EP1784613B1 - Intervention method on a heat exchanger - Google Patents

Abstract

A heat exchanger includes two mutually isolated fluid circuits in close thermal contact, a first fluid circuit, or bundle ( 3 ), consisting of a helical winding of two walls and the second circuit consisting of a chamber containing the bundle ( 3 ), each circuit including its own fluid input and output elements. The heat exchanger is characterized in that the bundle is elastically deformable under the effect of excess pressure or low pressure.

Description

The present invention relates to exchangers and in particular exchangers intended to ensure a heat exchange between two fluids.

On a general level, it is known that the heat exchangers using fluids consist of two circuits isolated from each other but which are in the highest possible thermal contact, and which are respectively traversed by the two fluids.

It is also known that the maintenance of heat exchangers, and in particular their cleaning, is generally a long and difficult operation to perform efficiently, or even sometimes impossible. Finally, it is known that such cleaning sometimes consists of eliminating, for example, the scale that has settled in the exchanger throughout the use of the latter.

The so-called plates and seals type exchangers made from more sheets of sheet metal can be dismantled plate by plate so that it is thus possible to access their circuits, even if this is an operation. long to implement. However, these exchangers, because of their very design, are therefore an expensive operation.

Furthermore, brazed plate type exchangers are not removable and therefore their circuits are also difficult to clean.

This is why we turned to spiral exchangers which consist of two sheets of sheet metal which are rolled up and are kept apart from each other by pins (see in particular FR-A-2 0.96 719 or FR-A-2,811,068 ). After winding, the edges of sheet metal are welded so as to create two independent fluid circuits, namely a first circuit between the two sheets wound and welded sheet and a second circuit between the different turns of the winding. For reasons relating to the method of construction, the user does not have access to the space between the two rolled sheets as well as that between the various turns of the winding, so that it is in the impossibility of performing an effective mechanical cleaning of this exchanger and that one must then be content with cleaning chemical type, which is often insufficient for some applications.

However these exchangers, by their constitution, require for a good efficient maintenance that we can access not only the windings themselves but also their interspires space. But this one is more reduced which makes even more problematic their cleaning exchangers especially when it comes to removing deposits such as the scale of these

However, many applications that would be open to this type of exchangers, such as uses in the food, medical, pharmaceutical, fine chemicals, or electronics in particular, involve periodic cleanings. 'a great efficiency.

The present invention aims to provide means for a user to perform such cleaning, and this simply and quickly.

The heat exchanger comprises two fluid circuits insulated from each other in intimate heat exchange contact, a first fluid circuit, or beam, consisting of a spiral winding of two walls and the second circuit consisting of by an enclosure containing the beam, each circuit having its own fluid inlet and outlet means. The beam is elastically deformable under the effect of an overpressure or a depression.

The enclosure will preferably be tubular and, when the internal pressure of the beam is equal to its external pressure, its outer diameter will be slightly less than or equal to the internal diameter of the enclosure. The difference in diameter between the inner face of the enclosure and the outer face of the beam will be less than 6% of the diameter of the latter.

The tubular casing may comprise two bottoms, at least one of which may be removable, these bottoms being traversed respectively by the means of entry and exit of the fluids, and means capable of sealing between the bottoms and the input and output means of the beam fluid. These inlet and outlet means may consist respectively of two longitudinal tubes and the means capable of sealing between the tubes and the bottoms may consist of O-rings or a gland.

• soumettre, avant son retrait, le faisceau à une dépression et/ou à un refroidissement relatif par rapport à son enveloppe, de façon à le faire se contracter,
• une fois le faisceau extrait de son enveloppe interrompre la dépression,
• procéder à l'intervention sur le faisceau,
• soumettre de nouveau le faisceau à une dépression et/ou à un refroidissement relatif par rapport à son enveloppe, afin de le faire se contracter avant sa mise en place dans l'enveloppe,
• remettre le faisceau à la pression et/ou à la température ambiante une fois qu'il a été remis en place dans son enveloppe.

The subject of the present invention is an intervention method, such as, for example, a cleaning, on a bundle, of a spiral type exchanger comprising two fluid circuits isolated from each other in intimate heat exchange contact, a first fluid circuit, or beam, consisting of a spiral winding of two walls, or a beam, and the second circuit consisting of a volume delimited by an envelope containing the beam, each circuit comprising its own input and output means; fluid outlet, characterized in that it comprises the steps of:

• subject, before removal, the beam to a depression and / or a relative cooling with respect to its envelope, so as to make it contract,
• once the beam extracted from its envelope interrupt the depression,
• proceed with the intervention on the beam,
• resubmitting the beam to a depression and / or a relative cooling relative to its envelope, in order to make it contract before it is placed in the envelope,
• put the beam back to the pressure and / or ambient temperature once it has been put back in its envelope.

The beam can be made so that it is deformable under the effect of a pressure difference between the beam and the enclosure of an overpressure or a vacuum and give it an external diameter smaller than the internal diameter of the beam. envelope and apply to the beam overpressures and / or periodic depressions to change its outer diameter and break the fragile elements that can adhere to the walls (scale) that are deposited on him.

The method may include a preliminary step of disconnecting the beam from its circuit.

According to the invention, it is also possible to favor the intervention operation by subjecting the beam, once it has been extracted from its envelope, and before the intervention, to an overpressure and / or a relative heating with respect to the envelope, which will have the effect of spreading the turns of the winding from each other.

In order to avoid subjecting the beam to too high a pressure having the consequences of deforming the metal constituting the winding beyond its elastic limit, a limiter will be placed around the beam whose internal diameter will be equal to the maximum diameter that is wish not to exceed. This limiter may consist of a ring or a sleeve.

• La figure 1 est une vue schématique en coupe transversale d'un échangeur suivant l'invention.
• La figure 2 est une vue en perspective d'un faisceau constituant l'échangeur représenté sur la figure 1.
• La figure 3 est une vue en perspective de l'enveloppe renfermant le faisceau représenté sur la figure 2.
• Les figures 4 et 5 sont des vues en perspective d'un faisceau d'un échangeur suivant l'invention respectivement équipé d'un manchon et de bagues de limitation de son diamètre extérieur.

An embodiment of the present invention will be described hereinafter by way of nonlimiting example, with reference to the appended drawing in which:

• The figure 1 is a schematic cross-sectional view of an exchanger according to the invention.
• The figure 2 is a perspective view of a beam constituting the exchanger represented on the figure 1 .
• The figure 3 is a perspective view of the envelope enclosing the beam represented on the figure 2 .
• The Figures 4 and 5 are perspective views of a beam of an exchanger according to the invention respectively equipped with a sleeve and rings for limiting its outside diameter.

We have shown on Figures 1 to 3 an exchanger which consists essentially of an envelope 1 which is intended to receive a beam 3.

The beam 3 consists of a spiral winding of two sheet sheets 5 which are spaced from each other and welded to provide a fluid circuit therebetween. The spacing of these two sheets of sheet metal 5 is ensured by a series of "pins" 7 which are created and distributed over the surface of the sheet before folding it. These pins 7, once the winding performed, also ensure a regular and controlled spacing between the turns. The space between the two sheets of folded sheet comprises a supply duct 9 and a discharge duct 11.

The envelope 1 consists of a cylindrical tube 13 whose inner diameter corresponds to the outer diameter of the beam 3, so as to receive it. The envelope 1, as represented on the figure 3 has a fluid supply duct 15 and a discharge duct 17. The tube 13 is closed on the one hand by a bottom 19 which is fixed and which is traversed by the exhaust duct 11 of the bundle 3 with interposition of an O-ring seal 23 and on the other hand, at its other end, by a removable base 25 and which, for this purpose, is held by clamping flanges 27 which bear on a flange 29 of the tube 13. An O-ring 31 seals between the cover 25 and the supply duct 9 of the bundle 3.

Thus, by a simple disassembly of the removable bottom 25 one has access to the beam 3, after having disconnected it from the supply pipes connected to its lines 9 and 11, or by having an outlet 11 of sufficient length.

It is known that this type of exchanger requires a minimum clearance between the beam 3 and the inner face of the tube in which it is disposed. However, in certain heat exchangers, particularly stainless steel heat exchangers, which are intended for applications requiring particular attention, particularly in the field of pharmacy or in the food industry, it is necessary that the bundle be removed from its envelope without, during this operation, forming scratches on the inner wall of the tube, such scratches constituting in particular nesting sites for bacteria.

To solve this problem, it is made sure that the beam 3 is deformable at its diameter under the effect of a constraint. To make the deformable beam thus we will play on the thickness and the nature of the steel used.

On an assembled exchanger which it is desired to disassemble, the retraction of the beam 3 will be brought about by connecting one of the inputs 9 or 11 thereof to a vacuum pump, after having closed the other input, in order to create a vacuum part. It will then be possible to dismantle the beam without the risk of scratching the inner face of the casing 1. Once the beam 3 has been dismantled, the vacuum will be eliminated so that it expands and resumes its initial natural diameter, then the procedure will be carried out. (including mechanical cleaning) on it.

The intervention can be made easier and more effective if the beam 3 is expanded beyond its nominal diameter by applying this time an overpressure. Care should be taken during this operation not to deform beyond the elastic limit of the material used, so that it can resume its nominal diameter from the end of cleaning and the interruption of the overpressure.

In order to limit the deformation to a maximum controlled value of the beam 3, it will be possible, as shown in FIG. figure 4 surround it, before applying the overpressure, a ring or a sleeve 20 whose inner diameter is equal to the maximum possible diameter that can take the beam 3 without undergoing deformation beyond its elastic limit. It is also possible to use rings 20 as shown in FIG. figure 5 .

Once the intervention on the finished beam is evacuated in it so that it can be easily put into place in the envelope 1, then the vacuum pump is disconnected so that the beam resumes its dimensions and nominal form.

It is also possible according to the invention to use a relative variation in temperature to contract or expand the beam. Thus, before dismounting the bundle of its envelope, it will be possible to circulate in the bundle a strongly cooled liquid, in particular close to or even below 0 ° C., in order to make it contract, and it will be possible, at the same time, to subject the envelope to a temperature above room temperature to expand.

Of course, according to the invention can be made to act simultaneously on the beam is depression and cooling, or the pressure and heating.

For some applications it is possible to give the beam 3 a diameter smaller than the internal diameter of the casing 1. Such an arrangement is particularly advantageous in that it allows for an automatic or almost automatic elimination of fragile deposits (eg limestones ) that occur on the walls of the beam. It suffices to subject the beam, for example during its operation, to an overpressure (or depression) of the fluid that passes through it to deform and burst the tartar plates that cover it. These operations can even be performed automatically.

Claims (5)

1. An intervention process, such as cleaning in particular, on a heat exchanger bundle of spiral type comprising two fluid circuits insulated from one another in close thermal exchange contact, a first fluid circuit being constituted by a spiral winding of two walls, or bundle, and the second circuit being constituted by a volume delimited by an envelope containing the bundle, each circuit comprising its own fluid input and output means, characterised in that it comprises steps consisting of:

   - subjecting the bundle to low pressure, and/or relative cooling relative to its envelope so as to have it contract prior to shrinkage,

   - returning the bundle to pressure and/or ambient temperature once it has been extracted from its envelope so as to have it resume its initial dimensions,

   - proceeding with intervention on the bundle,

   - again subjecting the bundle to low pressure and/or relative cooling relative to its envelope, so as to have it contract prior to being placed in the envelope,

   - returning the bundle to pressure and/or to ambient temperature once it has been replaced in its envelope.
2. The process as claimed in Claim 8, characterised in that it comprises a preliminary step consisting of disconnecting the bundle from its circuit.
3. The process as claimed in any one of Claims 8 or 9, characterised in that it comprises an intermediate step before the intervention step on the bundle consisting of subjecting the bundle to excess pressure and/or to an increase in temperature relative to the ambient temperature so as to dilate it.
4. The process as claimed in Claim 10, characterised in that before said excess pressure and/or said increase in temperature is applied to the bundle (3), a device for limiting its diameter is placed around it.
5. The process as claimed in any one of Claims 8 to 11, characterised in that it consists of embodying the bundle (3) such that it is deformable under the effect of a difference in pressure between the bundle and the chamber and of giving it an external diameter less than the internal diameter of the envelope (1) and applying periodic excess pressure and/or low pressure to the bundle so as to modify its external diameter.

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