FR2740784A1 - DEVICE FOR THE CATHODIC PROTECTION OF A WATER HEATER TANK AND A WATER HEATER PROVIDED WITH 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

i

  CATHODIC PROTECTION DEVICE FOR A WATER HEATER TANK

  AND WATER HEATER EQUIPPED WITH SUCH A DEVICE

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

cathodic.

  In this application, the term "heater

  water "any tank capable of containing hot water equipped

  or not a permanent heating means.

  Cathodic protection is a technique for protecting a metallic metal 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-anode

  consumable in 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 it in a helix and crossing it to be

  connected inside of it.

  Document US Pat. No. 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 to 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 the type

  known 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 crossed by said non-consumable anode, so that an electronic circuit is connected to the non-consumable anode

  by an insulated conductor inside said thermowell.

  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 sealing flange, so as to ensure mechanical stress producing permanent electrical contact between the tank of the water heater and said flange

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 block

signaling.

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  the insulating support element is in the form of a pierced cap enclosing on the one hand said non-anode

  consumable and on the other hand the end of the thermowell.

  the cap is made of a resilient material, for example an elastomeric material resistant to heat, and

  with agri-food compatibility.

  The invention also relates to a water heater comprising a metal tank 1 i closed by a cover

  carrying a device according to the invention.

  The invention will be better understood thanks to the

  description which will follow given by way of example not

  limiting with reference to the accompanying drawings in which: - Figure i schematically shows a side elevation view with partial diametral sections of a

device according to the invention.

  - Figure 2 shows schematically a circuit

  supply for device according to the invention.

  - Figure 3 schematically shows a diagram of an electronic device circuit according to

the invention.

  - Figure 4 shows schematically an element

  anode support for 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 i also carries a thermowell 4 containing a first safety bulb 5 and a second regulation bulb 6 connected to a set 7 and forming a thermostat for supplying the heating element or a heating resistor of the heater. water. The thermostat 7 is mounted outside the tank of the water heater on the flange 1 by means of a bracket 8

in folded sheet.

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  According to the invention, the thermowell 4 carries an assembly comprising an insulating support element 9 of a

noble metal anode 10.

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

  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 i 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 i 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 main thing being that the outer sheath of the immersion heater or of the equivalent heating element either in continuity of material with the flange i directly or via a compensating resistor, so as to be constantly at the same

2740784

  electrical potential than flange 1 and 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. 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 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

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  transformer. A filter capacitor 20f is arranged at the output of the above-mentioned mixed rectifier bridge. The polarization block 21 comprises 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 block 22 for charging 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 limiting 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 part

  metal in contact with the water contained in the heater

  water is constantly protected even in the absence of water heating. The battery or batteries 23 are preferably determined to obtain continuous protection for at least 72 hours of the jacket of the water heater in

  providing a bias current of less than 5 milli-

  amperes and capable of imposing a cathodic protection potential at least equal to 1.2 Volts, regardless of the characteristics of the domestic water contained in the water heater. With reference to FIG. 4, a non-consumable anode insulating support element 10 is preferably formed in the form of a cap made of heat-resistant elastomeric material and compatible with agri-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 inserted at force in a channel 30 of diameter provided 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 1 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

blanking plug 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.

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Claims (8)

  1. Cathodic heater protection device   water 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 an anode (10) which cannot be consumed , in that said insulating element (9) is crossed by said non-consumable anode (10), so that an electronic circuit (11) is connected to the non-consumable anode (10) by an inner insulated conductor (12) said thermowell (4).   2. 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 flange (1) shutter, so ensuring mechanical stress producing permanent electrical contact between the tank of the water heater and said flange (1) shutter.   3. 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).   4. Device according to one of claims   previous, 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 battery recharging unit (22) (23 ), a polarization block (24) using the   battery (23) in service without heating.   5. Device according to claim 3, characterized in that the electronic circuit further comprises a block signaling (25).   6. Device according to one of claims   above, characterized in that the insulating support element (9) is in the form of a pierced cap (30) enclosing a 9 2740784   on the one hand said non-consumable anode (10) and on the other hand the end of the thermowell (4).   7. Device according to claim 5, characterized in that the cap (9) is made of a resilient material, for example an elastomeric material resistant to heat and   with agri-food compatibility.   8. Water heater comprising a cathodic protection device according to any one of previous claims.