Abstract: A method for operating a pump controller to pressurize a liquid product line for thermal stabilization during a leak test is accomplished as follows. A microprocessor controlled timer is installed in a petroleum service station product dispensing system that includes a pump relay, a pump, a dispenser, and a leak detection monitor. The timer activates pump relays to pressurize a liquid product line that runs from a tank to the dispenser at predetermined intervals to compensate for thermal contraction during product line leakage testing. Prior to activating pump relays, the timer has circuitry and program determines if product is currently being dispensed. If product is being dispensed, the timer waits until dispensing has halted then starts a timer to provide a delay before activating pump relays to pressurize the product line. Also prior to activating pump relays, the timer has circuitry and program determines if pump operation should be inhibited and if so halts before activating pump relays.

Abstract: A microprocessor controlled timer is installed in a petroleum service station product dispensing system that includes a pump relay, a pump, a dispenser, and a leak detection monitor. The timer activates pump relays to pressurize a liquid product line that runs from a tank to the dispenser at predetermined intervals to compensate for thermal contraction during product line leakage testing. Prior to activating pump relays, the timer has circuitry to determines if product is currently being dispensed. If product is being dispensed, the timer waits until dispensing has halted before activating pump relays to pressurize the product line. Also prior to activating pump relays, the timer has circuitry to determine if pump operation should be inhibited and if so halts before activating pump relays. Optical isolation is used between the timer and pump relays and a dispenser switch.

Abstract: A hydrocarbon leak detection system has a microprocessor based controller for receiving inputs from transducers and comparing the inputs against stored decision criteria to determine if hydrocarbons are leaking. The controller can receive and distinguish inputs from line pressure probes used for a product line tightness test, compare the line pressure probe inputs against stored decision criteria to determine status, and report the status.

Abstract: A pressure transducer, a microprocessor, and associated electronics are enclosed in a probe housing which may be attached to a liquid product line with the pressure transducer responsive to the pressure of the liquid in the liquid product line to provide an electrical signal representative of the pressure. The probe microprocessor contains a software program to detect leakage from a pressurized liquid product line in which the liquid is subject to a pressure increase caused by thermal contraction. The probe also has the capability to directly operate a product pump with a signal connection between the probe and the pump.

Abstract: A fluid detection system includes a central monitor, an overfill probe for detecting the approach of the overfill condition of a tank of liquid, and n other probes, where n is an integer greater than or equal to 1. The probes are connected to the monitor via electronic cables. The monitor communicates with the probes by producing probe identifier signals comprising integers starting with zero up to the number n. Each probe includes a signal receiving and sending means which compares the identifier signal sent by the monitor to a preset identifier number for that probe and sends a status signal indicative of the fluid status at that probe when it receives the identifier signal that is the same as the preset number. The overfill probe is set with the identifier zero. The monitor includes a timing circuit which determines a six second probe check cycle.

Abstract: A detector for sensing the presence of polar fluids includes a pair of detection probes and a circuit for providing an oscillating voltage across the probes. A power supply for the detector includes a transformer with a split secondary, with at least one secondary having a floating ground. One of the probes is connected to the floating ground. The other probe is connected to the input of a fluid detection logic circuit. The input is applied to an inverter having an activation threshold of approximately six volts. The resulting activation threshold of the detector circuit is sufficiently low to be activated by the oscillating voltage so as to produce a polar fluid output signal when the probes are immersed in a polar fluid, but sufficiently high so as not to be affected by stray voltages induced in the probes by conventional power lines, such as 120 VAC lines, contacting the polar fluid.

Abstract: A fluid detection system capable of displaying the conditions in the environs of a large number of fluid detection probes and correlating each condition with the particular probe that detected it. There are a plurality of probes, each having a comparator preset with a unique probe identifier, such as a binary number. A counter produces digital signals representative of the binary numbers. The probe comparators are responsive to the numbers outputted by the counter and are connected to the probe power circuitry. When each comparator receives the signal corresponding to its preset number, it triggers its associated probe to produce status signals. A display circuit responds to both the number output by the counter and the probe status signals to simultaneously display the probe number and an indication of probe status.

Abstract: A system for detecting fluid pollutants includes probes for sensing the presence of a polar liquid, a non-polar liquid, and a dry condition, and for producing a polar liquid signal, a non-polar liquid signal, and a dry condition signal. A reference circuit which includes a tunable element, such as a variable resistor, is used to set the probe output signals to a predetermined voltage value: e.g. a 1-volt value indicates a polar liquid, a 2-volt value indicates a non-polar liquid, a 3-volt value indicates a dry state, and a 5-volt value indicates that the circuit is on and operating. The output signals are multiplexed and output on a single output line. The definitive signal levels and the serial output mode permit an inexpensive single channel recorder to be used to provide a permanent and complete record of the probe status.