Contaminant Removal
dav...@enterprise.net
I am about to tackle the follow situation and am looking for opinions.
A supermarket rack operating on R22 running ice-cream/frozen food. The
problem I am told is that the sytem expansion valve inlets are being
blocked with a containant, believed to be the result of an engineer
adding mineral oil when the rack is designed for synthetic (PAO) oil.
I have been told that the oil has been removed and replaced with the
correct brand twice,although I suspect that only the compressor oil
was replaced, leaving the separator oil. Filter/driers have been
changed as have oil filters. Liquid liner driers have been added to
individual cases, two way driers to enable liquid return on saturated
gas defrost, but the driers have been breaking up. Information that
concerns me at the moment is that the rack apparently has to operate
at roughly a 250psi condensing pressure to ensure a positive liquid
supply to the cases. For those that know of it the system uses a
Hussman Turbashed type oil separator.
Any opinions.
David.
George Goble
between stages) or uses liquid injection into the compressor inlet
(to keep discharge temps down), then this system is probably a wreck already.
R22 cannot be used, in most cases below 20F or so evaporating temp, due
to it's high heat of compression and temps over 300F being produced
in the compressor discharge valves. This is why R502 was invented.
R22 was tried in home freezers years ago.. There were many failures from
the cap tube becomming plugged with carbon from R22 breakdown.
The Breakdown also creates acids which break down drier cores, eat away
at motor winding insulation (if internal motor), cause copper plating,
break down the oil, form "sludge". I dont think some mineral oil
in the system is going to make it any worse than it already is.
Was this some R502 system, that somebody just charged R22 into?
I would run away from this one.
--ghg
Marc L O'Brien
In article <4qoc1t$p...@mozo.cc.purdue.edu>, George Goble (g...@cidmac.ecn.purdue.edu) writes:
>In article <4qjvjk$m...@news.enterprise.net> dav...@enterprise.net (dav...@enteprise.net) writes:
> >I am about to tackle the follow situation and am looking for opinions.
> >A supermarket rack operating on R22 running ice-cream/frozen food. The
> >problem I am told is that the sytem expansion valve inlets are being
> >blocked with a containant, believed to be the result of an engineer
> >adding mineral oil when the rack is designed for synthetic (PAO) oil.
> >I have been told that the oil has been removed and replaced with the
> >correct brand twice,although I suspect that only the compressor oil
> >was replaced, leaving the separator oil. Filter/driers have been
> >changed as have oil filters. Liquid liner driers have been added to
> >individual cases, two way driers to enable liquid return on saturated
> >gas defrost, but the driers have been breaking up. Information that
> >concerns me at the moment is that the rack apparently has to operate
> >at roughly a 250psi condensing pressure to ensure a positive liquid
> >supply to the cases. For those that know of it the system uses a
> >Hussman Turbashed type oil separator.
> >Any opinions.
> >
> >David.
>
>My $.02 .. Unless this system is multi-stage compression (with intercooling
>between stages) or uses liquid injection into the compressor inlet
>(to keep discharge temps down), then this system is probably a wreck already.
What about, or if the compressor motor is not suction cooled.
>R22 cannot be used, in most cases below 20F or so evaporating temp, due
>to it's high heat of compression and temps over 300F being produced
>in the compressor discharge valves. This is why R502 was invented.
>R22 was tried in home freezers years ago.. There were many failures from
>the cap tube becomming plugged with carbon from R22 breakdown.
R22 has a high isentropic index, and this can produce problems if,
for example, the compressor motor increases suction superheat at low
temps. I think it's the oil that carbon and sludging comes from,
although the freon contains carbon.
>The Breakdown also creates acids which break down drier cores, eat away
>at motor winding insulation (if internal motor), cause copper plating,
>break down the oil, form "sludge". I dont think some mineral oil
>in the system is going to make it any worse than it already is.
I'm wondering if the POE oil was used here to allow high discharge
temps. POE can tollerate much higher temps with out decomposing or
transforming. If this is the case then the design operating temps
may have been higher than mineral oil norms but lower than
refrigerant decomposition temps????????????????
>Was this some R502 system, that somebody just charged R22 into?
>I would run away from this one.
No no no, stay and experiment, "the world is my laboratory".
Marc O'Brien
Industrial refrigeration mechanic
10073...@compuserve.com
http://ourworld.compuserve.com/homepages/marc_vicky
dav...@enterprise.net
and give some idea of the steps I intend to take.
The rack was a new installation (approx 4 years old) designed to use
R22 and synthetic oil. The compressor are cooled using the copeland
demand cooling system but there has been multiple compessor failures,
usually electric suggesting that even with this cooling the discharge
temps are too high. Being in line with what George Goble said
previously. The information that I have been given states that the
system runs with a high discharge pressure to prevent liquid
starvation, to rectify this I intend to fit a condensor flooding valve
to ensure a positive supply, with lower pressures. At the moment
pressure is controlled by condensor fan cycling, I would say that the
condensor return line is oversized causing a pressure drop, the
flooding valve should cure this.
For the oil situation all I can see to do is change the oil, hoping to
gain some level of cleanliness. I may work on getting the rack shut
down overnight removing the oil and refrigerant vacuuming it then
re-charging. But permission for this is doubtfull.
I will remove all individual case driers.I may install a drier core to
the main saturated gas line. Do you all agree with the above ?
And Marc O'Brien "the world is my laboratory" nice sentiments.
David
George Goble
>
>In article <4qoc1t$p...@mozo.cc.purdue.edu>, George Goble (g...@cidmac.ecn.purdue.edu) writes:
>>In article <4qjvjk$m...@news.enterprise.net> dav...@enterprise.net (dav...@enteprise.net) writes:
>> >I am about to tackle the follow situation and am looking for opinions.
>>My $.02 .. Unless this system is multi-stage compression (with intercooling
>>between stages) or uses liquid injection into the compressor inlet
>>(to keep discharge temps down), then this system is probably a wreck already.
>
>What about, or if the compressor motor is not suction cooled.
>
>>R22 cannot be used, in most cases below 20F or so evaporating temp, due
>>to it's high heat of compression and temps over 300F being produced
>>in the compressor discharge valves. This is why R502 was invented.
R22 breaks down just above 300F. You get HCl, HF, R12 and other things
being produced. Most other HFCs would be similar due to the weaker
hydrogen bonds. Motor cooling or not.. same thing.. Oil sludges from
all the acid and partly breaks down. Carbon everywhere. If motor windings
are in contact with the refrigerant, they may fail also. When the suction
pressures are below 20F evaporator pressures you are in danger of
hitting 300F in the discharge valves due to increasing compression ratio.
Liquid injection or multi stage compression must be used to prevent
hitting 300F.
POE oils cant even hold their own in newly built equipment, let alone
with refrigerant breakdown going on. Steel is a catalyst to cause
POE's to break down.. Mfgr's add "passivators" to try to counter this
effect.. but they are not always perfect.. High temps greatly increase
the speed of breakdown reactions of the POE oil.
--ghg
George Goble
>This information should fill in the blanks I left in my previous post
>and give some idea of the steps I intend to take.
>The rack was a new installation (approx 4 years old) designed to use
>R22 and synthetic oil. The compressor are cooled using the copeland
>demand cooling system but there has been multiple compessor failures,
>usually electric suggesting that even with this cooling the discharge
>temps are too high. Being in line with what George Goble said
I assume you mean motor "burnout"? (shorting to ground?) If so, there is
a huge amount of acid produced and other contaminates from the red hot
windings breaking down ALL the refrigerant they touch, and if the compressor
continued to turn, even for a few seconds, the acid is pumped through out
the whole system and anything connected to it.
The Best burnout cleanup procedure used to be to "power flush" everything
with R11 to get out all bad oil from the lines, etc, then install
new compressor. Today some
people use isopentane (same BP as R11, around 77F), but that
is extremely flammable so precautions must be taken. Other nonflammable
solvents are starting to emerge now.
There are local technicians who dont believe in proper burnout
cleanup, and they use "new compressors" to clean up previous
burnouts.. The new compressors last 3 or 4 months and burnout
again.. I have seen this go on for 12 or 13 compressors, at which
time they declare the system was poorly designed and replace
the whole system at tens of thousands of $$$.. Good job security.
In the 20 or so compressors I have changed (R11 or isopentane flush),
none has since failed.
--ghg
Marc L O'Brien
In article <4r098c$l...@mozo.cc.purdue.edu>, George Goble (g...@cidmac.ecn.purdue.edu) writes:
>In article <1...@fridgemech.win-uk.net> mlob...@fridgemech.win-uk.net (Marc L O'Brien) writes:
>>
>>In article <4qoc1t$p...@mozo.cc.purdue.edu>, George Goble (g...@cidmac.ecn.purdue.edu) writes:
>>>In article <4qjvjk$m...@news.enterprise.net> dav...@enterprise.net (dav...@enteprise.net) writes:
>>> >I am about to tackle the follow situation and am looking for opinions.
>[snip]
>>>My $.02 .. Unless this system is multi-stage compression (with intercooling
>>>between stages) or uses liquid injection into the compressor inlet
>>>(to keep discharge temps down), then this system is probably a wreck already.
>>
>>What about, or if the compressor motor is not suction cooled.
>>
>>>R22 cannot be used, in most cases below 20F or so evaporating temp, due
>>>to it's high heat of compression and temps over 300F being produced
>>>in the compressor discharge valves. This is why R502 was invented.
Old hat :-)
>R22 breaks down just above 300F. You get HCl, HF, R12 and other things
>being produced. Most other HFCs would be similar due to the weaker
>hydrogen bonds. Motor cooling or not.. same thing.. Oil sludges from
>all the acid and partly breaks down. Carbon everywhere. If motor windings
>are in contact with the refrigerant, they may fail also. When the suction
>pressures are below 20F evaporator pressures you are in danger of
>hitting 300F in the discharge valves due to increasing compression ratio.
>Liquid injection or multi stage compression must be used to prevent
>hitting 300F.
You trying to tell me that acids are going to damage the
winding varnish, wow! you learn something every day, don't you
George? And to think for the last ten years I've been dosing all my
systems regularly with a strong HCL solution. I figuered this
would keep all heat-ex surfaces clean and help Freon molecules
maintain there square profile.
George, multistage interstage cooling , pre-compression
liquid injection or whatever, 150 deg C discharge is 150 deg C
discharge.
>POE oils cant even hold their own in newly built equipment, let
>alone with refrigerant breakdown going on. Steel is a catalyst to
>cause POE's to break down.. Mfgr's add "passivators" to try to
>counter this effect.. but they are not always perfect.. High temps
>greatly increase the speed of breakdown reactions of the POE oil.
Yes George :-( these are recent revelations, R80 (Mike
Magee) mensioned this a while back. But this system may be older
than the revelation. Also I think we are on about POE's when the
original post mensioned PAO's. PAO's have excellent thermal
stability and a high viscosity index. They contain no wax and have
low pour points. They're suitable for both very high and very low
temperature duties. However, POE's have similar properties but
better still they have high solubity with R22 providing for good oil
return.
Now take a look at some typicaly good quality German
engineering. The "Bock Kaltemaschinen" HA model(Air cooled motor).
Using R22 for a deep freezing application. At a constant saturated
condensing temperature of 50 deg C the discharge temperature at a
saturated evaporating temperature of -35 deg C is about 118 deg C.
Then at -40 it's about 116 deg C. Then at -45 it's 115 deg C.
Considering 140 deg C discharge temperature is the limit this
compressor is very safe with out added stages or pre-compression
desuperheating.
Interstage cooling assists in compression by reducing the
specific volume which is what compression is all about.
Superheating the suction gas while cooling the motor increases
specific volume which increases the amount of compression
required.
Marc L O'Brien
>In article <4r0729$7...@news.enterprise.net> dav...@enterprise.net (dav...@enteprise.net) writes:
>>This information should fill in the blanks I left in my previous post
>>and give some idea of the steps I intend to take.
>>The rack was a new installation (approx 4 years old) designed to use
>>R22 and synthetic oil. The compressor are cooled using the copeland
>>demand cooling system but there has been multiple compessor failures,
>>usually electric suggesting that even with this cooling the discharge
>>temps are too high. Being in line with what George Goble said
>
>I assume you mean motor "burnout"? (shorting to ground?) If so, there is
>a huge amount of acid produced and other contaminates from the red hot
>windings breaking down ALL the refrigerant they touch, and if the compressor
>continued to turn, even for a few seconds, the acid is pumped through out
>the whole system and anything connected to it.
Really!?
>The Best burnout cleanup procedure used to be to "power flush" everything
>with R11 to get out all bad oil from the lines, etc, then install
>new compressor. Today some
>people use isopentane (same BP as R11, around 77F), but that
>is extremely flammable so precautions must be taken. Other nonflammable
>solvents are starting to emerge now.
Except me! Flushing the system is only good for high velocity
areas. I use the filter clean up method and never had a re-burn.
However, I do replace items such as oil seps and accumulators.
>There are local technicians who dont believe in proper burnout
>cleanup, and they use "new compressors" to clean up previous
>burnouts.. The new compressors last 3 or 4 months and burnout
>again.. I have seen this go on for 12 or 13 compressors, at which
>time they declare the system was poorly designed and replace
>the whole system at tens of thousands of $$$.. Good job security.
>In the 20 or so compressors I have changed (R11 or isopentane flush),
>none has since failed.
They're not Technicians George, those are ambitious laborers. They
make ordinary people like you and me look good. We need them!
asc...@mo.net
>I am about to tackle the follow situation and am looking for opinions.
>problem I am told is that the sytem expansion valve inlets are being
>blocked with a containant, believed to be the result of an engineer
>adding mineral oil when the rack is designed for synthetic (PAO) oil.
>I have been told that the oil has been removed and replaced with the
>correct brand twice,although I suspect that only the compressor oil
>was replaced, leaving the separator oil. Filter/driers have been
>changed as have oil filters. Liquid liner driers have been added to
>individual cases, two way driers to enable liquid return on saturated
>gas defrost, but the driers have been breaking up. Information that
>concerns me at the moment is that the rack apparently has to operate
>at roughly a 250psi condensing pressure to ensure a positive liquid
>supply to the cases. For those that know of it the system uses a
>Hussman Turbashed type oil separator.
>Any opinions.
David, I assume you have a POE (polyol ester) oil in the system.
Having some amount of mineral oil in the system using R-22 as a
refrigerant shouldn't be causing your problems. If an HFC
refrigerant was being used, e.g., R-134a, R-404A, R-507, whatever
mineral oil you have in the system will tend to get trapped in the
refrigerated cases, and may affect their cooling capacity. Mineral
oil, however, is miscible enough with R-22 that it should be
carried along with the POE oil. Your problem would more than
likely be with the POE oil itself. POE oil is a much better
solvent than mineral oil, and it will remove contaminants from
within the system that mineral oil won't bother with, and carry it
throughout the system.
If you have filter-driers ahead of the TEVs, and you are still
plugging up the inlet strainers, the contaminant must be soluble in
R-22, and precipitating out at the TEV strainer or port due to
the drop in temperature. Some POE oils contain additives which can
promote this type of problem. By cleaning the valves and strainers,
you'll eventually get rid of this type of contaminant.
Your're breaking up some filter-driers???!!! This would concern
me most. If the filter-driers you are using are the 'core' type,
e.g., Sporlan C-083, or the bi-directional HPC series, about the
only way the binder in the core can be weakened is in the
presence of a very high level of moisture or acid in the system.
This needs to be checked if it hasn't been done. BTW, water in the
presence of POE oil will form carboxylic acid.
If you have an alkylbenzene oil in the system, e.g., Zerol, the
mineral oil you have in the system is even less of a concern, as is
the oil solubility issues. I would not have bothered with the
oil change in this case, but tried to identify the contaminant
plugging up the TEVs and its source.
Andy Schoen
asc...@mo.net