Expansion tank with a predictive sensor

Abstract

An expansion tank which comprises a tank having a predetermined volume capacity; an expandable diaphragm in the tank, partitioning tank volume into a liquid-containing portion for holding liquid and a gas-containing portion for holding a gas under a pressure that defines a normal pressurized gas volume when the liquid-containing portion holds a predetermined liquid volume; and a proximity sensor mounted to the tank at the gas-containing portion thereof and adapted to emit an alarm signal when volume of the gas-containing portion is reduced.

1 . An expansion tank which comprises
 a tank having a predetermined volume capacity;   an expandable diaphragm in the tank, partitioning tank volume into a liquid-containing portion for holding liquid and a gas-containing portion for holding a gas under a pressure that defines a normal pressurized gas volume when the liquid-containing portion holds a predetermined liquid volume; and   a proximity sensor mounted to the tank at the gas-containing portion thereof and adapted to emit an alarm signal when volume of the gas-containing portion is reduced.   
   
   
       2 . The expansion tank in accordance with  claim 1  wherein the proximity sensor is a dielectric type capacitive proximity sensor. 
   
   
       3 . The expansion tank in accordance with  claim 1  wherein the proximity sensor is a conductive type capacitive proximity sensor. 
   
   
       4 . The expansion tank in accordance with  claim 1  wherein the proximity sensor is a mechanical sensor situated in the gas-containing portion of the tank. 
   
   
       5 . The expansion tank in accordance with  claim 1  wherein the proximity sensor is an electro-mechanical sensor situated in the gas-containing portion of the tank. 
   
   
       6 . The expansion tank in accordance with  claim 1  wherein the expandable diaphragm is a bladder that together with a portion of tank wall defines the liquid-containing portion of the tank. 
   
   
       7 . The expansion tank in accordance with  claim 1  wherein the proximity sensor emits an alarm signal when volume of the gas-containing portion is reduced by at least 40 percent of normal pressurized gas volume. 
   
   
       8 . A method of monitoring size of an expandable diaphragm in an expansion tank which comprises the steps of
 detecting by a proximity sensor mounted to the tank wall the presence of a liquid-containing bladder-type diaphragm in vicinity of a tank wall that defines a gas-containing portion of the tank; and   generating an alarm in response to a signal from the proximity sensor.   
   
   
       9 . A method of determining degree of expansion of an elastomeric diaphragm in an expansion tank wherein said diaphragm together with a wall portion of said tank define a closed, gas-containing compartment for holding a gas under pressure and a liquid-containing compartment for storing a liquid, the method comprising;
 providing a proximity sensor in the closed, gas-containing compartment;   positioning the proximity sensor for detection of the elastomeric diaphragm when the diaphragm has expanded to a predetermined size; and   energizing an alarm in response to a detection signal emitted by the proximity sensor.   
   
   
       10 . A hydronics system which includes an expansion tank having an expandable diaphragm therewithin and partitioning tank volume into a liquid-containing portion and a gas-containing portion, and a diaphragm proximity sensor mounted to the tank and adapted to emit an alarm signal when volume of the gas-containing portion is reduced by a predetermined amount. 
   
   
       11 . The hydronics system in accordance with  claim 10  wherein the diaphragm is a bladder-type diaphragm. 
   
   
       12 . The hydronics system in accordance with  claim 10  wherein the diaphragm is a membrane fixed to periphery of the tank.