Pressure monitoring and leak detection method and apparatus

Pressure monitoring apparatus comprising:

• (a) a pump which draws gas in at an inlet and delivers gas under pressure at an outlet;
• (b) a pressure sensor including:
• (1) a cup shaped housing having an open mouth and having an inlet and outlet formed therein;
• (2) a flexible diaphragm sealed over the open mouth of the housing to define a plenum between the walls of the mouth in the housing and the diaphragm, and wherein the inlet formed within the housing is in communication with the plenum;
• (3) an exhaust tube centrally mounted in the housing within the plenum with an end thereof terminating adjacent the inner side of the diaphram and connected to be in communication with the outlet from the housing;
• (c) a supply line connected from the outlet of the pump to the inlet in the sensor housing to supply gas under pressure to the sensor and a return line connected from the outlet in the sensor housing to the inlet of the pump;
• (d) a first accumulator chamber connected in the supply line;
• (e) a second accumulator chamber connected in the return line;
• (f) a flow restrictor connected in the supply line between the first accumulator chamber and the inlet to the pressure sensor housing;
• (g) load pressure transducer means for measuring the pressure in the supply line between the restrictor and the pressure sensor and providing an output signal indicative thereof, whereby changes in ambient pressure at the pressure sensor will result in movement of the diaphragm to alternately open and close the exhaust tube to automatically maintain the pressure within the plenum approximately equal to the ambient pressure, and whereby the load pressure transducer means will measure a pressure which is approximately equal to the pressure surrounding the sensor including pressures lower than the ambient atmospheric pressure which are no lower than the pressure within the second accumulator chamber.

In a closed circulating gas system having a pump which draws gas at an inlet from a return line and delivers gas under pressure at an outlet to a supply line, and also having a load device which receives gas from the supply line and delivers it to the return line, apparatus for detecting leaks in the system comprising:

• (a) a first accumulator chamber connected in the supply line;
• (b) a second accumulator chamber connected in the return line;
• (c) first pressure transducer means for measuring the pressure in the first accumulator chamber and providing an output signal indicative thereof;
• (d) second pressure transducer means for measuring the pressure in the second accumulator chamber and providing an output signal indicative thereof;
• (e) control means responsive to the output signals of the first and second pressure transducer means for comparing the pressure measured in the first accumulator chamber with the pressure measured in the second accumulator chamber and providing a leak warning output signal if the compared pressure change with respect to one another in excess of a selected range, thereby indicating that the flow through the two accumulator chambers is not equal and a leak in the system has occurred;
• (f) a bypass valve connected around the pump and responsive to the leak warning signal from the control means, the bypass valve being operative to open when the leak warning signal is received to shunt the outlet of the pump back to its inlet and to relieve pressure within the system including equalizing the pressures within the first and second accumulator chambers;
• and
• (g) a pressure release valve connected to the return line, the pressure release valve being responsive to a signal from the control means to open at the same time that the bypass valve opens and to place the return line in communication with the ambient atmosphere.

In a closed circulating gas system having a pump which draws gas at an inlet from a return line and delivers gas under presure at an outlet to a supply line, and also having a load device which receives gas from the supply line and delivers it to the return line, apparatus for detecting leaks in the system comprising:

• (a) a first accumulator chamber connected in the supply line;
• (b) a second accumulator chamber connected in the return line;
• (c) first pressure transducer means for measuring the pressure in the first accumulator chamber and providing an output signal indicative thereof;
• (d) second pressure transducer means for measuring the pressure in the second accumulator chamber and providing an output signal indicative thereof;
• (e) control means responsive to the output signals of the first and second pressure transducer means for comparing the pressure measured in the first accumulator chamber with the pressure measured in the second accumulator chamber and providing a leak warning output signal if the compared pressures change with respect to one another in excess of a selected range, thereby indicating that the flow through the two accumulator chambers is not equal and a leak in the system has occurred;
• and
• (f) means for converting the output signals of the first and second pressure transducer means to digital data signals, and wherein the control means compares the digital pressure signals from the first and second transducer means by periodically dividing one of the digitized output signals into the other to provide an initial digital ratio which is stored and a latest ratio, the control means comparing the latest ratio with the initial ratio and providing a leak warning output signal if the latest ratio deviates from the initial ratio in excess of a selected tolerance amount.