Learning Event 2
DESCRIBE THE TANK UNIT ASSEMBLY OF THE M12A1 PDDA
The tank assembly (Figure 1) is used to store the water needed for the M12A1 PDDA. The tank is
bolted to a skid. When the equipment is operating, water is blended with the STB decontaminating
agent in the tank. An agitator at the bottom of the tank prevents solids from settling out of the slurry. A
hopper-blender assembly and the agitator in the tank are used to blend STB decontaminating agent and
water.
PARTS
The tank unit assembly and personnel shower assembly consist of the tank, suction hose, blender hose,
foot valve, tank drain valve, hopper-blender assembly, and personnel shower. Four clevises are
provided for picking up the tank unit assembly.
Tank
The skid-mounted stainless-steel tank has a volume of 500 gallons. However, the maximum working
capacity of the tank is approximately 447 gallons of water. The working capacity for the tank with
slurry mix is 317 gallons. The remaining volume should be reserved for expansion due to foaming
action. When using STB to mix slurry, 225 gallons of water and 1,300 pounds of STB are used.
Capacities of the tank are summarized in Figure 7.
Figure 7. Tank unit assembly capacities.
Tank Drain valve. The tank drain valve is used to drain liquids or slurry from the tank. The elbow and
quick-disconnect coupling half connect to the quick-disconnect coupling half on the suction hose.
Suction Hose and Blender Hose. The suction hose is used when the tank is filled from a water source.
The blender hose is used when heating water and blending decontaminants. These hoses are described
below and are shown in Figure 8.
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