FORM 160.73-O2 (605)
31
YORK INTERNATIONAL
CONDENSERS AND EVAPORATORS
GENERAL
Maintenance of condenser and evaporator shells is im-
por tant to provide trouble free operation of the chiller.
The water side of the tubes in the shell must be kept
clean and free from scale. Proper maintenance such as
tube cleaning, and testing for leaks, is covered on the
fol low ing pages.
CHEMICAL WATER TREATMENT
Since the mineral content of the water circulated through
evaporators and condensers varies with almost every
source of supply, it is possible that the water be ing used
may corrode the tubes or deposit heat re sis tant scale in
them. Reliable water treatment com pa nies are available
in most larger cities to supply a wa ter treating process
which will greatly reduce the cor ro sive and scale form-
ing prop er ties of almost any type of water.
As a preventive measure against scale and corrosion and
to prolong the life of evaporator and condenser tubes, a
chemical analysis of the water should be made pref er a bly
before the system is installed. A reliable water treat ment
company can be consulted to determine wheth er water
treatment is necessary, and if so, to fur nish the proper
treatment for the particular water con di tion.
CLEANING EVAPORATOR AND CONDENSER TUBES
Evaporator
It is diffi cult to determine by any particular test wheth er
possible lack of performance of the water evaporator
is due to fouled tubes alone or due to a combination
of trou bles. Trouble which may be due to fouled tubes
is indicated when, over a period of time, the cooling
ca pac i ty de creas es and the split (temperature differ-
ence between water leaving the evaporator and the
refrigerant tem per a ture in the evaporator) increases. A
gradual drop-off in cool ing capacity can also be caused
by a gradual leak of refrigerant from the system or by a
com bi na tion of fouled tubes and shortage of refrigerant
charge. An ex ces sive quantity of oil in the evaporator
can also con trib ute to erratic performance.
Condenser
In a condenser, trouble due to fouled tubes is usually
indicated by a steady rise in head pressure, over a pe ri od
of time, accompanied by a steady rise in con dens ing
temperature, and noisy operation. These symp toms may
also be due to foul gas buildup. Purging will re move the
foul gas revealing the effect of fouling.
TUBE FOULING
Fouling of the tubes can be due to deposits of two types
as fol lows:
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 thor ough
brushing process.
2.
Scale
– due to mineral deposits. These deposits, even
though very thin and scarcely detectable upon phys-
i cal inspection, are highly resistant to heat trans fer.
They can be removed most effectively by cir cu lat ing
an acid solution through the tubes.
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 con nect ing the other
end by means of a hose to the water 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 im por tant that before acid
clean ing, the tubes be cleaned by the brushing pro cess
de scribed above. If the relatively loose foreign material
is removed be fore the acid cleaning, the acid so lu tion will
have less material to dis solve and fl ush from the tubes
with the re sult that a more satisfactory clean ing job will
be accomplished with a prob a ble sav ing of time.
Acid cleaning should only be per-
formed by an ex pert. Please consult
your local water treatment rep re -
sen ta tive for as sis tance in removing
scale buildup and pre ven ta tive main-
te nance pro grams to elim i nate future
prob lems.
6