Marley MH Especificaciones descargar pdf (Pagina 7)

MH Fluid Cooler —

Engineering Data: Freeze Prevention

FLUID COOLER COIL

When the ambient temperature falls below 32°F, heat

loss from the coil 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 45°F 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 45°F, the

ambient temperature is below freezing and the coils are not

protected with industrial antifreeze.

Cycling of the recirculating water pumps to control process

flow temperatures must be approached with caution. Frequent

cycling of the recirculating water pump may lead to an

excessive scale buildup resulting in a decrease in efficiency.

FLUID COOLING RECIRCULATING WATER

When the ambient air temperature falls below 32°F, the

recirculating water within the fluid cooler can freeze. Marley

Technical Report #H-003 “Operating Cooling Towers in

Freezing Weather” describes how to prevent freezing during

operation. Ask your Marley sales representative for a copy or

download a copy at spxcooling.com.

During shutdown, water collects in the basin and may

freeze solid. You can prevent freezing by adding heat to the

water left in the basin—or, you can drain the tower and all

exposed pipework at shutdown.

ELECTRIC BASIN HEATERS

An automatic basin water heater system, consisting of the

following components:

• Stainless steel electric immersion heater(s).

Threaded couplings are provided in the side of

the collection basin.

• NEMA 4 enclosure containing:

Magnetic contactor to energize heater.

Transformer to convert power supply to 24 volts

for control circuit.

Solid state circuit board for temperature and

low-water cutoff.

The enclosure may be mounted on the side of the

fluid cooler.

• Control probe in the collection basin to monitor

water temperature and level.

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 tower 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 on volume of water

contained in the piping system to and from the tower. 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.

CAUTION

Freezing ambient conditions could cause significant

damage to the heat exchanger coil of the MH Fluid

Cooler. To avoid possible damage, it is imperative to

provide for adequate freeze protection.

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Marley MH Especificaciones Pagina 7

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