| [GMCnet] Find/fix Dash A/C Leak [message #175316] |
Mon, 02 July 2012 14:33  |
paul h cashman
Messages: 176
Registered: May 2005
Karma: 0
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Senior Member |
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Johnny,
Water boils at about 1500 microns of vacuum .Good practice requires 500-700
microns.
29 inches of vacuum is 25,400 microns.
A perfect vacuum is 29.921 inches of vacuum or 0 micron.
It takes a very good vacuum pump to reach this level.
Paul Cashman
Riverdale GA.
78 Transmode
I'd evacuate it overnight, if you have time and a vacuum pump.? This will
boil out any moisture which may have found its way into the system including
the receiver/dryer.?
?
--johnny
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Paul H Cashman
Riverdale Ga
1978 Transmode
1975 Corvette
1978 Beetle Convertible
1989 Harley Davidson Sportster
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| Re: [GMCnet] Find/fix Dash A/C Leak [message #175324 is a reply to message #175316] |
Mon, 02 July 2012 16:42  |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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G'day,
Being the pedantic bastard that I am water "sublimates" and goes from a
liquid - solid (ice) - vapor in a vacuum, that's how we kept the Apollo
astronauts comfy in their suits on the moon. They were so well insulated we
had to remove heat.
It is damn near impossible to get to 0 microns, I ga-ron-tee you won't get
anywhere near that with a common vacuum pump.
To get down to levels of vacuum that exist in outer space you need a
cryogenic vacuum pump. I've forgotten how they work, hell it's been over 40
years!
http://en.wikipedia.org/wiki/Vacuum_pump
Regards,
Rob M.
-----Original Message-----
From: Paul Cashman
Johnny,
Water boils at about 1500 microns of vacuum .Good practice requires 500-700
microns.
29 inches of vacuum is 25,400 microns.
A perfect vacuum is 29.921 inches of vacuum or 0 micron.
It takes a very good vacuum pump to reach this level.
Paul
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Find/fix Dash A/C Leak [message #175387 is a reply to message #175316] |
Tue, 03 July 2012 06:25 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Well, depending temperature and other factors. But, it evaporates (which it will happily do without boiling) at room temp much faster at the lower pressure. Consequently, overnight with a good service pump will normally purge the moisture in the silica gel in the dryer.
--johnny
'76 23' transmode norris
'76 palm beach
From: Paul Cashman <paulcashman@bellsouth.net>
To: gmclist <gmclist@temp.gmcnet.org>
Sent: Monday, July 2, 2012 3:33 PM
Subject: [GMCnet] Find/fix Dash A/C Leak
Johnny,
Water boils at about 1500 microns of vacuum .Good practice requires 500-700
microns.
29 inches of vacuum is 25,400 microns.
A perfect vacuum is 29.921 inches of vacuum or 0 micron.
It takes a very good vacuum pump to reach this level.
Paul Cashman
Riverdale GA.
78 Transmode
I'd evacuate it overnight, if you have time and a vacuum pump.? This will
boil out any moisture which may have found its way into the system including
the receiver/dryer.?
?
--johnny
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http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Find/fix Dash A/C Leak [message #175390 is a reply to message #175324] |
Tue, 03 July 2012 06:36 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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One of my tube rebuilders (Freeland Products, now a division of Econco) bought their pumps surplus from NASA. Mr. Freeland told me they were some sort of turbine - like thing, he bought them for cheap surplu but said they must have cost NASA a fortune.
--johnny
'76 23' transmode norris
'76 palm beach
From: Rob Mueller <robmueller@iinet.net.au>
To: gmclist@temp.gmcnet.org
Sent: Monday, July 2, 2012 5:42 PM
Subject: Re: [GMCnet] Find/fix Dash A/C Leak
G'day,
Being the pedantic bastard that I am water "sublimates" and goes from a
liquid - solid (ice) - vapor in a vacuum, that's how we kept the Apollo
astronauts comfy in their suits on the moon. They were so well insulated we
had to remove heat.
It is damn near impossible to get to 0 microns, I ga-ron-tee you won't get
anywhere near that with a common vacuum pump.
To get down to levels of vacuum that exist in outer space you need a
cryogenic vacuum pump. I've forgotten how they work, hell it's been over 40
years!
http://en.wikipedia.org/wiki/Vacuum_pump
Regards,
Rob M.
-----Original Message-----
From: Paul Cashman
Johnny,
Water boils at about 1500 microns of vacuum .Good practice requires 500-700
microns.
29 inches of vacuum is 25,400 microns.
A perfect vacuum is 29.921 inches of vacuum or 0 micron.
It takes a very good vacuum pump to reach this level.
Paul
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Find/fix Dash A/C Leak [message #175408 is a reply to message #175324] |
Tue, 03 July 2012 09:59 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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| Robert Mueller wrote on Mon, 02 July 2012 14:42 |
... It is damn near impossible to get to 0 microns, I ga-ron-tee you won't get
anywhere near that with a common vacuum pump.
To get down to levels of vacuum that exist in outer space you need a
cryogenic vacuum pump. I've forgotten how they work, hell it's been over 40
years! ...
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Defiantly non-GMC, but as you brought it up...
cryogenic "pumps" actually trap molecules in an existing vacuum, by freezing them. This lowers the pressure creating "more" vacuum. The "pump" has to be regenerated from time to time. (Heated up while under vacuum to "burn" off the trapped molecules.) While noting that I currently work on uses vacuum at that level, I do see them on other equipment at work. (That I do NOT work on.)
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: [GMCnet] Find/fix Dash A/C Leak [message #175409 is a reply to message #175387] |
Tue, 03 July 2012 10:07 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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I had some silica devices that are made to plug into a spark plug hole to keep the cylinders dry. Actually they are Rob's. They turn pink when saturated.
4 of these turned pink so I put them in my vacuum cabinet. Under vacuum they would immediately turn back blue again and water would condense on the inside of the clear plastic housings. I let them sit overnight under vacuum a couple of times but I never could get the water out of the tubes. They are still sitting in my vacuum cabinet not under a vacuum and they are pink again under normal atmospheric pressure. I need to ship these to Arizona and have someone leave them out in the sun for a few weeks.
Based on the above experience, I'm not sure that the silica contained in a dryer will release all of it's moisture under a vacuum.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Find/fix Dash A/C Leak [message #175423 is a reply to message #175409] |
Tue, 03 July 2012 12:21 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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Senior Member |
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| Ken Burton wrote on Tue, 03 July 2012 08:07 |
I had some silica devices that are made to plug into a spark plug hole to keep the cylinders dry. Actually they are Rob's. They turn pink when saturated.
4 of these turned pink so I put them in my vacuum cabinet. Under vacuum they would immediately turn back blue again and water would condense on the inside of the clear plastic housings. I let them sit overnight under vacuum a couple of times but I never could get the water out of the tubes. They are still sitting in my vacuum cabinet not under a vacuum and they are pink again under normal atmospheric pressure. I need to ship these to Arizona and have someone leave them out in the sun for a few weeks. ...
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you might try heat. maybe just put in the oven for a while. (low heat)
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: [GMCnet] Find/fix Dash A/C Leak [message #175501 is a reply to message #175488] |
Wed, 04 July 2012 09:08 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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I heated them to 150 with my oven and then threw them in the vacuum cabinet. I had the same thing. I'm afraid to heat them too much higher since they are plastic and I might melt them. I also microwaved them followed by the vacuum cabinet. Unfortunately they are glued together so I can not get to the actual desiccant. I can see the desiccant through the clear plastic.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Find/fix Dash A/C Leak [message #175505 is a reply to message #175501] |
Wed, 04 July 2012 10:02 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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| Ken Burton wrote on Wed, 04 July 2012 09:08 |
I heated them to 150 with my oven and then threw them in the vacuum cabinet. I had the same thing. I'm afraid to heat them too much higher since they are plastic and I might melt them. I also microwaved them followed by the vacuum cabinet. Unfortunately they are glued together so I can not get to the actual desiccant. I can see the desiccant through the clear plastic.
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Perhaps the plastic is a one way membrane -- only allowing moisture vapor in.
Could you put a small hole in the plastc, dry the dessicant and then seal the hole?
Dennis
Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: [GMCnet] Find/fix Dash A/C Leak [message #175519 is a reply to message #175501] |
Wed, 04 July 2012 11:40 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Before we had the nitrogen generators, we used dessicant dryers. They cycled the dessicant chambers and heated them. Then later, they developed PSA dehydrators with a totally different mode of operation and chamber material. No heat required, just the pressure swing. Then Litton Life Support started selling the little nitrogen concentrators, and we use those now. My problem being Litton dropped the line, and the people who fix them are the folks who have the DOD contract to fix the ones out of jet fighters..... and they want jet fighter prices to mess with them.
--johnny
'76 23' transmode norris
'76 palm beach
From: Ken Burton <n9cv@comcast.net>
To: gmclist@temp.gmcnet.org
Sent: Wednesday, July 4, 2012 10:08 AM
Subject: Re: [GMCnet] Find/fix Dash A/C Leak
I heated them to 150 with my oven and then threw them in the vacuum cabinet. I had the same thing. I'm afraid to heat them too much higher since they are plastic and I might melt them. I also microwaved them followed by the vacuum cabinet. Unfortunately they are glued together so I can not get to the actual desiccant. I can see the desiccant through the clear plastic.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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