EP0952240B1 - Device for the cathodic protection of a water heater - 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

The invention relates to a cathodic protection device for water heater.

The document EP 0 771 889 A1 describes a cathodic protection device of water heaters. In this device, a thermowell is carried by a flange closing the tank of the water heater; this thermowell carries at its end a insulating support element for a non-consumable anode; said insulating element is through which said non-consumable anode so as to connect the non-consumable anode consumable to an electronic circuit thanks to an insulated conductor inside said audit glove finger.

This device is generally satisfactory, but presents the risk of degradation of the insulating support element by electrolytic oxidation of the water in the tank.

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

The subject of the invention is a cathodic protection device for water heater, of the type comprising a tubular thermowell carrying at its end a insulating support element for a non-consumable anode, characterized in that a waterproof 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.

• ladite gaine étanche de protection enserre l'anode extérieurement à l'élément isolant et sur une partie de la longueur d'emmanchement de l'anode à l'intérieur de l'élément isolant,
• ladite gaine étanche de protection est une gaine composée à partir de deux matériaux, le premier matériau radialement intérieur présentant une température de fusion inférieure à celle du deuxième matériau radialement intérieur,, de manière à assurer un contact étroit de l'anode et du premier matériau par fusion du premier matériau et application du premier matériau fondu contre l'anode par thermorétraction du deuxième matériau,
• le premier matériau est un matériau thermoplastique fluoré,
• le deuxième matériau est un polymère fluoré thermorétractable,
• la gaine étanche de protection est interrompue pour permettre un serrage et un maintien de l'anode par l'élément isolant et éviter l'expulsion de l'anode à travers l'élément isolant lors de la montée en pression de la cuve,
• l'anode est une anode en titane ou en titane revêtu extérieurement d'un oxyde métallique ou tout autre matériau passivable,
• la gaine étanche de protection est appliquée sur l'anode avant emmanchement de l'anode gainée à travers l'élément isolant,
• ranode gainée est montée dans un support de connexion avant emmanchement de l'anode jusqu'à une position de butée dudit support de connexion sur l'élément isolant,
• le montage comportant l'anode gainée emmanchée dans l'élément isolant jusqu'à une position de butée est ensuite enfilé sur le doigt de gant.

According to other characteristics of the invention:

• said sealed protective sheath encloses the anode outside the insulating element and over part of the fitting length of the anode inside the insulating element,
• said waterproof protective sheath is a sheath made from two materials, the first radially inner material having a melting temperature lower than that of the second radially inner material, so as to ensure close contact between the anode and the first material by melting the first material and applying the first molten material against the anode by heat shrinking the second material,
• the first material is a fluorinated thermoplastic material,
• the second material is a heat-shrinkable fluoropolymer,
• the sealed protective sheath is interrupted to allow the anode to be clamped and held by the insulating element and to prevent the anode from being expelled through the insulating element during the pressure rise in the tank,
• the anode is a titanium or titanium anode coated externally with a metal oxide or any other passivable material,
• the waterproof protective sheath is applied to the anode before fitting the sheathed anode through the insulating element,
• the sheathed rod is mounted in a connection support before fitting the anode to a stop position of said connection support on the insulating element,
• the assembly comprising the sheathed anode fitted into the insulating element to a stop position is then threaded onto the thermowell.

• la figure 1 représente schématiquement une vue partielle en section diamétrale d'un dispositif de l'art antérieur,
• la figure 2 représente schématiquement une vue agrandie analogue à la figure 1 illustrant le phénomène d'oxydation électrolytique,
• la figure 3 représente schématiquement un assemblage d'anodes pour dispositif selon l'invention,
• la figure 4 représente schématiquement une vue en section diamétrale d'un 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:

• FIG. 1 schematically represents a partial view in diametral section of a device of the prior art,
• FIG. 2 schematically represents an enlarged view analogous to FIG. 1 illustrating the phenomenon of electrolytic oxidation,
• FIG. 3 schematically represents an assembly of anodes for the device according to the invention,
• FIG. 4 schematically represents a view in diametral section of a device according to the invention.

Referring to Figures 1 and 2, a device according to the invention comprises a generally metallic thermowell 1, carrying an assembly with an element of insulating support 2 of an anode 3 of noble metal.

The noble metal anode 3 passes through 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 metallic material usable for anode 3, one can choose a material in the group comprising passivated ferritic stainless steels externally by electrochemical passivation, austenitic stainless steels externally passivated by electrochemical passivation, aluminum, ferrosilicon, platinum titanium, platinum niobium, platinum titanium and coated titanium a layer of metal oxide coating. Preferably, an anode is used 3 made of titanium or titanium coated on the outside 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 0 771 889 A1.

In FIG. 2, the end of the insulating support element 2 is attacked by electrolytic oxidation resulting from the passage of cathodic protection current in the tank water and disintegrates at the location where the anode 3 opens the insulating support element 2. This disintegration releases 6 small particles size which spread in the water of the tank for example by following the path of arrows 7.

This disaggregation is important for insulating support elements constituted by a protective cap made of elastomeric material.

Referring to Figure 3, according to the invention, a sealed protective sheath 8 is provided to be placed between the anode 3 and the insulating element 2, so as to avoid degradation of the insulating element 2 by electrolytic oxidation of the tank water.

The waterproof protective sheath 8 is advantageously a sheath composed of from two materials. The first material forms a coating 9 radially interior, while the second material forms a covering 10 radially exterior applying the first coating 9 against the anode 3, so as to ensure sealing.

Preferably, the first radially inner material has a melting temperature lower than that of the radially outer material: thus, during heating the sheath 8 to an intermediate temperature between the temperatures of fusion of the two materials, the first interior material melts and is applied against the anode 3 by the retraction of the second material. The sheath thus formed is waterproof and encloses the anode 3 so as to avoid any slipping during the subsequent fitting through the insulating element 2.

Advantageously, the first material constituting the coating 9 is a fluorinated thermoplastic material, while the second material is a polymer heat-shrinkable fluoride, for example polytetrafluoroethylene (PTFE).

The waterproof protective sheath 8 is interrupted over a length 1 for allow clamping and holding of the anode 3 by the insulating support element 2 and avoid the expulsion of the sheathed anode through the insulating element 2 during the rise in tank pressure.

Advantageously, the order of operations is as follows: we prepare everything first anode 3 and we apply the sheath made of two materials that we heats to ensure proper application of the sheath 8 on the anode 3 providing water tightness, even under pressure at the interface between anode 3 and the coating 9; then the sheathed anode is mounted in the connector or support of connection 4 with its insulated conductor 5.

The assembly thus formed and shown in Figure 3 is then fitted by force from the inside 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 carried out by forming the sheath, assembly to connector 4 and fitting of this assembly through the cap 2 is shown in a position prior to threading 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.

The tank can then be filled with water and is likely to increase in pressure when heating the water, since the seal will be automatically obtained by the external pressure exerted on the insulating cap 2. Indeed, this increase in pressure produces a contraction of the cap 2 by tightening the tube 1 and a contraction of the clamping part extending over a length 1 corresponding to the interruption of the sealed sheath 8. This contraction around the anode 3 prevents any expulsion of the sheathed anode through the fitting hole.

The invention thus makes it possible to avoid electrolytic oxidation of the cap. resilient 2, while ensuring pressure retention and tightness identical to that of the prior art.

The nature of the material or materials used to constitute the sheath 8 surrounding the metal anode 3 does not constitute an obstacle to the good 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 not there in no way limited, but on the contrary covers any modification of form and any variant embodiment in the context of the invention.

Claims (10)

1. A device for the cathodic protection of a water heater, of the type comprising a member like the finger of a glove (1) having at its end an insulating member (2) for supporting a non-consumable anode (3), characterised in that an impermeable protective sheath (8) is placed between the anode (3) and the insulating member (2) inside the tank so as to avoid degradation of the insulating member (2) by electrolytic oxidation of the water in the tank.
2. A device according to Claim 1, characterised in that the said impermeable protective sheath (8) encloses the anode (3) externally to the insulating member (2) and on a part of the insertion length of the anode (3) on the inside of the insulating member (2).
3. A device according to Claim 1 or Claim 2, characterised in that the said impermeable protective sheath (8) is a sheath composed of two materials, the first, radially inner, material (9) having a melting point lower than that of the second, radially outer, material (10) in such a way as to ensure close contact between the anode (3) and the first material (9) by melting of the first material (9) and application of the melted first material (9) against the anode by heat-shrinking of the second material (10).
4. A device according to Claim 3, characterised in that the first material (9) is a fluorine-containing thermoplastic material.
5. A device according to Claim 3 or Claim 4, characterised in that the second material (10) is a heat-shrinkable fluorine-containing polymer.
6. A device according to any one of the preceding claims, characterised in that the protective sheath (8) is truncated to allow the anode (3) to be gripped and held by the insulating member (2) and to avoid expulsion of the anode (3) via the insulating member (2) when the pressure builds up in the tank.
7. A device according to any one of the preceding claims, characterised in that the anode (3) is an anode made of titanium or of titanium coated on the outside with a metal oxide or any other passivatable material.
8. A device according to any one of the preceding claims, characterised in that the impermeable protective sheath (8) is applied to the anode (3) prior to insertion of the sheathed anode (3) through the insulating member (2).
9. A device according to Claim 8, characterised in that the sheathed (8) anode (3) is mounted in a connecting support (4) prior to insertion of the anode up to a stop position of the said connecting support (4) on the insulating member (2).
10. A device according to Claim 9, characterised in that the mounting comprising the sheathed (8) anode (3) inserted in the insulating member (2) up to a stop position is then threaded on to the glove-finger (1).

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