Expansion tank with a predictive sensor

Abstract

An expansion tank which comprises a tank having a predetermined volume capacity; an expandable elastomeric bladder 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.

Claims

1. An expansion tank for a hydronic system which comprises a tank having a predetermined volume capacity; an expandable elastomeric bladder suspended in the tank, partitioning tank volume into a liquid-containing portion defined by the bladder for holding liquid and a gas-containing portion defined by the tank together with the bladder for holding a gas under a pressure; and a proximity sensor mounted to the tank in the gas-containing portion thereof and configured to emit an alarm signal when the expanded bladder occupies more than 40 percent of total tank volume.

2. The expansion tank in accordance with claim 1 wherein the proximity sensor is a dielectric capacitive proximity sensor.

3. The expansion tank in accordance with claim 1 wherein the proximity sensor is a conductive 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. A hydronics system which includes an expansion tank having an expandable elastomeric bladder suspended therewithin and partitioning tank volume into a liquid-containing portion for holding liquid and a gas-containing portion for holding a gas, and a proximity sensor for said elastomeric bladder mounted in the tank and configured to emit an alarm signal when volume of the gas-containing portion is reduced by a predetermined amount as a result of expansion of the elastomeric bladder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings.

(2) FIG. 1 is a schematic illustration of a closed-loop hydronics system that utilizes an expansion tank embodying the present invention;

(3) FIG. 2 is an enlarged elevational view of the expansion tank shown in FIG. 1.

(4) FIG. 3 is a schematic illustration of an air separation and expansion tank detail of a hydronics system, the expansion tank being provided with a bladder type diaphragm;

(5) FIG. 4 is a schematic illustration of a hydropneumatic expansion tank embodying the present invention and utilizing a diaphragm in the form of an elastomeric web that partitions the tank volume into a gas-containing portion and a liquid containing portion;

(6) FIG. 5 is a schematic illustration of an electro-mechanical proximity sensor mounted in the wall of an expansion tank at flooding conditions;

(7) FIG. 6 is a schematic illustration of an electro-mechanical proximity sensor mounted in the wall of an expansion tank;

(8) FIG. 7 is a schematic illustration of another type of electro-mechanical proximity sensor;

(9) FIG. 8 is a schematic illustration of an expansion tank embodying the present invention and under normal operating conditions;

(10) FIG. 9 is a schematic illustration of an expansion tank embodying the present invention and under abnormal, excessive system pressure condition; and

(11) FIG. 10 is a schematic illustration of an expansion tank embodying the present invention and showing a ruptured diaphragm as well as a flooded condition.

DESCRIPTION OF PREFERRED EMBODIMENTS

(12) The invention described herein is, of course, susceptible of embodiment in many forms. Shown in the drawings and described hereinbelow in detail are preferred embodiments of the present invention. It is to be understood, however, that the present disclosure is an exemplification of the principles of this invention but does not limit this invention to the illustrated embodiments.

(13) Referring to FIGS. 1 and 2, a closed loop heating system 12 includes expansion tank 10 equipped with proximity sensor 11 and alarm module 20 mounted to tank 10. Proximity sensor 11 preferably is a dielectric type capacitive proximity sensor such as Model C1ALLAN1-P, commercially available from Stedham Electronics Corporation, Reno, Nev. 89502, U.S.A. Boiler 14 supplies hot water which is circulated through radiators 13 and 16 by pump 26 via lines 15, 17, 18 and 19. Line 24 is in fluid flow communication with line 15 as well as with bladder-type diaphragm 21 in expansion tank 20. Excess system water 23 is held within bladder-type diaphragm 21. System pressure, typically about 12 to about 30 pounds per square inch gage (psig) is maintained by reason of pressurized gas within gas-containing portion 22. Tank 10 is also equipped with air charging valve 27 for adjusting air pressure in the gas-containing portion 22.

(14) FIG. 3 illustrates a hydronics installation. Floor mounted, vertical expansion tank 30 is equipped with suspended bladder 32 that holds excess system water 34. Pressure gage 36 monitors system water pressure. Air charging valve 38 is provided on tank 30 for pressurization of gas-containing portion 40 of tank 30. Proximity sensor 42 is mounted to tank 30 and monitors conditions within the gas-containing portion 40. If bladder 32 expands beyond a predetermined limit due to an abnormal increase in system pressure or an air leak in gas-containing portion 40, proximity sensor 42 detects such an expansion and emits a signal that energizes an appropriate alarm so that system water pressure can be relieved before excessive stress or bursting pressure is reached within bladder 32. If overexpansion of bladder 32 is due to an air leak from gas-containing portion 40, additional air pressure can be supplied through air charging valve 38.

(15) Air separator 45 is provided in feed line 47 that communicates via water line 49 with the input or suction side of a pump (not shown). Expansion tank 30 and its bladder 32 are, in turn, in fluid flow communication with water line 49 via line 51. Tee connection 53 is provided in line 54 to facilitate connection with another, parallel expansion tank if desired. System pressure relief valve 56 is also provided in communication with water line 49.

(16) FIG. 4 illustrates a typical installation of a vertical, floor mounted expansion tank 58 that is provided with proximity sensor 60 mounted to tank 58 in the region that defines gas-containing portion 62 within tank 58. Membrane 64 partitions tank 58 into a gas-containing portion 62 and liquid containing portion 66. Tank 58 also has an air charging valve 68 and inspection port 59.

(17) Liquid-containing portion 66 is in fluid flow communication with a water system via line 67. Pressure gage 69 in line 67 monitors system water pressure.

(18) FIG. 5 illustrates a flooding condition in expansion tank 10. Bladder-type diaphragm 21 has burst and water held within the liquid-containing portion 23 has entered gas-containing portion 22. Proximity sensor 11 mounted to tank detects the approaching water level, emits an alarm signal that, in turn, energizes alarm module 20 equipped with audible alarm 81 as well as with visual indicator light 82 and on/off/reset button 84. Remote alarm capabilities can be incorporated as well, if desired.

(19) FIG. 6 illustrates electro-mechanical proximity sensor 70 equipped with alarm module 90 mounted in the wall of an expansion tank. Proximity sensor 70 extends into the gas-containing portion of the tank and alarm module 90 associated with sensor 70 is situated outside the expansion tank.

(20) Proximity sensor 70 includes a float 77 mounted at the distal end of arm 76 which forms an integral, substantially L-shaped piece 73 with arm 74 that carries a magnet 75 at the distal end thereof. The L-shaped piece 73 is pivotably mounted at 72 to bar 71 supported by housing 98. When float 77 is moved upwardly either by an expanding bladder or the buoyant force exerted on float 77 by a rising water level, magnet 75 approaches and closes contact points 94 and 96 in housing 98, thereby closing the alarm circuit in alarm module 90. This alarm circuit includes, in addition to contact points 94 and 96, leads 101 and 102, a power source such as battery 85, audible alarm 81, visual alarm 82, and on/off/reset button 84.

(21) FIG. 7 depicts another proximity sensor suitable for use in practicing the present invention.

(22) In this particular embodiment float 107 is affixed to the distal end of a wire spring 109 mounted in a conductive sleeve 111 but electrically isolated therefrom. Leads 119 and 121 are connected, respectively, to wire spring 109 and conductive sleeve 111 and to the same alarm module as that shown in FIG. 6. Wire spring 109 is held in place inside conductive sleeve 111 by epoxy disc 117. The alarm circuit is closed and an alarm signal emitted when float 120 is urged upwardly either by an expanding diaphragm or a rising water level and wire spring 109 which contacts conductive sleeve 111.

(23) FIGS. 8, 9 and 10 illustrate the position of the diaphragm in an expansion tank under various conditions. In FIG. 8 expansion tank 130 is shown under normal operating conditions, the liquid 132 held in tank 130 occupying about 40 percent of tank volume, pressurized gas 134 occupying about 60 percent of tank volume and being separated from liquid 132 by diaphragm 136. In this particular example the system water pressure is in the range of about 12 to about 30 psig and is counterbalanced by pressurized gas 134. Proximity sensor 140 is mounted in the wall of tank 130. Alarm module 142 associated with sensor 140 is on the outside of the tank 130.

(24) When the system water pressure rises (FIG. 9), more of liquid 132 occupies the tank volume and diaphragm 136 becomes distended, shifting proximity sensor 140 upwardly and energizing the alarm. Similarly, when diaphragm 136 has burst, rising water level in tank 130 maintains proximity sensor 140 in an upwardly position as shown in FIG. 10.

(25) Under normal operating conditions in a hydronics system, the liquid volume in the expansion tank is about 40 percent of total tank volume and the pressurized gas or air volume is about 60 percent of total tank volume. An alarm condition occurs when the diaphragm is distended to near its maximum tensile or burst strength. The latter, of course, is dependent on the material of construction and thickness of the diaphragm. Expansion tank diaphragm are butyl rubber, natural rubber, nitrile rubber, and the like.

(26) Preferably, the proximity sensor is positioned at or in the expansion tank so that an alarm signal is emitted when the gas-containing portion of the tank has been reduced by at least about 40 percent of normal value.

(27) The emitted alarm signal can be processed in a variety of ways. As described hereinabove, the alarm signal can be utilized to energize an audible alarm or a visual alarm. The alarm signal can also be transmitted to a remote site having a centrally located monitor or data logger that can receive alarm signals from more than one expansion tank in a hydronics system or systems. The choice of a particular expansion tank monitoring arrangement depends largely on the size of the involved hydronic system or systems involved.