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5. OPERATION
5.1 Operating conditions
The normal conditions of usage of the
CEHV
series cooling towers are as follows:
- maximum water supply pressure
0,5 bar (5 meters W.G.)
- maximum water inlet temperature
55 °C (standard versions)
75 °C (ATT version)
5.2 Make-up with river water
When river water is employed for cooling tower make-up, apart from the problems of acidity and hardness
normally associated with make-up water of any origin, one must evaluate with great care the possible presence
of suspended solids, which could even be of significant size, of slime, sand, clay.
In this case, it is useful to have available a suitable filtration system, preceded upstream by net- screens to stop
the largest foreign bodies (from entering the system).
5.3 Make-up with slightly salty water
Recalling that the fibreglass parts do not suffer at all from the presence of salts in the water, some difficulty can
on the other hand arise for the metallic parts in as much as the salty water (by which is intended water with traces
of chlorides) gives rise to chemical action, particularly on galvanised steel components, when there are faults,
even if only minimal, in the protective zinc layer.
Therefore, in this particular situation, it is advisable to have a preference for the cooling tower in the INOX (sst)
version, i.e. with all the metallic parts executed in stainless steel AISI 304/AISI 316.
5.4 Winter operation
In areas in which the ambient winter temperature descends below 0°C, there is a possibility of ice formation in or
upon the tower components and in the immediately surrounding area.
The equipment and the zones most subject to freezing and to ice formation are:
- the water collecting basins
- the water supply and return pipes, as well as those of the auxiliary circuits
- the fans
- occasionally, the ground area surrounding the cooling tower
Generally speaking, When the cooling tower is in normal operation also during the winter la season, no danger
of freezing exists. It is however possible that, with outside temperatures below -2°C / -3°C, ice formation occurs
even in the case of very brief shut-downs.
5.4.1 Ice formation in the basins
Ice formation starts from the surface of the water, then the process extends to the entire water mass contained in
the basin; progressively as the phenomenon proceeds the volume of ice increases, its speed of formation
diminishes.
To remedy this problem one can install one or more electric heaters, of adequately sized electric power, and
controlled by an appropriate regulating thermostat, which assure a water temperature b3°C and 5°C in
the whole basin or, in the case of very big basins, in an area of them sufficiently large to ensure that remains
liquid at least the volume of water necessary to start-up the system.
One can also resort to an auxiliary, remote sump, situated in a closed space or underground, in which the water
cooled by the tower can drain freely in such a manner that the tower collecting basin remains always empty.
NOTE
: he thermostat supplied together with the electrical resistance heaters acts exclusively as a function of the
basin water temperature, and not on the basis of the heat produced by the heater itself.
Hence, in the case of absence of water, the heater being still operative could be irremediably damaged: it is thus
recommended to foresee a low-level cut-out switch, as a protection of the electrical resistance heater in the
eventuality that it is not covered by water.
