21 JANUARY 2003
tank walls allows the free flow and containment of all leaked product from the tank. The leak
detection system attached to the interstitial monitor is either vacuum maintenance, positive air
pressure maintenance, hydrostatic pressure maintenance, or probe detection. Monitoring is
continuous and indicated in the pump control room. The control console generates a visual and
audible alarm if a leak is detected. The audible alarm has a remote alarm annunciator that can be
heard around the system.
6.5.2. Pumps. The fuel transfer pump for the product recovery tank is a deep-well turbine pump with
a capacity of 189 liters per minute (50 gallons per minute) when driven at 1800 revolutions per
minute. It can be automatically or manually operated. In the automatic mode, the float switch
assembly operates the pump. The switch is either a magnetically latching reed or a mercury-actuated
switch that operates on 120 volts, 60 hertz, AC power. When the tank is 70% full, the switch
assembly automatically energizes the pump. Fuel is then routed through the receiving separators and
into the operating storage tanks. Once the fuel level is pumped down to 20% full, the pump shuts off.
If the pump fails to start and the tank reaches 80% full, the switch assembly sounds an alarm.
NOTE: The overfill valve (OV) will be mechanically activated to close at 80%. This tank also has a
hand-operated pump for removing water.
6.5.3. Product Recovery Piping System. The entire product recovery system consists of 19- to
50-millimeter (0.75- to 2-inch) piping routed throughout the Type III system. This piping connects
the pressure relief, water draw-off, some low/high-point drains, and F/S water drains to the product
recovery tank fill line that is equipped with a hydraulically operated OV.
6.5.4. Product Recovery Tank OV (2129AF). The OV is a diaphragm-operated angle valve located
on the fill line of the product recovery tank (Figure 6.10). This valve closes any time the liquid level
in the tank reaches 80% full. It uses a float assembly similar to the float assembly used on all
belowground storage tanks. This float also has a manual test lever designed to test the operation of
the 2129AF valve. When the 2129AF valve is open, a limit switch illuminates a green light on the
PCP graphic display. A red light illuminates and a vibrating horn will sound when the valve is
closed. This valve uses a pressure reservoir tank connected to the discharge of the product recovery
tank fuel transfer pump. The fuel transfer pump supplies pressure to the pressure reservoir and a
check valve system holds the pressure in the reservoir. A supply line from the pressure reservoir is
connected to a rotary disc assembly in the float. When the tank is less than 80% full, the float is in
the bottom position, aligning common supply with port 2 and common drain with port 1. In this
position the pressure maintained in the pressure reservoir is applied to the 2129AF sensing chamber.
Since the cover chamber of the main valve is vented through the common drain of the float assembly,
the pressure in the sensing chamber overcomes spring tension on top of the diaphragm, holding the
valve in the fully open position. When the tank is 80% full, the float rises, aligning the common
drain to port 2 and common supply with port 1. Since the sensing chamber is now vented and
pressure from the pressure reservoir is applied to the main valve cover chamber, the main valve