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OVERVIEW ISM-4080 and ISM-4081 Integrated Shutdown Module Over the last thirteen years, Vmi has earned the reputation of building the best mechanical line leak detectors available. With the"99"series of mechanical leak detectors, Vm1 continues to strengthen its technological lead by providing the most reliable line leak detection.These products perform the most reliable operation in the broadest range of fuel and piping systems, providing the longest service life, within the EPA mandated Catastrophic Line Leak Detection threshold of 3 gallons per hour @ 10 PSI. In July of 2000, Vmi advanced the state of the art of mechanical line leak detection by introducing a way to eliminate thermal induced slow-flow, the Achilles heel of line leak detection. The introduction of the ARM-4073 Automatic Repress u rization Module provided the ability to match a mechanical line leak detector and an Auto- Repressurization system to eliminate thermally induced false alarms for mechanical line leak detection without reducing leak detection sensitivity. The ISM Modules take Auto-Repressurization technology to a new level, monitoring line pressure directly by tracking leak detector piston movement at all times. Monitoring line pressure through the mechanical line leak detector determines if the leak detector is open, establishes the appropriate time to repressurize the line, and allows the ability to determine when to disable the submersible pump for a detected line leak. The ISM line leak detection system continuously monitors the line and performs line leak checks anytime the pressure falls in the line, even when the submersible pump is off! Whether thermal contraction is occurring, a mechanical failure in the submersible pump (pressure relief or functional element), or a line leak, this system is at work. Station operators now have automatic notification of line leaks, not thermal problems. No more drive-off customers from thermal problems! Line leak detection generally takes longer today than in the past.Today's pipe delivery systems are usually longer, have more flexible connectors, and are often made of flexible material. Additionally, vapor entrapment due to thermal contraction adds to the problem. These conditions may result in a leak detector taking more than five seconds to open, resulting in slow flow(false alarms). The ISM compensates for these conditions. If line pressure falls below 12 PSI for any reason, enough time for the leak detector to reset is allowed to pass. After the delay time for the leak detector to reset (leak or thermal contraction) has passed, the delivery line is repressurized. During repressurization, a line test occurs detecting leaks or ensuring the delivery system is charged and ready to deliver fuel. Many manifolded piping systems,such as those seen at high volume stations and truck stops, have more than one submersible pump delivering fuel into a manifolded (single) pipe system. If these submersibles are allowed to start at the same time,they will not be capable of detecting a 3 GPH line leak. The ISM-4080 and ISM-4081 will authorize one pump first, allow one leak detector to search for a line leak, and then start the (additional) submersibles at delayed intervals. The ISM will control all fractional horsepower submersibles as well as Big Flow 3 and 5 horsepower submersibles. In some jurisdictions, it is required that the submersible pump be disabled when the sump sensor alarm is activated or when a catastrophic line leak (3 GPH @ 10 PSI) is detected. The installation of the ISM-4080 meets these requirements with or without a site monitoring system. In other jurisdictions, full shutdown of the submersible pump is not required following the detection of a sump sensor alarm. The ISM-4081 allows the operator to select either an alarm only response when the sump sensor has been activated or a full shutdown of the submersible pump. Full shutdown of the submersible pump(s) is initiated in the event of catastrophic line leak detection. To prevent the interruption of scheduled tank testing events, the ISM may be programmed to prevent Auto- Repressurization based on time of day. The ISM Auto Repressurization cycle may also be disabled by an input from the tank test system to prevent interference when a tank test is being conducted.