Marley / MC Fluid Cooler/ Engineering Data: Freeze Prevention
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Fluid Cooler Coil
When the ambient temperature falls below 0°C, heat loss from the coil can be substantial even without recirculating water flowing over the coil. The process fluid, without an applied heat load, may be prone to freezing. There are various methods to protect against coil freezing.
Ethylene and propylene glycol solutions are the best means to protect against coil freezing and are recommended for most installations. The appropriate concentration of ethylene or propylene glycol should be determined based on the required protection from low ambient temperatures.
If the use of an industrial antifreeze solution is not compatible with the system, another accepted method of preventing coil freezing is to maintain a sufficient flow rate and heat load on the process fluid. The fluid exiting the coil must be maintained at or above 7°C at the full process flow rate. If the process load does not yield such a heat load, it may be necessary to apply a supplementary heat load to the process fluid.
Draining the coil is not considered to be an acceptable means of protection against freezing. Introducing air to the interior of the bundle will promote corrosion of the heat exchanger coil. In an emergency, this alternative can be used in the event that the process fluid drops below 7°C, the ambient temperature is below freezing and the coils are not protected with industrial antifreeze.
Cycling of the recirculating water pumps should not be used to control process flow temperatures. Coils may be used for seasonal dry operation followed by seasonal wet operation, but not for frequent cycling of the recirculating water pump. Such operation may lead to an excessive scale buildup resulting in a decrease in efficiency.
CAUTION
Freezing ambient conditions could cause significant damage to the heat exchanger coil of the MC Fluid Cooler. To avoid possible damage, it is imperative to provide for adequate freeze protection.
Fluid Cooling Recirculating Water
When the ambient air temperature falls below 0°C, the recirculating water within the fluid cooler can freeze. Marley Technical Report
During shutdown, water collects in the basin and may freeze solid. You can prevent freezing by adding heat to the water left in the
Electric Basin Heaters
An automatic basin water heater system, consisting of the following components:
•Standard weatherproof (IP55) enclosure, rating depending on model and minimum expected winter temperature (see table below):
•Ratings are in kW for specified ambient temperature.
For lower ambient temperatures refer to SPX engineering for advice.
•Standard electircal supply is 380/415 V 3ph (220/240V 1 ph available as extra cost option).
•Heater has an integral thermostat, set point nominally
3°C but adjustable to suit operating requirements.
The basin heater option is only for freeze protection of the recirculation water in collection basin. The basin heater option does not protect the coil during freezing weather.
Heater components are normally shipped separately for installation by others.
Indoor Storage Tank
With this type of system, water flows from an indoor tank and back to the fluid cooler where it is cooled and recirculated. The water flows by gravity from the fluid cooler to the tank located in a heated space. At shutdown, all exposed water drains into the tank where it is safe from freezing.
The amount of water needed to successfully operate the system depends on the fluid cooler size and m3/hr and on the volume of water contained in the piping system to and from the fluid cooler. You must select a tank large enough to contain those combined volumes— plus a level sufficient to maintain a flooded suction on your pump. Control makeup water according to the level where the tank stabilizes during operation.