FR2777573A1 - CATHODIC PROTECTION DEVICE FOR A WATER HEATER TANK - Google Patents

Abstract

A device for the cathodic protection of the tank of a water heater, of the type incorporating a glove finger (1) carrying an insulating element (2) at its end supporting a non-consumable anode (3), has an impervious protective sleeve (8) placed between the anode (3) and the insulating element (2) inside the tank, in a manner that avoids degradation of the insulating element (2) by electrolytic oxidation of the water in the tank. The impervious sleeve (8) is made up of two materials, a thermoplastic fluoride with a lower melting point than the second material which is a thermo-retracting polymer fluoride, both applied radially in a manner that ensure sealing and prevents any sliding during the fitting of the anode (3) through the insulating support element (2). The anode (3) is of titanium or of titanium externally coated with a metal oxide or other material that can be passivated.

Description

1 2777573

  CATHODIC TANK PROTECTION DEVICE

WATER HEATER

  The invention relates to a cathodic protection device for a water heater tank. The document FP O 771 889 Ai describes a cathodic protection device for water heaters. In this device, a thermowell is carried by a closure flange of the tank of the water heater; this thermowell carries at its end an insulating element for supporting a non-consumable anode; said insulating element is traversed by said non-consumable anode so as to connect the non-consumable anode to an electronic circuit by means of an insulated conductor internal to said

glove finger.

  This device is generally satisfactory, but presents the risk of damage to the insulating support element by electrolytic oxidation of the water.

tank.

  The object of the invention is to remedy this drawback by improving the existing device, by increasing the reliability and the duration of use of the element.

support insulator.

  The subject of the invention is a device for cathodic protection of a water heater tank, of the type comprising a tubular thermowell carrying at its end an insulating element for supporting a non-consumable anode, characterized in that a tight protective sheath is placed inside the tank, between the anode and the insulating element, so as to avoid degradation of the insulating element by

  electrolytic oxidation of the tank water.

  According to other characteristics of the invention: - said tight protective sheath encloses the rod outside the insulating element and over part of the fitting length of the anode inside the insulating element, - said tight sheath protection is a sheath made from two materials, the first radially inner material having a temperature of

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  lower fusion than that of the second radially interior material, so as to ensure close contact between the rod and the first material by fusion of the first material and application of the first molten material against the anode by thermal reaction of the second material, s5 - l the first material is a fluoroplastic themmoplastic material, - the second material is a fluorotractable fluoropolymer, - the waterproof protective sheath is interrupted to allow the anode to be tightened and held in place by an insulating element and to prevent the anode from being expelled through the element insulator during the pressure rise of the tank, - ranod is a titanium or titanium anode coated externally with a metal oxide or any passivable material, - the waterproof protective sheath is applied to ranode before fitting the anode sheathed through the insulating element, the sheathed anode is mounted in a connection support before the anode is inserted up to a point osition of abutment of said connection support on insulating element, - the assembly comprising gainc ranode fitted in insulating element

  until a stop position is then threaded onto the thermowell.

  The invention will be better understood thanks to the description which follows given to

  by way of nonlimiting example with reference to the appended drawings in which: - Figure 1 schematically shows a partial view in diametral section of a device of the prior art, - Figure 2 shows schematically an enlarged view similar to Figure 1 illustrating the phenomenon of electrolytic oxidation, - FIG. 3 schematically represents an assembly of anodes for device according to the invention, - FIG. 4 schematically represents a view in diametrical section of a

device according to the invention.

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  Referring to Figures 1 and 2, a device according to the invention comprises a thermowell 1 generally metal, carrying an assembly with an element of

  insulating support 2 of an anode 3 on noble metal.

  The noble metal anode 3 crosses the insulating support element 2 and is connected to a connector 4 connecting the metal anode 3 to a conductive wire.

insulated electric 5.

  As a metallic material which can be used for anode 3, a material can be chosen from the group comprising ferritic stainless steels externally passivated by electrochemical passivation, austenitic stainless steels externally passivated by electrochemical passivation, raluminium, ferosilicon, platinum titanium, niobium platinized, platinum titanium and titanium coated with a coating layer (metal oxide. Preferably, an anode is used

  3 made of titanium or titanium coated externally with a metal oxide.

  In a manner known per se, the anode 3 is connected by the connector 4 and the insulated conductor 5 to a current generator of a type known per se, for example

  type described in document EP O 771 889 Ai.

  In FIG. 2, the end of the insulating support element 2 is attacked by electrolytic oxidation resulting from the passage of the cathodic protection current in the water of the tank and breaks up to replacement where the anode 3 opens out from the insulating support element 2 This disintegration releases particles 6 of small size which spread in the tank core for example by following the path of the

arrows 7.

  This disaggregation is important for insulating support elements

  constituted by a protective cap made of elastomeric material.

  With reference to FIG. 3, according to the invention, a waterproof protective sheath 8 is provided to be placed between the ranode 3 and the insulating element 2, so as to avoid

  degradation of the insulating element 2 by electrolytic oxidation of the tank core.

  The waterproof protective sheath 8 is advantageously a sheath composed of two materials. The first material forms a radially inner covering 9, while the second material forms a radially covering 10.

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  exterior applying the first coating 9 against the anode 3, so as to ensure sealing. Preferably, the first radially inner material has a lower melting temperature than that of the radially outer material: thus, when the sheath g is heated to an intermediate temperature between the melting points of the two materials, the first inner material melts and is applied against the anode 3 by the retraction of the second material. The sheath thus formed is sealed and encloses the rod 3 so as to prevent any slipping during

  subsequent fitting through insulating element 2.

  Advantageously, the first material constituting the coating 9 is a fluorinated thermoplastic material, while the second material is a polymer

  fluoroplastic, for example a polyttafluorethylene (PTFE).

  The waterproof protective sheath 8 is interrupted over a length I to allow the anode 3 to be clamped and held by the insulating support element 2 and to avoid the expulsion of the sheathed ranode through the insulating element 2 during the rise in

tank pressure.

  Advantageously, the order of operations is as follows: firstly prepare the rod 3 and apply to it the sheath composed of two materials which are heated to ensure proper application of the sheath 8 on the anode 3 providing a watertightness, even under pressure at the interface between the anode 3 and the coating 9; then mount the sheathed rod in the connector or support

  connection 4 with its insulated conductor 5.

  The assembly thus formed and shown in Figure 3 is then force fitted by the interior of the cap or insulating support element 2 until the

  support 4 for connection comes to abut against the edge of the insulating element.

  With reference to FIG. 4, the assembly produced by forming the sheath, assembly to the connector 4 and fitting of this assembly through the cap 2 is shown in a position prior to reinforcement of this assembly.

  on the thermowell tube 1 by pushing in the direction of the arrow 11.

  When this assembly is fully threaded on the thermowell 1, the position

  obtained is analogous to that shown with reference to FIG. 1.

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  The tank can then be filled with water and is likely to increase in pressure during water heating, since the seal will be automatically obtained by the external pressure exerted on the insulating cap 2. In fact, this increase in pressure produces a contraction of the cap 2 by tightening the tube 1 and a contraction of the tightening part extending over a length 1 corresponding to the interruption of the sealed sheath 8. This contraction around the rod 3 prevents

  any expulsion of the sheathed anode through the fitting hole.

  The invention thus makes it possible to avoid electrolytic oxidation of the resilient cap 2, while ensuring maintenance and sealing under pressure identical to

that of the prior art.

  The nature of the material or materials used to form the sheath 8 surrounding the metal anode 3 does not constitute an obstacle to the proper sealing of the device due to the preservation of a clamping length 1 ensuring direct contact of the

  anode metal and resilient cap material 2.

  The invention described with reference to a particular embodiment is in no way limited thereto, but on the contrary covers any modification of shape and any

  variant in the context and spirit of the invention.

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Claims (10)

  1. Cathodic protection device for a water heater tank, of the type comprising a thermowell (1) carrying at its end an insulating element (2) for suppolxnt of an anode (3) which is not consumable, characterized in that a tight protective sheath (8) is placed between the anode (3) and the insulating element (2) inside the tank, so as to avoid degradation of the insulating element (2) by oxidation   electrolytic treatment of the tank.   2. Device according to rm ndication 1, characterized in that said sealed sheath (8) of ensen ranode protection (3) externally with insulating element (2) and on a part of the length d (ranode fitting (3) to the interior of element insulator (2).   3. Device according to claim 1 or claim 2, characterized in that said sealed protective sheath (8) is a sheath made from two materials, the first radially inner material (9) having a melting temperature lower than that of the second radially outer material (10), so as to ensure close contact between the rod (3) and the first material (9) by melting the first material (9) and applying the first material (9) melted against   the anode by theirmortraction of the second material (10).   4. Device according to claim 3, characterized in that the first   material (9) is a fluorinated thermoplastic material.   5. Device according to claim 3 or claim 4, characterized in that   that the second material (10) is a heat-shrinkable fluoropolymer.   6. Device according to any one of the preceding claims,   characterized in that the watertight protective sheath (8) is interrupted to allow tightening and holding of the anode (3) by the insulating element (2) and to prevent the expulsion of the ranode (3) through the insulating element (2) during the pressure rise of the tank   7. Device according to any one of the preceding claims,   characterized in that the anode (3) is a titanium or coated titanium anode   externally of a metal oxide or any other passivable material. 7 2777573   8. Device according to any one of the preceding claims,   characterized in that the tight protective sheath (8) is applied to the anode (3)   before fitting of the anode (3) sheathed through the insulating element (2).   9. Device according to claim 8, characterized in that the sheathed anode (3) (8) is mounted in a support (4) for connection before fitting the anode to a stop position of said connection support ( 4) on the insulating element (2). 10. Device according to claim 9, characterized in that the assembly including the anode (3) sheathed (8) fitted in the insulating element (2) to a   stop position is then threaded onto the thermowell (1).