ES2415908T3 - Device for reducing fouling inside a tube - Google Patents

Abstract

Inlay reducing device inside a tube (1) crossed by a fluid (F), of the type comprising at least one turbulence generating element, said device being constituted by a mobile rotating element (2) connected to a fixed element by way bearing (3), suitable for making a solid connection with the upstream end of the tube (1), said mobile rotary element (2) comprising: - an upstream portion (4) as a journal comprising a mechanical connection (5) with the bearing element as a bearing (3) and allowing the free rotation of the mobile element (2) about itself around the axis of the tube (1), - a downstream part (6) in the form of a helix consisting of several turns and formed in order to be driven in rotation by the circulation of the fluid (F) in the tube (1), in which - the upstream (4) and downstream (6) parts of the mobile rotating element (2) are connected to each other by means of a flexible longilín fitting eo deformable along its entire length (7), and characterized in that - the downstream part (6) contains at least one spiral part whose passage is inverted (8) with respect to the other turns

Description

Device for reducing fouling inside a tube

The present invention relates to a device for reducing the fouling inside a tube in which a fluid circulates, of the type comprising a turbulence generating rotating element, in particular in the tubes that constitute the heat exchangers.

The present invention can specifically find its application in industries, in particular the petroleum or petrochemical industry, which implement tubular heat exchangers in which fluids circulating that can be at high temperature and / or be corrosive.

Approximately twenty years ago, devices installed in a mobile manner in rotation inside heat exchanger tubes have been known for the purpose of preventing any incrustation, for example due to suspended impurities, deposits of mineral salts dissolved in the fluid, to coke in formation in a thermal cracking process or even to sulfur species soluble in hydrocarbons. These impurities, coke or other deposits, have a tendency, in particular under certain conditions of temperatures and pressures, to deposit on the inner walls of the ducts that receive the fluid. This may cause restrictions on flow rates that are detrimental to the proper functioning of the downstream procedure and / or hot spots on the inner surface of the tube. These restrictions and / or hot spots may lead to deterioration of the metal structure of said tube and thus cause leaks of products that may be dangerous for the operating company and / or the material.

Another consequence of the formation of these deposits on the inner walls of the exchanger tubes may be the decrease over time of the quality of thermal transfers between the fluids circulating inside and outside the tubes, decrease likely to eventually become detrimental to the energy efficiency of the treatment or manufacturing unit considered.

They have in common a mobile element, generally in the form of a propeller consisting of several turns that all have the same passage orientation, fixed at the end upstream of the tube such that the mobile element can rotate freely in the tube under the effect of The circulation of the fluid. In numerous devices described in the prior art, the dimensions of the movable element and the interior of the tube are such that the movable element does not continuously scratch the inner wall of the tube, in order to avoid any dire consequences in the useful life of the tube. metal structure of said tube and / or the mobile element.

The reduction of the incrustation of the interior of the tubes is mainly due to the increase in the turbulence of the fluid that diminishes, even prevents, the formation of hot spots and the formation of deposits. Without wishing to be limited by this theory, it is possible that this reduction in scale is obtained thanks to a thermal homogenization effect (breakage of the insulating thermal boundary layer) and an important shear effect near the wall. This may allow to reduce, even prevent, the formation of deposit (s), and / or detach, totally or partially, any deposits weakly attached to this same wall before they begin to increase in size and therefore become more resistant to their plucking

The applicant further describes in the application EP 0 369 851 a moving element comprising, in all its cross sections, at least one living edge specifically shaped in order to scratch the inner surface of the tube.

In addition to the latest improvements provided to the device by the applicant, as described in document FR 2 890 162 which describes a device according to the preamble of claim 1, and more precisely the use of a flexible longilinear fitting for connecting the mobile element to the fixed upstream element integral with the tube, the applicant has continued his investigations to extend the duration of operation of said inlay reducing devices inside the tubes and specifically of the heat exchanger tubes used in the oil refineries . In fact, the longer this duration of operation is extended, the less necessary it will be to replace said devices after a possible breakage at the level of the fixed upstream element, that is, that the operating company will thus prevent the opening of the heat exchanger. heat considered, will also avoid in fact the risk of a complete shutdown of the installation in which said exchanger is implemented, and therefore finally, will avoid risks to people, expenses and a loss of benefits.

In addition, when the speed of the fluid inside the tube exceeds a limit value, for example, greater than 1.5 m / s, the speed of rotation of the moving element can become very important (greater than 1500 rpm). In this case, the use of such a mobile element is not recommended since wear phenomena at the level of the fixed upstream element can become very important and result in premature rupture of the mobile element junction at the level of this upstream part fixed. This breakage may lead to insufficient operating time for most operating companies, for example, limited to 4 years.

It may be, in particular, the application of this fluid velocity / rotation speed of the moving element, which makes the use of the applicant's devices problematic for fluid velocities greater than 1.5 m / s, speeds nonetheless found in numerous heat exchangers.

Thus, the present invention aims at a device with the aim of completely or partially remedying the aforementioned problems, in particular, presenting greater reliability and / or a greater range of use, while still being easy to manufacture, Economical and / or easy to fix.

According to a first aspect, the object of the invention is a device for reducing the embedding of the inside of a tube crossed by a fluid according to claim 1, of the type comprising at least one turbulence generating element, said device being constituted by a rotating element mobile connected to a fixed element as a bearing, suitable to become rigidly integral with the end upstream of the tube, said mobile rotating element comprising, even being constituted by:

-

 an upstream part as a journal comprising a mechanical connection with the fixed element as a bearing and allowing the free rotation of the movable element on itself about the axis of the tube,

-

 a downstream part in the form of a propeller consisting of several turns and shaped in order to be operated in rotation by the circulation of the fluid in the tube, in which:

-

 the upstream and downstream parts of the mobile rotary element are connected to each other by a longilinear flexible hose deformable along its entire length, and characterized in that

-

 The downstream part contains at least one spiral part whose passage is reversed with respect to the other turns.

Thus, the invention relates to a device that has a reduction in the speed of rotation of the mobile part, associated with a joint system, for example as described in document FR 2 890 162, which comprises a fitting flexible that connects the mobile element journal, located at the level of the fixed upstream element, to the generally helical part, formed by several turns, which extends along a part or in the entire length of the tube and actuated in rotation by the circulation of the fluid circulating in said tube.

The investigations carried out by the applicant show that the known device may have insufficient resistance to the level of the joint of the mobile element in the fixed upstream element. These studies have also shown that a reduction in the rotational speed of the moving element can minimize wear phenomena at the level of said fixed upstream element, and in particular in places in friction contact with live edges of a bearing or a wear washer, if present.

In addition, a reduction in the speed of rotation of the mobile element can allow a use for fluid velocities greater than 1.5 m / s while remaining in fields of rotation speeds limited to 1500 rpm, a field that allows limiting the phenomena of wear

The object of the invention is also a heat exchanger comprising a plurality of tubes crossed by a fluid, which comprises at least one inlay reducing device according to the invention installed inside at least one of these tubes, in particular fixed in the upstream end of at least one of these tubes.

The flexible fitting, used in the present invention, for example, that described in FR 2 890 162, can be of any material provided it has sufficient chemical and mechanical resistance under the operating conditions of the device. The flexible fitting is preferably made of metal, in particular of steel, and more particularly of stainless steel.

The flexible fitting can be, for example, a cable formed by twisted or twisted filaments preferably comprising a number of filaments between 1 and 100, and more preferably between 1 and 50.

For a mobile element of 6 meters, a flexible fitting with a length between 1 cm and 5 cm, and preferably between 2 and 4 cm, may be preferred. Its diameter can range from 2 to 10 mm and preferably from 4 to 8 mm.

This flexible fitting is fixed between the downstream end of the journal and the upstream end of the propelled rotating part. Fixing on these two pieces can be carried out according to known techniques, for example, by welding, crimping, screwing or even bonding.

The rotating downstream propeller shaped portion may in principle have any appropriate asymmetric shape that allows the fluid circulating through the tube to rotate it about the axis of said tube. The most efficient way, which creates maximum turbulence for a minimum head loss, is the propeller that is used in this way in almost all the devices of the type described in the introduction and is also preferred for

The present invention.

This propeller must have an outside diameter smaller than the inside diameter of the tube so as not to continuously scrape the inner wall of the tube. However, the outside diameter of the propeller may be sufficiently close to the inside diameter of the tube to create, in addition to turbulence, sufficient shear forces near the surface of the tube, for example, to release deposits or particles loosely attached to the wall. . Satisfactory turbulence and shear effects are generally obtained for systems in which the ratio between the outer diameter of the propeller and the inner diameter of the tube ranges from 0.5 to 0.9, preferably from 0.6 to 0.8.

Reasons between the above intervals have proved sufficient to avoid a friction contact that is too important, even to prevent a friction contact, between the tube and the propeller almost the entire length of the latter, with the exception of the first turn or turns. of the propeller. As indicated above, the applicant has in fact found that, for the reasons between the outer diameter of the propeller and the inner diameter of the tube within the ranges indicated above, at least the first turn of the propeller, and sometimes also The next two or three turns could show friction wear marks. Although this phenomenon is attenuated for flexible fitting connection systems such as those described in the present application, it may nevertheless persist under certain operating conditions of the device according to the invention. This problem can be solved totally or partially thanks to the use of a propeller in which the outer diameter of the first turn, or of the first turns, is smaller than the outside diameter of the other turns of the propeller. The first loop is the one closest to the union.

The number of "first" turns affected by this decrease in diameter does not generally exceed 1 to 5% of all the turns of the helix. For these turns, the ratio between its outer diameter and the inner diameter of the tube may be between 0.1 and 0.6, preferably between 0.2 and 0.6. When several turns are affected, their outer diameter preferably increases progressively from upstream to downstream.

The fixed bearing-like element, intended to accommodate and support the journal, can have a wide variety of shapes, insofar as it fulfills two functions that are on the one hand, guaranteeing the robustness of the joint at the end of the tube. exchanger, and on the other hand, minimize restrictions on fluid circulation. It preferably has the shape of a stirrup comprising a central part perforated with a hole intended to accommodate the journal of the mobile element, and two arms, symmetrical with each other, which have a shape that allows them to be fixed at the end upstream of the tube. This stirrup shape of the bearing-like part is known and described, for example, in applications EP 0 233 092, EP 0 282 406 and EP 0 369 851 of the applicant. It can be, for example, a stirrup whose ends form a hollow cylinder intended to tighten the end of the tube, as described in EP 0 233 092, or, preferably, a stirrup of a rigid but elastic material, in which the ends of the two arms can be pressurized at the end upstream of the tube to rest elastically against the inner wall thereof. However, the invention also encompasses any other system that allows a rigidly integral bearing part to be made with the upstream end of the tube.

In a particular embodiment of the device according to the invention, the journal is retained in the bore of the bearing thanks to a first stop provided at its upstream end and integral with it. A second, tubular, stop can be provided in the central part of the stirrup in prolongation of the hole intended to accommodate the journal of the movable element. This second stop, integral with the bearing, can have a function of securing the journal on the axis of rotation of the mobile element and is preferably relatively long. When the mobile element is driven in rotation by the fluid flowing through the tube, the first buttress integral with the journal can come into friction contact with the second, tubular buttress, integral with the fixed element.

In a preferred embodiment of the device of the present invention, one or more wear washers are provided between the first stop and the second stop. This wear washer is free, that is, it is not integral with either the movable element or the fixed element. It is preferably constituted by a different material or of different hardness, or even anti-friction type of very small friction coefficient, generally softer than the materials of the first and second stops. Examples of such materials can be cited, steels, specifically heat treated steels, copper alloys, ceramics, as well as graphites.

Known wear washers, for example, of EP 0 233 092, EP 2 637 659 and EP 0 282 406, have flat or complementary friction surfaces to the friction surface of the stop. Preferably, it will be sought to reduce as much as possible the surfaces in contact by adopting specific shapes in the wear washers and / or in the tubular stops.

In another preferred mode of the invention, the metal journal is replaced by an extension of the flexible fitting whose downstream end is made integral with the stop. Obviously, all possible configurations of the wear washer and stopper apply to this particular application of the present invention.

The mobile rotating element and more particularly its propeller-shaped downstream part may be constituted by several turns and shaped such that said downstream part is rotated by the circulation of the fluid in the tube. The speed of rotation of the mobile element depends essentially on the flow of fluid flowing through the tube, said flow being able to vary, for example in the heat exchanger tubes, from 0.5 m / s to 3 m / s, for a pressure that can evolve between 5 and 30 bars.

The arrangement of the turns and more exactly the direction of the passage of the most numerous turns that present an identical step is what determines, at least in part, the direction of rotation of the moving element. This direction of rotation can be, depending on the assembly of the turns that constitute the downstream part of the moving element in the direction (right-hand side) or inverse (left-hand side) with respect to the direction of rotation of the hands of a clock, without disturb the effectiveness of the inlay reducing device inside a tube.

In the present description, the part of turns that have an inverted step with respect to that of the other turns is represented by a percentage of the length of the moving element.

Thus, in the present description, the expression "X (for example 0.5%) of inverted turns" means, for a mobile element of a total length of Y (for example 6 m) constituted by a winding of turns all with a pitch of Z cm (for example 3 cm), an inverted pitch length of Y x X cm (in this case 3 cm), that is a number of turns of (Y x X) / Z (in the case exemplified: 1 full turn).

The minimum fluid velocity that passes through the tube, in order to set in motion a 6 m long device that has an inverted passage part, will be more important the more important the% of inverted turns is.

This minimum speed will always be higher than that of a conventional device in which the downstream part of the mobile element is constituted by a propeller comprising only turns that have a passage in the same direction. This minimum speed can be around 1.5 to 2 m / s while in general it is 0.5 m / s for a conventional device.

The reduction of the rotation speed with respect to a conventional device varies according to the speed of the fluid and the amount of turns of inverted passage. The slower the fluid velocity associated with a significant number of turns that have an inverted passage with respect to the other turns, the more important is the slowing down of the rotation speed of the moving element. In this way, the intervals of reduction of the rotational speed of the moving element can range from 95% (fluid velocity of 2.0 m / s) to 54% (fluid velocity of 3.0 m / s) for the 15% length of the mobile element consisting of turns that have an inverted passage. The reduction of the rotational speed of the mobile element can vary from 56% for a fluid velocity of 2.0 m / s to 16% for a fluid velocity of 3.0 m / s for 0.5% of turns Inverse step. Other data on reducing the speed of rotation of the moving element are indicated in the following example.

If the objective of maximum rotation speed of the mobile element is 1500 rpm to minimize the wear of the joint in the fixed upstream element, the use of turns that have an inverted passage in 15% of the total length of the mobile element of a total length of 6 m can allow the device object of the present invention to be used with a fluid velocity of 2.85 m / s, while this speed is limited to 1.5 m / s for a conventional device. This rotation speed of 1500 rpm can also be achieved with 0.5% of inverted turns for a fluid velocity of 2.25 m / s (see Figure 1).

The same is true for an objective speed of rotation of the mobile element of 1000 rpm obtained with fluid velocities that vary from 2.05 m / s to 2.55 m / s, with turns lengths respectively that have inverted steps of 0.5% at 15% The permissible fluid velocity with a conventional device for a rotation speed of 1000 rpm is 1.45 m / s, without the possibility of going further without increasing the rotation speed of the moving element.

The use of different amounts of inverted turns in the downstream part of the mobile element can therefore reduce the speed of rotation of the mobile element that can go up to 95% of its initial speed, or use at iso speed (1500 revolutions or 1000 rpm) said moving element for fluid velocities in the exchanger tube which may be more than 50% to 75% higher than the maximum permissible fluid velocity with a conventional device. This improvement allows the possibility of installing devices object of the invention in exchangers or the flow rate of the fluid in the tubes varies from 1.5 m / s to 3 m / s.

As a counterpart to this improvement in the use of the mobile element comprising inverted turns, the total load loss (that is, the sum of the pressure losses due to the fixed upstream element as described in document FR 2 890 162, to the length of the tube and to the device object of the present invention) may be more important than that of a tube of the same length equipped with a conventional device. Thus, the increase in head loss for a rotational speed of the mobile element set at 1500 rpm can vary from 84% to 220% when the% of inverted turns varies from 0.5 to 15%, respectively. from 500 to 920 mbar and from 500 to 1600 mbar.

For a rotation speed of 1000 rpm, the total head loss can vary from 93% to 206%, from 440 to 850 mbar and from 440 to 1380 mbar when the% of inverted turns varies from 0.5% to fifteen%.

Depending on the parameters of the fluid flowing through the heat exchanger tubes and specifically their flow rate, solutions that integrate as small amounts of inverted turns as small as possible can be preferably chosen, for example, to minimize head losses. Thus, for a 6 m moving element of which only 0.5% of its total length is reversed, a rotation speed of 1500 rpm can be expected for a fluid velocity of 2.25 m / s, that is to say a speed superior in 32% with respect to a conventional device (1.5 m / s) for a total load loss corresponding to 950 mbar, that is to say, superior in 40% to the one registered with respect to a device conventional with the same fluid velocity.

It is interesting to note that this loss of load recorded for the device object of the invention is of the same order of magnitude as that obtained with another device to reduce the fouling inside a tube and available in the art, as described in the FR 2 479 964.

Brief description of the figures

-

 Figure 1 represents a device according to the invention,

-

 Figure 2 is a diagram representing the rotation speed as a function of the fluid velocity for different% of turns in length with an inverted passage,

-

 Figure 3 is a diagram representing the% reduction of the rotation speed of the device for different% of turns in length with an inverted passage, and

-

 Figure 4 represents the loss of load in a tube as a function of speed for different% of turns in length with an inverted passage.

The present invention is illustrated below with reference to the following figure 1, which is a longitudinal sectional view of a tube with a device for reducing the embedding inside a tube, object of the present invention, fixed in the upstream end of said tube.

In this figure 1, the device consists of a movable part 2 and a fixed part 3, fixed at the level of the upstream end of a tube 1. In the whole of the present application, the terms "upstream" and "waters below ”are defined with respect to the direction of circulation of the fluid flowing through the tube 1 represented by the arrow F.

The fixed part 3 of the device has the form of a stirrup constituted by a plate 9 perforated with a central hole, and by two arms 10, in principle symmetrical with respect to the axis of the tube, the ends of which rest against the inner wall of the tube. The fixed part further comprises a tubular stop 11 integral with the plate 9. The channel of this stop 11 is aligned with the hole of the plate and forms with it a fairly long single channel which mainly serves to keep the journal 4 on the axis of rotation of the mobile element 2.

In the fixed part 3, the mobile element 2 is mounted, free in rotation. This mobile element is constituted, starting from the upstream end thereof, by a stop 5, a journal 4 integral with the stop 5, a flexible fitting 7 of stainless steel cable, and finally by the helical part 6 actuated in rotation, in the direction of the arrow F, by the circulation of the fluid.

It should be noted that all turns of the propeller do not have the same size but that the first two have an outside diameter smaller than the following turns. On the other hand, a wear washer 12 is provided between the stop 5 integral with the journal and the stop 11 integral with the stirrup.

Obviously, all possible configurations of the washer 11 and the stop 4 described above can be applied to this particular application of the present invention.

The downstream element 6 of the movable element 2 is constituted by several turns with an identical passage. Only the turn 8 in Figure 1 has, according to the invention, an inverted step to that of the other turns.

The assembly of this loop (or of these turns) can be carried out by means of a simple inverted winding of the metallic wire, for example, of stainless steel, which constitutes the helix-shaped downstream element of the mobile element, or it can be attached to the downstream element by any means known in the art such as welding, crimping, screwing, gluing, etc.

The only limitation to the installation of this or these inverted turns is that its longitudinal axis is aligned with the longitudinal axis of most of the turns that constitute the downstream element.

The invention is illustrated below with the aid of the following exemplary embodiment.

Example

To test the effectiveness of the device according to the invention, the applicant has used a model that implements cold water that circulates in a 6 m long plexiglass tube and allows measurements of water flow, of head losses to different lengths as well as the speed of rotation of the mobile element of the device object of the present invention.

The parameters of the tests are as follows:

-

 inner diameter of the tube: 2.00 cm,

-

 water velocity in the tube that can vary from 0.5 to 3.0 m / s,

-

 fluid pressure inside the tube: 16 bar,

-

 outer diameter of the mobile element of the device: 1.96 cm,

-

 moving element length: 6.0m,

-

 diameter of the stainless steel wire that constitutes the mobile element: 0.18 cm,

-

 composition of the alloy that constitutes the wire: 64.9% nickel, 8.75% molybdenum and 26.35% iron,

-

 turn angle: 55 °,

-

turn of the turns: 3.0 cm,

-

direction of the turn of the turns: right,

-

 Flexible fitting length: 4.0 cm,

-

 flexible fitting diameter: 0.5 cm,

-

 number of metallic filaments wound in the direction of rotation of the mobile element constituting the flexible fitting: 50,

The upstream part of the mobile element is constituted by a journal with a length of 8.0 cm and a diameter of 0.2 cm, according to the present invention, and is connected by crimping to the flexible fitting.

The fixed upstream element is also constituted according to FR 2 890 162.

The rotational speeds of the moving element have been recorded as a function of the speed of the fluid measured in the tube (Figure 2).

Figure 2 represents the rotation speed (rpm) and the fluid speed (m / s) in abscissa. These data have been measured for mobile elements with a length of 6 m that have respectively (reference 1 in figure 2) 0% of inverted turns, (2) 0.5% of inverted turns, (3 ) 2.0%, (4) 4.0%,

(5) 10%, (6) 12.2%, (7) 13.5% and finally (8) 15.0% of inverted turns.

Figure 2 shows that the more the number of turns that have an inverted step increases, the more important is the reduction of the rotational speed of the moving element. This reduction also increases when the fluid velocity decreases.

The following tables 1, 2 and 3 gather the permissible fluid velocities respectively at 1500 rpm, 1000 rpm and 500 rpm, the permissible fluid velocities according to the% of inverted step.

It is recalled that the speed of 1500 rpm frequently represents the limit for a wear rate considered admissible of the fixed upstream element with a moving element that only comprises turns with one step in one direction, and that this speed of 1500 rpm is obtained only for a fluid velocity equal to 1.5 m / s.

Table 1: Rotational speed of the 1500 rpm moving element

Speed of the fluid in the tube in m / s

% length of turns that have an inverted step

1.50

0.0

2.25

0.5

2.33

2.0

2.39

4.0

2.44

10.0

2.55

12.2

2.64

13.5

2.85

15.0

Table 2: Rotation speed of the 1000 rpm moving element

Speed of the fluid in the tube in m / s

% length of turns that have an inverted step

1.45

0.0

2.05

0.5

2.10

2.0

2.16

4.0

2.23

10.0

2.30

12.2

2.37

13.5

2.55

15.0

Table 3: Rotating speed of the 500 rpm moving element

Speed of the fluid in the tube in m / s

% length of turns that have an inverted step

1.25

0.0

1.83

0.5

1.90

2.0

1.93

4.0

1.99

10.0

2.04

12.2

2.10

13.5

2.23

15.0

From the teaching of these 3 tables it follows that when the mobile element of the device comprises inverted turns, according to the present invention, it is now possible to use the device according to the invention, for a rotation speed of the determined mobile element, increase the speed of the fluid under the following conditions:

15 - for 1500 rpm, from 1.50 m / s to 2.85 m / s, that is, a 67% increase in fluid velocity,

-

 for 1000 rpm, from 1.4 m / s to 2.55 m / s, that is, an increase in fluid velocity of 82%,

-

 for 500 rpm from 1.15 m / s to 2.23 m / s, that is an increase in fluid velocity of 93%.

20 The reduction in rotation speed is now measured based on the percentage of step reversed. Figure 3 represents in ordinates the% reduction of the rotation speed of the device and in abscissa the% of length of inverted turns.

25 These data have been measured for mobile elements with a length of 6 m that have respectively (reference 1 in figure 2) 0% of inverted turns, (2) 0.5% of inverted turns, ( 3) 2.0%,

(4) 4.0%, (5) 10%, (6) 12.2%, (7) 13.5% and finally (8) 15.0% of inverted turns.

It is seen that for a fluid velocity of 1.5 m / s, the rotational speed of the mobile element can be reduced by 30 8% with 0.5% of inverted turns, and this up to 90% with 12 % of turns turned. These reductions favor the decrease of head wear.

Figure 4 represents in ordinates the total load loss (mbar) recorded in a 6.00 m tube as a function of the rotational speed of the mobile element presented in abscissa. These data have been measured for mobile elements 35 with a length of 6 m, which have respectively (reference 1 in Figure 2) 0% of inverted turns, (2) 0.5% of inverted turns, ( 3) 2.0%, (4) 4.0%, (5) 10%, (6) 12.2%, (7)

13.5% and finally (8) 15.0% of turns in reverse.

This loss of load is the expression of the sum of the load losses corresponding to the upstream fixed element (fixing bracket), the tube itself and the device object of the present invention.

5 This head loss increases when the rotation speed increases. It is more important as the number of turns that have an inverted step increases.

Therefore, to minimize this loss of load, amounts of inverted turns as small as possible will be chosen.

In document FR 2 890 162, the operating time of the described device was less than 4 years. Under these same operating conditions of said device and also with a reduction in the rotation speed of the mobile element, for example for a fluid flow rate of 1.5 m / s and a rotation speed of 1000 rpm, the life

The usefulness of the device object of the present invention should reach 5 years or more, a period required by the operating company of an oil refinery.

Claims (14)

1. Inlay reducing device inside a tube (1) crossed by a fluid (F), of the type comprising at least one turbulence generating element, said device being constituted by a mobile rotating element (2) connected to a fixed bearing-like element (3), suitable for becoming rigidly integral with the upstream end of the tube (1), said mobile rotating element (2) comprising:

-

 an upstream part (4) as a journal comprising a mechanical connection (5) with the fixed element as a bearing (3) and which allows the free rotation of the mobile element (2) about itself around the axis of the tube (one),

-

 a downstream part (6) in the form of a helix consisting of several turns and formed in order to be operated in rotation by the circulation of the fluid (F) in the tube (1),

in which

-

 the upstream (4) and downstream (6) parts of the mobile rotary element (2) are connected to each other by means of a deformable longilinear flexible fitting along its entire length (7), and

 characterized because

-

 The downstream part (6) contains at least one spiral part whose passage is reversed (8) with respect to the other turns.

2.

Device according to claim 1, characterized in that the flexible fitting (7) is preferably made of metal, in particular of steel and preferably of stainless steel.

3.

Device according to claim 1 or 2, characterized in that the flexible fitting (7) is a cable formed by twisted or twisted filaments comprising a number of filaments between 1 and 100, and preferably between 1 and 50.

Four.

Device according to any one of the preceding claims, characterized in that the length of the flexible fitting (7) is between 1 cm and 5 cm, and preferably between 2 and 4 cm.

5.

Device according to any one of the preceding claims, characterized in that the diameter of the flexible fitting (7) is between 2 and 10 mm and preferably between 4 and 8 mm.

6.

Device according to any one of claims 1 to 5, characterized in that the ratio between the outer diameter of the propeller and the inner diameter of the tube (1) is between 0.5 and 0.9, preferably between 0.6 and 0, 8.

7.

Device according to any one of claims 1 to 6, characterized in that the outer diameter of the first turn or of the first turns of the propeller is smaller than the outside diameter of the other turns of the propeller.

8.

Device according to claim 7, characterized in that the ratio between the outer diameter of the first turn, or of the first turns, and the inner diameter of the tube (1) is between 0.1 and 0.6, and preferably between 0, 2 and 0.6.

9.

Device according to any one of the preceding claims, characterized in that the fixed element

(3) as a bearing is a stirrup comprising a central part (9) perforated with a hole intended to accommodate the journal (4) of the movable element (2), and two arms (10), symmetrical with each other, which have a form that allows fixing them at the upstream end of the tube (1).

10.

Device according to claim 9, characterized in that a first stop (5) is provided at the end of the journal (4) and a second stop (11), tubular, is provided in the central part (9) of the stirrup in extension of the intended hole to accommodate the journal of the mobile element, which forms a channel for securing the journal.

eleven.

Device according to any one of the preceding claims, characterized in that the journal (4) is replaced by an extension of the flexible fitting (7).

12.

Device according to claim 11, characterized in that the end of the flexible fitting (7) is integral with the stop (5).

13.

Device according to any one of the preceding claims, characterized in that a part of the

Mobile element (2) is constituted by 15% of inverted turns. 14. Heat exchanger comprising a plurality of tubes (1) crossed by a fluid, characterized in that it comprises an inlay reducing device according to any one of the preceding claims, in particular fixed at the upstream end of at least one of these tubes