035-19569-101 (0109)
7-6
GB
Condenser
Condenser trouble due to fouled tubes is usually
indicated by a steady rise in head pressure, over a period
of time, accompanied by a steady rise in condensing
temperature, and noisy operation. These symptoms may
also be due to foul gas build-up. Purging will remove the
foul gas revealing the effect of fouling.
Tube Fouling
Fouling of the tubes can be due to deposits of two types
as follows:
1. Rust or sludge - which fi nds its way into the tubes
and accumulates there. This material usually does
not build up on the inner tube surfaces as scale,
but does interfere with the heat transfer. Rust or
sludge can generally be removed from the tubes by
a thorough brushing process.
2. Scale - due to mineral deposits. These deposits,
even though very thin and scarcely detectable upon
physical inspection, are highly resistant to heat
transfer. They can be removed most effectively by
circulating an acid solution through the tubes.
7.5.3 Tube Cleaning Procedures
Brush Cleaning of Tubes
If the tube consists of dirt and sludge, it can usually be
removed by means of the brushing process. Drain the
water sides of the circuit to be cleaned (cooling water or
chilled water) remove the heads and thoroughly 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" pipe
with a few small holes at the brush end and connecting
the other end by means of a hose to the water supply.
NOTE
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 fl ush from the tubes
with the result that a more satisfactory cleaning job will
be accomplished with a probable saving of time.
Acid cleaning should only be performed by an expert.
Please consult your local water treatment representative
for assistance in removing scale build-up and preventative
maintenance programs to eliminate future problems.
7.5.4 Tube Leaks
Evaporator and condenser tube leaks 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
effi ciency 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 defi nite,
all the tubes will require investigation).
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.
Pressurise the dry system with 350 to 690 kPag 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.
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