TM-5-855-4
b. Cooling towers.
(1) Cooling towers till be of the counterflow or crossflow, spray-filled type, desired to withstand
the effects of an attack. Towers will generally be cylindrical and constructed of reinforced concrete to
resist severe shock loading on the aboveground tower structure, including all internals of the tower, and
fan overspeeding due to weapon effects such as the blast wave. Towers exposed to direct thermal radiation
will have critical parts of the system shielded from this effect.
(2) Sufficient water will be stored in heat sink storage tanks to provide for cooling tower makeup
for the entire post-attack period, to provide water to flush dust from combustion air dust collectors, and to
provide cooling while towers are shut down.
(3) Consideration will be given to using hardened wells, rather than hardened storage tanks, to
provide for cooling tower makeup and domestic water requirements for the entire post-attack period.
Wells will be used if aquifers with adequate flow capacity are available. Wells must remain a
dependable source of water under all weapons effects. Where possible, two or more aquifers with flow
from different directions, and separated as much as practicable will be tapped to preclude complete loss of
water if one aquifer is damaged during attack. Makeup water used during normal operation will be
from domestic supply or wells located on the site.
(4) Where cooling towers are required to operate in extreme winter conditions, provisions will be
made to prevent freezing and ice buildup on the tower. Hardened facilities will generally have an indoor
collection basin as part of the heat sink/cooling tower configuration. Additional freeze protection
features, such as thermostatic cycling of the cooling tower fans controlled by leaving water temperature
and reversal of the fans' direction to melt ice buildup on the tower fill, will be evaluated and incorporated
into the design where necessary.
(5) Cooling towers will have fire protection system designed in accordance with NFPA 214.
c. Basins. Hardened concrete basins include the tower basin, settling basin, and disposal basin.
(1) The tower basin will be sized and have a flow pattern such that dirt, dust, and fallout will not
settle within it during flushing of the spray towers. Flushing valves will be installed between the tower
basin and the settling and disposal basins. Valves will be positive shutoff type, capable of being
automatically positioned to divert water flow to the disposal basin. Valves will be constructed of
materials that will not corrode or foul from the dust and dirt of a weapons blast.
(2) The settling basin will have sufficient storage capacity above the minimum suction level of
the circulating pumps to provide system flow requirements for a minimum of five minutes. The basin
will be of a size, design, and flow pattern to permit settlement of all dust and dirt particles having a
specific gravity of 2.5 and having a size of 50 microns or larger.
(3) The disposal basin will have sufficient capacity to permit intermittent operation of the sand
pumps.
d. Pumps.
(1) All pumps installed in the cooling tower circulating water system will be inherently capable of
withstanding ground shock or will be dynamically mounted to reduce the shock to an acceptable level.
Where possible, commercial pumps will be used if they have demonstrated resistance to the required
input shock spectra. Pumps that are dynamically mounted for shock isolation will have expansion joints
capable of accepting the full differential movement.
(2) Particular attention will be given to design of the pump frame, mountings, base-plates, and
casings and to hold-down bolts and their proper torque specifications. Barrels of vertical pumps will be
as short as possible. The use of vertical-frame pumps with excessive cantilevering in frame design will
be avoided.
e. Cooling water filters. Filters used for post-attack and post-blast removal of dust and fallout from
cooling tower water will be capable of removing all particulate matter larger than 2 microns and will be
suitable for operation with chemically treated cooling water. Filter assemblies will be constructed of
steel; cast-iron will not be used.
5-7. Radiators.
a. A finned-coil heat exchanger (radiator or air cooled condenser) exposed directly to the ambient air
may be used above-ground or in a buried chamber to dissipate heat generated by prime movers, chillers,
etc., in underground facilities.
(1) An underground radiator or air cooled condenser that utilizes auxiliary fans to draw (or force)
cooling air from the outside through the coil and exhaust the rejected heat to the outside offers a greater
degree of protection against the elements (dust or sandstorms) and weapon effects but requires more fan
.
5-14
Previous Page
