WO1996028691A1

WO1996028691A1 - Device and process for cleaning a pipe base of a steam generator

Info

Publication number: WO1996028691A1
Application number: PCT/DE1996/000450
Authority: WO
Inventors: Rudolf Baumgartl
Original assignee: Siemens Aktiengesellschaft
Priority date: 1995-03-15
Filing date: 1996-03-13
Publication date: 1996-09-19

Abstract

According to the invention a device for cleaning a pipe base (6) of a steam generator (2) with a sprayed fluid contains a spray lance (50) extending parallel to its longitudinal axis (62) in which a spray head (63) is fitted at a free end (53). In the spray lance (50) there is a pipe (58) for the supply of the spray fluid on which there are at least two exit apertures (65) for the spray fluid from which said fluid is ejected at different angles (βa, βb) in such a way that the resultant (F) of the recoil forces (Fa, Fb) generated by the outflow of the spray fluid is directed at least approximately parallel to the longitudinal axis (62) of the spray lance (50).

Description

description

Device and method for cleaning a tube sheet of a steam generator

The invention relates to a device and a method for cleaning a tube sheet of a steam generator.

Endoscopic inspections of the tube sheets of steam generators show that in areas which are poorly flowed through by the water of the secondary circuit, adhering contaminants remain, the height of which in some places can be a few centimeters.

Because of the geometric shape of their distribution on the tube sheet, these deposits are referred to as deposit kidneys. They arise because loose deposits remain in the poorly flowed inside area of the heating tube bundle, while in the better flowed outside area they are entrained by the flow of the feed water flow on the secondary side. With increasing operating time, these deposits adhere more and more firmly to the tube sheet. Through further accumulation processes, in the course of several operating cycles, deposit conglomerates with an increased metal and salt quantity concentration compared to loose impurities increase in an extent of several centimeters.

Analyzes of these solid conglomerates of deposits show a mixed structure that consists essentially of magnetite. In addition to further oxidation levels of iron, there are also increased salt concentrations, especially sulfates, silicates and phosphates. Likewise, increased chromium and nickel contents can result from the storage of metal chips. The mechanical hardness can in some places exceed the hardness of the heating tube material, so that if the growth is limited in space there is a risk of damage to the heating tubes (denting). For this reason, the tube side of steam generators must be regularly checked on the secondary side to see whether and to what extent deposits have formed between the heating tubes. These deposits must then be removed in order to avoid damage to the heating pipes.

For the adherent deposits, this is primarily done by spraying. The gaps between the heating pipes are difficult to reach due to the small distance between the pipes, which is usually around 8 - 11 mm with a square arrangement of the heating pipes and can be between 3 and 4 mm in narrower triangular arrangements. Spraying methods are therefore primarily used, as are known, for example, from European Patent 0 084 867. In these spraying processes, a high-pressure water jet is sprayed from a spray head located in the pipe lane into the spaces between the heating pipes.

However, it has been shown that deposits adhering to the interior of the tube bundle cannot be completely removed. In order to ensure efficient cleaning of the tube sheet, it is therefore necessary to guide a spray head directly into the spaces between the heating tubes and to direct a high-pressure liquid jet directly onto the deposits inside the heating ear bundle.

A device suitable for this is known, for example, from European Patent 0 305 483. In the device disclosed there, a flexible spray lance is provided, which has a spray head with a plurality of nozzles at its free end, from which the spray liquid emerges. The flexible spray lance is constructed from a flexible band in which there are channels with a circular cross section. Metallic capillaries are inserted into these channels, through which the spray liquid flows to the spray head. leads. The band and the channels are made in one piece by extrusion from a plastic.

The belt is mounted in a rigid guide with a curved end, with which it can be deflected by a predetermined angle. The rigid guide is mounted in a transport device which can be introduced into the tube lane of the steam generator and can be moved along this tube lane. To drive the belt, several jointly driven gear wheels are provided, the teeth of which engage in corresponding perforations of the belt. The free end of the spray lance is aligned with the pipe gap through the curved end of the rigid guide. At the free end of the spray lance there is a spray head with several nozzles from which spray jets emerge horizontally to the front, horizontally to the side and downwards towards the tube sheet.

From US-A-4,407, 236 a flexible spray lance is known which is constructed from a band of spring steel on which one or more capillaries for the spray liquid are attached on one side. The narrow sides of the belt are guided in grooves in an upper and a lower plate which are introduced into the pipe lane of the steam generator. The groove in the lower plate causes the belt to deflect onto a pipe gap. The belt is driven by a pushing force exerted on the belt from behind. The capillaries are laid in a wave shape on the band and open downwards at the free end of the band into a semicircular recess on the underside of the band, so that the spray liquid emerging from them is directed downwards onto the tube sheet.

In the known spray heads, however, the downward spray jets parallel to the flat side of the strip exert reaction forces directed upward away from the tube sheet, which cause the free end of the spray lance to lift off can cause. This lifting makes it difficult to remove adherent deposits.

The invention is based on the object of specifying a device for cleaning a tube sheet of a steam generator which can be introduced into the tube gaps and can be held in a stable position above the tube sheet even at high spray pressure, so that firmly adhering deposit can be removed safely. The invention is also based on the object of specifying a method for cleaning a tube sheet of a steam generator.

The first-mentioned object is achieved with a device having the features of claim 1. The device for cleaning a tube sheet of a steam generator with a spray liquid contains according to the invention

a) a flexible spray lance extended parallel to a longitudinal axis, in which a spray head is arranged at a free end,

b) at least one line arranged on the flexible spray lance for supplying the spray liquid to the spray head,

c) at least two outlet openings arranged on the spray head for the spray liquid, wherein

d) the normals of the outlet openings are inclined at different angles to the longitudinal axis.

These measures make it possible to compensate for the force components directed transversely to the longitudinal axis of the recoil forces generated by the outflow of the spray liquid. As a result, the spray head is prevented from being lifted off the tube sheet and efficient deposition of even adherent deposits is made possible. Preferably, two outlet openings are provided in the spray head, the normals of which are inclined at angles to the longitudinal axis which, in relation to this longitudinal axis, are of equal size in opposite directions.

In an advantageous embodiment, a steel band is provided as the spray lance.

In a particularly advantageous embodiment, the strip has a plurality of holes in its longitudinal direction, through which at least one flexible, preferably metallic capillary made of a nickel-titanium alloy is threaded as a line.

In particular, in each case in the longitudinal direction of the band between the holes are formed for receiving the capillary, which alternately extend to one and the other side of the band.

The second-mentioned object is achieved with a method having the features of claim 8. The method for cleaning a tube sheet of a steam generator with a spray liquid comprises the following features according to the invention:

a) A spray head is guided over the tube plate of the steam generator, which at one free end parallel to one

Long flexible spray lance is arranged longitudinal axis,

b) spray liquid is fed to the spray head via at least one line arranged on the flexible spray lance,

c) the spray liquid emerges from at least two outlet openings arranged on the spray head at different angles (βa, βb) against the longitudinal axis in such a way that the resultant (F) of the recoil forces (Fa, Fb) generated by the spray liquid flowing out is at least approximately parallel to the longitudinal axis of the spray lance. To further explain the invention, reference is made to the exemplary embodiments of the drawing, in which:

1, 2 and 3, a device according to the invention in a working position in the steam generator is illustrated in a top view or in a side view parallel or transverse to a pipe lane. FIGS. 4 and 5 show a further embodiment of a device according to the invention within the steam generator in a side view transversely to the Rohrgasse or in a plan view. 6 and 7 show a side view (flat side) and a top view (narrow side) of a spray lance according to the invention and in FIG. 8 the free end of the spray lance is shown enlarged.

1 shows a steam generator 2 in a horizontal partial section at the height of a hand hole 4. A plurality of heating tubes 10, which are arranged parallel to one another, open into a tube plate 6, which is visible in a plan view 8, into a tube alley 12 via the hand hole 4, a transport device 20 introduced, with which a free end 53 of a flexible spray lance 50 can be introduced, starting from the tube line 12, into a tube gap 14 running perpendicular to the tube line 12. In the figure, a steam generator 2 is shown with a triangular arrangement of the heating pipes 10, in which there are particularly narrow pipe gaps 14.

The flexible spray lance 50 is constructed from a band 52 on which lines 58 for supplying a spray head 63 arranged at the free end 53 are laid.

The transport device 20 comprises a slide plate 21 with which it is placed on the tube sheet 6. For moving forward within the tube alley 12, a walking mechanism is provided in the transport device 20, as is the case for example European patent specification 0 084 867 is known. For this purpose, the transport device 20 comprises two support bodies 22 and 24, which can be displaced relative to one another in a longitudinal axis 26 of the transport device by a pneumatically actuated piston 28. On each of the support bodies 22 and 24, pneumatically extendable support elements 30 are provided in pairs, each of which is supported on opposite heating pipes 10 at the edge of the pipe alley 12. By alternately locking the support elements 30 and actuating the piston 28, the transport device 20 moves forward in the tube alley 12.

On the transport device 20, a feed device 40 is arranged, which contains a motor-driven drive roller 41 and an associated guide roller 42 which is set against its circumference. The flexible spray lance 50 is threaded into the drive roller 41 and guide roller 42.

The feed device 40 contains two further guide rollers 43 and 44, which are mounted against one another on their circumference and receive the lance 50 threaded between the drive roller 41 and the guide roller 42 and at an angle α1 to the longitudinal axis 26 and thus to a central axis 14 of the pipe line parallel to it Set 12. In the example of the figure, this angle is 90 °, so that the lance 50 can be moved into the pipe gaps 14.

In the advantageous embodiment shown in the figure, the drive roller 41 and the guide roller 43 are coupled to one another by a circumferential belt 45. In the same way, a belt 47 is also guided around the guide rollers 42 and 44 and a deflection roller 46, which lies in the area of the drive roller 41 on the belt 45. This measure results in a particularly secure guidance of the lance 50. The deflection angle α1 of the lance 50 is determined by the mutual position of the drive roller 41 and the guide rollers 42, 43 and 44 on the transport device 20.

In a further advantageous embodiment, the feed device 40 can additionally be displaced relative to the transport device 20 parallel to the longitudinal axis 26 or rotated about a vertical axis in order to enable the flexible spray lance 50 to be precisely aligned with the pipe gaps 14.

FIG. 2 shows how the lance 50 constructed from the band 52 is passed through the hand hole 4 from the outside. Since the band 52 cannot be bent in the plane defined by its flat sides and the tube sheet 6 is located below the lower edge of the hand hole 4, the band 52 must be guided through the hand hole 4 with the flat side horizontally oriented and inside the steam generator 2 Can be turned 90 °.

According to FIG. 3, the feed device 40 is arranged in the transport device 20 so as to be pivotable about an axis of rotation 48 running parallel to the longitudinal axis 26. As a result, the free end 53 of the lance 50 can be positioned directly above the tube sheet 6 even with a different extension length 1.

In the advantageous embodiment according to FIG. 4, the feed device 40 is also mounted on a slide 28, which enables the height of the feed device 40 to be adjusted perpendicular to the longitudinal axis 26 and thus parallel to the heating tubes 10.

5 shows an embodiment in which the spray lance 50 is oriented at an angle oc2 = 30 ° relative to the longitudinal axis 26 of the transport device 20, so that the pipe gaps 16 which extend at an angle of 30 ° to the central axis 14 of the pipe path 12 can be driven by the lance 50. As a result, dead areas can only be poorly detected at an angle α1 = 90 °. In this special embodiment, too, a feed device 400 is provided which is pivotable in its entirety about an axis 49 running parallel to the tube sheet. In this exemplary embodiment, too, rollers 410, 420, 430 and 440 are provided for driving, deflecting and aligning the spray lance 50. In addition, it may be advantageous if the entire feed device 400 is arranged to be displaceable on the transport device 20 or to be pivotable about an axis perpendicular to the longitudinal axis 26, in order to enable precise threading into the pipe gaps 16.

According to FIGS. 6 and 7, the spray lance 50 is preferably constructed from a flexible metallic band 52 made of chromium-nickel steel with a wall thickness between 0.1 and 0.2 mm, into which recesses or holes 54 which are equidistant from one another parallel to its longitudinal direction are punched which form two rows 56a and 56b. A line or a capillary 58 for the spray head 63 is threaded through each of these rows 56a and 56b.

The capillaries 58 preferably consist of a memory metal consisting of a nickel-titanium alloy, for example a metal commercially available under the name Nitinol SE 502. Their compressive strength is greater than 1000 bar with an outside diameter between 2 and 3 mm.

The capillaries 58 are guided through the holes 54 alternately from opposite sides of the band 52. Between the holes 54 of a row 56a or 56b, parallel to a longitudinal axis 62 of the band 52, groove-shaped formations or beads 60 with a semicircular cross-section are embossed into the band 52, which alternately alternately on one and on the other side of the band 52 are formed. In this way, the formations 60, together with the holes 54 in a row 56a or 56b, form a straight line towards the channel into which the capillary 58 can simply be inserted.

Instead of the circular holes shown in FIGS. 6 and 7, recesses in the form of narrow slots transverse to the longitudinal axis 62 can also be provided, through which the capillary 58 can be threaded.

According to FIG. 8, the capillaries 58 assigned to the rows 56a and b are bent away from a longitudinal axis 62 of the band 52 in the plane defined by the flat side of the band 52. At the end of the capillaries 58, nozzles 64 are preferably arranged, in which the emerging spray jet is accelerated and emerges from outlet openings 65. In the exemplary embodiment, the outlet openings 65 are arranged perpendicular to the flat side of the band 52, i. H. the normal or central axes of the outlet openings 65 lie approximately in the plane (band plane) defined by the flat side. The outlet openings 65 are arranged with their normals at an angle βa or βb to the longitudinal axis 62. These angles βa and βb have opposite signs with respect to this longitudinal axis 62. The outlet openings 65 are adapted to the respective mass flow of the spray liquid emerging from them, i. H. adapted to the quantity of spray liquid exiting from them per unit of time, arranged so inclined to the longitudinal axis 62 in the belt plane that the sum or resultant F of the reaction forces Fa and Fb exerted on the belt 52 by the spray liquid emerging is approximately parallel to the Longitudinal axis 62 of the band 52 acts. In other words: the across

Longitudinal axis 62 and reaction forces acting approximately in the band plane in the exemplary embodiment of the drawing are compensated. This prevents the band 52 from being pushed away from the tube bottom.

The nozzles 64 are preferably of identical construction, so that a symmetrical arrangement (ßa = -ßb) of the nozzles 64 in the band plane compensation of the transverse forces is effected when the mass flows through the two nozzles 64 are the same. Such a symmetrical arrangement is particularly necessary in the case of a structurally identical design of the nozzles 64 if instead of the two capillaries 58 provided in the exemplary embodiment only one capillary is provided, from which two paths are only branched off directly in front of the spray head 63.

In the case of an asymmetrical arrangement of the nozzles, the mass flows must be adjusted accordingly until the transverse forces are compensated. This can be done by a fixed setting or by controlling the mass flows distributed over the capillaries 58.

Likewise, instead of two nozzles 64 or outlet openings 65, a plurality of outlet openings can also be provided, the orientation of the outlet openings and the respective mass flows also having to be coordinated in this case in such a way that compensation of the transverse forces occurs.

The nozzles 64 or outlet openings 65 can also be arranged with their normal or central axis obliquely to the flat side of the band 52. In this case too, the angles and the respective mass flows can be coordinated or controlled in such a way that the force components occurring transversely to the flat side of the band 52 are compensated for in this case, so that a lateral deflection of the band 52 is avoided.

In addition, an optical fiber cable of an endoscope with which the spraying process is observed can also be laid in the band.

Claims

claims

1. Device for cleaning a tube sheet (6) of a steam generator (2) with a spray liquid, with a) a flexible spray lance (50) extended parallel to a longitudinal axis (62), with a free end (53) a spray head (63) is arranged, ^" b) at least one line (58) arranged on the flexible spray lance (50) for supplying the spray liquid, c) at least two outlet openings (64) arranged on the spray head (63) for the Spray liquid, where d) the normals of the outlet openings (65) are inclined at different angles (βa, βb) against the longitudinal axis (62).

2. Device according to claim 1, that in the spray head (63) two outlet openings (65) are provided, the normals of which are inclined at angles (ßa, ßb) against the longitudinal axis (62), which are of the same size in relation to this longitudinal axis (62) are.

3. Device according to one of the preceding claims, in which a band (52) made of steel is provided as the spray lance (50).

4. The device according to claim 3, wherein the band (52) has a plurality of recesses (54) in its longitudinal direction, through which at least one flexible capillary (58) is threaded as a line.

5. The device according to claim 4, in which in the longitudinal direction of the band between the recesses (54) in each case formations (60) for receiving the capillary (58) are introduced, which alternately extend to one and the other side of the band (52) .

6. Device according to one of claims 4 or 5, is provided in the ei¬ ne metallic capillary (58).

7. The device according to claim 6, with a capillary (58) made of a nickel-titanium alloy.

8. A method for cleaning a tube sheet (6) of a steam generator (2) with a spray liquid, with the following features:

a) a spray head (63) is guided over the tube plate (6) of the steam generator (2) and is arranged at a free end (53) of a flexible spray lance (50) which is extended parallel to a longitudinal axis (62),

b) the spray head (63) is supplied with spray liquid via at least one line (58) arranged on the flexible spray lance (50), wherein

c) the spray liquid emerges from at least two outlet openings (65) arranged on the spray head (63), at mutually different angles (βa, βb), in such a way that the resultant (F) is the one caused by the outflow of the spray liquid recoil forces (Fa, Fb) is at least approximately parallel to the longitudinal axis (62) of the spray lance (50).