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MODEL 20-TX LEAK ALARM FOR DOUBLE WALLED TANKS. <br /> The tank leak: alarm system is -Fully automatic, has no moving parts or <br /> electronics within the tank, and operates on the principles of hyd ostatics. <br /> The leaf: alarm is capable of detecting an inner tank leak that per its <br /> tank' product to enter the annular spare between the tank walls, or an <br /> Outer tank leak: that permits ground water to enter the annular spa e. <br /> The sensing device for the alarm system is an open ended air bell hat is <br /> installed either at the bottom of the annular space or at the butt m of <br /> a monitoring standpipe, and is connected to a pressure switch via /4" <br /> D. D. tubing. Entery of tank product or ground water into the annu ar <br /> space will immerse the air bell in liquid causing an increase in pressure <br /> cf the trapped air. This increase activates the pressure switch, which <br /> :. n turn activates, an audible and visual alarm. <br /> The audible alarm is silenced by a pushbutton silencing circuit, aid <br /> the visual alarm automatically resets when the annular space is <br /> Pumped out. An alarm test pushbutton permits verification that th alarm <br /> circuits funcitions correctly. <br /> ' i the annualr space is not 100% vented to atmosphere, the pressure switch <br /> nest also be connected to the top of the annular space via a 3/16" O. D. <br /> tubing equalizing line. This compenstates for any pressure or vacuum <br /> w'' thin the annular space. <br /> THE SYSTEM CONSISTS OF THE FOLLOWING: <br /> i. . THE ALARM UNIT: Model 20-TX alarm unit consists of a nema 1 enclosure <br /> complete with 3 status lights (GREEN-NORMAL/POWER ON, RED-ALARM, RED- <br /> ALARM SILENCED) , buzzer, relays, pushbutton silencer switch, pushbutton <br /> alarm test switch, printed circuit board and gems safe-pak relay ( ' ntrin- <br /> s.cally safe to prevent any possibility of ignition source at thetank) . <br /> 2. PRESSURE SWITCH (#1950) : Combines a Model 1900 Dwyer switch with an <br /> weather-proof housing approved for use in class I group <br /> C' & D, class II E, F, G, and class III hazardous atmospheres. The switch <br /> iLi intended to ,be mounted at the tank: top manway, in a vertical position. <br /> e>;plosion proof female "Y" is provided so that there is no chance of <br /> hazardous fumes working up through the conduit in the event of a switch <br /> rupture. The switch is connected electrically to the alarm box wi h two <br /> conductor wire, and pneumatically to the tank annular space by the tank <br /> . .:serbly unit and equalizing line if needed. <br /> 1 <br />