EP0285464B1 - Erhitzungsvorrichtung, insbesondere zur Wärmebehandlung von gebogenen Rohren mit niedrigem Durchmesser - Google Patents
Erhitzungsvorrichtung, insbesondere zur Wärmebehandlung von gebogenen Rohren mit niedrigem Durchmesser Download PDFInfo
- Publication number
- EP0285464B1 EP0285464B1 EP88400413A EP88400413A EP0285464B1 EP 0285464 B1 EP0285464 B1 EP 0285464B1 EP 88400413 A EP88400413 A EP 88400413A EP 88400413 A EP88400413 A EP 88400413A EP 0285464 B1 EP0285464 B1 EP 0285464B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- winding
- tube
- heating element
- heating device
- heating
- 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.)
- Expired - Lifetime
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/40—Heating elements having the shape of rods or tubes
- H05B3/54—Heating elements having the shape of rods or tubes flexible
-
- 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
- C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B37/00—Component parts or details of steam boilers
- F22B37/002—Component parts or details of steam boilers specially adapted for nuclear steam generators, e.g. maintenance, repairing or inspecting equipment not otherwise provided for
- F22B37/003—Maintenance, repairing or inspecting equipment positioned in or via the headers
Definitions
- the invention relates to a heating device for the thermal treatment of a tube of small diameter and of curved shape over at least part of its length and the use of this heating device, in particular for the thermal treatment of tubes of steam generator.
- the steam generators of pressurized water nuclear reactors comprise a bundle made up of several thousand tubes with a diameter close to two centimeters, in the shape of a U.
- Each of the tubes has two rectilinear branches having a length close to ten meters, the ends are fixed in the tubular plate of the steam generator and a substantially semi-circular curved part joining the two rectilinear branches to their upper part.
- the curved parts or hangers of the tubes of a bundle are not identical to each other, the dimension and the radius of curvature of the hangers depend on the position of the tubes in the bundle.
- the tube hangers placed in the central part of the bundle or small hangers have a much smaller radius of curvature than the tube hangers located towards the outside of the bundle.
- the tubes of the bundle of a steam generator of a pressurized water nuclear reactor are in contact, during the operation of the reactor, on their inner surface, with the pressurized water circulating in the primary circuit and the reactor vessel. and, by their outer surface, with the feed water which is introduced into the envelope of the steam generator to be heated and vaporized by the heat provided by the primary water.
- the tubes of a steam generator of a pressurized water nuclear reactor are subjected to corrosion in service which can result, after a long period of operation, by cracking of these tubes in certain sensitive areas such as the area of transition between the part of the tube deformed inside the tube plate, during its fixing by crimping and the non-deformed part of the tube or even the area of the hangers and of connection with the rectilinear branches.
- This increased corrosion and cracking in certain zones of the tube is linked to the presence, in the wall of this tube, of internal stresses resulting from the mechanical operations implemented during the forming and the positioning of the bundle and from the external stresses of thermal or mechanical origin undergone by the beam, during the operation of the reactor.
- Such heating elements may include a flexible mandrel on which an electrical resistance wire is wound in a helix to form a winding whose outside diameter is less than the inside diameter of the tube to be treated.
- the tubes of the steam generator are very often slightly ovalized in the area of the hangers, so that it is necessary to provide heating elements whose diameter is very much smaller than the inside diameter of the tube and the efficiency and the efficiency of electric heating are then poor.
- the known heating elements also do not make it possible to inject a sweeping gas into the heating zone in order to homogenize the treatment temperature along the hanger.
- the object of the invention is therefore to propose a heating device for the heat treatment of a tube of small diameter and of curved shape over at least part of its length, comprising a flexible heating element comprising an electrical resistance wire. helically wound to form a winding whose outside diameter is less than the inside diameter of the tube, as well as a set of means for guiding, moving and locating the heating element in the tube, this device being of a simple and inexpensive structure which can easily be adapted to the shape of the tube to be treated and which makes it possible to scan the heating zone with gas.
- the electric resistance heating wire constitutes the central core of a coaxial cable comprising an external metallic envelope and an insulator interposed between the central core and the outer casing and the coaxial cable is wound to form a helical winding.
- the invention also relates to the use of the device according to the invention, in particular for carrying out the thermal stress relieving treatment of small hangers of a bundle of steam generator of a pressurized water nuclear reactor.
- FIG. 1 we see the lower part of a steam generator 1 comprising a tubular plate 2 of great thickness in which are crimped the ends of U-shaped tubes 3 constituting the bundle of the steam generator.
- the diameter of the tubes 3 has been considerably exaggerated in relation to the dimensions of the tube plate and of the bundle, to facilitate the representation of the heating device.
- two tubes 3 arranged towards the central part of the bundle the upper part 3a of which is bent in a semicircular shape constitutes a small beam hanger.
- the device according to the invention shown in FIG. 1 is used for the heat treatment of the parts 3a of the tubes 3.
- the part of the steam generator located below the tube plate 2 constitutes a water box 4 in two parts 4a and 4b separated by a partition 5.
- One of the parts of the water box is connected to a pipe of the primary circuit of the reactor bringing, during the operation of the nuclear reactor, the primary water under pressure heated in contact with the core, from the reactor vessel to the generator steam.
- the other part of the water box 4 is connected to a pipe of the primary circuit of the reactor ensuring, during the operation of the reactor, the return of the primary water cooled in the steam generator to the tank.
- the primary water circulates inside the tubes 3 between one of their ends constituting an inlet end opening into one of the parts 4a or 4b of the water box 4 and their other end, or outlet end , opening into the other part 4a or 4b of the water box 4.
- Each of the parts 4a, 4b of the water box has a respective manhole 6a, 6b which is closed by a tight and pressure-resistant tape, during the normal operation of the nuclear reactor.
- the treatment of the steam generator tubes is carried out, when the nuclear reactor is stopped, during a maintenance and repair phase of this reactor.
- the heating device according to the invention is implemented inside the steam generator using the parts 4a and 4b of the water box as access compartments to the tubes of the reactor.
- the manholes 6a and 6b are then opened to allow the passage of the tools necessary for the treatment of the tubes.
- a handling machine of a known type fix under the entry face of the tubular plate, in the through ends of tubes of the bundle and allowing the installation of tools successively at each end of the tubes to be treated flush with the entry face of the tube plate .
- a handling machine is well known and is commonly used for checking, sealing, mechanical treatment or repair by lining the tubes of the bundle.
- All handling operations can be controlled remotely from a control station outside the water box of the steam generator in which a certain radioactivity prevails.
- the handling machine makes it possible to set up, in the part 4a of the water box, under the entry face of the tubular plate 2, a carrier device 8, in the extension of one end of a flush-fitting tube 3 this entry face.
- the handling device also makes it possible to set up in the part 4b of the water box, a device for teur 9 on which are fixed a pusher shooter 10 and a guide duct 11 of curved shape.
- the conduit 11 and the pusher-puller 10 are located in the extension of the end of the tube 3 to be treated, opening out into the part 4b of the water box.
- the heating device comprises, in addition to the support, guide and displacement means 8, 9, 10, 11 located in the water box 4, a set of means arranged outside the box water and in particular a battery of coils 12 rotatably mounted on a horizontal axis on the side of part 4b of the water box.
- each of the coils 12 On each of the coils 12 is wound a heating element 14 according to the invention intended to be introduced into the tube 3, to carry out the heat treatment.
- Each of the coils 12 can be connected, for supplying the heating element 14 with electric heating current, to a supply bench 15, itself connected to supply and control cabinets 16 and 17 placed in a command post from which operations are controlled.
- Each heating element 14 is connected at its front part to an extension 14 'which is wound on the coil 12, above the heating element 14.
- the heating device also includes a push-pull device 18 making it possible to move in one direction or the other a traction cable 20 comprising at one of its ends a mechanical connection device 21 and a position control probe 22 to eddy current.
- a coil 19 makes it possible to store the cable 20 upstream of the push-pull device 18.
- a flexible guide duct 24, constituted for example by a thin stainless steel tube having waves in its wall, makes it possible to join the outlet of the push-pull 18 to bearer 8.
- An eddy current position measurement unit 25 and control or command units 26, 27 of the pusher shooters 10 and 18 are arranged in the control station.
- a set of electrical connections 28 makes it possible to connect the push-pullers 10 and 18 and position control means, to the control units 26 and 27.
- This element 14 comprises a front part 14a, the end of which is constituted by an end piece 30 of ogive shape, an intermediate part 14b ensuring the passage of the electrical and sweep gas connections and an end part 14c ensuring the connection of the heating element with electrical sources and purge gas source.
- the entire heating element is produced in flexible form allowing it to be wound on a coil 12.
- the diameter of this heating element, at least in its parts 14a and 14b, is less than the inside diameter of a tube 3.
- the front part 14a constitutes the heating element proper produced in the form of a helical winding with contiguous turns of a coaxial cable 32, the section of which is shown in FIG. 4.
- the winding of the coaxial cable 32 is a multiple winding with nested turns, the midpoint of which is disposed at the level of the end piece 30.
- the winding shown is a double winding formed from two identical coaxial cables 32 and 32 ′, the midpoints of which are located at the end piece 30.
- the figure 2a relates to a single winding whose midpoint is located in room 30.
- the part 30 has a general ogive shape allowing the heating element to be guided in the tube to be treated.
- This part 30 has at its front end an opening 36 allowing its connection to the extension 14 '.
- the part 30 also comprises, at the rear of the opening 36, a channel 37 for the passage of the coaxial cable 32 passing through the part 30 right through, in a radial direction.
- the coaxial cables 32 and 32 ' are engaged in two channels 37 and 37' of perpendicular direction crossing the part 30 in positions offset longitudinally.
- the channels 37 and 37 ' make it possible to constitute the midpoints on the windings with nested turns of the coaxial cables 32 and 32'.
- the cable 32 or the cables 32 and 32 ' are wound with contiguous or practically contiguous turns, as can be seen in FIGS. 2a, 2b and 3.
- the coaxial cable 32 comprises a central conductor 33 constituted by an electrical resistance heating wire, for example made of nickel-chromium alloy.
- the coaxial cable also includes an external metallic envelope 34, for example made of stainless steel, a nickel alloy or another metallic material, coaxial with the resistance wire 33. Between the wire 33 and the envelope 34 is insulated an electrical insulator 35.
- a coaxial cable such as the cable 32 has a certain rigidity due to the presence of the tubular external envelope 34.
- this winding has fairly good properties. analogous to that of a coil spring.
- This winding constitutes in particular a stable structure but capable of elastic deformation, in particular in bending.
- the heating element according to the invention Compared to the heating elements according to the prior art constituted by winding a simple electrical resistance wire on a flexible mandrel, the heating element according to the invention has a defined shape and sufficient cohesion, without it it is necessary to wind its turns in contact with an internal mandrel.
- the heating element however comprises in its part 14a, a central part constituted by a small diameter tie rod 40 and by a winding 41 produced from a flat metallic strip .
- the tie rod 40 may advantageously consist of a flexible rod or tube but having a good tensile rigidity and capable of withstanding the temperature prevailing inside the heating element 14.
- the tie rod 40 is integral with the end piece 30 at one of its ends and extends axially inside the heating element 14 over its entire part 14a, before passing through an axial bore an end piece or core 43 constituting the junction element between the parts 14a and 14b of the heating element 14.
- the end the tie rod 40 opposite the end piece 30 is secured to an annular piece 44 capable of abutting on a fixed annular piece 45 fixed in the end part of the part 14b of the heating element.
- the end of the part 45 is separated from the corresponding end of the part 43 to allow some adjustment.
- the part 14a of the heating element can thus deform in bending and possibly in compression if the turns are not perfectly contiguous but is not likely to undergo an elongation under the effect of a traction, thanks to the presence of the tie rod 40 ensuring the connection in traction of the end piece 30 and of the part 14b of the heating element.
- the winding 41 constituted by a flat metallic ribbon has turns inclined in the opposite direction to the turns of the winding 31.
- This perfectly flexible winding 41 thus makes it possible to prevent excessive deformation of the winding 31 by displacement of its turns radial directions.
- a radial space is formed between the internal surface of the winding 31 and the external surface of the winding 41 constituting with the tie rod 40 the central part of the heating element 14.
- This central part does not constitute in any case a mandrel on which the coaxial cable 32 is wound, a radial space always being provided between the winding 31 and the central part.
- the winding 31 thus constitutes a tubular self-supporting element having the properties of a spring with contiguous turns.
- the part 14b of the heating element 14 is constituted by a stainless steel tube 50 having successive waves giving it good flexibility.
- the coaxial cables 32 and 32 ' in the case of a double winding with two conductors, are arranged in the axial direction inside the tubular sheath 50 and connectors 51 allow these cables 32 and 32' to be connected to flexible power supply cables.
- connection will be provided by flexible cables of the conventional type which are connected to the coaxial cables 32 and 32 ′ by the connectors 51 stepped inside the part 14b of the heating element.
- At least one thermocouple 54 is placed in the part 14a of the heating element and makes it possible to measure the temperature during heating; this thermocouple comprises a measurement cable 53 also passing in the axial direction, inside the tubular sheath 50.
- the ends of the flexible cables connected to the coaxial cables 32 and 32 ′ and of the measurement cable 53 of the thermocouple constitute the part 14c connecting the heating element to the fixed installations located outside the steam generator.
- the tubular sheath 50 is supplied with a purging gas which may for example be an inert gas such as argon or helium, via a pipe 55 connected to a reservoir of inert gas outside the steam generator.
- the scavenging gas can circulate inside the sheath 50 to the part of this sheath adjacent to the part 43 where the sheath has small openings 50 ′ through which the sweeping gas can pass and then circulate through the inside the tube 3 into which the heating element 14 has been introduced.
- Part of the gas can also pass through the part 43 in the assembly clearance remaining around the conductors 32 and the tie rod 40.
- This gas then flows inside the winding 31 constituting the active part 14a of the heating element 40.
- This winding 31 constitutes a non-gas-tight tubular conduit, the turns not being perfectly contiguous. The gas therefore ends up flowing in the tube 3 and it is thus possible to carry out an effective scanning of the heating zone of the tube.
- FIG. 5 the arrangement of the coaxial cables 32 and of the tie rod 40 is seen, inside the corrugated tubular sheath 50.
- the position of the coaxial cables 32 ′ has also been shown, in the case of a double winding, as shown in Figures 2 and 2b.
- FIGS. 7a, 7b, 7c and 7d describe an operation of placing and using the heating element for the thermal treatment of the hanger of a tube 3 disposed at the central part of the generator. steam.
- FIGS. 7a to 7d a single coil 12 and a single heating element have been shown which will be used for the heat treatment of the hanger of the tube 3.
- the carriers 8 and 9 were placed at the ends of the tube 3, thus ensuring the installation of the conduit 24, the pusher-shooter 10 and its guide conduit 11.
- the traction cable 20 comprising at its end a hooking device 21 is sent into the conduit 24 by means of the puller-pusher 18, which allows its introduction through one of the ends of the tube 3 (FIG. 7a).
- the action of the push-puller 18 makes it possible to move cer then the traction cable 20 inside the tube 3, this cable having sufficient rigidity to be moved by pushing.
- the end of the cable 20 thus reaches the outlet of the tube 3 and then of the guide duct 11.
- a chute 60 then ensures its extraction through the manhole 6b.
- the hooking device 21 is brought close to the end piece 61 of the extension 14 'wound on the coil 12.
- the attachment of the extension 14' is then carried out manually or automatically. cable 20, by engaging the device 21 in an opening of the part 61.
- the pusher-shooter 18 is then put into operation to exert traction on the cable 20, on the extender 14 'and on the heating element 14.
- the pusher-shooter 10 is put into operation in the direction of the thrust , to facilitate the introduction of the heating element 14 into the tube 3.
- the eddy current coil 22 of the traction cable 20 reaches the level of the upper spacer 56 of the bundle and this position is identified by the eddy current measuring device 25 disposed at the control station.
- the position of the puller-pusher 18 is identified then the movement of the extension 14 'and of the heating element 14 continues until the eddy current coil 22 of the cable 20 reaches the level of the upper spacer plate 56 , during its downward movement in the tube 3, at the outlet of the small hanger 3a. The position of the pusher-shooter 18 is then identified.
- the two position measurements on the push-pull device 18 make it possible to determine the length of flexible cable 20 introduced into the tube when the end of the cable is in two symmetrical positions on either side of the small hanger 14a.
- the average of these two lengths makes it possible to perfectly determine the position of the midpoint of the hanger which is also its highest point.
- the heating element 14 When the position of the flexible cable shown in FIG. 7d has been identified by means of the eddy current coil 22, the heating element 14 is then brought into its service position inside the hanger as shown in FIGS. 7d and 8.
- the active part 14a of this heating element constituted by the helical winding 31 has a length at least equal to the length of the largest hangers to be treated, so that the entire hanger 3a is occupied by the winding heating 31.
- the heating element 14 is capable of adapting perfectly to the shape of a small hanger on the walls of which it comes into contact to ensure good heat transmission.
- the presence of the tie rod 40 inside the heating element 14 makes it possible to avoid any abnormal elongation of the winding 31 by extension under the pull effect.
- the traction exerted by the cable 20 is in fact transmitted from the end piece 30 to the tubular sheath 50 of the part 14b of the heating element, by the tie rod 40.
- the turns of the winding 31 which are not rigidly held by a central mandrel can move or slightly deform to facilitate the passage of the heating element in the hanger .
- the displacement or deformation of the turns of the winding 31 is limited to a low level but sufficient to allow the passage of the heating element in the hanger, by the internal winding 41 of this heating element.
- the heat treatment of the curved part of the tube 3 is ensured by performing the connection of the electrical supply to the coil 12 to which the ends of the power cables constituting the end part 14c of the heating element are connected.
- the heating current is controlled and controlled by the devices 16 and 17 located in the installation control station.
- the treatment can be carried out simultaneously on a very large number of tubes so that the operation of placing a heating element which has just been described is carried out successively for all of the tubes to be treated.
- the heating elements are supplied and the heating current is controlled simultaneously and in parallel for all the tubes to be treated.
- the hooking device 21 of the cable 20 is detached from the part 61 of the extension 14 ′ of the heating element 14 which has just been set up, by a remote operation at the level of the carrier 8.
- the traction cable 20 is then removed, the element 14 and the extension 14 'remaining in place in the tube 3.
- sweeping gas is sent into the heating zone inside the tube 3, through the tube 50.
- thermocouple 54 The temperature is constantly monitored by the thermocouple 54, the measurements of which are transmitted to the control station.
- the device according to the invention therefore has the advantage of having a simple structure, of being of a moderate cost price and of being able to be easily installed inside the small hangers of the bundle.
- the device according to the invention also makes it possible to perfectly control the heat treatment operation and the position of the heating elements in the hangers before they are put into service.
- heating coils consisting of any number of coaxial cables whose coils are nested.
- the various successive sections of the core of the variable resistivity cable can be constituted by sections of different resistant wires welded end to end.
- the coaxial cable can comprise sections with low electrical resistance, for example made of copper, intended to join sections with high electrical resistance and constituting non-heating conductive zones of the heating element.
- the means for moving, positioning and controlling the heating element may also have a shape different from that which has been described.
- the device according to the invention can be used for the heat treatment of any tube of small diameter, of curved shape over part of its length or, of course, for the treatment of straight tubes.
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Mechanical Engineering (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- High Energy & Nuclear Physics (AREA)
- General Engineering & Computer Science (AREA)
- Resistance Heating (AREA)
- Heat Treatment Of Articles (AREA)
Claims (16)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR8704158A FR2612941B1 (fr) | 1987-03-25 | 1987-03-25 | Dispositif de chauffage en particulier pour le traitement thermique d'un tube de petit diametre et de forme courbe et utilisation de ce dispositif |
FR8704158 | 1987-03-25 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0285464A1 EP0285464A1 (de) | 1988-10-05 |
EP0285464B1 true EP0285464B1 (de) | 1990-08-29 |
Family
ID=9349419
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP88400413A Expired - Lifetime EP0285464B1 (de) | 1987-03-25 | 1988-02-23 | Erhitzungsvorrichtung, insbesondere zur Wärmebehandlung von gebogenen Rohren mit niedrigem Durchmesser |
Country Status (8)
Country | Link |
---|---|
US (1) | US4883946A (de) |
EP (1) | EP0285464B1 (de) |
JP (1) | JPS63262423A (de) |
KR (1) | KR880011349A (de) |
DE (1) | DE3860507D1 (de) |
ES (1) | ES2017113B3 (de) |
FR (1) | FR2612941B1 (de) |
ZA (1) | ZA881134B (de) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5017761A (en) * | 1989-01-18 | 1991-05-21 | Westinghouse Electric Corp. | Fiber-optic heater probe assembly for heat treating metallic conduits |
US6522709B1 (en) * | 1999-11-12 | 2003-02-18 | Westinghouse Electric Company Llc | Nuclear in-core instrument (ICI) assembly with compressed flexible hose sheath |
US20040075432A1 (en) * | 2002-10-16 | 2004-04-22 | Loud Christopher R. | Flexible shaft with a helically wound data cable supporting a smooth outer sleeve for eddy current probe |
DE102011054718B4 (de) * | 2011-10-21 | 2014-02-13 | Hitachi Power Europe Gmbh | Verfahren zur Erzeugung einer Spannungsverminderung in errichteten Rohrwänden eines Dampferzeugers |
US9113501B2 (en) | 2012-05-25 | 2015-08-18 | Watlow Electric Manufacturing Company | Variable pitch resistance coil heater |
RU2684907C1 (ru) * | 2018-07-06 | 2019-04-16 | Акционерное общество "Ордена Трудового Красного Знамени и ордена труда ЧССР опытное конструкторское бюро "ГИДРОПРЕСС" | Ошиновка блока трубчатых электронагревателей |
Family Cites Families (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1326964A (en) * | 1915-02-09 | 1920-01-06 | Poole Fred | Water-heater |
DE1104086B (de) * | 1955-04-09 | 1961-04-06 | Bleckmann & Co | Elektrischer Rohrheizkoerper zur Erhitzung von Wasser und anderen, kesselsteinbildende Substanzen enthaltenden Fluessigkeiten ueber jenen Temperaturbereich hinaus, in dem es zur Anlagerung von Kesselstein an seinem Mantelrohr kommt |
FR1483726A (fr) * | 1964-05-19 | 1967-06-09 | Kanthal Ab | Isolant électrique et élément tubulaire comprenant un tel isolant |
US3407283A (en) * | 1965-10-22 | 1968-10-22 | Charles P Mcmanus | Ice fishing hole heating device |
US3410984A (en) * | 1966-05-03 | 1968-11-12 | Gen Electric | Flexible electrically heated personal warming device |
US3417230A (en) * | 1966-12-15 | 1968-12-17 | Gen Electric | Electric heat lamp and electric devices |
US3906358A (en) * | 1973-11-12 | 1975-09-16 | Combustion Eng | Probe train including a flaw detector and a radiation responsive recording means with alignment means having a natural curved cast |
DE2438800C3 (de) * | 1974-08-13 | 1980-01-24 | Esser-Werke Gmbh Vorm. Westmontan- Werke, 4788 Warstein | Vorrichtung zum fortlaufenden Oberflächenhärten der inneren Oberfläche von Rohrbögen mittels Flammhärtung |
GB2076618B (en) * | 1980-05-23 | 1984-02-01 | Daido Ind | Preheater for mounting in a well tube |
EP0109843B1 (de) * | 1982-11-23 | 1987-08-26 | United Kingdom Atomic Energy Authority | Widerstandsheizsonde |
-
1987
- 1987-03-25 FR FR8704158A patent/FR2612941B1/fr not_active Expired - Fee Related
-
1988
- 1988-02-18 ZA ZA881134A patent/ZA881134B/xx unknown
- 1988-02-23 DE DE8888400413T patent/DE3860507D1/de not_active Expired - Lifetime
- 1988-02-23 ES ES88400413T patent/ES2017113B3/es not_active Expired - Lifetime
- 1988-02-23 EP EP88400413A patent/EP0285464B1/de not_active Expired - Lifetime
- 1988-03-23 JP JP63069191A patent/JPS63262423A/ja active Pending
- 1988-03-25 US US07/172,819 patent/US4883946A/en not_active Expired - Fee Related
- 1988-03-25 KR KR1019880003212A patent/KR880011349A/ko not_active Application Discontinuation
Also Published As
Publication number | Publication date |
---|---|
JPS63262423A (ja) | 1988-10-28 |
ZA881134B (en) | 1989-11-29 |
EP0285464A1 (de) | 1988-10-05 |
FR2612941A1 (fr) | 1988-09-30 |
ES2017113B3 (es) | 1991-01-01 |
DE3860507D1 (de) | 1990-10-04 |
US4883946A (en) | 1989-11-28 |
FR2612941B1 (fr) | 1993-03-05 |
KR880011349A (ko) | 1988-10-28 |
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