RHOSS H51369, Инструкция по эксплуатации

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5.4.2 Ice formation in the circuit piping
The water in the piping forms ice starting from the layers in contact with the tube wall and the phenomenon slows
progressively as the freezing proceeds towards the centre.
The water, transforming itself into ice inside the pipes, increases in volume by about 8%, nearly always causing
the splitting open of the latter.
As a remedy to this eventuality, one can execute the circuit in such a manner that, at plant shut-down, the water
drains into a remote (auxiliary) sump located inside or below ground level, or one can adopt the installation of
heat-tracing cable wound around the pipework and its subsequent protection with shells of insulating material.
5.4.3 Fan icing
On occasions when the plant is shut-down contemporary with low temperatures or snow falls, a thin layer ice may
form between the inside of the fan support ring and the extremity of the fan blades.
If the ice formation becomes a single block between fan and support ring, then at the moment of restarting the
fan, it will be locked in place and either the motor could be burnt-out or, occasionally, one or more fan blades
could be broken.
To obviate this problem, one can install externally on the fan cylinder a heat-tracing cable, suitably protected with
insulating material, in order to always maintain the steel ring at a certain temperature and thus avoid that icing
can occur.
NOTE : never cover the motor-fan assembly with lids-covers, shields or other types of protection since , apart
from serving no useful practical purpose (all the motors are in a totally closed execution), in case of
operation with the air discharge occluded the electric motor could burn-out..
5.4.4 Ice formation around the cooling tower
At very low ambient temperature, ice formation on the ground areas close to the cooling tower can occur: this
situation may represent a danger for any eventual operations or activities that must be performed in that area.
5.4.5 Tower operation in dusty and polluted environments
In the case of tower operation in dusty and polluted environments, apart from employing the special version with
suitable fill pack for operation in the presence of solids suspended in the water and possibly with metallic parts
in stainless steel , it is recommended to foresee an adequate water filtration system upstream of the return water
pump.
6. SAFETY WARNINGS
6.1 Motor-fan assembly
- prior to carrying out any kind of intervention son the tower, wait for the heat energy to dissipate and verify
that the fan has come completely to rest
- do not carrying out any kind of intervention if the electrical power supply to the motor has not previously not
been shut-off
- do not allow the motor-fan unit to operate if, for some reason, the protective screen has been removed
- NOTE: the protective screen should not be considered a protection-shelter as defined by the machinery
directive, but a device apt to prevent the risk of expelling parts of the fan from the related fan-cylinder
- do not modify for any reason whatsoever the inclination of the fan blades: this could be cause of absorbed
electric current beyond the name-plate value, vibrations due to fan imbalance, breakage of the motor
bearings and of the fan blades.
6.2 Protection against biological risks
The recirculating water can contain chemical products or biological pollutants which could be dangerous for
health if breathed in or ingested. Hence the personnel that may be directly exposed to the discharge air flow and
to the related mist from entrainment, generated during the operation of the water spray system and/or of the
compressed air eventually employed in cleaning, must wear respiratory protection (face-masks) approved by the
authorities competent and/or in accordance with directive 89/686/EEC.
NOTE: Tower maintenance personnel are advised to adhere to the recommendations made in the EUROVENT
9-5 (2nd edition 2002) guidelines for the prevention of biological contamination in evaporative cooling systems.