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1. GENERAL SAFETY RULES AND MACHINERY DESCRIPTION
1.1
General Safety use:
The content of this manual is to be considered as an integration to the general safety rules applied in your country, in the environment
you are working in and also to the rules to be followed by law. In case of conflict with any of the previously mentioned rules in place,
please contact our technical office for alternative procedures that will not create conflict.
Always remember that any operation with mechanical machinery could be dangerous and make sure all possible precautions are
followed before and during assembly & maintenance.
SAFETY FIRST !
1.2
General description
Closed circuit cooling towers of the RAA series are counter-flow induced draught coolers with the fluid to be cooled (primary circuit)
circulating in a closed sealed loop.
The fluid to be cooled pass through a coil, externally sprayed continuously with water, pumped in an open circuit (secondary circuit)
from the collection water basin. The evaporation of part of this water removes most of the heat from the fluid in the primary circuit.
Evaporation is achieved thanks to a high quantity of air moved, by the use of axial fan(s) installed on top of the unit, counter-flow
against the water of the secondary circuit.
The closed circuit cooling tower is composed by the following elements:
Primary circuit:
•
Coil
Secondary circuit:
•
Water pumping system
•
Water distribution system
Other:
•
Air system
•
Casing, water collection basin, air intake and louver panels.
•
Drift eliminator
1.3
Primary circuit (coil)
Coil is made by high quality carbon steel bended and welded. A further process of hot dip galvanization assures the necessary
protection against external corrosion. Coil can be supplied on request in stainless steel both 304 and 316 grade.
During assembly the coil is tested in accordance to actual rules (PED). A further test is done before fitting the coil into the machine.
Different test procedures or witnessed tests are possible with extra costs.
1.4
Secondary circuit
1.4.1
Water pumping system
The exchange coil is sprayed with water collected from the basin of the unit and pumped by the use a centrifugal pump inside
a water distribution system. The motor of the pump is directly coupled on the bronze impeller and installed in a vertical
position facilitating inspection and maintenance. The water is then collected in the basin of the unit and ready to be pumped
again, after passing through a stainless steel filter/strainer installed in the bottom of the basin.
1.4.2
Water distribution system
Water is pumped in the top of the closed circuit cooler and distributed through a galvanised steel collector and polypropylene
(PP) pipe network. It could also be supplied in Stainless Steel with extra cost.
Spray nozzles (made by static fibreglass reinforced polypropylene) are screwed into the PP pipes and allow water to drop onto
the coil. Nozzles have a wide water passage, with minimum possibilities of clogging, breaking down or blocking. The design of
the nozzles is studied to allow the perfect water distribution (full cone) over the coil.
In case of clogging or breaking or just for simple maintenance, they can be dissembled from the PP pipes and easy cleaned or
replaced.
Make-up water, to replace depletion through evaporation or elimination to avoid scaling, is carried out automatically by
means of an intake valve installed in the basin.
1.5
Air system
Air is supplied in counter-flow to the water and is provided by axial fan(s) statically and dynamically balanced, installed at the top of
the cooling tower (induced draught).
The fan can be manufactured in different materials (PP, Aluminium, etc.) being placed inside the diffusers, which can also be
manufactured in different materials like painted galvanised steel (standard) or stainless steel. An arrow indicates the fan direction to
be used. In order to protect the fan from any external object and to prevent injuries a stainless steel safe-guard grid is installed in the
upper part of the diffuser.
The electric motor(s), totally sealed and self-ventilated, are provided standard with class F insulation, capable of withstanding a
temperature of 155°C. Electric motors are in accordance to the EU 690/2009 norm (if applicable). Running speed can vary in
accordance to each single machine project specification. Special motors can be fitted on demand. Motor(s) are mounted on a
galvanized steel support or plate, and installed inside the cooling tower, just below the fan.
In order to eliminate frictions, wearing or unnecessary maintenance (typical of an indirect coupling) the coupling between electric
motor(s) and fan(s) is direct.
Between the coil(s) and fan(s), a layer of drift eliminator made by PVC is provided.
Summary of Contents for RAA Series
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