Alfa Laval ACFC/M Series, Инструкция по установке, использованию и обслуживанию

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3.2 SAFETY SYSTEMS
Below are a number of recommendations that
must be observed during the installation, start-up
and maintenance of the system.
The safety accessories required in point 2.5 of
this manual must be installed, in particular the
water inlet filter and the water flow control valve.
3.2.1 Freezing
The freezing of water inside the tubes is not a
common phenomenon in condensers. Freezing
may occur when a high charge of refrigerant is
rapidly dispersed outside of the refrigerant circuit
from the condenser or nearby. One of the most
frequent cases involves the opening of the valve
due to excessive pressure head. This occurs
when the water temperature is high or the flow of
water is closed. Another cause may be the acci-
dental breakage of a refrigerant line or the
removal of the refrigerant from an inactive unit.
Freezing may also be caused by the incomplete
draining of the exchanger, which is exposed to
low temperatures during the periods of system
inactivity. In this regard, the procedure indicated
in the chapter on Inspection and Maintenance
should be carefully followed.
3.2.2 Vibrations
Excessive vibrations on both the water side and
the refrigerant side may cause significant dam-
age to the condenser over time. To reduce the
transmission of vibrations on the water side,
install vibration dampers near the water connec-
tions, on the supports and on the structure. For
the refrigerant side, on the other hand, use the
vibration-damping devices described in point 2.5
of this manual. In the case where the condenser
is installed as a support element for the compres-
sor, measures must be taken to avoid the trans-
mission of vibrations to the condenser.
3.2.3 Water pump shut-down
When stopping the system, a delay should be set
for shutting down and starting the pumps, so as
to avoid an increase in the water temperature
inside the tubes, with the risk of deposit forma-
tion.
3.3 WATER QUALITY AND TREATMENT
It is the user’s responsibility to establish the qual-
ity of the water and make sure that this is compat-
ible with the materials used in the condenser, see
Table 9 . The quality of the water, for the reasons
described above, may significantly affect the
operation and the life of the exchanger. The first
step in planning the treatment of the water is
chemical analysis, which must be performed by
qualified personnel from specialist organisations.
For information and suggestions on this subject,
refer to chapter 6 of the "Plate heat exchangers
for refrigeration applications - Technical refer-
ence manual" published by Alfa Laval.
The following methods can be used to clean the
inside of the tubes:
• mechanical, by swabbing inside the tubes: this
procedure can be applied only to units with tra-
ditional smooth tubes;
• chemical, performed by running commercially-
available solutions through the tubes, accord-
ing to the type of fouling, organic or inorganic.
This method can be used with all types of tube,
both smooth and fluted on the inside, and must
be performed by qualified personnel only.
Cleaning may be performed with mechanical
methods, or chemical methods using commer-
cially-available products with a dual action, that
is, the removal of the scale and the prevention of
corrosion. One recommended product is P3 T288
by Henkel.
In tower water, as shown above, the tendency to
form deposits may be high: to reduce this phe-
nomenon, there are various types of water sof-
tening treatments available, including the use of
ion exchange resins.
3.4 WATER SPEED INSIDE THE TUBE
Erosion and impingement may occur if the speed
exceeds the required limits, as the solid particles,
such as sand and dust, suspended in the mass of
water combine to erode the surface of the metal.
The use of filters and the observance of the set
water speed limits in the hydraulic system
reduces the risk of corrosion to an acceptable
limit.
Never exceed the maximum water flow rate lim-
its. The values can be checked using the data in
the "Alfa Laval Condensers Catalogue".
3.5 CORROSION
The oxygen dissolved in water increases the rate
of corrosion. The main factors causing corrosion
are sulphur and carbon dioxide acids, see the
Langelier and Ryznar indices. A combined effect
of fouling due to dust and organic material pro-
vides a support for bacteria, fungi and algae; the
growth of organisms may produce an oxygen
gradient and this results in rather severe pitting of
the surface of the metal.
The phenomenon of corrosion is obviously
related to the materials used on the liquid side of
the heat exchanger, see
Table 9 .
Table 10 shows the reference values for corro-
sion on copper; these values must be considered
as guidelines to avoid corrosion.
3.6 USE OF BRINE
Secondary fluids consisting of water and ethylene
or propylene glycol solutions are generally not
corrosive, unless contaminated by other sub-
stances. If using calcium chloride, refer to the
warnings in paragraph 5.3.2, chapter 6, of the
"Plate heat exchangers for refrigeration applica-
tions - Technical reference manual" published by
Alfa Laval.
Before using any other secondary fluid, check
with Alfa Laval that it is compatible with the
exchanger.