Compressors for AVANCE 400 - Summary
Guillermo Moyna (g.moyna@usip.edu)
Fri, 10 Aug 2001 10:39:41 -0400
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Content-Type: text/plain; charset="iso-8859-1" ; format="flowed"
Content-Transfer-Encoding: quoted-printable
Dear All,
Thanks to all those who replied to my e-mail regarding compressed air=20
for our new 400. As customary with this kind of requests, I summarize=20
here the responses I got.
By the way, the project contractor had already 'designed' a system,=20
which consisted in an Beacon continuous duty oil-less rotary scroll=20
1HP compressor, 30 galon receiver tank, and Hankison refrigerated=20
dryer, plus filters/valves. I requested the dryer to be changed to a=20
Hankison heatless desiccating dryer (the things with two towers that=20
switch back and forth and make hissing and popping noises...). The=20
price difference is only 700 USD, and you can get dew points of -70 F.
Again, thanks to all who responded. I'll let you know how things turn out...
Guillermo
*** RESPONSES ***
(1)=20
----------------------------------------------------------------------=20
------
Hi Guillermo:
Some my customers have used the Jun-Air 2000-25MD with success. It also
incorporates a drying system.
Regards:
Paul Cope
NMR Sales Representative, Northeast
Bruker BioSpin Corporation
(a member of the worldwide Bruker BioSpin oganization)
NOTE: MY E-MAIL ADDRESS HAS CHANGED!
e-mail: paul.cope@Bruker-Biospin.com
Tel: 978-667-9580 x443
=46AX: 978-667-0985
(2)=20
----------------------------------------------------------------------=20
------
Hi Guillermo:
We get our compressors from Grainger Industrial Supply:=20
grainger.com . They carry several models, one of which=20
is bound to fill your requirements. Of course, the larger, the=20
noisier, so I hope you have a separate room available.
At Sherwin-Williams we had the larger model Whatman-Balston drier,=20
which ran for years needing only one repair and regular filter=20
changes. Now, Parker has apparently taken them over; they're at:
http://www.=
=20
parker.com/parkersql/default.asp?type=3D2&id=3D444
Or just parker.com and go to the filtration/separation link.
Also, my belated thanks for mentioning Anasazi Instruments in the=20
acknowledgements of the paper on shaped pulses. Finally, how does the=20
prospect of a person filling the temporary teaching position you=20
advertised potentially impact your work and responsibilities?
Take care,
Greg
(3)=20
----------------------------------------------------------------------=20
------
Definately go oil-less. You might want to go with a heatless regenerating
dryer instead of refrigerated. They can take you dew point down to
-70 deg C if needed, while a refreigerated one can't. Our Avance console
(no solids) needs about 65 psi, with the QNP probe switching air
solenoids being the fussyest about low pressure.
Make sure that you have good filters as well.
-Kirk
(4)=20
----------------------------------------------------------------------=20
------
Hello,
I have no suggestions regarding manufacturers, but I can say that we had
trouble with our compressor constantly. Two things I have learned: 1.
locate the compressor far away from offices, so nobody has to listen to
its noisy gurgling and pumping. 2. Locate it in a room with good air flow
- these things generate huge amounts of heat and can burn themselves out
if they are put in a utility closet, as ours was, with no active air
circulation.
Good luck!
- Jessica Dion
University of Vermont
(5)=20
----------------------------------------------------------------------=20
------
Guillermo,
We have an Avance DMX 400 instrument with a dedicated=20
compressed air supply since we, too, lack an adequate house air=20
system. It is based on a Powerex oil-free rotary scroll compressor=20
and has been in service with this instrument and its predecessor for=20
five years now. There is a complete description of this system on the=20
web at:
http://www.spincore.com/nmrinfo/
Look for an article titled "Air Supply for NMR". Since I wrote that=20
letter, we have upgraded our compressor to 5 HP, which reduces=20
cycling and should prolong the life of the compressor head, and have=20
replaced all the pneumatic and solenoid drain valves with=20
electrically-operated ball valves, which are much more resistant to=20
sticking in the open position. I would be happy to answer and=20
questions you might have about compressed air supplies for NMR and=20
can provide a list of vendors, pictures of the system, etc.
Best regards,
Ken Fishbein, Ph.D.
Facility Manager, NMR Unit
NIH/NIA/GRC
Ph. (410) 558-8512
=46AX (410) 558-8318 or 8376
E-mail: fishbein@vms.grc.nia.nih.gov
Address: Ken Fishbein
National Institutes of Health
National Institute on Aging
Gerontology Research Center
5600 Nathan Shock Drive
Baltimore, MD 21224 USA
(6)=20
----------------------------------------------------------------------=20
------
Dear Guillermo,
Aim high. If you are putting TMC anti vibration posts on your magnet, you
will need 70-80 psi minimum, plus air for spinning, VT, etc. An air
compressor with higher capacity may actually have less maintenance problems
since it being run under less harsh conditions. A bigger capacity also
gives you the opportunity to use the same unit if you add another smaller
spectrometer.
Good Luck,
Bill
(7)=20
----------------------------------------------------------------------=20
------
Guillermo,
for solid state DMX 400
2*scroll compressors working parallel with slight delay for power on( Atlas
Copco from Japaneese Patent or equivalent), 10 bars is better although flux
is lower because Regenerative air dryer can be better optimized to lower
dew point -70=B0C
1 tank as cool as possible (automatic water purge, risk or corrosion at the
bottom of tank)
stainless steel piping
1 small refrigerating air dryer (modified to have non rewarmed cooled air
at exhaust) or possibly membrane ( too dry air might hamper regenerative
system to cycle properly)
2 filters
1 regenerative (zeolithe+ alumina) air dryer such as Zander in Europe,
Balston more expensive and not better to reach thermodynamical limits
one smaller tank 100l oil free (needs initial cleaning (we almost ruined
our equipment forgetting to check that oil free for manufacturers does not
mean grease free tanks ! ideally stainless steel
2 post filters (particles and activated carbon)
manifolds to distribute to spectrometer, rotor cleaning , ventury vaccum
cleaner around spectrometer, ....
possibility to implement a cooling exchanger on the dry gaz line for VT
applications dew point below -80=B0C for the moment but 30% flux lost in air
dryer regeneration
not that expensive and works fine up to now.
Room is also set in slight overpressure and partially dust filtered
=46ans of Power Amps seem to be a (frequent) cause of burnout
More if needed
Best regards ou Salutations cordiales, :-)
**************************************************************************.
Herve Bizot / Unit=E9 de Physicochimie des Macromolecules
Inst. Nat. Recherche Agronomique / BP# 71627 /44316 NANTES Cedex 03 / FRANC=
E
Tel.: 33 (0)2 40 67 50 00 / FAX.: 33 (0)2 40 67 50 43 or 50 05 / E-Mail :
bizot@nantes.inra.fr
**************************************************************************.
(8)=20
----------------------------------------------------------------------=20
------
Hi Guillermo,
There are several factors that you must consider in selecting a compressor:
1. Is it only going to supply one spectrometer in the future?=20
If this is the case you probably only need about 7 CFM system.
2. How "rugged" do you want to go?
The most rugged types of compressors are the oil lubed reciprocating=20
(oil in the crankcase) type. If located inside in a clean=20
environment they can give many years service with only annual or=20
semi-annual oil (synthetic oil) changes. How ever you should have=20
oil traps installed on the output. There are a number of=20
manufacturers of these type. I would recommend Ingersol-Rand but I=20
am sure there are others.
Less "rugged" types are the oil less types, with "no" oil in the=20
crankcase. Be careful talking with vendors on these. An "oil free"=20
compressor can mean it has oil in the crank case but no oil is=20
suppose to enter the air stream, an oil less is no oil at all. To my=20
knowledge there are only two vendors of oil less compressors,=20
Ingersol-Rand is one and I don't recall the other. The oil less type=20
have teflon rings and special bearings. The compressors and used in=20
the medical profession and are costly. They also need to be rebuilt=20
~ every three to four years or so depending on application and usage.=20
The next type are the rotary ones, I have no experience personally=20
with them but we do have a couple in our Mass Spec Labs and they seem=20
to work OK. I would suggest contacting a Parker-Balston rep. The=20
major advantage to these is they have an integral refrigerator air=20
dryer system built in.
3. Will it need a pre-dryer and post dryer?
If you decide on a reciprocating type if you have high humidity you=20
will need a refrigerator pre-dryer and a post dryer of about -40C Dew=20
point if you are getting a Bruker NMR where air passes through a=20
chiller before entering the probe. I would recommend a=20
Parker-Balston dryer for this, here again P-B designs these systems=20
for labs and hospitals.
You should also have an auto receiver tank drain on the receiver tank=20
of the system.
I hope this helps, if you have any more questions let me know!!!!
Good luck,
Elwood
(9)=20
----------------------------------------------------------------------=20
------
We purchased a Gast oil-less compressor, a ballast tank, and a Whatman
dryer for our Avance 400. The Whatman representative recommended the
wrong Gast compressor which burned out after several months of operation!
The Whatman air dryer uses a signficant portion of the input air to
regenerate its drying columns. Hence, make sure that the compressor is
equal to the task!!! The capacity of the compressor must exceed the
requirements of the spectrometer. Overkill in this case is necessary.
=46urthermore, the unit is quite noisy and you don't want to install
the compressor in the same room as the spectrometer.
We also installed a second line that is connected to a high-pressure
liquid nitrogen tank. The boiloff from the liquid nitrogen provides
very dry nitrogen that is used for low-temperature runs. The
system is plumbed so that we can easily switch from dry air to very
dry nitrogen.
(10)=20
----------------------------------------------------------------------=20
------
Guillermo:
Instead of a refrigerated air dryer, look into using a=20
membrane/molecular sieve air dryer (Balstron is a good name). They=20
seem to work better, and the membrane ones don't need electricity.
Also, look into a screw-compressor design. They, unlike=20
piston types, are designed to run continually. We had problems with=20
our piston-type compressors until we finally got a Quincy screw. A=20
caveat to that is to make sure either your physical plant people or a=20
local vendor does preventive maintenance -> they have to be babied a=20
little to work reliably.
Regards,
(11)=20
----------------------------------------------------------------------=20
-----
Guillermo:
Compressed air is always a problem. When our air system was=20
installed no one bothered to ask my opinion so we got everything=20
wrong. You are lucky that at least you are in at the beginning. Our=20
system has an oil lubricated pump but we have solved the problem of=20
oil with an coalescing oil filter in the line. This works very well.=20
Oil-less pumps tend to have shorter life spans then oiled one. Our=20
next big problem was water in the line so much so that it overwhelmed=20
the refrigerated air dryer. We solved this problem but putting in an=20
air cooled aftercooler to remove excess water and oil before the air=20
every gets to the filter or refrigerated air dryer. I would like to=20
make one more suggestion and that is to get a regenerative desiccant=20
compressed air dryer. This can bring your dew point to -70 deg so=20
that you can run experiments below zero without having to use=20
nitrogen gas. Remember that refrigerated air dryers have dew points=20
of 35 deg F.
All air pumps require regular maintenance. This includes changing the=20
air filters and the valves. I usually change that valves in the pump=20
every year. This helps keep up the pumping efficiency.
If you are interested the Grainger Co. catalogue has a nice diagram=20
for the proper way to set up an air system. You can find it in their=20
catalog. In their 2000-2001 catalog it is on page 2919.
Best regards,
Les
(12)=20
----------------------------------------------------------------------=20
-----
Hi,
I have had problems for 20 years with air delivery to the department for
the IR,NMR, etc. The piston compressors seem to wear out frequently and
if the demand is high they cant keep up because the original
installation didnt have any reserve for future demands. A compressor
that runs all the time is probably going to have problems. Finally,
after much complainig, a turbine type compressor was installed. It is
much smaller and doesnt hammer like a older piston design. The belts
have to be changed periodically and the oil checked. So far it is able
to keep up with the demand. It is designed to run continuously and is
controlled by a small "computer". I do have filters, dryer and ballast
tank on the system. The tank does trap a small amount of water. The air
lines werent pitched properly to allow back flow of accululated water so
we have to live with that. There are some low spots in the over 200
feet of pipe.
I would buy a compressor that has some percentage in excess of the
present demands for future expansion. Goodluck.
Jim
(13)=20
----------------------------------------------------------------------=20
-----
Hi Guillermo,
Bruker installed the air system for our 600 Avance 5 years ago and we
had many problems. They installed a compressor, a mechanical water trap
(air cooled), and standard Zander drier. It turned out we needed a
system suited for tropical conditions although humidity here is around
40% and temps are c.a. 2-15C in winter and 20-31C in summer. Then we
started adding parts - an electronic water trap, an additional drier
(the double driers are probably unnecessary but they kept getting
clogged and the second one would save us) and, of course, a 120 lit
ballast tank in addition to the usual filters, etc. The compressor
worked almost continually during its cycle, we had numerous breakdowns
and T1 noise in our spectra due to humidity until we installed all the
additional measures, and the compressor died after about 4 years.
Our new compressor (also Atlas Copco) is a rotary screw and well above
the recommended output. It carries all the auxiliary driers and has been
great so far. It needs periodic belt change and filter change that we
have done by contract with Atlas Copco. They can do the maintenance
during the off-time of the compressor (about a minute at a time) so
there is no down-time for us. The system is very noisy but it is out of
the room so we don't hear it.
Good luck!
Debbie
(14)=20
----------------------------------------------------------------------=20
-----
Guillermo,
We installed a piston compressor for our lab, and it has been OK. It=20
is a 2-piston model, not oil-less. The reservoir is about 40=20
gallons; the compressor turns on at 70 psi and turns off at 100 psi.=20
We had problems with the compressor motor tripping its breaker in the=20
beginning. Reducing the turn-on pressure by 10 psi made a big=20
difference, but didn't completely solve the problem. They replaced=20
the 2-phase motor with a 3-phase motor to fix it completely. I=20
think the little compressors ($200 - $500) used by construction=20
workers would be dead in a couple of months; they aren't continuous=20
duty.
60 psi is needed for our TMC anti-vibration legs (is 70 psi before=20
the air dryer). 45 psi would be enough to feed reliable 35 psi to=20
the ejector. The spinner and cooling air I think are even lower than=20
that.
The compressor is loud. We were able to install it in a utility room=20
30 feet away and can't hear it (but bet the ladies in the restroom=20
adjacent to it make some interesting movements!). It is well worth=20
the money for a "scroll-type" compressor, which can be in the same=20
room as the spectrometer. Better is in a closet. Quiet is something=20
you will later wish you had paid for.
Auto-drain on the reservoir is important.
Having a "drip leg" or some sort of water trap just before the air=20
dryer is critical. I had our dryer repaired three times from being=20
flooded. The water trap should have an autodrain as well. I have=20
to drain mine twice a week (1 liter each time) in summer in Boston.=20
(But not at all in winter).
The pipes between the compressor and the spectrometer tend to fill=20
with water, then burp it all at once. The drip leg catches it. It=20
would be worth warning the plumbers to tilt the pipes slightly, so=20
there's no low point which fills slowly then burps.
Have the plumbers put in valves & fittings so you can easily switch=20
to a gas supply ( e.g liq nitrogen boiloff GP240 tank).
The air dryer uses more air than the spectrometer, and so is=20
responsible for most of the wear-and-tear on the compressor. Whatman=20
only offered a big one when we were looking. See if you can turn it=20
down, or get a smaller one. The air dryer also makes noise -=20
popping when it changes towers and hissing the rest of the time.=20
Even with the dryer in the closet, new users ask if that noise isn't=20
something going wrong.
*** END RESPONSES ***
+=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D-------------- --- --=
- - - -
Guillermo Moyna, PhD
Department of Chemistry & Biochemistry
University of the Sciences in Philadelphia
600 South 43rd Street
Philadelphia, PA 19104-4495
"The only existing things are atoms and empty space.
All else is mere opinion" - Democritus, 370 B.C.
Office: Grifith Hall 360
Phone: (215) 596-8526
=46ax: (215) 596-8543
e-mail: g.moyna@usip.edu
WWW: http://tonga.usip.edu/gmoyna/index.html
http://www.usip.edu/chemistry/faculty/moyna.asp
- - - - -- --- -----------=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D+
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Content-Type: text/enriched; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
Dear All,
Thanks to all those who replied to my e-mail regarding compressed air
for our new 400. As customary with this kind of requests, I summarize
here the responses I got.
By the way, the project contractor had already 'designed' a system,
which consisted in an Beacon continuous duty oil-less rotary scroll 1HP
compressor, 30 galon receiver tank, and Hankison refrigerated dryer,
plus filters/valves. I requested the dryer to be changed to a Hankison
heatless desiccating dryer (the things with two towers that switch back
and forth and make hissing and popping noises...). The price difference
is only 700 USD, and you can get dew points of -70 F.
Again, thanks to all who responded. I'll let you know how things turn
out...
Guillermo
*** RESPONSES ***
(1)
----------------------------------------------------------------------------
Hi Guillermo:
Some my customers have used the Jun-Air 2000-25MD with success. It
also
incorporates a drying system.
Regards:
Paul Cope
NMR Sales Representative, Northeast
Bruker BioSpin Corporation
(a member of the worldwide Bruker BioSpin oganization)
NOTE: MY E-MAIL ADDRESS HAS CHANGED!
e-mail: paul.cope@Bruker-Biospin.com
Tel: 978-667-9580 x443
=46AX: 978-667-0985
(2)
----------------------------------------------------------------------------
Hi Guillermo:
We get our compressors from Grainger Industrial Supply:
<grainger.com . They carry several models, one of which
is bound to fill your requirements. Of course, the larger, the
noisier, so I hope you have a separate room available.
At Sherwin-Williams we had the larger model Whatman-Balston drier,
which ran for years needing only one repair and regular filter changes.
Now, Parker has apparently taken them over; they're at:
<http://www.p=
arker.com/parkersql/default.asp?type=3D2&id=3D444
Or just <parker.com and go to the filtration/separation
link.
Also, my belated thanks for mentioning Anasazi Instruments in the
acknowledgements of the paper on shaped pulses. Finally, how does the
prospect of a person filling the temporary teaching position you
advertised potentially impact your work and responsibilities?
Take care,
Greg
(3)
----------------------------------------------------------------------------
Definately go oil-less. You might want to go with a heatless
regenerating
dryer instead of refrigerated. They can take you dew point down to
-70 deg C if needed, while a refreigerated one can't. Our Avance
console
(no solids) needs about 65 psi, with the QNP probe switching air
solenoids being the fussyest about low pressure.
Make sure that you have good filters as well.
-Kirk
(4)
----------------------------------------------------------------------------
Hello,
I have no suggestions regarding manufacturers, but I can say that we
had
trouble with our compressor constantly. Two things I have learned: 1.
locate the compressor far away from offices, so nobody has to listen
to
its noisy gurgling and pumping. 2. Locate it in a room with good air
flow
- these things generate huge amounts of heat and can burn themselves
out
if they are put in a utility closet, as ours was, with no active air
circulation.
Good luck!
- Jessica Dion
University of Vermont
(5)
----------------------------------------------------------------------------
Guillermo,
We have an Avance DMX 400 instrument with a dedicated compressed air
supply since we, too, lack an adequate house air system. It is based on
a Powerex oil-free rotary scroll compressor and has been in service
with this instrument and its predecessor for five years now. There is a
complete description of this system on the web at:
http://www.spincore.com/nmrinfo/
Look for an article titled "Air Supply for NMR". Since I wrote that
letter, we have upgraded our compressor to 5 HP, which reduces cycling
and should prolong the life of the compressor head, and have replaced
all the pneumatic and solenoid drain valves with electrically-operated
ball valves, which are much more resistant to sticking in the open
position. I would be happy to answer and questions you might have about
compressed air supplies for NMR and can provide a list of vendors,
pictures of the system, etc.
Best regards,
Ken Fishbein, Ph.D.
Facility Manager, NMR Unit
NIH/NIA/GRC
Ph. (410) 558-8512
=46AX (410) 558-8318 or 8376
E-mail: fishbein@vms.grc.nia.nih.gov
Address: Ken Fishbein
National Institutes of Health
National Institute on Aging
Gerontology Research Center
5600 Nathan Shock Drive
Baltimore, MD 21224 USA
(6)
----------------------------------------------------------------------------
Dear Guillermo,
Aim high. If you are putting TMC anti vibration posts on your magnet,
you
will need 70-80 psi minimum, plus air for spinning, VT, etc. An air
compressor with higher capacity may actually have less maintenance
problems
since it being run under less harsh conditions. A bigger capacity
also
gives you the opportunity to use the same unit if you add another
smaller
spectrometer.
Good Luck,
Bill
(7)
----------------------------------------------------------------------------
Guillermo,
for solid state DMX 400
2*scroll compressors working parallel with slight delay for power on(
Atlas
Copco from Japaneese Patent or equivalent), 10 bars is better although
flux
is lower because Regenerative air dryer can be better optimized to=20
lower
dew point -70=B0C
1 tank as cool as possible (automatic water purge, risk or corrosion at
the
bottom of tank)
stainless steel piping
1 small refrigerating air dryer (modified to have non rewarmed cooled
air
at exhaust) or possibly membrane ( too dry air might hamper
regenerative
system to cycle properly)
2 filters
1 regenerative (zeolithe+ alumina) air dryer such as Zander in Europe,
Balston more expensive and not better to reach thermodynamical limits
one smaller tank 100l oil free (needs initial cleaning (we almost
ruined
our equipment forgetting to check that oil free for manufacturers does
not
mean grease free tanks ! ideally stainless steel
2 post filters (particles and activated carbon)
manifolds to distribute to spectrometer, rotor cleaning , ventury
vaccum
cleaner around spectrometer, ....
possibility to implement a cooling exchanger on the dry gaz line for
VT
applications dew point below -80=B0C for the moment but 30% flux lost in
air
dryer regeneration
not that expensive and works fine up to now.
Room is also set in slight overpressure and partially dust filtered
=46ans of Power Amps seem to be a (frequent) cause of burnout
More if needed
Best regards ou Salutations cordiales, :-)
**************************************************************************.
Herve Bizot / Unit=E9 de Physicochimie des Macromolecules
Inst. Nat. Recherche Agronomique / BP# 71627 /44316 NANTES Cedex 03 /
=46RANCE
Tel.: 33 (0)2 40 67 50 00 / FAX.: 33 (0)2 40 67 50 43 or 50 05 /
E-Mail :
bizot@nantes.inra.fr
**************************************************************************.
(8)
----------------------------------------------------------------------------
Hi Guillermo,
There are several factors that you must consider in selecting a
compressor:
1. Is it only going to supply one spectrometer in the future?=20
If this is the case you probably only need about 7 CFM system.
2. How "rugged" do you want to go?
The most rugged types of compressors are the oil lubed reciprocating
(oil in the crankcase) type. If located inside in a clean environment
they can give many years service with only annual or semi-annual oil
(synthetic oil) changes. How ever you should have oil traps installed
on the output. There are a number of manufacturers of these type. I
would recommend Ingersol-Rand but I am sure there are others.
Less "rugged" types are the oil less types, with "no" oil in the
crankcase. Be careful talking with vendors on these. An "oil free"
compressor 0000,0000,FFFFcan mean it has
oil in the crank case but no oil is suppose to enter the air stream, an
oil less is no oil at all. To my knowledge there are only two vendors
of oil less compressors, Ingersol-Rand is one and I don't recall the
other. The oil less type have teflon rings and special bearings. The
compressors and used in the medical profession and are costly. They
also need to be rebuilt ~ every three to four years or so depending on
application and usage.=20
The next type are the rotary ones, I have no experience personally with
them but we do have a couple in our Mass Spec Labs and they seem to
work OK. I would suggest contacting a Parker-Balston rep. The major
advantage to these is they have an integral refrigerator air dryer
system built in.
3. Will it need a pre-dryer and post dryer?
If you decide on a reciprocating type if you have high humidity you
will need a refrigerator pre-dryer and a post dryer of about -40C Dew
point if you are getting a Bruker NMR where air passes through a
chiller before entering the probe. I would recommend a Parker-Balston
dryer for this, here again P-B designs these systems for labs and
hospitals.
You should also have an auto receiver tank drain on the receiver tank
of the system.
I hope this helps, if you have any more questions let me know!!!!
Good luck,
Elwood
(9)
----------------------------------------------------------------------------
We purchased a Gast oil-less compressor, a ballast tank, and a
Whatman
dryer for our Avance 400. The Whatman representative recommended the
wrong Gast compressor which burned out after several months of
operation!
The Whatman air dryer uses a signficant portion of the input air to
regenerate its drying columns. Hence, make sure that the compressor
is
equal to the task!!! The capacity of the compressor must exceed the
requirements of the spectrometer. Overkill in this case is necessary.
=46urthermore, the unit is quite noisy and you don't want to install=20
the compressor in the same room as the spectrometer.
We also installed a second line that is connected to a high-pressure
liquid nitrogen tank. The boiloff from the liquid nitrogen provides
very dry nitrogen that is used for low-temperature runs. The
system is plumbed so that we can easily switch from dry air to very
dry nitrogen.
(10)
----------------------------------------------------------------------------
Guillermo:
Instead of a refrigerated air dryer, look into using a
membrane/molecular sieve air dryer (Balstron is a good name). They
seem to work better, and the membrane ones don't need electricity.
Also, look into a screw-compressor design. They, unlike piston types,
are designed to run continually. We had problems with our piston-type
compressors until we finally got a Quincy screw. A caveat to that is
to make sure either your physical plant people or a local vendor does
preventive maintenance -> they have to be babied a little to work
reliably.
Regards,
(11)
---------------------------------------------------------------------------
Guillermo:
Compressed air is always a problem. When our air system was installed
no one bothered to ask my opinion so we got everything wrong. You are
lucky that at least you are in at the beginning. Our system has an oil
lubricated pump but we have solved the problem of oil with an
coalescing oil filter in the line. This works very well. Oil-less pumps
tend to have shorter life spans then oiled one. Our next big problem
was water in the line so much so that it overwhelmed the refrigerated
air dryer. We solved this problem but putting in an air cooled
aftercooler to remove excess water and oil before the air every gets to
the filter or refrigerated air dryer. I would like to make one more
suggestion and that is to get a regenerative desiccant compressed air
dryer. This can bring your dew point to -70 deg so that you can run
experiments below zero without having to use nitrogen gas. Remember
that refrigerated air dryers have dew points of 35 deg F.
All air pumps require regular maintenance. This includes changing the
air filters and the valves. I usually change that valves in the pump
every year. This helps keep up the pumping efficiency.
If you are interested the Grainger Co. catalogue has a nice diagram for
the proper way to set up an air system. You can find it in their
catalog. In their 2000-2001 catalog it is on page 2919.
Best regards,
Les
(12)
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Hi,
I have had problems for 20 years with air delivery to the department
for
the IR,NMR, etc. The piston compressors seem to wear out frequently
and
if the demand is high they cant keep up because the original
installation didnt have any reserve for future demands. A compressor
that runs all the time is probably going to have problems. Finally,
after much complainig, a turbine type compressor was installed. It is
much smaller and doesnt hammer like a older piston design. The belts
have to be changed periodically and the oil checked. So far it is able
to keep up with the demand. It is designed to run continuously and is
controlled by a small "computer". I do have filters, dryer and ballast
tank on the system. The tank does trap a small amount of water. The
air
lines werent pitched properly to allow back flow of accululated water
so
we have to live with that. There are some low spots in the over 200
feet of pipe.
I would buy a compressor that has some percentage in excess of the
present demands for future expansion. Goodluck.
Jim
(13)
---------------------------------------------------------------------------
Hi Guillermo,
Bruker installed the air system for our 600 Avance 5 years ago and we
had many problems. They installed a compressor, a mechanical water
trap
(air cooled), and standard Zander drier. It turned out we needed a
system suited for tropical conditions although humidity here is around
40% and temps are c.a. 2-15C in winter and 20-31C in summer. Then we
started adding parts - an electronic water trap, an additional drier
(the double driers are probably unnecessary but they kept getting
clogged and the second one would save us) and, of course, a 120 lit
ballast tank in addition to the usual filters, etc. The compressor
worked almost continually during its cycle, we had numerous breakdowns
and T1 noise in our spectra due to humidity until we installed all the
additional measures, and the compressor died after about 4 years.
Our new compressor (also Atlas Copco) is a rotary screw and well above
the recommended output. It carries all the auxiliary driers and has
been
great so far. It needs periodic belt change and filter change that we
have done by contract with Atlas Copco. They can do the maintenance
during the off-time of the compressor (about a minute at a time) so
there is no down-time for us. The system is very noisy but it is out
of
the room so we don't hear it.
Good luck!
Debbie
(14)
---------------------------------------------------------------------------
Guillermo,
We installed a piston compressor for our lab, and it has been OK. It
is a 2-piston model, not oil-less. The reservoir is about 40 gallons;
the compressor turns on at 70 psi and turns off at 100 psi. We had
problems with the compressor motor tripping its breaker in the
beginning. Reducing the turn-on pressure by 10 psi made a big
difference, but didn't completely solve the problem. They replaced the
2-phase motor with a 3-phase motor to fix it completely. I think the
little compressors ($200 - $500) used by construction workers would be
dead in a couple of months; they aren't continuous duty.
60 psi is needed for our TMC anti-vibration legs (is 70 psi before the
air dryer). 45 psi would be enough to feed reliable 35 psi to the
ejector. The spinner and cooling air I think are even lower than
that.
The compressor is loud. We were able to install it in a utility room
30 feet away and can't hear it (but bet the ladies in the restroom
adjacent to it make some interesting movements!). It is well worth
the money for a "scroll-type" compressor, which can be in the same room
as the spectrometer. Better is in a closet. Quiet is something you
will later wish you had paid for.
Auto-drain on the reservoir is important.
Having a "drip leg" or some sort of water trap just before the air
dryer is critical. I had our dryer repaired three times from being
flooded. The water trap should have an autodrain as well. I have to
drain mine twice a week (1 liter each time) in summer in Boston. (But
not at all in winter).
The pipes between the compressor and the spectrometer tend to fill with
water, then burp it all at once. The drip leg catches it. It would be
worth warning the plumbers to tilt the pipes slightly, so there's no
low point which fills slowly then burps.
Have the plumbers put in valves & fittings so you can easily switch to
a gas supply ( e.g liq nitrogen boiloff GP240 tank).
The air dryer uses more air than the spectrometer, and so is
responsible for most of the wear-and-tear on the compressor. Whatman
only offered a big one when we were looking. See if you can turn it
down, or get a smaller one. The air dryer also makes noise - popping
when it changes towers and hissing the rest of the time. Even with the
dryer in the closet, new users ask if that noise isn't something going
wrong.
*** END RESPONSES ***
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Guillermo Moyna, PhD
Department of Chemistry & Biochemistry
University of the Sciences in Philadelphia
600 South 43rd Street
Philadelphia, PA 19104-4495
"The only existing things are atoms and empty space.
All else is mere opinion" - Democritus, 370 B.C.
Office: Grifith Hall 360
Phone: (215) 596-8526
=46ax: (215) 596-8543
e-mail: g.moyna@usip.edu
WWW: http://tonga.usip.edu/gmoyna/index.html
http://www.usip.edu/chemistry/faculty/moyna.asp
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