Laserfiche WebLink
Tripped or <br />Bottom <br />Position <br />When the system is less <br />than 1 psi, the piston and <br />poppet are in the "bottom" or <br />"tripped" position. In this <br />position of the poppet, <br />product flows through the <br />horizontal hole in the poppet <br />and around the metering pin <br />at a rate of approximately 2 <br />GPM flow into the delivery <br />line when the submersible <br />pump is running. In normal <br />operations the piping <br />remains full of fluid and <br />when the submersible pump <br />is turned on, with a flow rate <br />of 2 GPM through the <br />poppet, pressure builds <br />rapidly and the poppet <br />moves to the leak sensing <br />position. <br />MLDB001 <br />8/26/2004 <br />In this position the system <br />pressure has increased to <br />approximately 12 psi and all <br />the flow must travel around <br />the metering pin which limits <br />it to approximately a 3 GPH <br />rate (at 10psi). If there is a <br />leak in the system which will <br />allow leakage to exceed this <br />amount, the line pressure will <br />not build beyond this point <br />and the valve will remain in <br />the leak sensing position with <br />the main flow blocked. If there <br />is an attempt to dispense <br />while the valve is in this <br />position, the line pressure will <br />drop to less than 1 psi, the <br />piston will respond, and the <br />poppet will return to Position <br />1 where 2 GPM will flow to <br />the dispensers. Leaks smaller <br />than 3 GPH will be indicated <br />by the STP -MLD taking <br />longer than three seconds to <br />open completely because <br />some of the flow leaks out of <br />the system and the rest builds <br />pressure. If there is no <br />leakage in the system, the <br />small flow around the <br />metering pin increases the <br />line pressure and in <br />approximately three seconds <br />the piston will move the <br />poppet to Position 3. <br />Page 3 of 3 <br />This position allows full flow. <br />The poppet will remain in <br />approximately this position <br />as long as the system <br />pressure remains at about <br />the pumping pressure. If the <br />pressure in the system drops <br />when the pump is turned off, <br />either due to thermal <br />contraction of the product or <br />due to a leak, the piston <br />moves downward and the <br />poppet engages and seals <br />inside the cage at about 3 <br />psi, or approximately 10 feet <br />of head, in gasoline. Any <br />time the pump is turned on <br />after the seal on the poppet <br />is inside the cage, a line test <br />will be performed. <br />Rev. 07/99 <br />