JOHNSON CONTROLS
29
SECTION 6 - MAINTENANCE
FORM 160.76-O1
ISSUE DATE: 05/22/2019
6
ly clean each tube with a soft bristle bronze or nylon
brush. DO NOT USE A STEEL BRISTLE BRUSH. A
steel brush may damage the tubes.
Improved results can be obtained by admitting water
into the tube during the cleaning process. This can be
done by mounting the brush on a suitable length of 1/8
in. pipe with a few small holes at the brush end and
connecting the other end by means of a hose to the wa-
ter supply.
The tubes should always be brush cleaned before acid
cleaning.
Acid Cleaning Of Tubes
If the tubes are fouled with a hard scale deposit, they
may require acid cleaning. It is important that before
acid cleaning, the tubes be cleaned by the brushing
process described above. If the relatively loose foreign
material is removed before the acid cleaning, the acid
solution will have less material to dissolve and flush
from the tubes with the result that a more satisfactory
cleaning job will be accomplished with a probable sav-
ing of time.
Acid cleaning should only be performed
by an expert. Please consult your local
water treatment representative for as-
sistance in removing scale buildup and
preventative maintenance programs to
eliminate future problems.
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 may result in re-
frigerant leaking into the water circuit, or water leak-
ing into the shell depending on the pressure 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 leak-
ing 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 nitrogen to
prevent severe rusting and corrosion. If a tube leak is
indicated, the exact location of the leak may be deter-
mined 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 refrigerant
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. Pressurize the dry system with 50 psig to
100 psig (345 kPa 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,
it 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
section 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