Operation - SPX MARLEY CLASS 800 User Manual

Operation

Tower Performance
The following is intended to serve as a guideline for the operation of this
counterflow mechanical draft cooling tower. The owner may use this information
to develop preliminary operating procedures. As operational experience with
the system accumulates, more definitive responses to specific conditions will
be developed by the owner's operating personnel.
Keep the tower clean and the water distribution uniform to obtain continued
maximum cooling capacity. (See Caution note on page 15 and Warning
note on page 17.) Do not allow excessive deposits of scale or algae to build
up on the filling or eliminators. Keep the nozzles free of debris to assure correct
distribution and cooling of water. Uniform water distribution over the entire fill
plan area is vital to the efficient operation of a film-filled cooling tower.
The capacity of a tower to cool water to a given cold water temperature varies
with the wet-bulb temperature and the heat load on the tower. As the wet-
bulb temperature drops, the cold water temperature also drops. However, the
cold water temperature does not drop as much as the wet-bulb temperature.
(Wet-bulb temperature is the temperature indicated by the wet-bulb
thermometer of a sling or mechanically aspirated psychrometer.)
A tower does not control the heat load. For a given heat load, the quantity
of water circulated determines the cooling range. The hot and cold water
temperatures increase with higher heat loads. (Cooling range is the
temperature difference between the hot water coming into the cooling
tower and the cold water leaving the tower.)
Fan Drive
Air is caused to move through the tower by the operation of electric motor-driven
fans. At full speed, these fans are designed (and pitched) to move the amount
of air required to accomplish the design thermal performance. Proper utilization
of these fans provides the operator a means by which to adjust the level of
thermal performance to suit the requirements of the load. (See Temperature
Control and Energy Management on pages 13 and 14.)
If two-speed motors are used, allow a time delay of a minimum of
Caution
20 seconds after de-energizing the high speed winding and before
energizing the low speed winding. Tremendous stresses are placed
on driven machinery and motor unless the motor is allowed to slow
to low speed rpm or less before the low speed winding is energized.
When changing fan direction of rotation, allow a minimum of two
minutes time delay before energizing the fan motor.
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