EP1137819A1 - Installation for controlling the sealed condition of water-gas heat exchangers for industrial furnaces - Google Patents

Installation for controlling the sealed condition of water-gas heat exchangers for industrial furnaces

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Publication number
EP1137819A1
EP1137819A1 EP00960797A EP00960797A EP1137819A1 EP 1137819 A1 EP1137819 A1 EP 1137819A1 EP 00960797 A EP00960797 A EP 00960797A EP 00960797 A EP00960797 A EP 00960797A EP 1137819 A1 EP1137819 A1 EP 1137819A1
Authority
EP
European Patent Office
Prior art keywords
hot gas
gas
cooled
hygrometer
installation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00960797A
Other languages
German (de)
French (fr)
Inventor
Gilles Zander
André GAGGIOLI
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
USINOR SA
Original Assignee
USINOR SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by USINOR SA filed Critical USINOR SA
Publication of EP1137819A1 publication Critical patent/EP1137819A1/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/561—Continuous furnaces for strip or wire with a controlled atmosphere or vacuum
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/573—Continuous furnaces for strip or wire with cooling
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
    • F27D17/004—Systems for reclaiming waste heat
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D21/00—Arrangements of monitoring devices; Arrangements of safety devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M3/00—Investigating fluid-tightness of structures
    • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
    • G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M3/00—Investigating fluid-tightness of structures
    • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
    • G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point
    • G01M3/20—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using special tracer materials, e.g. dye, fluorescent material, radioactive material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
    • F27B9/28—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity for treating continuous lengths of work
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D21/00—Arrangements of monitoring devices; Arrangements of safety devices
    • F27D2021/0057—Security or safety devices, e.g. for protection against heat, noise, pollution or too much duress; Ergonomic aspects

Definitions

  • the invention relates to industrial ovens ensuring the thermal treatment of various objects, such as metal parts, and in particular moving bands. More specifically, it relates to the control of the tightness of the water-gas heat exchangers by which cooling of the internal atmosphere of the ovens is carried out in the areas where such cooling is necessary.
  • the dip coating of steel strips with zinc initially in the liquid state is generally carried out in an installation for continuous galvanization of moving strips.
  • This installation usually comprises, first of all, an annealing furnace in which the strip is successively heated and cooled.
  • the strip On leaving the oven, the strip passes inside a "bell", which is a tubular piece connected to the oven and the lower end of which, through which the strip exits, plunges into the bath of liquid zinc.
  • the function of this bell is to isolate the moving strip from the external atmosphere between its exit from the annealing furnace and its entry into the zinc bath.
  • the strip is then extracted vertically from the zinc bath, and then comprises on its two faces a zinc coating whose thickness is then equalized by wringing.
  • the passage of the strip in the annealing furnace is an essential step for the quality of the realization of the galvanization. It is essential to maintain a non-oxidizing atmosphere there for the steel strip, so as to avoid the formation of scale on the surface of the strip. Such a scale formation would have disastrous consequences on the adhesion of the zinc deposit on the surface of the strip.
  • an atmosphere is imposed throughout the furnace comprising mainly nitrogen, and containing, in addition, hydrogen at a content of about 2% or more which can react with traces of oxygen. possibly present. For this reason, the gas making up this atmosphere is usually called "HN X ".
  • the annealing furnace is made up of several successive zones, which are not leaktight with respect to each other, in which different temperatures are imposed, first increasing then decreasing, namely:
  • Continuous annealing furnaces for steel strips which are not placed at the head of a galvanizing line can also operate on this same principle, and end in one or more cooling zones.
  • the target temperature is obtained by injecting HN X previously heated to the desired temperature.
  • This HN passes then in the cooling zones, where it must be cooled itself to play its role.
  • the cooling zones of the furnace comprise, arranged opposite each of the two faces of the strip, a succession of devices which each extract a part of the gases present in the zone of the furnace through which the strip passes, pass these gases in a heat exchanger, and re-inject the gases thus cooled in the furnace, in the vicinity of the strip and downstream from the preceding extraction zone, so as to allow them to cool the strip over a portion of the path of the latter.
  • the heat exchangers which ensure the cooling of the extracted gases are conventionally constituted by copper se ⁇ entins in which cold water circulates, and around which the hot gases to be cooled are passed. These se ⁇ entins are therefore subjected to thermal cycles of large amplitudes which deteriorate them over time. In particular, their solders are fragile points where cracks are particularly likely to occur relatively quickly. The consequence of such cracks is that cooling water escapes from the se ⁇ entin and comes into contact with the gas to be cooled. It vaporizes and is injected into the furnace with the gas, which leads to humidification of the furnace atmosphere. When the water vapor content of the atmosphere becomes too high due to these leaks, the surface of the metal oxidizes and the galvanization is poorly carried out.
  • the quality of the atmosphere in the oven in each of its zones is usually checked by periodically measuring its humidity by determining its dew point.
  • the dew point of a dry HN X atmosphere is from -30 to -40 ° C. It is measured with a hygrometer, generally of the capacitive type.
  • a hygrometer generally of the capacitive type.
  • the usual measuring devices can only detect the existence of relatively large water leaks (of the order of 0.2 1 / h, which lowers the dew point of HN X by 1 ° C at -35 ° C), when they may have already caused the deterioration of a notable length of strip at the earlier stages of their evolution.
  • the usual devices do not make it possible to determine which exchanger is defective.
  • This method does not make it possible to correctly detect microcracks, and moreover, it accelerates the deterioration of defective but not yet fully cracked solders.
  • the object of the invention is to provide users of ovens with water-gas heat exchangers to cool their atmosphere a device for checking the tightness of these exchangers capable of detecting leaks at an early stage of their evolution, while identifying the defective exchanger.
  • the subject of the invention is an installation for checking the tightness of water-gas heat exchangers fitted to an industrial oven, said oven comprising at least one assembly formed by means of extracting a hot gas. present in a given zone of said furnace, a water-gas heat exchanger intended to cool said hot gas and means for reintroducing said cooled hot gas into a zone of said furnace situated downstream of said zone where said gas extraction took place hot, characterized in that it comprises:
  • - Means such as a three-way valve and its outlet pipe, for selecting said hot gas or said cooled gas and sending it to a hygrometer;
  • the invention is based on the principle of a differential measurement of the dew point upstream and downstream of each exchanger.
  • a differential measurement requires the use of a high sensitivity hygrometer, capable of detecting deviations of about 0.3 ° C on the dew points at the level of -35 ° C.
  • an infrared absorption hygrometer is preferably used.
  • FIG. 1 which schematically shows a portion of an oven traversed by a moving strip, such as an annealing oven, and the installation for cooling the gases present in this portion, comprising water-gas exchangers;
  • FIG. 1 which schematically shows an installation for checking the tightness of the water-gas exchangers according to the invention.
  • the portion of the annealing furnace 1 shown is crossed by a strip 2 of moving steel which passes over rollers 3, 4, 5, 6, 7, 8.
  • This atmosphere can be a nitrogen-hydrogen mixture (HNJ, or any other normally dry atmosphere suitable for the specific metallurgical treatment undergone by the strip 2 in the furnace 1.
  • the portion of the furnace 1 shown is fitted with two identical devices, which are each placed on either side of the strip!, so as to obtain an identical cooling effect on the two faces of the strip 2.
  • These devices each include: - means for extracting the hot gases entering at a temperature ⁇ , in the represented portion of the oven 1, constituted here by a collector 9, 9 ', connected by a line 10, 10' to a fan 11, 1 1 ';
  • each cooling zone of the furnace 1 comprises a plurality of pairs of such cooling devices, the number and cooling power of which vary according to the desired results.
  • the installation is not distinguished from the known prior art.
  • a pipe 16 is implanted for sampling a fraction of these gases.
  • Points A and B and lines 16, 17 have their equivalents A ', B', 16 ', 17' on the gas cooling device symmetrical to the previous one with respect to strip 2, as well as on all similar devices installed on the oven 1.
  • the gases thus sampled are sent to the installation which is shown diagrammatically in FIG. 2 in its preferred configuration.
  • FIG. 2 it has been assumed that the entire furnace 1 was equipped with four devices of the type shown in FIG. 1, and that there are therefore in total eight exchangers identical to the exchangers 12, 12 ′ which must be checked sealing. It goes without saying that this number of devices is only a nonlimiting example, and that the invention can be put into practice even in the case where the furnace 1 would comprise only one water-gas exchanger.
  • the pipes 16, 16 'and their equivalents (not referenced in FIG.
  • Filters 28, 29 are preferably placed on the lines 22, 27, so as to rid the gases circulating there of impurities which could disturb the functioning of the following organs.
  • these filters In the case of a control installation placed on the annealing furnace of a galvanizing line, these filters must in particular be capable of capturing the vapors and particles of zinc that the gases can contain, following the difficult avoidable rise of such vapors from the galvanizing bath to the oven, via the bell.
  • Sintered bronze pellets with a porosity of about 1 ⁇ m are well suited for this use.
  • these filters 28, 29 can be replaced by other filters located further upstream, namely on each of the pipes 16, 16 ', 17, 17' and their equivalents, or can be added to such filters.
  • the lines 22, 27 are each connected to a pump which controls the suction of the gases taken off either upstream or downstream of the exchangers 12, 12 'and their equivalents.
  • a pump which controls the suction of the gases taken off either upstream or downstream of the exchangers 12, 12 'and their equivalents.
  • the first cost 31 is connected to the pipe
  • the line 35 is connected to an overflow valve 36 which has the function of allowing the evacuation to the atmosphere of a determined proportion, adjustable to the request, gases sucked in by the first co ⁇ s 32 of the pump 30 and present in the pipe 33.
  • This evacuation is carried out by a pipe 37, on which is installed a rotameter 38 for controlling the flow of exhaust gas.
  • the gases which do not pass through the outlet 36 continue their course in the pipe 34, at a pressure which the adjustment of the operating parameters of the outlet 36 makes it possible to maintain constant, whatever the variations in the pressure of the gases leaving the first co ⁇ s 31 of the pump 30. This maintenance at constant pressure makes the operation of the entire installation more reliable, in particular of its “analysis” part which will be seen below.
  • a pipe 39 is connected which is itself subdivided into two pipes 40, 41.
  • the pipe 40 is connected to an overflow valve 42 which has the function of allowing the evacuation to the atmosphere of a determined proportion, adjustable on demand, of the gases sucked in by the second co 32s 32 of the pump 30 and present in the pipe 39.
  • This evacuation is carried out by a pipe 43, on which a rotameter is installed 44 used to control the flow of exhaust gases.
  • the gases which do not pass through the outlet 42 continue their course in the pipe 41, at a pressure which the adjustment of the operating parameters of the outlet 42 allows to maintain constant, whatever the variations in the pressure of the gases leaving the second co ⁇ s 32 of the pump 30.
  • the rotameters 38, 44 can be provided with an alarm indicating whether the gas flow rate passing through them becomes abnormally low.
  • the triggering of this alarm means that too small a quantity of gas is circulating in the installation, for example because the filters 28, 29 are in the process of being clogged and must be cleaned or replaced.
  • each cost 31, 32 of the pump 30 sucks a normal volume of gas of 500 1 / h, it is approximately 100 1 / h which are sent by each cost 31, 32 to the "analysis" part of the installation, the remainder of the gases being sent into the atmosphere through the outlets 36, 42.
  • Line 34 which therefore conveys hot gases to be analyzed, and line 41, which therefore conveys cooled gases to be analyzed, are connected to the two inputs of a three-way solenoid valve 45.
  • a line 46 is connected to the output of this solenoid valve 45, the function of which is therefore to select the gases, hot / or cooled, which will be sent in the rest of the installation to be analyzed (any other device ensuring this function can, of course, be substituted for this three-way solenoid valve 45).
  • These gases then preferably pass through a flow regulator 47 which makes it possible to send said gases at a constant flow rate in the rest of the installation. This flow is measured, for example using a rotameter 48.
  • the hygrometer 49 is located, which determines the dew point of the gases sent to it. It is equipped with means 50 for returning the results of its analyzes to the operator, and with an outlet pipe 51 for discharging the gases into the atmosphere after their analysis. Measuring this dew point indirectly gives access to the water vapor content of the gas analyzed.
  • this hygrometer 50 In order to be able to ensure with satisfactory precision a differential measurement of the dew points of the gases sampled before and after their passage through an exchanger 12, 12 ′, this hygrometer 50 must have a better sensitivity than that of conventional capacitive hygrometers. It must be able to detect differences in these dew points below 0.5 ° C at the level of -30 to -40 ° C, such differences corresponding to the humidity levels of the gases already sufficient to deteriorate the quality of strip surface 2. Their response time should also be as rapid as possible. From all these points of view, infrared hygrometers are very well suited.
  • the installation according to the invention is used in the following manner. First, it is necessary to calibrate the hygrometer 50. This calibration can be carried out by means of an independent installation, but it is advantageous to integrate the calibration means with the control installation itself. , as shown in FIG. 2. To this end, a two-way solenoid valve 52 which allows interruption at will is inserted on the line 46, which connects the outlet of the three-way solenoid valve 45 to the flow regulator 47. the passage of gases from the oven 1. Downstream of this solenoid valve 52 is connected to the pipe 46 a pipe 53 for introducing a standard gas in place of the gases from the oven.
  • this standard gas into line 53 is controlled by a three-way solenoid valve 54, to which the receptacles 55, 56 containing the two standard gases capable of being used are connected.
  • gases are, for example as shown, on the one hand pure nitrogen, and on the other hand one or more mixtures containing nitrogen and a known proportion of water vapor, or of a gas such as sulfur hexafluoride SF 6 which it is known that its absorption band in the infrared is close to that of water vapor.
  • N 2 -SF 6 mixture rather than an N 2 -H 2 O mixture
  • the N 2 -H, O mixtures are not very stable over time, and that it does not it is not possible to inflate the bottles of these mixtures under high pressures without causing condensation of the water vapor (for example, for a water content of 400 ppm, the maximum tolerable pressure is 11 bar).
  • the bottles of N 2 -H 2 O mixtures by virtue of their necessarily reduced capacity and their limited period of use, are therefore not well suited for use under industrial conditions.
  • Bottles of N2-SF 6 mixtures are, from this point of view, much superior, because this mixture tolerates significant pressurization, is stable over time, and moreover does not cost significantly more than N 2 mixtures -H 2 O industrially prepared. If we have previously determined, by calibration with N 2 - H 2 O mixtures, on the one hand the correspondence between the SF 6 content of a standard gas and the output signal supplied by the hygrometer, and on the other apart from what water vapor content this same output signal would correspond to, it is possible to calibrate the infrared hygrometer 49 with N 2 -SF 6 mixtures before any series of humidity measurements atmosphere of an oven.
  • valve 52 is closed and the valve 54 is open, so as to allow the conduits 53 and 46 to enter one of the standard gases contained in the containers 55, 56 as desired. It is of course possible to use a higher number of standard gases, and modify the installation accordingly.
  • the valve 54 is closed and the valve 52 open, and the analysis of the gases coming from the furnace 1 can begin.
  • the solenoid valve 45 is open so as to admit into its outlet pipe 46 only hot gas from the pipe 34, and this gas is therefore sent to the hygrometer 49 for a sufficient time for the realization of the determination of its dew point, from which its water vapor content is deduced.
  • the solenoid valve 45 is actuated so that it admits into its outlet pipe 46 only cooled gas coming from the pipe 41, which in turn is sent to the hygrometer 49
  • the results of the analyzes of the hot gas and the cooled gas are then returned to the operator by the means 50, so as to allow an immediate comparison of the respective dew points of the hot gas as taken from the oven and of this same gas. cooled after passing through the exchanger 12.
  • the solenoid valves 18, 23 are closed and the solenoid valves 18 ', 23' are open, so as to carry out the same control operation as above on the exchanger 12 '.
  • the operation is then similarly repeated for each of the installation exchangers, by closing and opening the appropriate solenoid valves.
  • the exchanger control series as just described is carried out during the operation of the furnace, without requiring it to be stopped, with a periodicity chosen by the operator.
  • the various opening and closing operations of the solenoid valves can be carried out manually, and the comparison between the humidities of the gas before and after its passage through a given exchanger can be carried out by the operator in view of the results which the means 50 restore to him. .
  • a particularly advantageous characteristic of the installation which has just been described and shown resides in the use of a pump 30 with double co ⁇ s (or two separate pumps operating simultaneously), which is followed by the three-way solenoid valve 45 which controls the admission into the hygrometer 49 of either hot gas or cooled gas.
  • a pump 30 with double co ⁇ s or two separate pumps operating simultaneously
  • the solenoid valve 45 which controls the admission into the hygrometer 49 of either hot gas or cooled gas.
  • the arrangement adopted in the invention has the advantage of allowing as rapid a passage as possible between the analysis of the sample of hot gas and the analysis of the sample of gas cooled by a given exchanger, speed which is very important in the case of a differential measurement of the humidity of these gases.
  • the materials used for the various components of the installation must be compatible with the properties of the gases intended to pass through it, which can be corrosive at the temperatures encountered, especially if they are charged with humidity.
  • metals such as stainless steel to make the pump costs 30, and plastic materials such as PTFE for the membranes of the pump 30 and of the flow regulator 47.
  • PTFE plastic materials
  • they When to various pipes, they must be, for example, made of copper or stainless steel, and have their internal walls polished or coated with a material such as fused silica, in order to prevent water vapor from clinging to it , which would distort the results of the analyzes.
  • solenoid valves of various types which have been mentioned in the above description can be replaced by manually operated valves (or any other device) ensuring the same functions of authorizing or not the circulation of such and such. gases in the different parts of the installation.
  • the solenoid valves have the obvious advantage of being able to be controlled remotely by the operator or the automatic installation management device.
  • Air inlets in the sampling and measuring system are to be avoided absolutely. To this end, it is advisable, even when the installation is not used in "analysis" mode, to maintain a permanent circulation of gases extracted from the oven, which also has the advantage of reducing the number and extent of thermal shock to which the installation is subject.
  • the invention is applicable to checking the tightness of any installation comprising water-gas exchangers intended to lower the temperature of a gas constituting the atmosphere of an oven, the annealing oven previously described being only a example where the use of the invention is particularly advantageous.

Abstract

The invention concerns an installation for controlling the sealed condition of water-gas heat exchangers equipping an industrial furnace (1), said furnace (1) comprising at least as assembly formed by means (9, 10, 11, 9', 10', 11') extracting a hot gas present in a specific zone of said furnace (1), a water-gas heat exchanger (12, 12') designed to cool the hot gas and means (14, 15, 14', 15') for reintroducing said hot gas which has been cooled into a zone of said furnace (1) located downstream of said zone where said hot gas is extracted. The invention is characterised in that it comprises: means (16, 16', 22 31) for sampling said hot gas at points (A, A') each located upstream of an exchanger (12, 12') and two-way valves (18-21, 18'-21') enabling said sampling; means (17, 17', 27, 32) for sampling said hot gas which has been cooled at points (B, B') each located downstream of an exchanger (12, 12') and two-way valves (23-26, 23'-26') enabling said sampling; means (36, 42) for regulating the respective pressure levels of said hot gas and the hot gas which has been cooled downstream of said sampling means (16, 16', 22, 31, 17, 17', 27, 32); means, such as a three-way valve (45) and its outlet pipe (46), for selecting said hot gas or said hot gas which has been cooled and sending it into an hygrometer (49); and means (50) for restoring to the operator the results of the analyses carried out by the hygrometer (49) enabling him to compare the degree of humidity of said hot gas and said hot gas which has been cooled for each of the exchangers (12, 12').

Description

INSTALLATION DE CONTRÔLE DE L'ETANCHEITE D'ECHANGEURS DE CHALEUR EAU-GAZ POUR FOURS INDUSTRIELS WATER-GAS HEAT EXCHANGER SEALING SYSTEM FOR INDUSTRIAL OVENS
L'invention concerne les fours industriels assurant le traitement thermique d'objets divers, tels que des pièces métalliques, et notamment des bandes en défilement. Plus précisément, elle concerne le contrôle de l'étanchéité des échangeurs thermiques eau- gaz grâce auxquels on réalise un refroidissement de l'atmosphère interne des fours dans les zones où un tel refroidissement est nécessaire.The invention relates to industrial ovens ensuring the thermal treatment of various objects, such as metal parts, and in particular moving bands. More specifically, it relates to the control of the tightness of the water-gas heat exchangers by which cooling of the internal atmosphere of the ovens is carried out in the areas where such cooling is necessary.
Le revêtement au trempé de bandes d'acier par du zinc initialement à l'état liquide (galvanisation) est généralement réalisé dans une installation de galvanisation en continu de bandes en défilement. Cette installation comporte habituellement, en premier lieu, un four de recuit dans lequel la bande est successivement réchauffée et refroidie. A sa sortie du four, la bande passe à l'intérieur d'une « cloche », qui est une pièce tubulaire connectée au four et dont l'extrémité inférieure, par laquelle sort la bande, plonge dans le bain de zinc liquide. Cette cloche a pour fonction d'isoler la bande en défilement par rapport à l'atmosphère extérieure entre sa sortie du four de recuit et son entrée dans le bain de zinc. La bande est ensuite extraite verticalement du bain de zinc, et comporte alors sur ses deux faces un revêtement de zinc dont l'épaisseur est ensuite égalisée par essorage.The dip coating of steel strips with zinc initially in the liquid state (galvanization) is generally carried out in an installation for continuous galvanization of moving strips. This installation usually comprises, first of all, an annealing furnace in which the strip is successively heated and cooled. On leaving the oven, the strip passes inside a "bell", which is a tubular piece connected to the oven and the lower end of which, through which the strip exits, plunges into the bath of liquid zinc. The function of this bell is to isolate the moving strip from the external atmosphere between its exit from the annealing furnace and its entry into the zinc bath. The strip is then extracted vertically from the zinc bath, and then comprises on its two faces a zinc coating whose thickness is then equalized by wringing.
Le passage de la bande dans le four de recuit est une étape essentielle pour la qualité de la réalisation de la galvanisation. Il est indispensable d'y maintenir une atmosphère non oxydante pour la bande d'acier, de manière à éviter la formation de calamine à la surface de la bande. Un telle formation de calamine aurait des conséquences désastreuses sur l'adhérence du dépôt de zinc sur la surface de la bande. A cet effet, on impose dans tout l'intérieur du four une atmosphère comportant principalement de l'azote, et renfermant, en outre, de l'hydrogène à une teneur d'environ 2% ou plus pouvant réagir avec les traces d'oxygène éventuellement présentes. Pour cette raison, le gaz composant cette atmosphère est appelé habituellement « HNX ».The passage of the strip in the annealing furnace is an essential step for the quality of the realization of the galvanization. It is essential to maintain a non-oxidizing atmosphere there for the steel strip, so as to avoid the formation of scale on the surface of the strip. Such a scale formation would have disastrous consequences on the adhesion of the zinc deposit on the surface of the strip. To this end, an atmosphere is imposed throughout the furnace comprising mainly nitrogen, and containing, in addition, hydrogen at a content of about 2% or more which can react with traces of oxygen. possibly present. For this reason, the gas making up this atmosphere is usually called "HN X ".
Le four de recuit se compose de plusieurs zones successives, non étanches les unes par rapport aux autres, dans lesquelles on impose des températures différentes, d'abord croissantes puis décroissantes, à savoir :The annealing furnace is made up of several successive zones, which are not leaktight with respect to each other, in which different temperatures are imposed, first increasing then decreasing, namely:
- une zone de préchauffage de la bande ;- a belt preheating zone;
- une zone de chauffage, où la bande atteint sa température maximale ;- a heating zone, where the strip reaches its maximum temperature;
- une zone de refroidissement lent ;- a slow cooling zone;
- et une zone de refroidissement rapide. Les fours de recuit continu des bandes d'acier qui ne sont pas placés en tête d'une ligne de galvanisation peuvent également fonctionner sur ce même principe, et se terminer par une ou des zones de refroidissement.- and a rapid cooling zone. Continuous annealing furnaces for steel strips which are not placed at the head of a galvanizing line can also operate on this same principle, and end in one or more cooling zones.
Dans les zones de préchauffage et de chauffage, la température visée est obtenue par l'injection de HNX préalablement réchauffé à la température voulue. Ce HN passe ensuite dans les zones de refroidissement, où il doit être lui-même refroidi pour jouer son rôle. A cet effet, les zones de refroidissement du four comportent, disposés en regard de chacune des deux faces de la bande, une succession de dispositifs qui extraient chacun une partie des gaz présents dans la zone du four que traverse la bande, font passer ces gaz dans un echangeur thermique, et réinjectent les gaz ainsi refroidis dans le four, au voisinage de la bande et en aval de la zone d'extraction précédente, de manière à leur permettre de refroidir la bande sur une portion du parcours de celle-ci. Les échangeurs thermiques qui assurent le refroidissement des gaz extraits sont classiquement constitués par des seφentins de cuivre dans lesquels circule de l'eau froide, et autour desquels on fait passer les gaz chauds à refroidir. Ces seφentins sont donc soumis à des cycles thermiques de grandes amplitudes qui les détériorent au fil du temps. En particulier, leurs brasures sont des points fragiles où des fissurations sont particulièrement susceptibles de se produire relativement rapidement. La conséquence de telles fissurations est que de l'eau de refroidissement s'échappe du seφentin et vient au contact du gaz à refroidir. Elle se vaporise et est injectée dans le four avec le gaz, ce qui conduit à une humidification de l'atmosphère du four. Lorsque la teneur en vapeur d'eau de l'atmosphère devient trop élevée du fait de ces fuites, la surface du métal s'oxyde et la galvanisation s'effectue mal. Dans les faits, un remplacement périodique des échangeurs est nécessaire. Mais comme cette opération nécessite un arrêt prolongé du four de recuit (il faut 24 heures pour remplacer un echangeur), elle ne doit être effectuée que quand elle est absolument nécessaire, sous peine de compromettre exagérément la productivité de l'installation.In the preheating and heating zones, the target temperature is obtained by injecting HN X previously heated to the desired temperature. This HN passes then in the cooling zones, where it must be cooled itself to play its role. For this purpose, the cooling zones of the furnace comprise, arranged opposite each of the two faces of the strip, a succession of devices which each extract a part of the gases present in the zone of the furnace through which the strip passes, pass these gases in a heat exchanger, and re-inject the gases thus cooled in the furnace, in the vicinity of the strip and downstream from the preceding extraction zone, so as to allow them to cool the strip over a portion of the path of the latter. The heat exchangers which ensure the cooling of the extracted gases are conventionally constituted by copper seφentins in which cold water circulates, and around which the hot gases to be cooled are passed. These seφentins are therefore subjected to thermal cycles of large amplitudes which deteriorate them over time. In particular, their solders are fragile points where cracks are particularly likely to occur relatively quickly. The consequence of such cracks is that cooling water escapes from the seφentin and comes into contact with the gas to be cooled. It vaporizes and is injected into the furnace with the gas, which leads to humidification of the furnace atmosphere. When the water vapor content of the atmosphere becomes too high due to these leaks, the surface of the metal oxidizes and the galvanization is poorly carried out. In fact, a periodic replacement of the exchangers is necessary. But as this operation requires a prolonged shutdown of the annealing furnace (it takes 24 hours to replace a heat exchanger), it should only be carried out when it is absolutely necessary, otherwise the productivity of the installation will be unduly compromised.
Pour déterminer quand il devient nécessaire de remplacer un echangeur, on contrôle habituellement la qualité de l'atmosphère du four dans chacune de ses zones en y mesurant périodiquement son humidité par détermination de son point de rosée. Typiquement, le point de rosée d'une atmosphère de HNX sèche est de -30 à -40°C. On le mesure avec un hygromètre, généralement de type capacitif. Lorsqu'un echangeur comporte une microfissure qui introduit environ 0,1 1/h d'eau dans l'atmosphère du four, le point de rosée est abaissé d'environ 0,6°C au niveau de -40°C. La détection d'une humidification si minime est hors de portée des hygromètres classiques, alors qu'elle serait déjà suffisante pour être susceptible de détériorer la surface de la bande. En fait, les dispositifs de mesure habituels ne permettent de détecter que l'existence de fuites d'eau relativement importantes (de l'ordre de 0,2 1/h, ce qui abaisse le point de rosée du HNX de 1°C au niveau de -35°C), alors qu'elles ont pu déjà provoquer la détérioration d'une longueur de bande notable aux stades antérieurs de leur évolution. D'autre part, les dispositifs habituels ne permettent pas de déterminer quel echangeur est défectueux. Lorsqu'un abaissement important du point de rosée est détecté, il faut donc arrêter l'installation de recuit (et aussi l'installation de galvanisation qui lui fait suite, s'il y en a une) et contrôler un par un les échangeurs, par exemple en y augmentant la pression de l'eau circulante. Cette méthode ne permet pas de bien détecter les microfissures, et de plus, elle accélère la détérioration des brasures défectueuses mais non encore fissurées de part en part.To determine when it becomes necessary to replace an exchanger, the quality of the atmosphere in the oven in each of its zones is usually checked by periodically measuring its humidity by determining its dew point. Typically, the dew point of a dry HN X atmosphere is from -30 to -40 ° C. It is measured with a hygrometer, generally of the capacitive type. When an exchanger has a microcrack which introduces about 0.1 l / h of water into the atmosphere of the oven, the dew point is lowered by about 0.6 ° C to the level of -40 ° C. The detection of such minimal humidification is beyond the reach of conventional hygrometers, when it would already be sufficient to be likely to deteriorate the surface of the strip. In fact, the usual measuring devices can only detect the existence of relatively large water leaks (of the order of 0.2 1 / h, which lowers the dew point of HN X by 1 ° C at -35 ° C), when they may have already caused the deterioration of a notable length of strip at the earlier stages of their evolution. On the other hand, the usual devices do not make it possible to determine which exchanger is defective. When a significant lowering of the dew point is detected, it is therefore necessary to stop the annealing installation (and also the galvanizing installation which follows it, if there is one) and check the exchangers one by one, for example by increasing the pressure of the circulating water. This method does not make it possible to correctly detect microcracks, and moreover, it accelerates the deterioration of defective but not yet fully cracked solders.
Le but de l'invention est de procurer aux utilisateurs de fours comportant des échangeurs de chaleur eau-gaz pour refroidir leur atmosphère un dispositif de contrôle de l'étanchéité de ces échangeurs susceptible de détecter des défauts d'étanchéité à un stade précoce de leur évolution, tout en identifiant l'échangeur défectueux.The object of the invention is to provide users of ovens with water-gas heat exchangers to cool their atmosphere a device for checking the tightness of these exchangers capable of detecting leaks at an early stage of their evolution, while identifying the defective exchanger.
A cet effet, l'invention a pour objet une installation de contrôle de l'étanchéité d'échangeurs de chaleur eau-gaz équipant un four industriel, ledit four comprenant au moins un ensemble formé par des moyens d'extraction d'un gaz chaud présent dans une zone donnée dudit four, un echangeur de chaleur eau-gaz destiné à refroidir ledit gaz chaud et des moyens pour réintroduire ledit gaz chaud refroidi dans une zone dudit four située en aval de ladite zone où a eu lieu l'extraction dudit gaz chaud, caractérisé en ce qu'elle comporte :To this end, the subject of the invention is an installation for checking the tightness of water-gas heat exchangers fitted to an industrial oven, said oven comprising at least one assembly formed by means of extracting a hot gas. present in a given zone of said furnace, a water-gas heat exchanger intended to cool said hot gas and means for reintroducing said cooled hot gas into a zone of said furnace situated downstream of said zone where said gas extraction took place hot, characterized in that it comprises:
- des moyens de prélèvement dudit gaz chaud en des points situés chacun en amont d'un echangeur et des vannes à deux voies autorisant la réalisation de ce prélèvement ;- means for sampling said hot gas at points each located upstream of an exchanger and two-way valves authorizing the carrying out of this sampling;
- des moyens de prélèvement dudit gaz chaud refroidi en des points situés chacun en aval d'un echangeur et des vannes à deux voies autorisant la réalisation de ce prélèvement ; - des moyens pour réguler les pressions respectives dudit gaz chaud et dudit gaz refroidi en aval desdits moyens de prélèvement ;- means for withdrawing said hot gas cooled at points each located downstream of an exchanger and two-way valves authorizing the carrying out of this withdrawal; - Means for regulating the respective pressures of said hot gas and said cooled gas downstream of said sampling means;
- des moyens, tels qu'une vanne à trois voies et sa conduite de sortie, pour sélectionner ledit gaz chaud ou ledit gaz refroidi et l'envoyer dans un hygromètre ;- Means, such as a three-way valve and its outlet pipe, for selecting said hot gas or said cooled gas and sending it to a hygrometer;
- et des moyens pour restituer à l'opérateur les résultats des analyses effectués par l'hygromètre en lui permettant de comparer le degré d'humidité dudit gaz chaud et dudit gaz refroidi pour chacun des échangeurs.- And means to return to the operator the results of the analyzes carried out by the hygrometer by allowing him to compare the degree of humidity of said hot gas and said cooled gas for each of the exchangers.
Comme on l'aura compris, l'invention repose sur le principe d'une mesure différentielle du point de rosée en amont et en aval de chaque echangeur. Une telle mesure nécessite l'utilisation d'un hygromètre de sensibilité élevée, capable de détecter des écarts de 0,3°C environ sur les points de rosée au niveau de -35°C. A cet effet, on emploie préférentiellement un hygromètre à absoφtion infrarouge.As will be understood, the invention is based on the principle of a differential measurement of the dew point upstream and downstream of each exchanger. Such a measurement requires the use of a high sensitivity hygrometer, capable of detecting deviations of about 0.3 ° C on the dew points at the level of -35 ° C. To this end, an infrared absorption hygrometer is preferably used.
L'invention sera mieux comprise à la lecture de la description qui suit, donnée en référence aux figures annexées suivantes :The invention will be better understood on reading the description which follows, given with reference to the following appended figures:
- la figure 1 qui montre schématiquement une portion d'un four traversé par une bande en défilement, tel qu'un four de recuit, et l'installation de refroidissement des gaz présents dans cette portion, comportant des échangeurs eau-gaz ;- Figure 1 which schematically shows a portion of an oven traversed by a moving strip, such as an annealing oven, and the installation for cooling the gases present in this portion, comprising water-gas exchangers;
- la figure 2 qui montre schématiquement une installation de contrôle de l'étanchéité des échangeurs eau-gaz selon l'invention. Sur la figure 1, la portion du four de recuit 1 représentée est traversée par une bande 2 d'acier en défilement qui passe sur des rouleaux 3, 4, 5, 6, 7, 8. Dans cette portion du four 1, on cherche à refroidir l'atmosphère environnant la bande 2, de manière à refroidir la bande 2 elle-même. Cette atmosphère peut être un mélange azote-hydrogène (HNJ, ou toute autre atmosphère normalement sèche adaptée au traitement métallurgique spécifique subi par la bande 2 dans le four 1. A cet effet, on équipe la portion du four 1 représentée de deux dispositifs identiques, qui sont placés chacun de part et d'autre de la bande! , de manière à obtenir un effet de refroidissement identique sur les deux faces de la bande 2. Ces dispositifs comportent chacun : - des moyens pour extraire les gaz chauds entrant à une température Θ, dans la portion représentée du four 1 , constitués ici par un collecteur 9, 9', relié par une conduite 10, 10' à un ventilateur 11, 1 1 ' ;- Figure 2 which schematically shows an installation for checking the tightness of the water-gas exchangers according to the invention. In FIG. 1, the portion of the annealing furnace 1 shown is crossed by a strip 2 of moving steel which passes over rollers 3, 4, 5, 6, 7, 8. In this portion of the furnace 1, it is sought cooling the atmosphere surrounding the strip 2, so as to cool the strip 2 itself. This atmosphere can be a nitrogen-hydrogen mixture (HNJ, or any other normally dry atmosphere suitable for the specific metallurgical treatment undergone by the strip 2 in the furnace 1. For this purpose, the portion of the furnace 1 shown is fitted with two identical devices, which are each placed on either side of the strip!, so as to obtain an identical cooling effect on the two faces of the strip 2. These devices each include: - means for extracting the hot gases entering at a temperature Θ, in the represented portion of the oven 1, constituted here by a collector 9, 9 ', connected by a line 10, 10' to a fan 11, 1 1 ';
- un echangeur de chaleur 12, 12' inséré sur la conduite 10, 10' entre le collecteur 9, 9' et le ventilateur 1 1 , 1 1 ' ; dans cet echangeur 12, 12' le gaz chaud est refroidi à une température Θ2 par un seφentin 13, 13' à circulation interne d'eau ;- a heat exchanger 12, 12 'inserted on the line 10, 10' between the manifold 9, 9 'and the fan 1 1, 1 1'; in this exchanger 12, 12 'the hot gas is cooled to a temperature Θ 2 by a valve 13, 13' with internal circulation of water;
- et des moyens pour renvoyer dans le four 1 le gaz refroidi, au voisinage de la bande 2, et comportant une conduite 14, 14' traversant la paroi du four 1 et un diffuseur 15, 15' qui répartit le gaz refroidi sur une large portion de la surface de la bande 2.- And means for returning the cooled gas to the furnace 1, in the vicinity of the strip 2, and comprising a pipe 14, 14 'passing through the wall of the furnace 1 and a diffuser 15, 15' which distributes the cooled gas over a wide portion of the surface of the strip 2.
Ainsi, principalement face aux diffuseurs 15, 15', mais aussi dans le restant de la portion du four 1 représentée, les gaz refroidis participent au refroidissement de la bande 2. Le plus généralement, chaque zone de refroidissement du four 1 comprend une pluralité de paires de tels dispositifs de refroidissement, dont le nombre et le pouvoir refroidissant varient en fonction des résultats souhaités. Pour tous les éléments que l'on vient de citer, l'installation ne se distingue pas de l'art antérieur connu. Selon l'invention, en un point A situé en amont de l'échangeur 12 sur le parcours des gaz aspirés par le ventilateur 1 1 et passant dans la conduite 10, on implante une conduite 16 de prélèvement d'une fraction de ces gaz. De même, en un point B situé en aval de ce même echangeur 12 sur la conduite 14 qui renvoie les gaz refroidis dans le four 1, on implante une autre conduite 17 de prélèvement d'une fraction de ces gaz. Les points A et B et les conduites 16, 17 ont leurs équivalents A', B', 16', 17' sur le dispositif de refroidissement des gaz symétrique du précédent par rapport à la bande 2, ainsi que sur tous les dispositifs similaires implantés sur le four 1. Les gaz ainsi prélevés sont envoyés dans l'installation qui est schématisée sur la figure 2 dans sa configuration préférée.Thus, mainly facing the diffusers 15, 15 ′, but also in the remainder of the portion of the furnace 1 shown, the cooled gases participate in the cooling of the strip 2. Most generally, each cooling zone of the furnace 1 comprises a plurality of pairs of such cooling devices, the number and cooling power of which vary according to the desired results. For all the elements that have just been mentioned, the installation is not distinguished from the known prior art. According to the invention, at a point A located upstream of the exchanger 12 on the path of the gases sucked in by the fan 11 and passing through the pipe 10, a pipe 16 is implanted for sampling a fraction of these gases. Similarly, at a point B located downstream of this same exchanger 12 on the pipe 14 which returns the cooled gases to the furnace 1, another pipe 17 is installed for sampling a fraction of these gases. Points A and B and lines 16, 17 have their equivalents A ', B', 16 ', 17' on the gas cooling device symmetrical to the previous one with respect to strip 2, as well as on all similar devices installed on the oven 1. The gases thus sampled are sent to the installation which is shown diagrammatically in FIG. 2 in its preferred configuration.
Sur la figure 2, on a supposé que l'ensemble du four 1 était équipé de quatre dispositifs du type représenté sur la figure 1, et qu'il y a donc au total huit échangeurs identiques aux échangeurs 12, 12' dont il faut contrôler l'étanchéité. Il va de soi que ce nombre de dispositifs n'est qu'un exemple non limitatif, et que l'invention peut être mise en pratique même dans le cas où le four 1 ne comporterait qu'un seul echangeur eau-gaz. Les conduites 16, 16' et leurs équivalentes (non référencées sur la figure 2) pour les autres échangeurs, qui prélèvent les gaz chauds aux points A, A' en amont des échangeurs 12, 12', débouchent chacune sur une électro vanne à deux voies 18-21, 18 '-21 ' qui autorise ou non, à la demande de l'opérateur (ou du dispositif automatique qui gère le fonctionnement de l'installation), la circulation du gaz dans la suite de la conduite correspondante, donc la réalisation de ce prélèvement. En aval desdites électrovannes 18-In FIG. 2, it has been assumed that the entire furnace 1 was equipped with four devices of the type shown in FIG. 1, and that there are therefore in total eight exchangers identical to the exchangers 12, 12 ′ which must be checked sealing. It goes without saying that this number of devices is only a nonlimiting example, and that the invention can be put into practice even in the case where the furnace 1 would comprise only one water-gas exchanger. The pipes 16, 16 'and their equivalents (not referenced in FIG. 2) for the other exchangers, which take the hot gases at points A, A' upstream of the exchangers 12, 12 ', each lead to a two-way solenoid valve tracks 18-21, 18 '-21' which authorizes or not, at the request of the operator (or the automatic device which manages the operation of the installation), the circulation of gas in the continuation of the corresponding pipe, therefore carrying out this levy. Downstream of said solenoid valves 18-
21 , 18'-21 ', les conduites 16, 16' et leurs équivalentes se rejoignent en formant une conduite unique 22. De la même façon, les conduites 17, 17' et leurs équivalentes pour les autres échangeurs, qui prélèvent les gaz refroidis aux points B, B' en aval des échangeurs 12, 12', débouchent chacune sur une électrovanne deux voies 23-26, 23'-26' qui autorise ou non, à la demande de l'opérateur (ou du dispositif automatique qui gère le fonctionnement de l'installation), la circulation du gaz dans la suite de la conduite correspondante. En aval desdites électrovannes 23-26, 23'-26', les conduites 17, 17' et leurs équivalentes se rejoignent en formant une conduite unique 27. Des filtres 28, 29 sont préférentiellement placés sur les conduites 22, 27, de manière à débarrasser les gaz qui y circulent des impuretés qui pourraient perturber le fonctionnement des organes suivants. Dans le cas d'une installation de contrôle placée sur le four de recuit d'une ligne de galvanisation, ces filtres doivent notamment être capables de capter les vapeurs et particules de zinc que les gaz peuvent renfermer, suite à la remontée difficilement évitable de telles vapeurs à partir du bain de galvanisation jusque dans le four, par l'intermédiaire de la cloche. Des pastilles de bronze frittées d'une porosité de 1 μm environ sont bien adaptées à cet usage. Bien entendu, ces filtres 28, 29 peuvent être remplacés par d'autres filtres situés plus en amont, à savoir sur chacune des conduites 16, 16', 17, 17' et de leurs équivalentes, ou s'ajouter à de tels filtres. En aval des filtres 28, 29, les conduites 22, 27 sont chacune connectées à une pompe qui commande l'aspiration des gaz prélevés soit en amont, soit en aval des échangeurs 12, 12' et de leurs équivalents. Dans l'exemple représenté sur la figure 2, on utilise une pompe unique 30 à double coφs. Le premier coφs 31 est connecté à la conduite21, 18'-21 ', the pipes 16, 16' and their equivalents meet to form a single pipe 22. Likewise, the pipes 17, 17 'and their equivalents for the other exchangers, which take the cooled gases at points B, B 'downstream of the exchangers 12, 12', each lead to a two-way solenoid valve 23-26, 23'-26 'which authorizes or not, at the request of the operator (or of the automatic device which manages the operation of the installation), gas circulation in the continuation of the corresponding pipe. Downstream of said solenoid valves 23-26, 23'-26 ', the lines 17, 17' and their equivalents join together to form a single line 27. Filters 28, 29 are preferably placed on the lines 22, 27, so as to rid the gases circulating there of impurities which could disturb the functioning of the following organs. In the case of a control installation placed on the annealing furnace of a galvanizing line, these filters must in particular be capable of capturing the vapors and particles of zinc that the gases can contain, following the difficult avoidable rise of such vapors from the galvanizing bath to the oven, via the bell. Sintered bronze pellets with a porosity of about 1 μm are well suited for this use. Of course, these filters 28, 29 can be replaced by other filters located further upstream, namely on each of the pipes 16, 16 ', 17, 17' and their equivalents, or can be added to such filters. Downstream of the filters 28, 29, the lines 22, 27 are each connected to a pump which controls the suction of the gases taken off either upstream or downstream of the exchangers 12, 12 'and their equivalents. In the example shown in Figure 2, using a single pump 30 with double coφs. The first cost 31 is connected to the pipe
22, et aspire donc les gaz chauds prélevés aux points A, A' et à leurs équivalents à l'entrée des échangeurs 12, 12' et de leurs équivalents. Le second coφs 32 est connecté à la conduite 27, et aspire donc les gaz refroidis prélevés aux points B, B' et à leurs équivalents à la sortie des échangeurs 12, 12' et de leurs équivalents. Mais, bien entendu, il demeurerait dans l'esprit de l'invention d'utiliser deux pompes totalement distinctes l'une de l'autre au lieu de cette pompe à double coφs 30. A la sortie du premier coφs 31 de la pompe 30, est connectée une conduite 33 qui se subdivise elle-même en deux conduites 34, 35. La conduite 35 est connectée à un déverseur 36 qui a pour fonction de permettre l'évacuation à l'atmosphère d'une proportion déterminée, réglable à la demande, des gaz aspirés par le premier coφs 32 de la pompe 30 et présents dans la conduite 33. Cette évacuation est réalisée par une conduite 37, sur laquelle est implanté un rotamètre 38 permettant de contrôler le débit des gaz évacués. Les gaz qui ne passent pas dans le déverseur 36 poursuivent leur parcours dans la conduite 34, à une pression que le réglage des paramètres de fonctionnement du déverseur 36 permet de maintenir constante, quelles que soient les variations de la pression des gaz en sortie du premier coφs 31 de la pompe 30. Ce maintien à pression constante permet de fiabiliser le fonctionnement de l'ensemble de l'installation, notamment de sa partie « analyse » qui sera vue plus loin. De même, à la sortie du second coφs 32 de la pompe 30, est connectée une conduite 39 qui se subdivise elle-même en deux conduites 40, 41. La conduite 40 est connectée à un déverseur 42 qui a pour fonction de permettre l'évacuation à l'atmosphère d'une proportion déterminée, réglable à la demande, des gaz aspirés par le second coφs 32 de la pompe 30 et présents dans la conduite 39. Cette évacuation est réalisée par une conduite 43, sur laquelle est implanté un rotamètre 44 permettant de contrôler le débit des gaz évacués. Les gaz qui ne passent pas dans le déverseur 42 poursuivent leur parcours dans la conduite 41, à une pression que le réglage des paramètres de fonctionnement du déverseur 42 permet de maintenir constante, quelles que soient les variations de la pression des gaz en sortie du second coφs 32 de la pompe 30. Les rotamètres 38, 44 peuvent être munis d'une alarme indiquant si le débit de gaz qui les traverse devient anormalement bas. Le déclenchement de cette alarme signifie qu'une quantité de gaz trop faible circule dans l'installation, par exemple parce que les filtres 28, 29 sont en passe d'être bouchés et doivent être nettoyés ou remplacés. Dans la pratique, si chaque coφs 31, 32 de la pompe 30 aspire en régime normal un volume de gaz de 500 1/h, ce sont environ 100 1/h qui sont envoyés par chaque coφs 31, 32 vers la partie « analyse » de l'installation, le restant des gaz étant envoyé dans l'atmosphère par les déverseurs 36, 42.22, and therefore sucks the hot gases sampled at points A, A 'and their equivalents at the inlet of the exchangers 12, 12' and their equivalents. The second coφs 32 is connected to the pipe 27, and therefore sucks the cooled gases sampled at points B, B 'and their equivalents at the outlet of the exchangers 12, 12' and their equivalents. But, of course, it would remain in the spirit of the invention to use two pumps that are completely separate from one another instead of this double-cost pump 30. At the outlet of the first cost 31 from the pump 30 , is connected a line 33 which is itself subdivided into two lines 34, 35. The line 35 is connected to an overflow valve 36 which has the function of allowing the evacuation to the atmosphere of a determined proportion, adjustable to the request, gases sucked in by the first coφs 32 of the pump 30 and present in the pipe 33. This evacuation is carried out by a pipe 37, on which is installed a rotameter 38 for controlling the flow of exhaust gas. The gases which do not pass through the outlet 36 continue their course in the pipe 34, at a pressure which the adjustment of the operating parameters of the outlet 36 makes it possible to maintain constant, whatever the variations in the pressure of the gases leaving the first coφs 31 of the pump 30. This maintenance at constant pressure makes the operation of the entire installation more reliable, in particular of its “analysis” part which will be seen below. Likewise, at the outlet of the second co 32s 32 of the pump 30, a pipe 39 is connected which is itself subdivided into two pipes 40, 41. The pipe 40 is connected to an overflow valve 42 which has the function of allowing the evacuation to the atmosphere of a determined proportion, adjustable on demand, of the gases sucked in by the second co 32s 32 of the pump 30 and present in the pipe 39. This evacuation is carried out by a pipe 43, on which a rotameter is installed 44 used to control the flow of exhaust gases. The gases which do not pass through the outlet 42 continue their course in the pipe 41, at a pressure which the adjustment of the operating parameters of the outlet 42 allows to maintain constant, whatever the variations in the pressure of the gases leaving the second coφs 32 of the pump 30. The rotameters 38, 44 can be provided with an alarm indicating whether the gas flow rate passing through them becomes abnormally low. The triggering of this alarm means that too small a quantity of gas is circulating in the installation, for example because the filters 28, 29 are in the process of being clogged and must be cleaned or replaced. In practice, if each cost 31, 32 of the pump 30 sucks a normal volume of gas of 500 1 / h, it is approximately 100 1 / h which are sent by each cost 31, 32 to the "analysis" part of the installation, the remainder of the gases being sent into the atmosphere through the outlets 36, 42.
La conduite 34, qui convoie donc des gaz chauds à analyser, et la conduite 41, qui convoie donc des gaz refroidis à analyser, sont connectées aux deux entrées d'une électro vanne à trois voies 45. Une conduite 46 est connectée à la sortie de cette électro vanne 45, dont la fonction est donc de sélectionner les gaz, chaud/ou refroidis, qui vont être envoyés dans la suite de l'installation pour être analysés (tout autre dispositif assurant cette fonction peut, bien entendu, être substitué à cette électrovanne à trois voies 45). Ces gaz passent ensuite, de préférence, dans un régulateur de débit 47 qui permet d'envoyer lesdits gaz à débit constant dans la suite de l'installation. Ce débit est mesuré, par exemple à l'aide d'un rotamètre 48.Line 34, which therefore conveys hot gases to be analyzed, and line 41, which therefore conveys cooled gases to be analyzed, are connected to the two inputs of a three-way solenoid valve 45. A line 46 is connected to the output of this solenoid valve 45, the function of which is therefore to select the gases, hot / or cooled, which will be sent in the rest of the installation to be analyzed (any other device ensuring this function can, of course, be substituted for this three-way solenoid valve 45). These gases then preferably pass through a flow regulator 47 which makes it possible to send said gases at a constant flow rate in the rest of the installation. This flow is measured, for example using a rotameter 48.
C'est à la sortie du rotamètre 48 qu'est implanté l'hygromètre 49 qui détermine le point de rosée des gaz qui lui sont envoyés. Il est équipé de moyens 50 pour restituer à l'opérateur les résultats de ses analyses, et d'une conduite de sortie 51 pour l'évacuation des gaz dans l'atmosphère après leur analyse. La mesure de ce point de rosée donne indirectement accès à la teneur en vapeur d'eau du gaz analysé.It is at the outlet of the rotameter 48 that the hygrometer 49 is located, which determines the dew point of the gases sent to it. It is equipped with means 50 for returning the results of its analyzes to the operator, and with an outlet pipe 51 for discharging the gases into the atmosphere after their analysis. Measuring this dew point indirectly gives access to the water vapor content of the gas analyzed.
Afin de pouvoir assurer avec une précision satisfaisante une mesure différentielle des points de rosée des gaz prélevés avant et après leur passage dans un echangeur 12, 12', cet hygromètre 50 doit avoir une sensibilité meilleure que celle des hygromètres capacitifs classiques. Il doit être capable de détecter des différences sur ces points de rosée inférieures à 0,5 °C au niveau de -30 à -40°C, de telles différences correspondant à des degrés d'humidité des gaz déjà suffisants pour détériorer la qualité de surface de la bande 2. Leur temps de réponse doit également être aussi rapide que possible. A tous ces points de vue, les hygromètres à infrarouge sont très bien adaptés. Leur sensibilité élevée leur permet de détecter des différences de 0,3 °C ou moins sur les points de rosée des gaz dans la zone de températures visée, et leur temps de réponse est inférieur à 20 s dans ces mêmes conditions. De plus, pour l'application à des fours de recuit intégrés à une ligne de galvanisation, de tels hygromètres ont l'avantage d'être peu sensibles à la présence résiduelle de vapeurs de zinc dans le gaz à analyser. A ce titre ils sont plus avantageux que les hygromètres à miroir, qui ont une bonne sensibilité, mais dont le fonctionnement serait rapidement perturbé par la présence de vapeurs de zinc qui se condenseraient sur le miroir. Les hygromètres à miroir sont également mal adaptés à la mesure de point de rosée aussi bas que ceux des mélanges HN , car leur miroir ne peut pas être refroidi assez efficacement. Cela dit, pour d'autres applications que le contrôle de l'humidité des HN des fours de recuit avant galvanisation où les problèmes précédents (ou d'autres similaires) ne se poseraient pas, l'utilisation d'un hygromètre à miroir peut être envisageable. De même, pour l'application aux fours de recuit intégrés à une ligne de galvanisation, tout autre type d'hygromètre qu'un hygromètre à infrarouge qui aurait les mêmes performances et la même facilité d'utilisation serait convenable.In order to be able to ensure with satisfactory precision a differential measurement of the dew points of the gases sampled before and after their passage through an exchanger 12, 12 ′, this hygrometer 50 must have a better sensitivity than that of conventional capacitive hygrometers. It must be able to detect differences in these dew points below 0.5 ° C at the level of -30 to -40 ° C, such differences corresponding to the humidity levels of the gases already sufficient to deteriorate the quality of strip surface 2. Their response time should also be as rapid as possible. From all these points of view, infrared hygrometers are very well suited. Their high sensitivity allows them to detect differences of 0.3 ° C or less in the dew points of gases in the target temperature zone, and their response time is less than 20 s under these same conditions. In addition, for application to annealing ovens integrated into a galvanizing line, such hygrometers have the advantage of being insensitive to the residual presence of zinc vapors in the gas to be analyzed. As such, they are more advantageous than mirror hygrometers, which have good sensitivity, but whose operation would be rapidly disturbed by the presence of zinc vapors which would condense on the mirror. Mirror hygrometers are also ill-suited to measuring dew point as low as those in HN mixtures, as their mirror cannot be cooled sufficiently effectively. That said, for applications other than controlling the humidity of HNs in annealing ovens before galvanizing where the above problems (or others similar) would not arise, the use of a mirror hygrometer may be possible. Similarly, for application to annealing ovens integrated into a galvanizing line, any other type of hygrometer than an infrared hygrometer which would have the same performance and the same ease of use would be suitable.
L'installation selon l'invention est utilisée de la façon suivante. Dans un premier temps, il est nécessaire d'étalonner l'hygromètre 50. Cet étalonnage peut être réalisé au moyen d'une installation indépendante, mais il est avantageux d'intégrer les moyens d'étalonnage à l'installation de contrôle elle-même, comme représenté sur la figure 2. A cet effet, on insère sur la conduite 46, qui relie la sortie de F électro vanne à trois voies 45 au régulateur de débit 47, une électrovanne à deux voies 52 qui permet d'interrompre à volonté le passage des gaz provenant du four 1. En aval de cette électrovanne 52 on connecte sur la conduite 46 une conduite 53 permettant d'y introduire un gaz étalon en lieu et place des gaz provenant du four. L'admission de ce gaz étalon dans la conduite 53 est commandée par une électrovanne à trois voies 54, à laquelle sont connectés les récipients 55, 56 renfermant les deux gaz étalons susceptibles d'être utilisés. Ces gaz sont, par exemple comme représenté, d'une part de l'azote pur, et d'autre part un ou des mélanges contenant de l'azote et une proportion connue de vapeur d'eau, ou d'un gaz tel que l'hexafluorure de soufre SF6 dont on sait que sa bande d'absoφtion dans l'infrarouge est voisine de celle de la vapeur d'eau. Les avantages de l'utilisation d'un mélange N2-SF6 plutôt que d'un mélange N2-H2O sont que les mélanges N2-H,O sont peu stables dans le temps, et qu'il n'est pas possible de gonfler les bouteilles de ces mélanges sous de fortes pressions sans provoquer une condensation de la vapeur d'eau (par exemple, pour une teneur en eau de 400 ppm, la pression maximale tolérable est de 11 bars). Les bouteilles de mélanges N2-H2O, de par leur capacité nécessairement réduite et leur durée d'utilisation limitée, ne sont donc pas bien adaptées à un emploi dans des conditions industrielles. Les bouteilles de mélanges N2-SF6 sont, de ce point de vue, bien supérieures, car ce mélange tolère les mises sous pression importantes, est stable dans le temps, et ne coûte d'ailleurs pas sensiblement plus cher que les mélanges N2-H2O préparés industriellement. Si on a préalablement déterminé, par étalonnage avec des mélanges N2- H2O, d'une part la correspondance entre la teneur en SF6 d'un gaz étalon et le signal de sortie fourni par l'hygromètre, et d'autre part à quelle teneur en vapeur d'eau correspondrait ce même signal de sortie, il est possible de réaliser un étalonnage de l'hygromètre à infrarouge 49 avec des mélanges N2-SF6 avant toute série de mesures de l'humidité de l'atmosphère d'un four. Pour cet étalonnage, la vanne 52 est fermée et la vanne 54 est ouverte, de manière à laisser pénétrer dans les conduites 53 et 46 l'un au choix des gaz étalons contenus dans les récipients 55, 56. On peut, bien entendu, utiliser un nombre plus élevé de gaz étalons, et modifier l'installation en conséquence. Une fois l'étalonnage de l'hygromètre 49 réalisé, la vanne 54 est fermée et la vanne 52 ouverte, et l'analyse des gaz en provenance du four 1 peut débuter.The installation according to the invention is used in the following manner. First, it is necessary to calibrate the hygrometer 50. This calibration can be carried out by means of an independent installation, but it is advantageous to integrate the calibration means with the control installation itself. , as shown in FIG. 2. To this end, a two-way solenoid valve 52 which allows interruption at will is inserted on the line 46, which connects the outlet of the three-way solenoid valve 45 to the flow regulator 47. the passage of gases from the oven 1. Downstream of this solenoid valve 52 is connected to the pipe 46 a pipe 53 for introducing a standard gas in place of the gases from the oven. The admission of this standard gas into line 53 is controlled by a three-way solenoid valve 54, to which the receptacles 55, 56 containing the two standard gases capable of being used are connected. These gases are, for example as shown, on the one hand pure nitrogen, and on the other hand one or more mixtures containing nitrogen and a known proportion of water vapor, or of a gas such as sulfur hexafluoride SF 6 which it is known that its absorption band in the infrared is close to that of water vapor. The advantages of using an N 2 -SF 6 mixture rather than an N 2 -H 2 O mixture are that the N 2 -H, O mixtures are not very stable over time, and that it does not it is not possible to inflate the bottles of these mixtures under high pressures without causing condensation of the water vapor (for example, for a water content of 400 ppm, the maximum tolerable pressure is 11 bar). The bottles of N 2 -H 2 O mixtures, by virtue of their necessarily reduced capacity and their limited period of use, are therefore not well suited for use under industrial conditions. Bottles of N2-SF 6 mixtures are, from this point of view, much superior, because this mixture tolerates significant pressurization, is stable over time, and moreover does not cost significantly more than N 2 mixtures -H 2 O industrially prepared. If we have previously determined, by calibration with N 2 - H 2 O mixtures, on the one hand the correspondence between the SF 6 content of a standard gas and the output signal supplied by the hygrometer, and on the other apart from what water vapor content this same output signal would correspond to, it is possible to calibrate the infrared hygrometer 49 with N 2 -SF 6 mixtures before any series of humidity measurements atmosphere of an oven. For this calibration, the valve 52 is closed and the valve 54 is open, so as to allow the conduits 53 and 46 to enter one of the standard gases contained in the containers 55, 56 as desired. It is of course possible to use a higher number of standard gases, and modify the installation accordingly. Once the hygrometer 49 has been calibrated, the valve 54 is closed and the valve 52 open, and the analysis of the gases coming from the furnace 1 can begin.
On commence d'abord par comparer les humidités des gaz prélevés en amont et en aval d'un premier echangeur, par exemple l'échangeur 12. A cet effet, on ouvre les électrovannes 18 et 23, on ferme toutes les autres électrovannes 19-21, 18'-21 ', 24-26, 23'- 26', et on fait fonctionner simultanément les deux coφs de la pompe 30. Le premier coφs 31 de la pompe 30 amène donc du gaz chaud en direction de l'électrovanne à trois voies 45 par l'intermédiaire de la conduite 34, et le second coφs 32 de la pompe 30 amène du gaz refroidi en direction de cette même électrovanne 45 par l'intermédiaire de la conduite 41. Dans la première étape de l'analyse, l'électrovanne 45 est ouverte de manière à n'admettre dans sa conduite de sortie 46 que du gaz chaud en provenance de la conduite 34, et ce gaz est donc envoyé à l'hygromètre 49 pendant une durée suffisante pour la réalisation de la détermination de son point de rosée, dont on déduit sa teneur en vapeur d'eau. Une fois cette durée écoulée, l'électrovanne 45 est actionnée de manière à ce qu'elle n'admette dans sa conduite de sortie 46 que du gaz refroidi en provenance de la conduite 41, qui est à son tour envoyé à l'hygromètre 49. Les résultats des analyses du gaz chaud et du gaz refroidi sont ensuite restitués à l'opérateur par les moyens 50, de manière à permettre une comparaison immédiate des points de rosée respectifs du gaz chaud tel que prélevé dans le four et de ce même gaz refroidi après son passage par l'échangeur 12. On peut déduire de cette comparaison des points de rosée la valeur ΔH2O de l'écart entre les teneurs en vapeur d'eau du gaz chaud et du gaz refroidi. Si cette valeur est nulle ou très faible (par exemple si elle se traduit par un écart inférieur à 0,5 °C sur les points de rosée respectifs des gaz), on peut conclure que l'échangeur 12 a encore une étanchéité suffisante et ne nécessite pas d'être remplacé. Si ΔH2O s'avère importante, c'est le signe qu'un défaut d'étanchéité existe sur cet echangeur, dont il faut alors envisager le remplacement pour éviter une détérioration de la qualité de l'atmosphère du four 1.We first start by comparing the humidities of the gases sampled upstream and downstream of a first exchanger, for example the exchanger 12. For this purpose, we open the solenoid valves 18 and 23, we close all the other solenoid valves 19- 21, 18'-21 ', 24-26, 23'- 26', and the two coφs of the pump 30 are operated simultaneously. The first coφs 31 of the pump 30 therefore brings hot gas towards the solenoid valve three-way 45 via the pipe 34, and the second co 32s 32 of the pump 30 brings cooled gas towards this same solenoid valve 45 via the pipe 41. In the first step of the analysis , the solenoid valve 45 is open so as to admit into its outlet pipe 46 only hot gas from the pipe 34, and this gas is therefore sent to the hygrometer 49 for a sufficient time for the realization of the determination of its dew point, from which its water vapor content is deduced. Once this time has elapsed, the solenoid valve 45 is actuated so that it admits into its outlet pipe 46 only cooled gas coming from the pipe 41, which in turn is sent to the hygrometer 49 The results of the analyzes of the hot gas and the cooled gas are then returned to the operator by the means 50, so as to allow an immediate comparison of the respective dew points of the hot gas as taken from the oven and of this same gas. cooled after passing through the exchanger 12. It is possible to deduce from this comparison of the dew points the value ΔH 2 O of the difference between the water vapor contents of the hot gas and of the cooled gas. If this value is zero or very low (for example if it results in a difference of less than 0.5 ° C. on the respective dew points of the gases), it can be concluded that the exchanger 12 still has sufficient tightness and does not not need to be replaced. If ΔH 2 O proves to be significant, this is a sign that a leakage exists on this exchanger, the replacement of which must then be considered in order to avoid a deterioration in the quality of the atmosphere of the furnace 1.
Une fois ce résultat obtenu, les électrovannes 18, 23 sont fermées et les électrovannes 18', 23' sont ouvertes, de manière à réaliser la même opération de contrôle que précédemment sur l'échangeur 12'. L'opération est ensuite similairement répétée pour chacun des échangeurs de l'installation, par fermeture et ouvertures des électro vannes adéquates. La série de contrôle des échangeurs telle qu'on vient de la décrire est effectuée pendant le fonctionnement du four, sans nécessiter son arrêt, avec une périodicité choisie par l'opérateur. Les différentes opérations d'ouverture et de fermeture des électrovannes peuvent être effectuées manuellement, et la comparaison entre les humidités du gaz avant et après son passage dans un echangeur donné peut être réalisée par l'opérateur au vu des résultats que les moyens 50 lui restituent. Mais il va de soi qu'un fonctionnement entièrement automatique de l'installation est envisageable ; il aboutit alors, le cas échéant, au déclenchement d'une alarme signalant qu'un echangeur donné est défectueux. La possibilité de détecter avec une grande finesse non seulement si un echangeur présente un défaut d'étanchéité et de quantifier ce défaut, mais encore de quel echangeur précis il s'agit, est un avantage important de l'installation par rapport à celles antérieurement connues, en ce qu'il permet de gagner beaucoup de temps sur les opérations de réfection. De plus, on évite ainsi le besoin d'augmenter temporairement la pression de l'eau circulant dans les échangeurs pour tenter de détecter les microfuites, opération dont on a dit qu'elle risquait d'accélérer la détérioration des brasures.Once this result has been obtained, the solenoid valves 18, 23 are closed and the solenoid valves 18 ', 23' are open, so as to carry out the same control operation as above on the exchanger 12 '. The operation is then similarly repeated for each of the installation exchangers, by closing and opening the appropriate solenoid valves. The exchanger control series as just described is carried out during the operation of the furnace, without requiring it to be stopped, with a periodicity chosen by the operator. The various opening and closing operations of the solenoid valves can be carried out manually, and the comparison between the humidities of the gas before and after its passage through a given exchanger can be carried out by the operator in view of the results which the means 50 restore to him. . However, it goes without saying that fully automatic operation of the installation is possible; it then results, if necessary, in the triggering of an alarm signaling that a given exchanger is defective. The possibility of detecting with great finesse not only if an exchanger exhibits a leak and to quantify this defect, but also of which precise exchanger it is, is an important advantage of the installation compared to those previously known. , in that it saves a lot of time on repair operations. In addition, this avoids the need to temporarily increase the pressure of the water circulating in the exchangers in an attempt to detect micro-leaks, an operation which has been said to risk accelerating the deterioration of the solder.
Si on constate lors des analyses que l'humidité du gaz chaud prélevé en amont d'un ou de plusieurs échangeurs est déjà anormalement élevée et qu'elle n'augmente pas après le passage de ce gaz dans ledit ou lesdits échangeurs, on peut en déduire l'existence d'entrées d'eau dans le four dues à des détériorations d'autres organes refroidis de l'installation que les échangeurs (par exemple les paliers des rouleaux 3-8, ou les tubes de visée des pyromètres qui mesurent la température à l'intérieur du four). Cette humidité peut également être due à des entrées d'air conduisant à faire réagir une quantité anormalement élevée d'oxygène avec l'hydrogène du HNX. La multiplicité des points de prélèvement de gaz chauds (un par echangeur) peut grandement aider à la localisation du défaut.If it is observed during the analyzes that the humidity of the hot gas taken upstream from one or more exchangers is already abnormally high and that it does not increase after the passage of this gas through said exchanger (s), it can be deduce the existence of water entries in the oven due to deterioration of other cooled organs of the installation than the exchangers (for example the bearings of rollers 3-8, or the sight tubes of the pyrometers which measure the temperature inside the oven). This humidity can also be due to air inlets causing an abnormally high amount of oxygen to react with the hydrogen of HN X. The multiplicity of hot gas sampling points (one per exchanger) can greatly help in locating the fault.
Une caractéristique particulièrement avantageuse de l'installation qui vient d'être décrite et représentée réside dans l'utilisation d'une pompe 30 à double coφs (ou de deux pompes séparées fonctionnant simultanément), à laquelle fait suite l'électrovanne à trois voies 45 qui commande l'admission dans l'hygromètre 49 soit du gaz chaud, soit du gaz refroidi. On pourrait, en effet, envisager d'utiliser une pompe unique à simple coφs, et de placer l'électrovanne 45 en amont de cette pompe. Mais la disposition retenue dans l'invention a pour avantage de permettre un passage aussi rapide que possible entre l'analyse du prélèvement de gaz chaud et l'analyse du prélèvement de gaz refroidi par un echangeur donné, rapidité qui est très importante dans le cas d'une mesure différentielle de l'humidité de ces gaz.A particularly advantageous characteristic of the installation which has just been described and shown resides in the use of a pump 30 with double coφs (or two separate pumps operating simultaneously), which is followed by the three-way solenoid valve 45 which controls the admission into the hygrometer 49 of either hot gas or cooled gas. One could, in fact, consider using a single pump with single costs, and placing the solenoid valve 45 upstream of this pump. However, the arrangement adopted in the invention has the advantage of allowing as rapid a passage as possible between the analysis of the sample of hot gas and the analysis of the sample of gas cooled by a given exchanger, speed which is very important in the case of a differential measurement of the humidity of these gases.
Les matériaux utilisés pour les différents organes de l'installation doivent être compatibles avec les propriétés des gaz destinés à la traverser, qui peuvent être corrosifs aux températures rencontrées, surtout s'ils sont chargés d'humidité. En particulier, il est conseillé d'utiliser des métaux tels que l'acier inoxydable pour réaliser les coφs de la pompe 30, et des matières plastiques telles que le PTFE pour les membranes de la pompe 30 et du régulateur de débit 47. Quand aux diverses conduites, elles doivent être, par exemple, en cuivre ou en acier inoxydable, et avoir leurs parois internes polies ou revêtues d'un matériau tel que la silice fondue, afin d'éviter que la vapeur d'eau ne s'y accroche, ce qui fausserait les résultats des analyses.The materials used for the various components of the installation must be compatible with the properties of the gases intended to pass through it, which can be corrosive at the temperatures encountered, especially if they are charged with humidity. In particular, it is advisable to use metals such as stainless steel to make the pump costs 30, and plastic materials such as PTFE for the membranes of the pump 30 and of the flow regulator 47. When to various pipes, they must be, for example, made of copper or stainless steel, and have their internal walls polished or coated with a material such as fused silica, in order to prevent water vapor from clinging to it , which would distort the results of the analyzes.
Il va de soi que les électrovannes de divers types qui ont été citées dans la description qui précède peuvent être remplacées par des vannes à commande manuelle (ou tous autres dispositifs) assurant les mêmes fonctions d'autorisation ou non de la circulation de tel ou tel gaz dans les différentes parties de l'installation. Les électrovannes ont l'avantage évident de pouvoir être commandées à distance par l'opérateur ou le dispositif automatique de gestion de l'installation.It goes without saying that the solenoid valves of various types which have been mentioned in the above description can be replaced by manually operated valves (or any other device) ensuring the same functions of authorizing or not the circulation of such and such. gases in the different parts of the installation. The solenoid valves have the obvious advantage of being able to be controlled remotely by the operator or the automatic installation management device.
Les entrées d'air dans l'installation de prélèvement et de mesure sont à proscrire absolument. A cet effet, il est conseillé, même lorsque l'installation n'est pas utilisée en mode « analyse », d'y maintenir une circulation permanente de gaz extraits du four, ce qui a aussi pour avantage de réduire le nombre et l'ampleur des chocs thermiques auxquels l'installation est soumise.Air inlets in the sampling and measuring system are to be avoided absolutely. To this end, it is advisable, even when the installation is not used in "analysis" mode, to maintain a permanent circulation of gases extracted from the oven, which also has the advantage of reducing the number and extent of thermal shock to which the installation is subject.
Si un même site industriel comporte plusieurs fours sur lesquels une installation de contrôle selon l'invention peut être avantageusement utilisée, il est envisageable de concevoir une installation mobile comprenant l'ensemble des organes précédemment décrits à partir des filtres 28, 29 ou de la pompe 30. Chaque four serait muni à demeure des vannes et conduites adéquates, jusqu'aux conduites 22, 27 inclusivement, auxquelles il suffirait de connecter l'installation mobile chaque fois qu'on jugerait nécessaire d'effectuer un contrôle de l'étanchéité des échangeurs dudit four. L'hygromètre 49, la pompe 30, etc pourront donc n'exister sur le site qu'à un seul exemplaire.If the same industrial site includes several ovens on which a control installation according to the invention can be advantageously used, it is conceivable to design a mobile installation comprising all of the members previously described using filters 28, 29 or the pump 30. Each oven would be permanently fitted with suitable valves and pipes, up to pipes 22, 27 inclusive, to which it would suffice to connect the mobile installation whenever it is deemed necessary to check the tightness of the exchangers. from said oven. The hygrometer 49, the pump 30, etc. may therefore only exist on the site in one copy.
L'invention est applicable au contrôle de l'étanchéité de toute installation comportant des échangeurs eau-gaz destinés à abaisser la température d'un gaz constituant l'atmosphère d'un four, le four de recuit précédemment décrit n'étant qu'un exemple où l'utilisation de l'invention est particulièrement avantageuse. The invention is applicable to checking the tightness of any installation comprising water-gas exchangers intended to lower the temperature of a gas constituting the atmosphere of an oven, the annealing oven previously described being only a example where the use of the invention is particularly advantageous.

Claims

REVENDICATIONS
1) Installation de contrôle de l'étanchéité d'échangeurs de chaleur eau-gaz équipant un four industriel (1), ledit four (1) comprenant au moins un ensemble formé par des moyens (9, 10, 11, 9', 10', 11 ') d'extraction d'un gaz chaud présent dans une zone donnée dudit four (1), un echangeur de chaleur eau-gaz (12, 12') destiné à refroidir ledit gaz chaud et des moyens (14, 15, 14', 15') pour réintroduire ledit gaz chaud refroidi dans une zone dudit four (1) située en aval de ladite zone où a eu lieu l'extraction dudit gaz chaud, caractérisé en ce qu'elle comporte : - des moyens (16, 16', 22, 31) de prélèvement dudit gaz chaud en des points (A,1) Installation for checking the tightness of water-gas heat exchangers fitted to an industrial oven (1), said oven (1) comprising at least one assembly formed by means (9, 10, 11, 9 ', 10 ', 11') for extracting a hot gas present in a given zone of said oven (1), a water-gas heat exchanger (12, 12 ') intended to cool said hot gas and means (14, 15 , 14 ', 15') for reintroducing said cooled hot gas into an area of said furnace (1) located downstream of said area where said hot gas was extracted, characterized in that it comprises: - means ( 16, 16 ', 22, 31) for sampling said hot gas at points (A,
A') situés chacun en amont d'un echangeur (12, 12') et des vannes à deux voies (18-21, 18 '-21 ') autorisant la réalisation de ce prélèvement ;A ') each located upstream of an exchanger (12, 12') and two-way valves (18-21, 18 '-21') authorizing the carrying out of this withdrawal;
- des moyens (17, 17', 27, 32) de prélèvement dudit gaz chaud refroidi en des points (B, B') situés chacun en aval d'un echangeur (12, 12') et des vannes à deux voies (23-26, 23 '-26') autorisant la réalisation de ce prélèvement ;- Means (17, 17 ', 27, 32) for withdrawing said hot gas cooled at points (B, B') each located downstream of an exchanger (12, 12 ') and two-way valves (23 -26, 23 '-26') authorizing the carrying out of this levy;
- des moyens (36, 42) pour réguler les pressions respectives dudit gaz chaud et dudit gaz refroidi en aval desdits moyens de prélèvement (16, 16', 22, 31, 17, 17', 27, 32) ;- Means (36, 42) for regulating the respective pressures of said hot gas and said cooled gas downstream of said sampling means (16, 16 ', 22, 31, 17, 17', 27, 32);
- des moyens, tels qu'une vanne à trois voies (45) et sa conduite de sortie (46), pour sélectionner ledit gaz chaud ou ledit gaz refroidi et l'envoyer dans un hygromètre (49) ;- Means, such as a three-way valve (45) and its outlet pipe (46), for selecting said hot gas or said cooled gas and sending it to a hygrometer (49);
- et des moyens (50) pour restituer à l'opérateur les résultats des analyses effectués par l'hygromètre (49) en lui permettant de comparer le degré d'humidité dudit gaz chaud et dudit gaz refroidi pour chacun des échangeurs (12, 12').- And means (50) for restoring to the operator the results of the analyzes carried out by the hygrometer (49) allowing him to compare the degree of humidity of said hot gas and of said cooled gas for each of the exchangers (12, 12 ').
2) Installation selon la revendication 1, caractérisée en ce qu'elle comporte des moyens (47, 48) pour réguler le débit du gaz parvenant à l'hygromètre (49) situés sur la conduite de sortie (46) de la vanne à trois voies (45).2) Installation according to claim 1, characterized in that it comprises means (47, 48) for regulating the flow of gas reaching the hygrometer (49) located on the outlet pipe (46) of the three-way valve tracks (45).
3) Installation selon la revendication 1 ou 2, caractérisée en ce qu'elle comporte des moyens (52, 53, 54, 55, 56) permettant d'étalonner l'hygromètre (49) avant la réalisation d'une série de mesures. 4) Installation selon la revendication 3, caractérisé en ce que lesdits moyens (52,3) Installation according to claim 1 or 2, characterized in that it comprises means (52, 53, 54, 55, 56) for calibrating the hygrometer (49) before carrying out a series of measurements. 4) Installation according to claim 3, characterized in that said means (52,
53, 54, 55, 56) permettant d'étalonner l'hygromètre comportent au moins un récipient contenant un mélange d'azote et d'hexafluorure de soufre.53, 54, 55, 56) for calibrating the hygrometer comprise at least one container containing a mixture of nitrogen and sulfur hexafluoride.
5) Installation selon l'une des revendications 1 à 4, caractérisée en ce que lesdits moyens de prélèvement du gaz chaud et du gaz refroidis comportent une pompe (30) à double coφs ou deux pompes indépendantes, la ou lesdites pompes étant situées en amont de ladite vanne à trois voies (45).5) Installation according to one of claims 1 to 4, characterized in that said means for withdrawing hot gas and cooled gas comprise a pump (30) with double coφs or two independent pumps, the said pump or pumps being located upstream of said three-way valve (45).
6) Installation selon l'une des revendications 1 à 5, caractérisée en ce que l'hygromètre (49) est un hygromètre à infrarouge. 6) Installation according to one of claims 1 to 5, characterized in that the hygrometer (49) is an infrared hygrometer.
EP00960797A 1999-09-09 2000-09-06 Installation for controlling the sealed condition of water-gas heat exchangers for industrial furnaces Withdrawn EP1137819A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR9911258A FR2799828B1 (en) 1999-09-09 1999-09-09 WATER-GAS HEAT EXCHANGER SEALING SYSTEM FOR INDUSTRIAL OVENS
FR9911258 1999-09-09
PCT/FR2000/002444 WO2001018261A1 (en) 1999-09-09 2000-09-06 Installation for controlling the sealed condition of water-gas heat exchangers for industrial furnaces

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EP1137819A1 true EP1137819A1 (en) 2001-10-04

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EP00960797A Withdrawn EP1137819A1 (en) 1999-09-09 2000-09-06 Installation for controlling the sealed condition of water-gas heat exchangers for industrial furnaces

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EP (1) EP1137819A1 (en)
BR (1) BR0007082A (en)
CA (1) CA2351633A1 (en)
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WO (1) WO2001018261A1 (en)

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Publication number Priority date Publication date Assignee Title
FR2799828B1 (en) 1999-09-09 2001-11-23 Lorraine Laminage WATER-GAS HEAT EXCHANGER SEALING SYSTEM FOR INDUSTRIAL OVENS
WO2014115190A1 (en) * 2013-01-28 2014-07-31 Ｊｆｅスチール株式会社 Method for adjusting in-furnace atmosphere of continuous heat-treating furnace

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US4815965A (en) * 1983-05-12 1989-03-28 Applied Automation, Inc. Monitoring and control of a furnace
US4492560A (en) * 1983-11-14 1985-01-08 Hardy Sundberg Gas combustion control apparatus
DE3809516A1 (en) * 1988-03-22 1989-10-05 Messer Griesheim Gmbh Method for supplying inert gas and reaction gas to a vertical or horizontal annealing unit
US4876889A (en) * 1988-07-05 1989-10-31 Parthasarathy Shakkottai Acoustic humidity sensor
US5137586A (en) * 1991-01-02 1992-08-11 Klink James H Method for continuous annealing of metal strips
FR2697939B1 (en) * 1992-11-06 1995-02-24 Electricite De France Method and device for detecting leaks from bushings of nuclear reactor vessel cover in operation.
US5387273A (en) * 1993-12-28 1995-02-07 The United States Of America As Represented By The Secretary Of The Interior Process for removing copper in a recoverable form from solid scrap metal
FR2799828B1 (en) 1999-09-09 2001-11-23 Lorraine Laminage WATER-GAS HEAT EXCHANGER SEALING SYSTEM FOR INDUSTRIAL OVENS

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Title
See references of WO0118261A1 *

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WO2001018261A1 (en) 2001-03-15
CA2351633A1 (en) 2001-03-15
FR2799828A1 (en) 2001-04-20
FR2799828B1 (en) 2001-11-23
US6659166B1 (en) 2003-12-09
BR0007082A (en) 2001-08-07

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