Page 161 - Boiler_Operators_Handbook,_Second_Edition

146 Boiler Operator’s Handbook

tioned first? Simply because paper properties change paratus) in a cabinet immediately inside the door. Do
with temperature and moisture content and keeping it not fail to read the instructions and, preferably, try out
consistently spaced between printing rolls containing the apparatus so you know how to operate and use it.
different colors of ink, a process called registration, re- Encourage other operators to do the same because they
quired maintaining the temperature and humidity in may have to use it to reach you and carry you out of the
the plant. space in the event of an incident.
Many other fluids can be used as refrigerants but Figure 5-1 is a tabulation of our more common re-
they have undesirable properties. Some known to cause frigerants including replacements for refrigerants that
cancer were used in early systems and others, such as are no longer allowed to be used in new equipment. You
propane, are not used because they’re flammable or will note that there are color codes for most refrigerants.
heavier than air. Along with water another natural sub- Containers of the refrigerant are painted that color in an
stance used as a refrigerant is ammonia. It’s an excellent effort to ensure a system is not charged with the wrong
refrigerant but it’s also flammable, corrosive, and poi- refrigerant or refrigerants are not mixed. Most refriger-
sonous. If it leaks from the refrigeration system it can ant systems will fail to operate properly when exposed
catch on fire, ruin materials stored in the refrigerated to a mixed refrigerant. There are, however some refrig-
spaces and kill people. That’s why it’s only used in facil- erants which are intentional mixtures; these are known
ities that aren’t normally open to the public and moni- as binary refrigerants, a mix of two.
tored constantly for leaks. The question mark for replacement of R-22 is there
Then, in the later half of the 20th century we dis- because; at the time of writing this there was no con-
covered that Freon (a trade name of the DuPont Com- sensus on a suitable replacement for it. Unlike the CFC
pany that became more or less a generic label for refrig- refrigerants which can not be made anymore the HCFC
erants) was not as safe as we thought. It wasn’t flam- R-22 is scheduled to be replaced and no longer manufac-
mable nor poisonous and it was lighter than air so it tured sometime between now and the year 2030. R-134a
wouldn’t pool inside a basement like propane does but, has become the standard for all applications that used to
being lighter than air it rose up in the atmosphere until use R-12. The orange containers of R-11 and containers
it got to the stratosphere then disassociated releasing of R-123 are actually drums because they are a liquid
chlorine atoms that break down ozone. Located about at normal atmospheric conditions; in use the evaporator
30 miles above the surface of the earth the stratosphere for those refrigerants operates in a vacuum.
contains an ozone layer that works like a filter to screen R-404a is one of the binary refrigerants which have a
out harmful ultraviolet radiation from the sun. By the range of saturation temperatures between two conditions
time the chemistry of the action of most refrigerants known as dew point and bubble point. Because it’s a mix-
(CFCs, short for chlorofluorocarbons) on the ozone lay- ture of two refrigerants with different saturation condi-
er was recognized the ozone deple-
tion was so extensive that there was
a “hole” in the ozone layer over the
North Pole. International efforts to
limit the release of refrigerants and
development of new refrigerants
that lack chlorine have reduced the
damage to the ozone layer and it is
now recovering.
Part of the solution is heavier
than air refrigerants that will not
reach the upper atmosphere. How-
ever, they can accumulate in spaces
containing the refrigeration equip-
ment with the potential of suffocat-
ing people. Should you happen to
go to work in a plant that uses one
of those refrigerants you should find
a SCBA (self contained breathing ap- Figure 5-1. Information on some common refrigerants