[BARNES] PRODUCTION OF RING ICE OR HOAR FROST 95 
in such a system will require approximate 163-3 cubic feet of air 
which will introduce about -1861 Ib. of water vapor, provided no 
change of temperature results. Most of the water will be condensed 
at the pump and go to the check valve, and that required to saturate 
60 cubic feet of air will be introduced. 
With air at the same temperature but of 50% humidity practi- 
cally the same amount of moisture will be introduced since a pressure 
increase to 30 Ibs. will cause the air to become saturated. Less mois- 
ture however, will be condensed at the pump. In general it may be 
safe to say that the air on the high pressure side beyond the heat of 
compression will always be saturated whatever the temperature or 
humidity of the air drawn into the pump. No more moisture can 
be introduced than the amount required to maintain the maximum 
vapor pressure no matter what the air pressure may be. Hence 
we have the amount of moisture introduced at one pumping into the 
60 cubic feet of pipe space equal to -0684 lb. of water vapor. If the 
system is pumped up once a week for six months we have 1-778 Ib. 
of water vapor introduced. This represents 1-7 pints or 49-1 cubic 
inches. 
Nearly all the vapor is condensed in the form of hoar frost at the 
coldest parts and avery considerable increase of volume results. 
Various estimates are given for the volume of snowy ice or hoar 
frost produced from a given volume of water which ranges from 4 to 40 
times the original bulk. If the increase is only 4 times then the 
volume of hoar frost deposited in a pipe from the above example 
would be 196-4 cubic inches. This would be sufficient to block a 
foot of 4 inch pipe or 33 feet of 24 inch pipe. In general the increase 
of volume is taken as 10 times the original water volume, hence it 
does not seem surprising that blocks occur in a sprinkler system 
maintained in cold rooms. The following table will show the amount 
of water required, when converted into ring ice, to fill one foot length 
of various sized pipes. 
