EP0771889A1 - Device for cathodically protecting a water heater and water heater featuring such a device - Google Patents

Abstract

The protection assembly consists of a sleeve (4) with its end covered by an insulating element (9) which acts as a support for a non-consumable anode (10). The anode passes through the cover and is connected to an electronic circuit (11) by a conductor (12) passing through the inside of the sleeve. The circuit (11) is connected to the heater tank by a screw (2) and a bracket (1) which ensures a constant electrical contact with the tank. The circuit (11) incorporates a feeder, a polariser and a battery recharger. The insulating cover (9) comprises a pierced cap (30) which surrounds the anode and fits onto the end of the sleeve, with a plastic insulating seal (34) between them. The cap is made from a resilient material, such as an elastomer which is resistant to heat and chlorinating agents.

Description

The invention relates to a cathodic protection device for a water heater tank, as well as to a water heater equipped with such a cathodic protection device.

In the present application, the term "water heater" designates any tank capable of containing hot water, whether or not equipped with a permanent heating means.

Cathodic protection is a technique for protecting a metallic structure against oxidation, consisting in bringing the metallic structure to be protected to a determined electrochemical potential so that the structure does not release metallic ions even on contact with oxidizing agents. The cathodic protection can be a so-called "passive" cathodic protection, in which a consumable electrode playing the role of anode gradually corrodes and the metal structure to be protected plays the role of cathode which does not release metal ions. A second protection technique called by specialists "with impressed current" makes it possible to protect the metallic structure by imposing an electrical potential between the metallic structure to be protected and a non-consumable anode made of noble metal or resistant to corrosion.

Document US 4,407,711 gives an example of a protection system for a hot water tank, in which a corrosion-resistant anode element is formed into a ribbon extending along a support tube or, alternatively , in the form of a noble metal wire fixed to the outside of a water intake tube, surrounding the latter in a helix and passing through it to be connected inside the latter.

Document US 4,975,560 describes an apparatus for supplying a corrosion protection system to an electric water heater, in which the protection anode is a consumable type anode.

Document DE 26 21962 describes a device for the cathodic protection of a hot water tank, in which the anode is in the form of an elongated tube fixed at its two ends by insulating supports.

The invention aims to improve the cathodic protection systems of water heaters, by providing a new simple and economical manufacturing device, easily adaptable to water heaters of known type without cathodic protection.

The subject of the invention is a cathodic protection device for water heaters of the type comprising a tank closed by a sealing flange, characterized in that the device comprises a tubular thermowell carrying at its end an insulating support element for a non-consumable anode, in that said insulating element is traversed by said non-consumable anode, so that an electronic circuit is connected to the non-consumable anode by an insulated conductor inside said glove finger.

• le dispositif comporte un circuit électronique relié à la cuve par l'intermédiaire d'une vis de fixation de la bride d'obturation, de manière à assurer une contrainte mécanique produisant un contact électrique permanent entre la cuve du chauffe-eau et ladite bride d'obturation.
• le dispositif comporte un circuit électronique relié à une patte soudée à la cuve, de manière à produire un contact électrique permanent entre la cuve et le circuit électronique.
• le dispositif comporte un circuit électronique comportant un bloc d'alimentation, un bloc de polarisation en service en cours de chauffage, un bloc de recharge de batterie, un bloc de polarisation à l'aide de la batterie en service en l'absence de chauffage.
• le circuit électronique comporte en outre un bloc de signalisation.
• l'élément isolant de support est en forme de capuchon percé enserrant d'une part ladite anode non consommable et d'autre part l'extrémité du doigt de gant.
• l'élément isolant de support est associé à une rondelle plastique d'isolation.
• le capuchon est en matériau résilient, par exemple un ou plusieurs matériau(x) élastomère(s) résistant à la chaleur et aux agents chlorés et présentant une compatibilité agro-alimentaire.

According to other characteristics of the invention:

• the device comprises an electronic circuit connected to the tank by means of a screw for fixing the closure flange, so as to ensure mechanical stress producing permanent electrical contact between the tank of the water heater and said flange d shutter.
• the device comprises an electronic circuit connected to a lug welded to the tank, so as to produce a permanent electrical contact between the tank and the electronic circuit.
• the device comprises an electronic circuit comprising a power supply unit, a polarization block in service during heating, a battery recharging block, a polarization block using the battery in service in the absence of heating .
• the electronic circuit also includes a signaling block.
• the insulating support element is in the form of a pierced cap enclosing on the one hand said non-consumable anode and on the other hand the end of the glove finger.
• the insulating support element is associated with a plastic insulation washer.
• the cap is made of a resilient material, for example one or more elastomeric material (s) resistant to heat and to chlorinated agents and having agrifood compatibility.

The invention also relates to a water heater comprising a metal tank closed by a cover carrying a device according to the invention.

• La figure 1 représente schématiquement une vue en élévation latérale avec coupes diamétrales partielles d'un dispositif selon l'invention.
• La figure 2 représente schématiquement un circuit d'alimentation pour dispositif selon l'invention.
• La figure 3 représente schématiquement un diagramme d'un circuit électronique de dispositif selon l'invention.
• La figure 4 représente schématiquement un élément de support d'anode pour dispositif selon l'invention.

The invention will be better understood thanks to the description which follows given by way of nonlimiting example with reference to the appended drawings in which:

• Figure 1 schematically shows a side elevational view with partial diametrical sections of a device according to the invention.
• FIG. 2 schematically represents a supply circuit for a device according to the invention.
• FIG. 3 schematically represents a diagram of an electronic circuit of a device according to the invention.
• FIG. 4 schematically represents an anode support element for a device according to the invention.

Referring to Figure 1, a device according to the invention has a flange 1 intended to close the lower end of the tank of an electric water heater to which it is screwed by screws 2 with possibly interposition of a seal sealing. The flange 1 carries a sheath 3 intended to receive a heating element, for example a soapstone assembly with resistances, comprising at least one metal winding mounted on an insulating ceramic. The disc-shaped flange 1 also carries a thermowell 4 containing a first safety bulb 5 and a second regulation bulb 6 connected to an assembly 7 and forming a thermostat for supplying the heating element or a heating resistor of the water heater. The thermostat 7 is mounted outside the tank of the water heater on the flange 1 by means of a bracket 8 made of folded sheet.

According to the invention, the thermowell 4 carries an assembly comprising an insulating support element 9 of an anode 10 of noble metal, with possible interposition of a washer (34) of synthetic material.

As metallic material which can be used for the anode 10, it is possible, for example, to choose a material from the group comprising ferritic stainless steels externally passivated by electrochemical passivation, austenitic stainless steels externally passivated by electrochemical passivation, aluminum, ferrosilicon, platinum titanium, platinum niobium, platinum tantalum and titanium coated with a coating layer of metal oxides.

The anode 10 of metallic material is connected to a current generator 11 via an insulated conductor 12, to which it is connected via an insulated connector 13. The electrochemical generator 11 is also connected to the closing flange 1 by an insulated conductor 14, preferably by a contact tightened by a screw 2 for fixing the flange 1 on the tank of the water heater.

Thus, by screwing the screws 2 for fixing the flange 1 on the tank of the water heater, the electrical contact is established by the mechanical pressure resulting from the screwing of the screw 2 in a corresponding tapping of the water heater, which establishes a permanent electrical connection between the flange 1 and the tank of the water heater and ensures that the envelope of the water heater comprising the tank and the flange 1 is constantly subjected to the same electrical potential fixed by the generator 11.

Of course, the invention described with reference to a resistor mounted in a sheath is applicable to any variant in which the heating resistor would consist of an immersion heater or any other equivalent heating element, the essential being that the outer sheath of the immersion heater or equivalent heating element either in continuity of material with the flange 1 directly or via a compensating resistor, so as to be constantly at the same electrical potential as the flange 1 and that the tank of the water heater.

With reference to FIG. 2, the thermostat 7 and the generator 11 are supplied via a common terminal block 15 usable for a three-phase three-phase supply L1, L2, L3, or for a two-phase supply in two phases L and N.

The thermostat 7 in turn feeds a set of resistors 16, 17, 18, connected in a star and located inside the sheath 3 to ensure the heating of the water contained in the water heater.

The generator 11 is connected on the one hand to the tank of the water heater which acts as a cathode and on the other hand to the non-consumable anode 10 ensuring cathodic protection of the tank of the water heater. The anode 10 is for example of a material of the titanium type coated with a protective coating.

The bulbs 5 and 6 are liquid expansion bulbs which are connected to the thermostat 7 by capillaries: this arrangement in one piece is of the type known per se and generally gives satisfaction.

With reference to FIG. 3, an electronic cathodic protection circuit for a device according to the invention comprises a power supply unit 20 capable of supplying a rectified and filtered voltage of the order of 7.5 volts, a polarization unit 21 of the anode 10, a recharging block 22 of an accumulator 23, a polarization block 24 discharging the accumulator 23 to maintain the tank C at a cathodic protection potential and a signaling block 25 indicating that the cathodic protection of the tank is provided by the rechargeable battery 23.

The block 20 comprises in a manner known per se a varistor 20a for protection against overvoltages and two Zener diodes 20b mounted at the terminals of the primary of a voltage lowering transformer 20c. The secondary of the transformer is connected via a PTC resistor 20d to a mixed bridge 20th of diodes to rectify the voltage delivered by the secondary of the transformer. A filter capacitor 20f is arranged at the output of the above-mentioned mixed rectifier bridge. The polarization block 21 includes a transistor 21a, two resistors 21b and 21c and two diodes 21d, so as to polarize the tank C relative to the anode 10 to obtain an electrochemical potential ensuring effective protection of the tank C.

The charging block 22 of the accumulator 23 comprises a charging transistor 22a, two resistors 22b and 22c, two diodes 22d and two resistors 22e and 22f mounted at the base of a tilting transistor 22g.

The bias circuit 24 using the discharge of the battery 23 comprises a switching transistor 24a, three resistors 24b, 24c, 24d for limiting the current, three diodes 24e for limiting the discharge current of the battery and two light-emitting diodes 24f for limiting of the battery charge 23.

The signaling unit 25 comprises a light-emitting diode 26 supplied by an oscillating assembly with three transistors 26a, 26b, 26c, two capacitors 26d, 26e and six resistors 26f to 26k to define time constants allowing an ignition of the light-emitting diode 26 all about 800 milliseconds.

Thus, thanks to the electronic circuit for cathodic protection according to the invention, the envelope of the water heater comprising the tank, the flange 1 and any metal part in contact with the water contained in the water heater is constantly protected even in l absence of water heating. The battery or batteries 23 are preferably determined to obtain continuous protection for at least 72 hours from the jacket of the water heater by providing a bias current of less than 5 milliamps and capable of imposing a protection potential. cathodic at least equal to 1.2 Volts, regardless of the characteristics of the sanitary water contained in the water heater.

With reference to FIG. 4, a non-consumable anode insulating support element 10 is preferably constituted in the form of a cap made of one or more elastomeric material (s) resistant to heat and to chlorinated agents and compatible with agro-food uses. The cap 30 makes it possible to adapt cathodic protection to a water heater of known type, by cutting the end of the thermowell containing the bulbs 5 and 6 and by covering it with a cap 9 equipped with an anode 10 inserted by force in a channel 30 of diameter intended to tightly tightly enclose the metal anode 10. The cap 9 advantageously comprises a lower recess 31 provided with clamping grooves intended to enclose a tubular thermowell 4. The upper end of the recess 31 is preferably adapted to the inside and outside diameters of the tubular thermowell 4, so that after having fitted the plug 9 onto the tubular thermowell 4, the inside diameter of the tubular thermowell 4 is centered on a wall 32 of the closure plug 9. To perfect the electrical insulation of the anode 10, a plastic washer 34 can easily be inserted between the upper end of the tube 4 and the fa this internal 33 of the cap 9.

The invention thus allows the rapid and easy modification of existing water heaters by adding a new device or by simple modification of an existing water heater.

The invention described with reference to a particular embodiment is in no way limited thereto, but on the contrary covers any modification of form and any variant of embodiment within the scope and spirit of the invention.

Claims (9)

Cathodic protection device for water heaters of the type comprising a tank closed by a sealing flange, characterized in that the device comprises a tubular thermowell (4) carrying at its end an insulating element (9) for supporting a non-consumable anode (10) in that said insulating element (9) is traversed by said non-consumable anode (10), so that an electronic circuit (11) is connected to the non-consumable anode (10) by an insulated conductor (12) inside said thimble (4). Device according to claim 1, characterized in that the device comprises an electronic circuit (11) connected to the tank by means of a screw (2) for fixing the closure flange (1), so as to ensure mechanical stress producing permanent electrical contact between the tank of the water heater and said sealing flange (1). Device according to claim 1, characterized in that the device comprises an electronic circuit (11) connected to a lug welded to the tank, so as to produce a permanent electrical contact between the tank and the electronic circuit (11). Device according to one of the preceding claims, characterized in that the device comprises an electronic circuit (11) comprising a power supply unit (20), a polarization unit (21) in service during heating, a recharging unit (22) battery (23), a polarization block (24) using the battery (23) in service in the absence of heating. Device according to claim 3, characterized in that the electronic circuit further comprises a signaling block (25). Device according to one of the preceding claims, characterized in that the insulating support element (9) is in the form of a pierced cap (30) enclosing a on the one hand said non-consumable anode (10) and on the other hand the end of the thermowell (4). Device according to any one of the preceding claims, characterized in that the insulating support element (9) is associated with a plastic washer (34) for insulation. Device according to claim 5, characterized in that the cap (9) is made of a resilient material, for example one or more elastomeric material (s) resistant to heat and to chlorinated agents and having agrifood compatibility. Water heater comprising a cathodic protection device according to any one of the preceding claims.

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