Johnson Controls York MaxE YK Series, Manual

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JOHNSON CONTROLS
FORM 160.75-O1 (309)
32
commercial acid cleaning
In many major cities, commercial organizations now
offer a specialized service of acid cleaning evaporators
and condensers. If acid cleaning is required, YORK
recommends the use of this type of organization. The
Dow Industries Service Division of the Dow Chemical
Company, Tulsa, Oklahoma, with branches in principal
cities is one of the most reliable of these companies.
testing for eVaporator and condenser
tuBe leaKs
Evaporator and condenser tube leaks in R-134a systems
may result in refrigerant leaking into the water circuit,
or water leaking into the shell depending on the pres-
sure levels. If refrigerant is leaking into the water, it
can be detected at the liquid head vents after a period
of shutdown. If water is leaking into the refrigerant,
system capacity and efficiency will drop off sharply. If
a tube is leaking and water has entered the system, the
evaporator and condenser should be valved off from
the rest of the water circuit and drained immediately to
prevent severe rusting and corrosion. The refrigerant
system should then be drained and purged with dry ni-
trogen to prevent severe rusting and corrosion. If a tube
leak is indicated, the exact location of the leak may be
determined as follows:
1. Remove the heads and listen at each section of tubes
for a hissing sound that would indicate gas leakage.
This will assist in locating the section of tubes to be
further investigated. If the probable location of the
leaky tubes has been determined, treat that section in
the following manner (if the location is not definite,
all the tubes will require investigations).
2. Wash off both tube heads and the ends of all tubes
with water.
Do not use carbon tetrachloride for
this purpose since its fumes give the
same flame discoloration that the re -
frigerant does.
3. With nitrogen or dry air, blow out the tubes to clear
them of traces of refrigerant laden moisture from the
circulation water. As soon as the tubes are clear, a
cork should be driven into each end of the tube. Pres-
surize the dry system with 50 to 100 PSIG (345 to
690 kPa) of nitrogen. Repeat this with all of the other
tubes in the suspected section or, if necessary, with
all the tubes in the evaporator or condenser. Allow
the evaporator or condenser to remain corked up to
12 to 24 hours before proceeding. Depending upon
the amount of leakage, the corks may blow from the
end of a tube, indicating the location of the leakage.
If not, if will be necessary to make a very thorough
test with the leak detector.
4. After the tubes have been corked for 12 to 24 hours,
it is recommended that two men working at both
ends of the evaporator carefully test each tube – one
man removing corks at one end and the other at the
opposite end to remove corks and handle the leak
detector. Start with the top row of tubes in the sec-
tion being investigated. Remove the corks at the ends
of one tube simultaneously and insert the exploring
tube for 5 seconds – this should be long enough to
draw into the detector any refrigerant gas that might
have leaked through the tube walls. A fan placed at
the end of the evaporator opposite the detector will
assure that any leakage will travel through the tube
to the detector.
5. Mark any leaking tubes for later identification.
6. If any of the tube sheet joints are leaking, the leak
should be indicated by the detector. If a tube sheet
leak is suspected, its exact location may be found
by using a soap solution. A continuous buildup of
bubbles around a tube indicates a tube sheet leak.
maintenance