrium levels range from 1 to
`5 percent depending on the humidity and the polymer struc-
`ture.
`
`It is important to remember that the water in PAG
`refrigeration lubricants is not "free" but is instead ‘bound’ to
`the polyalkylene glycol backbone. Therefore ice crystal for-
`mation has not been a problem.
`Despite their affinity for water, PAG refrigeration
`lubricants can be easily dried. Commercial batches can readily
`be dried to water levels of below 500 ppm. With care, the
`water concentrations can be reduced to below 100 ppm.
`However, it is difficult to accurately measure water levels of
`polyalkylene glycols below 100 ppm. This is because trace
`impurities in the PAG lubricant can react with the reagents
`used in Karl-Fischer water titrations, thereby giving misleading
`
`

`
`l)1I\\lllIl‘.l(l(‘(l lrum \ \l-I lnli-rnulinnul hi ltiuimu llulnilluii. I-'ri(l;i_\. I‘(‘l)l'll:ll'_\ ll. lull.
`
`evaluated in Figure 4. At a temperature of 19°-22°C and a
`relative humidity of 30-33 percent, the equilibrium water
`concentration of the polyalkylene glycol is 9000 ppm. If the
`relative humidity is increased to 51 to 55 percent, the equilib-
`rium water concentration rises to 20,000 ppm.
`It should be noted here that as shown in Figure 4,
`polyallcylene glycols with higher concentrations of polymer-
`ized propylene oxide or alkyl capped end groups will show
`significantly lower water absorption rates and lower equilibri-
`um water concentrations than the E0/PO copolymer.
`
`FIGURE 5
`
`H20 Absorption of PAG Lubricant
`Effect of Relative Humidity
`
`results.
`
`Because of their hygroscopicity, it is important to
`minimize the exposure of polyalkylene glycol refrigeration
`lubricants to humid air during storage. Bulk storage tanks and
`drums should be nitrogen blanketed. If this is not practical, a
`dryer containing active molecular sieves should be attached to
`the drum or tank vent to prevent humid air from contacting the
`PAG lubricant. When stored in small containers, minimizing
`air exposure is usually sufficient to keep PAG refrigeration
`lubricants in satisfactory condition.
`The water absorption rates and equilibrium or
`"saturation" levels of polyalkylenc glycols are affected by
`several factors. Two major factors are the PAG's structure and
`the relative humidity.
`The water absorption rates of
`polyalkylene glycol lubricants are also greatly influenced by
`the ratio of the exposed surface area to total lubricant volume.
`Figure 4 shows the effect of the structure of the
`polyallcylene glycol on water absorption. Three butanol started
`polyalkylene glycols were tested. The first PAG was made
`from a monomer feed containing 50 percent ethylene oxide
`(E0) and 50 percent propylene oxide (P0). The second PAG
`was made from 100 percent P0. The third PAG was made
`by capping the terminal hydroxyl of the second polyalkylene
`glycol sample. The samples were placed in identical beakers
`in an environmental chamber with a temperature of 20°-22°C
`and a relative humidity of 51-55 percent. The water concen-
`tration of the three lubricants was determined gravimetrically
`over a time span of 400 hours.
`
`FIGURE 4
`
`H20 Absorption of PAG Lubricants
`Effect of PAG Structure
`
`- 50:5OEO/P0 + 100'/SPO * l00‘/9P0-Capped
`
`200
`
`300
`
`400
`
`Time (hours)
`
`§ E221
`
`As expected, the E0/PO copolymer was the most
`hygroscopic, reaching an equilibrium water level of 17,000 to
`18,000 ppm. The polyallcylene glycol made from 100 percent
`P0 was significantly less hygroscopic, reaching an equilibrium
`water concentration of 10,000 ppm. By capping the terminal
`hydroxyl group of this polymer, its hygroscopicity was further
`reduced and its equilibrium water level was approximately
`6000 ppm.
`The other major factor affecting the equilibrium water
`content of polyalkylene glycol refrigeration lubricants is the
`relative humidity.
`Figure 5 shows the effect of relative
`humidity on the water absorption of the E0/PO copolymer
`
`Page 6 of 11
`
`
`
`Time (hours)
`can - sr-am -nut - coarse
`
`lnlthl I110 3 100-125 ppm
`
`The most important factor affecting the rate of water
`absorption by polyalkylene glycols is the ratio of the exposed
`lubricant surface area to the total lubricant volume. This ratio
`
`will be represented in Figure 6 as D/H, or the diameter of the
`beaker containing the polyalkylene glycol divided by the
`height of the lubricant in the container. When D/I-I is large for
`a given volume of lubricant, water absorption rates will be
`high. The converse is true when D/I-I is small.
`
`FIGURE 6
`
`H20 Absorption of PAG Lubricants
`Effect of SA:Vol Ratio
`
`H20ppIIIIDW
`
`In Figure 6, the water absorption rates of the E0/PO
`copolymer at different D/H ratios were determined at 19°-22°C
`and a relative humidity of 51-53 percent. As was shown in
`Figure 4,
`this is the most hygroscopic of the lubricants
`
`

`
`Downloaded from SAE International by Bianca Hamilton, Friday, February 12, 2016
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`Page 7 of 11
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`

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`Downloaded from SAE International by Bianca Hamilton, Friday, February 12, 2016
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`Page 8 of 11
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`

`
`l)muilmi(lo.-(I from .\,\l-I lnti-riizitiuniil h_\ liiiiiirii Hiiniillun. Fri(l:i_\. Ft-l)I'ii:ii‘_\ I2. 201(-
`
`in retrofit applications.
`MINERAL OIL COMPATIBILITY - Polyalkylene
`glycols are compatible with used mineral oils in that they do
`not undergo any adverse physical or chemical reactions when
`they are mixed. While polyalkylene glycols exhibit limited
`solubility in mineral oils, this has not adversely affect their
`performance in retrofit applications. PAG lubricants have been
`used in a number of retrofit trials where 50 to 100 percent of
`the original mineral oil charge was left in the AC system. In
`most of these trials, no lubricant related problems were experi-
`enced. The lubricant problems that did occur were related to
`lubricant slugging and subsequent compressor failure. Slug-
`ging is usually attributed to too much lubricant in the system.
`As a result, it is generally recommended to remove as much
`of the mineral oil as practically possible when retrofitting a
`vehicle from CFC-12 to refrigerant I-II-‘C-l34a.
`RETRO}-‘IT TRIALS WITH PAGS
`
`Since
`
`-
`
`lubricants exhibit good mineral oil
`polyalkylene glycol
`compatibility and sufficient stability in residual CFC-12 to be
`used as retrofit lubricants, some compressor stand tests were
`performed to simulate retrofitting from CFC - l 2 and mineral oil
`to HFC-l34a and a PAG lubricant.
`
`The first set of retrofit trials were run in the following
`manner. Test stands employing both wobble and swash plate
`compressors were run for H0 hours with refrigerant CFC-12
`and a mineral oil
`lubricant. The compressors were then
`drained and the system flushed with liquid CFC-l 2. The dryer
`was also changed, from one containing 4A-XH-S molecular
`sieves to one filled with XH-7 desiccant. The system was
`then charged with a PAG lubricant and refrigerant HI-‘C-l34a
`and run for 410 hours. The compressor tests were run to
`alternately simulate highway and idle conditions.
`Upon completion of the tests, the compressors were
`dismantled and the PAG lubricants analyzed. Overall, the
`
`Lubricant analysis
`compressors were in good condition.
`showed the polyalkylene glycol lubricants to be in excellent
`condition. As can be seen in Table 8, there was no change in
`the
`polyalkylene
`glycol's molecular weight
`(Mn)
`or
`polydispersity (Mw/Mn). There was no acid formation as
`measured by pll or acid number, and the metal content of the
`lubricants was low. Also, no fluoride ions were detected in
`the lubricants, and the chloride ion and total chlorine concen-
`trations were low.
`
`A second series of compressor retrofit tests were run
`to determine if removing the residual mineral oil through a
`flushing procedure is necessary.
`In these tests, wobble and
`swash plate compressors were run for 50 hours using refriger-
`ant CFC-l2 and a mineral oil lubricant. At the end of this
`
`break-in period, the CFC-l2 was removed. The system was
`then opened and the PAG lubricant was added to the accumu-
`lator/dryer. The unit was then evacuated and charged with
`refrigerant HI-‘C-l 34a. The original 4A-XH-S molecular sieves
`were left
`in the dryer. The test stands were then run for
`approximately 190 hours under conditions designed to simulate
`both idling and highway driving.
`After running for I90 hours with HI-‘C-l34a and a
`PAG lubricant. the tests were stopped. The compressors were
`dismantled and the FAG lubricants analyzed. The compressors
`
`Page 9 of 11
`
`were in good condition. and lubricant analysis showed the
`polyalkylene glycol lubricants to be in excellent shape. The
`data in Table 9 show that
`there was no change in the
`polyalkylene glycol's molecular weight or polydispersity. No
`acid formation was evident, and the metal content of the
`lubricants was low. Also, there was no fluoride ion found in
`
`the lubricants, and only low levels of chloride ion and total
`chlorine were detected.
`
`TA BLE 8
`
`RETROFIT TRIALS
`COMPRESSOR TEST STAND RESULTS
`
`Conditions:
`
`ll0 hrs with CFC-I2, minual oil
`liquid CFGIZ flush, change AD can
`410 In with HI-‘C-134:, PAO lube
`Results: No abnormal compessor wear.
`
`Compact __,
`Type
`
`NEH
`
`Mmfiflfll
`MMMHEHI
`MMEHII
`
`Note: Acid 34 in mg KOH/g; pH of 10% soln;
`F-, Cl-. total Cl (t-Cl), Fe. and Al in ppm.
`
`' Reference control sample, analyzed for
`comparison with the used lubricant samples
`from the compressor test stands.
`
`While no problems were seen running this later set of
`retrofit tests with the 4A-XH-5 desiccant, this does not imply
`that changing to XH-7 molecular sieves is not necessary.
`These tests were designed to determine compressor durability,
`not the long term chemical compatibility of the desiccant with
`refrigerant HI-‘C-l34a and the PAG lubricant.
`VEHICLE RETROF IT TESTS - Because of the
`
`promising performance of polyalkylene glycols as retrofit
`lubricants in compressor test stands, we are now in the process
`of retrofitting some CFC-l2 vehicles to HFC-134a and PAG
`lubricants. These vehicles are being retrofit using one of two
`procedures. The first involves flushing the AC system with
`liquid CFC-l2 to remove the mineral oil
`lubricant.
`The
`second requires draining the mineral oil lubricant from the
`compressor.
`In both methods, the dryer is replaced with one
`containing XI-I-7 molecular sieves.
`In both the flushing and nonflushing retrofit proce-
`dures, the CFC-l2 vehicles were first evaluated to determine
`
`if they were in good working order (7). The problems that
`were uncovered were repaired prior to charging with I-IFC-
`l34a. After completing the initial evaluation, the CFC-l2 in
`the system was removed and recovered.
`It was assumed during these retrofit trials that all of
`the components of the CFC-l2 vehicles were compatible with
`I-IFC-134a and polyalkylene glycol lubricants. This was done
`
`

`
`[hm nln-.ult-(I {rum N \l{ lnlt-rnulinnul hi ltiurmt llulnilluri. I-'ri(l;i_\. I-1-hru;u‘_\ ll. lulr.
`
`In
`primarily to see what might go wrong in various vehicles.
`actual commercial retrofits, the vehicle manufacturers retrofit
`
`guidelines should be followed. These guidelines will include
`infomiation on what components need to be replaced when
`performing a retrofit.
`
`TABLE 9
`
`RETROFIT TRIALS
`COMPRESSOR TEST STAND RESULTS
`
`Conditions: 50 hrs with CFC-12, mineral oil
`no flush. or equipment change
`I90 hrs with HFC-I344. FAG lube
`Results: No abnormal compressor wear.
`
`HM
`EHNHN
`IEIIIIIEIHIEIHII
`IMEIIIEIEEIIE
`Manama:
`mmrrainrlammn
`Eflflflflflflfllfl
`EEEHIEIIIEE
`flllfla
`
`
`
`Note: Acid # in mg KOH/g; pH of 10% soln;
`F-, Cl-, total Cl (t-Cl), Fe, and Al in ppm.
`
`‘ Reference control sample. analyzed for
`comparison with the used lubricant samples
`from the compressor test stands.
`
`RI-ITROFITTING USING A LIQUID CFC-12 FLUSH
`This retrofit procedure began by recovering the CFC-12 from
`the system and then flushing with clean liquid CFC-12. In the
`vehicles which we have retrofit, between 75 and 90 percent of
`the original mineral oil lubricant charge was removed. The
`CFC-l2 in the system was then evacuated and recovered.
`The system was then opened and any needed repairs
`made. The accumulator/dryer was replaced with one contain-
`ing XH-7 molecular sieves.
`In some vehicles the orifice tube
`was also replaced.
`A full charge of PAG lubricant was then added to the
`accumulator dryer or to the suction hose leading to the
`compressor. The system was reassembled, evacuated, and
`charged with refrigerant I-IFC-134a. The system was then
`checked for leaks and labeled to indicate that it contained
`
`lfnccessary, control adjustments were
`refrigerant HFC-l 34a.
`made to ensure good performance.
`All ofthe vehicles retrofit in this manner are currently
`running well, and their performance will continue to be
`monitored.
`
`RETROFITTING WITHOUT A LIQUID CFC-12
`FLUSH - After checking the AC system's viability, the CFC-
`12 was removed and recovered. The system was then opened
`and necessary repairs were made.
`The dryer was changed to one containing XI-l-7
`
`Page 10 of 11
`
`molecular sieves. The mineral oil lubricant was drained from
`
`the compressor and any other accessible component. PAG
`lubricant was then charged into the A/D can or suction hose.
`The system was then reassembled and evacuated. If
`the vacuum held, HFC-134a was charged into the system.
`If
`the vacuum did not hold, either there was a leak or residual
`
`If
`CFC-l2 was degassing from the remaining mineral oil.
`leaks were found, they were repaired. If no leaks were found,
`the evacuation process was continued to remove the residual
`CFC-12.
`
`After charging system with HFC-134a, a leak check
`was perfomied and a performance test run to make sure that
`the system was operating correctly. Appropriate labels were
`attached to indicate that the system contained refrigerant HFC-
`134a.
`
`SUMLMARY
`
`Polyalkylene glycol refrigeration lubricants are now
`being used in the new HFC-134a vehicles. The water issues
`associated with these lubricants are understood and controlla-
`
`Polyalkylene glycols are also compatible with most
`ble.
`elastomers. However, when choosing an elastomer,
`it
`is
`important to take into consideration the effect of the refrigerant
`on the specific gasket or seal.
`Polyalkylene glycols are also performing well as
`retrofit lubricants. They exhibit sufficient stability in residual
`CFC-I2 and have shown that they are compatible with mineral
`oils. Retrofit trials using polyalkylene glycol lubricants were
`run on compressor stand tests with good results. Trials are
`currently being run on vehicles converted from CFC-12 and
`mineral oils to HFC-134a and polyalkylene glycol lubricants
`using flushing and nonflushing retrofit procedures. To date all
`of these vehicles are performing well.
`There is still much work that needs to be done to
`
`determine the best ways to retrofit the many CFC-l2 vehicles
`that are currently on the road.
`In the end, the automotive
`manufacturers will have to make the final retrofit recommen-
`dations for their vehicles.
`
`REFERENCES:
`
`1) Matlock, P. L. and Clinton, N. A. (I992). Polyalkylene
`Glycols, Synthetic Lubricants and High-Performance
`Functional Fluids (R. L. Shubkin - editor) Chapt 4, Marcel
`Dekker, Inc., New York, NY.
`
`2) Oils for Alternative Refrigerants, DuPont Company, Wil-
`mington, DE, ARDT-l 1.
`
`3) Finkenstadt, W. R. (1992). Polyalkylene Glycol and Poly-
`olester Lubricant Candidates for use with I-IFC-134a in Refrig-
`eration Compressors, ASHRAE Transactions 1992, Vol. 98,
`Pt. I.
`
`4) Lache, W., Pocklington, J., and Laukotka, E. (I991). New
`Refrigeration Machine Oils for