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Coolant Cap Pressure Rating

12 posts in this topic

Posted

What are you guys running for a cap pressure on your 582's?  Mine says 8 PSI which seems awful low to me.

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Posted

13 

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Posted

I may be wrong but believe the grey top with the non ceramic seal needs the lower pressure.

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Posted (edited)

I may be wrong but believe the grey top with the non ceramic seal needs the lower pressure.

There must be some Engineering / Professor type person who has access to charts that show increase in boiling point of coolant for each pound of pressure, and also info on expansion of coolant for degrees of temperature, or something applicable.   I am Sgt. Schultz on this one, "I know Nothing".   EDMO

Edited by EDMO

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Posted

I hear ya Ed.  Easy enough to do.  I guess your concern might be possible pump cavitation or maybe excessive heat transfer in the two phase area's?

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Posted

I may be wrong but believe the grey top with the non ceramic seal needs the lower pressure.

My Repair Manual for the model 90 (Gray head) calls for .9 bar (13#).

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Posted

The latest Rotax manual for the 582 says 1.2 Bar, or 17 psi for every cap on every type of 582 radiator.

 

 

cap.jpg

cap2.jpg

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Posted

Here you go, EDMO:

 

water-pressure-boiling-temperature.png

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Posted

Thanks for the post Nick - Now can you tell me in some way where it boils with the pressure at 13 or 17 pounds pressure with a cap on the system?  I can see where it boils at 212F at 14.? psi - is the cap pressure added to that, or is it separate - what are marks from 10 to 100? 

And, how does this relate to not being able to boil coffee on Mt. Evans, Colorado at 13 or 14K altitude and lower atmospheric pressure? - (old family story, that during WPA times when working on the building there they had to make the coffee at lower altitude and bring it up, because it wouldn't boil up there). 

I think I stated before, "I know Nothing!", but hoped a chart might help someone. ???  EDMO

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Posted (edited)

It should still boil up there, just at a lower temp.  So maybe there is a temperature factor associated with the coffee production.  Kinda like needing to boil eggs longer at altitude.  The X axis is on a log scale, thats why it looks a bit funky to you.  Each mark represents a 10 PSIA increment between 10 and 100, and 100 between 100 and 10000.  Much farther to travel from say 10 to 20 psia vice 80 to 90 psia

His charts are showing absolute pressure (vice gage) so just add 13 or 17 psid to your local atmospheric pressure to get the pressure in the system when it relieves.  So... unless there is something funky about the cap design, as you climb in altitude the absolute pressure in your system will lower as well as a function of pressure outside the airplane.

Edited by LSaupe

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Posted (edited)

EDMO,

that chart I found is in PSIA, and we think in PSI Gauge, so you have to remember that our gauge ignores the atmospheric 14.7 pis all around us. It is also on a log scale so it really sucks to make your point, but the answer is in there. Try using 32 psia, which is what a 17 psi cap gives you, and see that boiling occurs at about 255 deg F on the upper chart. at 15 psia, it occurs at 212 deg F.

bpgraph.gif

Edited by nlappos

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Posted

EDMO,

that chart I found is in PSIA, and we think in PSI Gauge, so you have to remember that our gauge ignores the atmospheric 14.7 pis all around us. It is also on a log scale so it really sucks to make your point, but the answer is in there. Try using 32 psia, which is what a 17 psi cap gives you, and see that boiling occurs at about 255 deg F on the upper chart. at 15 psia, it occurs at 212 deg F.

Thanks to both of you for the enlightenment - getting morning coffee made - 360 msl, 29.92, so guess it will perk!  ;<)  EDMO

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