WARNING
Acid cleaning should only be performed by an expert. Please consult your local water treatment
representative for assistance 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, Johnson Controls 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
About this task:
Evaporator and condenser tube leaks in refrigerant circuits may result in refrigerant leaking into
the water circuit, or water leaking 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 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 nitrogen 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.
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 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 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 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.
167
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