Freezing Weather Operation - SPX Marley LW032 B Series User Manual

Note
12
operation

Freezing Weather Operation

During operation in subfreezing weather, the opportunity exists for ice to form
in the colder regions of the fluid cooler. Primary concerns are to protect the
heat transfer coil from freezing and prevent the formation of destructive ice
on the fluid cooler air inlet and louvers. Your understanding of cold weather
operation will be enhanced if you read Marley Technical Report H-003 "Cool-
ing Towers and Freezing Weather".
It is the operator's responsibility to prevent the formation of destruc-
tive (hard) ice on the fluid cooler air inlet louvers. Certain guidelines
should be followed:
1. Do not allow the fluid cooler's leaving process fluid temperature to drop
below 50°F. If low temperature operation is necessary or beneficial to
your process, establish the minimum allowable level as follows:
During the first coldest days of operation, observe whether any ice is
forming on the louver face, particularly near the bottom part of the louver
face. If hard ice is present on the louvers, you must increase the allowable
cold water temperature.
2. As cold air enters the louvers, it causes the water flowing over the coil(s)
to be drawn inward toward the center of the fluid cooler. Thus, under fan
operation, the louvers and lower periphery of the fluid cooler structure
remain partly dry, seeing only random splashing from within the fluid
cooler — plus normal atmospheric moisture from the entering air. Such
lightly wetted areas are most subject to freezing.
Therefore, if excessive ice forms on the louvers, stop the fan for a few
minutes. With the fan off, the water flow will increase in the vicinity of the
louvers and reduce the ice buildup.
Intermittent Freezing Weather Operation:
If periods of shutdown (nights, weekends, etc.) occur during freezing weather,
measures must be taken to prevent the water in the cold water basin and all
exposed pipework from freezing. Several methods are used to combat this,
including Marley automatic basin heater systems and pump freeze protection
systems.