TECHNICAL FIELD
[0001] The present invention relates to a scale removing device for removing scale, for
example, on the tube plate and in the tube nest of a heat exchanger such as a steam
generator used in a nuclear power plant or the like.
BACKGROUND ART
[0002] In order to understand the present invention, a description of a steam generator
used in a nuclear power plant or the like is necessary. Thus, such a steam generator
will be briefly described with reference to Fig. 10.
[0003] In Fig. 10, numeral 1 indicates a steam generating portion of a steam generator.
The steam generating portion 1 has a substantially cylindrical body portion 2 in which
hand holes or inspection holes (only one of which is indicated at numeral 17) are
diametrically opposed to each other. In the lower portion of the body portion 2, there
is arranged a tube plate 3, which defines, together with a bottom portion 2a of the
body portion 2, a water chamber 4. Above this tube plate 3, a large number of normally
U-shaped heat-transfer tubes 5 are arranged so as to communicate with the water chamber
4. Further, a plurality of tube support plates 6a, 6b, ..., 6f are horizontally arranged
so as to traverse the large number of heat-transfer tubes 5 and laterally support
them. Each of the heat-transfer tubes 5 extends vertically through oddly shaped holes
usually called BEC (Broached Egg Crate) holes formed in the tube support plates 6a,
6b, ...., 6f. In Fig. 10, some of the BEC holes formed in the tube support plate 6a
are schematically shown and indicated by numeral 7.
[0004] The space in the water chamber 4 is divided into a hot leg portion 4a and a cold
leg portion 4b by a partition 8. One end of each U-shaped heat-transfer tube 5 communicates
with the hot leg portion 4a, and the other end thereof communicates with the cold
leg portion 4b. Thus, the tube plate 3 also has a large number of holes which are
schematically indicated by numeral 3a and which serve to receive the end portions
of each of the heat-transfer tubes.
[0005] Further, in Fig. 10, numeral 9 indicates a man-hole which enables an operator to
enter the water chamber 4, numeral 10 indicates a coolant inlet nozzle communicating
with the hot leg portion 4a, numeral 11 indicates a coolant outlet nozzle communicating
with the cold leg portion 4b, and numeral 12 indicates trunnions for suspending the
steam generator. Though not shown, a steam outlet is formed at the top of the steam
generator. Further, above the steam generating portion 1, there is provided a water
supply nozzle (not shown) for introducing supply water into the body portion.
[0006] In the case, for example, of a steam generator of a nuclear power plant, coolant
at high temperature and high pressure supplied from the nuclear reactor enters the
hot leg portion 4a of the water chamber 4 through the coolant inlet nozzle 10 and
flows through the heat-transfer tubes 5 to reach the cold leg portion 4b before it
is returned to the nuclear reactor by way of the coolant outlet nozzle 11. Supply
water from the water supply nozzle is supplied into the body portion 2 to fill the
periphery of the heat-transfer tubes 5. This supply water is heated by the high-temperature/high-pressure
coolant flowing through the heat-transfer tubes 5 to become steam, which goes out
through the steam outlet and is supplied to a steam turbine (not shown) for power
generation.
[0007] As a result of the conversion of supply water into steam, impurities called scale
is likely to adhere to the top surface of the tube plate 3, in particular, to the
portions of the top surface of the tube plate 3 in the vicinity of the holes 3a into
which the end portions of the heat-transfer tubes 5 are inserted and to the peripheral
surfaces of the lower portions of the heat-transfer tubes 5 embedded in the tube plate
3 (In this specification, these regions will be referred to as "the portion centered
about the tube plate"). Further, scale is likely to adhere to the upper and lower
surfaces of each tube support plate, the regions near the portions directly below
the BEC holes 7 (In this specification, these regions will be referred to as "the
portions centered about the tube support plates"). If neglected, this scale will lead
to corrosion of the heat-transfer tubes, etc. Thus, it must be periodically removed.
[0008] In this way, steam generators, which find relatively wide use in various fields of
industry, involve, as they are used, generation of impurities called scale on the
heat-transfer tubes 5, the tube plate 3, the tube support plates 6a, 6b, ..., 6f,
etc. To maintain the performance of the steam generator and to prevent corrosion or
the like due to the scale, it is necessary to remove this scale.
[0009] For this purpose, various scale removing devices have been developed and proposed.
In the case of a steam generator for a nuclear power plant, care must be taken, from
a health care perspective, that an operator is not exposed to a dose of radiation
greater than a predetermined level. Further, despite the fact that a steam generator
is an apparatus of a considerably large size, the very large number of heat-transfer
tubes, are packed very tight. Furthermore, each heat-transfer tube has a diameter
of as small as approximately 20 mm, and is relatively thin-walled. Thus, the heat-transfer
tubes are subject to damage if a heavy impact is applied thereto. In addition, a plurality
of tube support plates are provided in the steam generator, and the distance between
adjacent tube support plates is short in comparison to the height of the entire steam
generator. These conditions have to be taken into account when developing a scale
removing device.
[0010] As described above, a steam generator has only one tube plate, whereas it has a plurality
of tube support plates. Thus, to clean the areas centered about the tube support plates,
the cleaning head of a scale removing device has to ascend and descend through flow
slots formed in the tube support plates (e.g., thin and narrow slots 13 formed in
the tube support plate 6a shown in Fig. 10). In view of this, a scale removing device
for cleaning the portion centered about the tube plate and a scale removing device
for cleaning the portions centered about the tube support plates have been separately
developed.
[0011] Fig. 11 shows a typical scale removing device for cleaning the portion centered about
the tube plate, as disclosed in Japanese Patent Application Laid-Open No.
4-503564. The scale removing device, generally indicated at 15, is laterally inserted into
a tube lane 16 directly above the tube plate 3 of a steam generator through a hand
hole or inspection hole 17. The device includes a transporter 20 adapted to move along
a support rail 18. A flexible lance 19 extends through this transporter 20 to a desired
cleaning position between tube rows.
[0012] Figs. 12 and 13 show in detail the flexible lance 19 and, in particular, a cleaning
head 26 provided at the forward end thereof. The flexible lance 19 includes four high-pressure
hoses 22 fixed together by a member 25 called a hose bar structure, a nitrogen purge
line 23, and a video probe optical fiber cable 24, the forward ends of these components
being connected to the cleaning head 26. Provided at the forward end of the cleaning
head 26 are a plurality of nozzles 27 communicating with the high-pressure hoses 22.
During cleaning, water 28 is jetted out from these nozzles (See Fig. 11).
[0013] Fig. 14 shows a typical example of a scale removing device for cleaning the portions
centered about the tube support plates, as disclosed in Japanese Patent Application
Laid-Open No.
9-026107 by the present applicant. This scale removing device, generally indicated at 30 in
Fig. 14, is provided with an insertion mechanism 31 and a guide mechanism 32. The
insertion mechanism 31 has on the operator side a driving device 33. Further, it has
a fixation plate 34 at its forward end, which is fixed in position by the operation
of a second jack 35. A receiving plate 36 and a first jack 37 are provided between
the operator-side end and the forward end, whereby the direction of the guide mechanism
32 is changed upwards by 90 degrees. The guide mechanism 32 is divided into a large
number of strip-like holding plates 38 so that the mechanism can move in a curve,
and a high-pressure hose and an electric wire cable 29 can be mounted to the back
surface of the guide mechanism 32. A cleaning portion main body 40 is provided at
the forward end of the guide mechanism 32, and a cleaning head 41 provided there is
capable of rotating by 180 degrees.
[0014] Though not shown, this cleaning head 41 also has a plurality of nozzles, from which
water is ejected to a portion to be cleaned. Through expansion and contraction of
this guide mechanism 32, the scale removing device is passed through the flow slots
13 of the tube support plates to remove the scales in the areas centered about the
plurality of tube support plates.
[0015] Regarding the removal of scale, there has been developed, apart from the technique
which removes adhering scale by a water jet from the lance, a technique which aims
to prevent adhesion of scale. Thus, in recent steam generators, the scale adhesion
range is smaller as compared with that in conventional steam generators. Further,
the adhesion thickness is much smaller. On the other hand, the adhesion force of adhering
scale is very strong, and it is difficult to remove adhering scale by the above-mentioned
water jet. Fig. 15 is a diagram showing an example of how scale adheres to a heat-transfer
tube on the tube plate. Shown on the left-hand side of the center line of the heat-transfer
tube is the scale (hard scale) adhering condition in a conventional steam generator,
and, shown on the right-hand side thereof is the scale (hard scale) adhering condition
in a recent steam generator.
[0016] In the prior-art techniques, to remove strongly adhering scale (called hard scale),
the pressure of the water jet is increased. This has proved effective to some extent
for scale which is in the water jet path. However, this is not effective at all for
scale which is out of the water jet path, and such scale is allowed to remain. To
remove such remaining scale, an attempt has been made to enlarge the width of the
water jet path by providing a plurality of washing nozzles or to change the direction
of water jets from the nozzles. However, the increase in ejection area has only resulted
in a reduction in impact per unit area. Thus, removal of the remaining scale could
not be realized as desired.
[0017] This will be explained in more detail with reference to Fig. 16. Fig. 16(a) is a
perspective view showing an example of the cleaning head used. The cleaning head has
eight nozzles A1 through A4 and A5 through A8 in the upper and lower portions of the
front surface A thereof, and four nozzles B1 through B4 (nozzles B3 and B4 are not
shown) at upper and lower positions in the side surfaces B thereof. As shown in Fig.
16(b), this cleaning head is inserted between heat-transfer tubes 5, and water jets
28A and 28B are ejected from each of the nozzles of the front surface A and the side
surfaces B of the cleaning head while drawing the cleaning head in the direction of
the arrow to thereby perform cleaning. In this case, the regions where the water jets
28A and 28B hit are the regions that can be cleaned, and the other regions are out
of the ejection paths. In Fig. 16(b), symbol Y indicates a direction which is perpendicular
in a plane to the X-direction in which the tube lane 16 extends. Thus, numerals Y14,
Y15, and Y16 indicate the fourteenth, fifteenth, and sixteenth heat-transfer tubes
of the tube lane 16.
[0018] Fig. 16(c) is a plan view showing the ejection paths of the water jets 28A and 28B
ejected as shown in Fig. 16(b). The central, wide shaded area is the region that can
be cleaned by the water jets 28A, and the relatively narrow shaded areas on the right
and left-hand sides thereof are regions that can be cleaned by the water jets 28B.
It can be seen, in plan view, that there exist on the tube plate 3 regions which are
out of the ejection paths. It has been difficult to remove scale in these regions
out of the ejection paths. In Fig. 16(d), the region that can be cleaned by the water
jets 28B are shown in shaded areas with respect to the height direction of the heat-transfer
tube 5. It can be seen from this drawing that there also exist regions out of the
ejection paths with respect to the height direction of the heat-transfer tube 5. In
the prior art, it has been difficult to remove scale in these regions out of the ejection
paths. In Fig. 16(d), the numerals given to the extension lines from the shaded areas
indicate the numbers of the nozzles in the side surfaces B.
SUMMARY OF THE INVENTION
[0019] According to the present invention, there is provided a scale removing device for
removing scale from a steam generator of the type which includes: a body portion;
a tube plate and a plurality of tube support plates arranged horizontally in the body
portion so as to traverse the body portion; a plurality of heat-transfer tubes which
extend from the tube plate and end at the tube plate and which extend through the
tube support plates in a row-like fashion, so as to define a tube lane in the body
portion; and a hand hole which is formed at a position above the tube plate and through
which the scale removing device is to be inserted to clean a portion centered about
the tube plate, the scale removing device comprising: a flexible lance holding a high-pressure
water hose and movable with respect to the tube plate and the heat-transfer tubes,
and a cleaning head mounted to the forward end of the flexible lance, wherein formed
inside the cleaning head are a fluid passage communicating with the high-pressure
water hose, a chamber communicating with the fluid passage, and a cavitation generating
nozzle hole communicating with the chamber.
[0020] Embodiments of the present invention can provide a scale removing device which makes
it possible to solve the following problems in existing scale removing devices or
which can satisfy the following requirements for existing scale removing devices:
- (1) In order to remove the remaining hard scale, it is necessary for the cleaning
liquid ejection range to cover the entire tube plate surface and a portion of the
heat-transfer tube side wall up to a height of 10 mm or more as measured from the
tube plate (including the regions which are out of the ejection path in the existing
scale removing devices).
- (2) The influence of ejection impact on the material is evaluated by using a locally
strong portion as a reference, so that, for the cleaning effect to be high over a
wide range, there should be no portion within the ejection range where the cleaning
power is locally high. Otherwise, the cleaning conditions would be rather lenient.
- (3) The effective cleaning diameter of an in-air water jet is small, so that it is
difficult to enlarge the cleaning range with a cleaning nozzle incorporated in the
lance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] For a better understanding of the invention and to show how the same may be carried
into effect, reference will now be made, by way of example, to the accompanying drawings,
in which:
Fig. 1 is a perspective view of a scale removing device according to an embodiment
of the present invention for removing scale from the portion centered about the tube
plate of a steam generator;
Fig. 2 is a perspective view of a scale removing device according to an embodiment
of the present invention for removing scale from the portions centered about the tube
support plates of a steam generator;
Fig. 3 is an enlarged perspective view of a main portion of the scale removing device
of Fig. 2;
Fig. 4(a) is a plan view, partially in section, of a cleaning head of a flexible lance
that can be used in the scale removing devices of Figs. 1 and 2, and Fig. 4(b) is
a side view thereof;
Fig. 5 is a plan view, which is an enlarged view of a part of Fig. 4(a), showing the
nozzle tip particularly clearly;
Figs. 6(a), 6(b), and 6(c) are diagrams schematically showing a test apparatus using
an embodiment of a cleaning head according to the present invention, and Fig. 6(d)
is an explanatory diagram showing the propagation of impact pressure when cleaning
is performed by using the cleaning head shown in Fig. 6(c);
Fig. 7 is a sectional view showing a modification of an embodiment of the cleaning
head of the present invention;
Fig. 8 is a sectional view showing another modification of an embodiment of the cleaning
head of the present invention;
Figs. 9(a) through 9(d) are sectional views showing various nozzle assemblies or nozzle
tips that can be used in embodiments of the cleaning head of the present invention;
Fig. 10 is a partially cutaway elevation view of a body portion of a conventional
steam generator which is given to aid the understanding of the present invention;
Fig. 11 is a perspective view of a conventional device for removing scales from the
portion centered about the tube plate;
Fig. 12 is a sectional view showing a cleaning head at the forward end of a flexible
lance used in the scale removing device of Fig. 11;
Fig. 13 is a side view of the cleaning head of Fig. 12;
Fig. 14 is a perspective view of a conventional device for removing scales from the
portions centered about the tube support plates;
Fig. 15 is a diagram illustrating scale removal using a conventional water jet; and
Fig. 16(a) is a partial view of a conventional cleaning head used in an experiment,
Fig. 16(b) is a plan view showing water jets ejected between heat-transfer tubes from
the nozzle holes of the cleaning head, Fig. 16(c) is a plan view showing regions of
the tube plate that can be cleaned by the water jets as well as regions out of the
ejection paths, and Fig. 16(d) is an elevation view showing regions of the heat-transfer
tube that can be cleaned by water jets as well as regions out of the ejection paths.
DETAILED DESCRIPTION
[0022] The following description relates generally to a scale removing device for a steam
generator of the type which includes: a body portion; a tube plate and a plurality
of tube support plates arranged horizontally in the body portion so as to traverse
the body portion; a plurality of heat-transfer tubes which extend from the tube plate
and end at the tube plate and which extend through the tube support plates in a row-like
fashion so as to define a tube lane in the body portion; and a hand hole which is
formed at a position above the tube plate and through which the scale removing device
is inserted to clean a portion centered about the tube plate, the scale removing device
comprising a flexible lance holding a high-pressure water hose and movable with respect
to the tube plate and the heat-transfer tubes, and a cleaning head mounted to the
forward end of the flexible lance, wherein formed inside the cleaning head are a fluid
passage communicating with the high-pressure water hose, a chamber communicating with
the fluid passage, and a cavitation generating nozzle hole communicating with the
chamber.
[0023] The scale removing device preferably further comprises a suspension guide device
horizontally arranged above the tube plate and a lance conveying member suspended
by the suspension guide device and guided in horizontal movement through the hand
hole, wherein the flexible lance runs through the lance conveying member and is paid
out from and drawn back to the lance conveying member, and wherein the forward end
portion of the cleaning head is formed in a curved surface not interfering with the
body portion wall surface defining the hand hole.
[0024] Further, it is desirable that the lance conveying member have a cylindrical main
body through which the flexible lance runs and that the forward end portion of the
cleaning head is configured such that when the flexible lance has been completely
drawn back, it does not protrude from the peripheral surface of the cylindrical main
body. As desired, it is possible to form one or a plurality of said cavitation generating
nozzle holes. The steam generator may comprise a pair of hand holes formed in the
body portion at a position directly above at least one of the tube support plates
so as to be diametrically opposed to each other; and flow slots formed in the portions
of the tube support plates corresponding to the tube lane, the scale removing device
being inserted through the hand holes, ascending and descending through the flow slots
formed in the tube support plates, and cleaning the portions centered about the tube
support plates.
[0025] Further, the cleaning head includes a head main body portion in which the fluid passage
and the chamber communicating with the fluid passage are formed, and a nozzle tip
detachably mounted to the head main body portion, the cavitation nozzle hole being
formed in the nozzle tip. Optionally, it is possible to mount an ultrasonic oscillator
to the nozzle tip.
[0026] Further, the nozzle tip includes a hexahedron defining the cavitation generation
hole, thin-plate-like mounting portions extending from two opposing surfaces of the
hexahedron except for the surfaces where there are a small-diameter end and a large-diameter
end of the cavitation generation hole, and a protruding portion defining a flow passage
communicating with the small-diameter end of the cavitation generation hole, wherein
a recess of a contour corresponding to the configuration of the nozzle tip is formed
in the head main body portion, and wherein the nozzle tip can be inserted into the
recess and mounted to the head main body portion by the mounting portion. Further,
a CCD camera can be suitably provided in the forward end portion of the cleaning head.
[0027] Next, preferred embodiments of the present invention will be described with reference
to the accompanying drawings. In the drawings, the components which are the same as
or in correspondence with those of the above-described example are indicated by the
same reference numerals. Further, as can be seen from the description below, the present
invention is not restricted to this embodiment, but various modifications are possible.
[0028] In Fig. 1, shown inside a body portion 2 is an embodiment of a scale removing device
50 for cleaning the portion centered about the tube plate in accordance with the present
invention. The tube plate 3 has a large number of holes 3a, into which the end portions
of the heat-transfer tubes 5 are inserted and secured therein in a watertight manner.
Further, in the body portion 2, there are formed, at positions relatively close to
the upper surface of the tube plate 3, a pair of diametrically opposed circular hand
holes or inspection holes 2b (of which only one is shown), and the scale removing
device 50 can be inserted into the body portion through these hand holes 2b. In this
embodiment, a region or portion 3b on the upper surface of the tube plate 3 which
is shown for convenience as a densely dotted area represents the adhering scale to
be removed.
[0029] In Fig. 1, the scale removing device 50 horizontally arranged above the tube plate
3 includes a downwardly open suspension guide device 51 called a monorail, and a cylindrical
lance conveying member 52 suspended and supported by the suspension guide device 51
and horizontally guided along the tube lane 16. The suspension guide device 51 has
a rail portion 53, and a portion to be guided (not shown) of the lance conveying member
52 engages with the rail portion 53, and is horizontally guided by the rail portion
53. A device for moving the lance conveying member 52 is not shown.
[0030] To support the suspension guide device 51 and the lance conveying member 52, one
end of the monorail 51 is connected to a length-adjustable support member 55 rotatably
mounted to a tube lane block 54a. And, the other end (not shown) of the monorail 51
is mounted to a similar support member (not shown) outside the body portion 2. As
indicated by numeral 54b, the tube lane block is also arranged on the hand hole 2b
side. Like a flow rate distribution plate 56 shown above the monorail 51, it functions
to achieve improvements in flow rate distribution.
[0031] The position in the height direction of the monorail 51 with respect to the tube
plate 3, and the position thereof in the horizontal direction with respect to the
hand hole 2b can be freely controlled by adjusting the amount by which the above-described
support member 55, etc. are rotated. Further, on either side of the upper half of
the monorail 51, there is longitudinally arranged a support/protection device 57 called
an air balloon. This support/protection device 57 consists, for example, of a flexible
sack member formed, for example, of rubber. After the positioning of the monorail
51 is performed, air is introduced to thereby expand the sack member, which comes
into contact with the tube group on either side of the monorail 51, whereby the monorail
51 is supported in a stable manner and the tube group is protected.
[0032] A flexible lance 58 is accommodated in the cylindrical main body 52a of the lance
conveying member 52. As its name suggests, the flexible lance 58 is flexible. In this
embodiment, it is bent substantially at right angles as shown in the drawing. Further,
although not shown, a lance driving device is arranged in the cylindrical main body
52a to enable the lance 58 to horizontally reciprocate as indicated by the arrows
and rotate around the axis of the cylindrical main body 52a. Mounted to the forward
end of the flexible lance 58 is a cleaning head 60 described below. By moving the
lance conveying member 52 by the above-mentioned moving device (not shown), the position
of the cleaning head 60 in the X-direction is adjusted. Further, by reciprocating
and rotating the lance 58 by the lance driving device, the position of the cleaning
head 60 in the Y- and Z-directions is adjusted.
[0033] In Fig. 1, numeral 59 indicates a blow down pipe. The blow down pipe 59 is inherently
provided in the steam generator, and is arranged separately from a water discharge
nozzle (not shown) for eliminating from the tube plate the scale 3b removed by the
lance. The moving device for the lance conveying member, the lance driving device,
the flexible lance, etc. may have well-known constructions, and will not be described
in more detail.
[0034] The construction of the scale removing device 50 for removing scale from the portion
centered about the tube plate is as described above. The present invention is also
applicable to devices for removing scale from the portions centered about the tube
support plates. An embodiment of the device will now be schematically described with
reference to Figs. 2 and 3.
[0035] Figs. 2 and 3 show a scale removing device 70 according to another embodiment of
the present invention. In this embodiment, an operating device assembly 71 consisting
of devices for operating the scale removing device 10 is attached to the outer peripheral
surface of the body portion 2. A guide rail assembly 72, which is operationally connected
to the operating device assembly 71, is incorporated into the body portion 2. In this
embodiment, this guide rail assembly 72 is placed on the first, lowermost tube support
plate 6a, and, in the vicinity of each end portion of the guide rail assembly 72,
there is provided a hand hole 2c, which is different from the above-mentioned hand
hole 2b.
[0036] Supported and guided by this guide rail assembly 72 is a movement/connection carriage
assembly (movement/connection means) 75 for supporting an ascent/descent device assembly
(hereinafter simply referred to as the "ascent/descent device") 74 so as to be capable
of movement, erection and inclination. In Fig. 2, the erection/inclination of the
ascent/descent device 74 extending vertically upwards is effected by a rigid hydraulic
erection/inclination device 77 with the aid of a winch 76, etc. Further, the ascent/descent
device 74 includes a tube guide device 78 and an extendable arm assembly 80, and a
lance feeding device 79 is mounted to the forward end of the extendable arm assembly
80. A cleaning head 82 provided at the forward end flexible lance 81 is fed to a predetermined
position in the tube group by the lance feeding device 79. The cleaning head 82 includes
a fluid ejection nozzle described below. By the pressure of the fluid ejected therefrom
and impinging upon the scale, the scale is peeled off and removed. The removed scale
dropped on the tube support plate are discharged to the exterior of the body portion
by some other means.
[0037] In Fig. 3, a lance feeding device 86 is mounted to the forward end of an extendable
arm portion 85. The lance feeding device 79 includes a lance insertion tube 87 through
which the flexible lance 81 passes, and a lance feeding mechanism (not shown), which
are attached to a base 88. Further, a lance insertion tube 87 which is capable of
rotating by 90 degrees is provided with a clamp mechanism 89 for supporting the lance
insertion tube 87 by a tube group after positioning its forward end between tube rows
to be cleaned.
[0038] The above-described scale removing device 70, which is in a semi-assembled state
when it is outside the body portion of the steam generator, is brought into the body
portion and assembled using the following procedures:
- 1. The operator inserts his hand through the hand hole 2c, and mounts a monitoring
camera 83 inside the body portion 2;
- 2. To protect the heat-transfer tubes 5 from damage at the time of assembling the
guide rail assembly, a heat-transfer tube protector 84 is installed in the tube group
lane;
- 3. A separation type guide rail (separated into two portions in the embodiment) 72a
constituting the guide rail assembly 72 is introduced into the body portion 2 through
the hand hole 2c. At this time, the movement carriage 75a is attached to the guide
rail beforehand;
- 4. After this, with the tube guide mechanism 78, the extendable arm assembly 80, the
lance feeding device 79, etc. being connected, the ascent/descent device 74 is inserted
in a horizontal position through the hand hole 2c to the deep end of the movement
carriage 75a;
- 5. Next, a connection carriage 75b is brought into the body portion by way of the
hand hole, and the movement carriage 75a and the connection carriage 75b are fixed
to each other to form a movement/connection carriage assembly 75;
- 6. Subsequently, the hydraulic erection/inclination device 77 is mounted to the ascent/descent
device 74, and then the ascent/descent device 74 is maintained in the erect state
as shown in the drawing with the aid of the winch and rack, whereby the preparation
for the cleaning of the contaminated portions, in particular, the lower sides of the
tube support plates is completed.
[0039] To perform cleaning, the rotatable arm portion 80b of the extendable arm assembly
80 is rotated to a position where it is perpendicular to the vertical arm portion
80a, and the extendable arm portion 85 is extended appropriately. Then, the lance
feeding device 86 is operated, and the lance insertion tube 87 is rotated from the
face-upward position shown in Fig. 2 to the lateral position shown in Fig. 3 to insert
it between heat-transfer tube rows. High-pressure water is ejected as shown in Fig.
3 from the cleaning head 82 inserted to a position to be cleaned, thereby removing
the scale at that position.
[0040] Next, various embodiments of the scale removing device for the portion centered about
the tube plate shown in Fig. 1 and the scale removing device 70 for the portions centered
about the tube support plates shown in Figs. 2 and 3 will be described. To prevent
overlap in description, only the former, i.e., the cleaning head 60 of the scale removing
device 50 for the portion centered about the tube plate will be described. However,
it is possible to regard the construction of the latter, i.e., the cleaning head 82,
to be basically the same as that of the former.
[0041] Figs. 4A, 4B and 5 show the forward end portion of the lance 58 and the cleaning
head 60 mounted thereto. It is possible for the lance 58 to have an ordinary construction
as shown, for example, in Fig. 10. To describe it briefly, in this embodiment, it
includes three high-pressure water hoses 91, one nitrogen purge line 92, and one video
probe optical fiber cable 93. These hoses, etc. are mutually fixed by integral blocks
93a, 93b, 93c, ... arranged longitudinally. And, to the mounting end portion block
94 in the foremost block 93a, the thin cleaning head 60 is mounted by an appropriate
fastening means 95.
[0042] The cleaning head 60 has socket portions 60a for receiving the high-pressure water
hoses 91, and the socket portions 60a communicate with a single chamber 60b. And,
a nozzle tip 96 is detachably mounted in a liquid-tight fashion so as to communicate
with the chamber 60b. The nozzle tip 96 has a cube-like main body portion (hexahedron)
96a, flange-like mounting portions 96b extending from the upper and lower surfaces
of the main body portion 96a, and a cylindrical communication portion (protruding
portion) 96c protruding from the inner surface of the main body portion 96a toward
the chamber 60b.
[0043] As can be seen from Figs. 4A, 4B and 5, the cleaning head 60 has a recess of a configuration
suitable for receiving the above-mentioned nozzle tip 96, and the nozzle tip 96 is
reliably secured to the cleaning head 60 by means of two fastening screws 97 in the
mounting portions 96b, and communicates with the chamber 60b through the communication
portion 96c. Around the communication portion 96c, there is arranged a sealing means
such as an O-ring 98 so that the nozzle tip 96 can be mounted to the cleaning head
60 in a liquid-tight fashion. Formed in the communication portion 96c is a flow passage
99a of substantially the same diameter, and, formed in the main body portion 96a is
a cone-shaped nozzle hole 99b. One end of the flow passage 99a communicates with the
chamber 60b, and the other end thereof communicates with the small-diameter end of
the nozzle hole 99b. The large-diameter end of the nozzle hole 99b is exposed to the
exterior.
[0044] When using the cleaning head 60 for the purpose of removing scales, water is poured
over the tube plate until at least the entire cleaning head 60 is immersed in water,
and then high-pressure water is supplied to the high-pressure water hose 91. The high-pressure
water passing through the high-pressure water hose 91 enters the chamber 60b of the
immersed cleaning head 60, from which it passes through the flow passage 99a of the
nozzle tip 96 as a water jet before it is ejected through the nozzle hole 99b. When
a water jet is ejected through the nozzle hole 99b of the configuration shown, the
liquid around this water jet is accelerated, the pressure is locally reduced to become
less than steam pressure, and the liquid is evaporated to become bubbles, which grow.
This phenomenon is called cavitation. When the cavitation bubbles collapse, a very
high impact pressure is generated.
[0045] Thus, when the cavitation bubbles are applied to firmly adhering scale, the bubbles
collapse to generate high impact pressure, which is capable of peeling off even hard
scale. The cavitation jet is
characterized in that it makes it possible to obtain high impact pressure over a wide range with a pressure
lower than that of high-pressure water. Further, the bubbles are scattered to generate
impact pressure over a wide range, so that they also reach areas which cannot be reached
by the conventional water jet. Thus, it is possible to suitably clean even those regions
out of the ejection paths. Further, since high impact pressure is obtained over a
wide range, the construction of the device for operating the lance with the cleaning
head is simplified, thus enabling the system to be easily formed as a robot.
[0046] By using the test apparatus shown in Figs. 6(a) and 6(b), a scale removal test was
conducted with the cleaning head or nozzle head of Fig. 6(c) having a nozzle configuration
substantially the same as that of the cleaning head shown in Figs. 4A, 4B and 5. As
shown in Fig. 6(d), cavitation bubbles were moved (propagated) to widen the area that
can be cleaned, so that, by appropriately setting the factors, such as ejection angle,
nozzle pressure, flow rate, stand-off distance, and tube plate surface depth, not
less than 80% of the cavitation action surface for the specimens (heat-transfer tubes)
reaches an impact pressure effective in scale removal, without generating any erosion
beyond the allowable value of surface roughness (ejection time: 60 minutes). Further,
under the assumption that it was being applied to an actual steam generator tube plate,
the ejection angle was set to 58 degrees. In this case, effective cavitation acted
over a range of 10 mm or more in the height direction from the tube plate, and over
substantially half the periphery in the circumferential direction. Thus, it was ascertained
that it was effective for the regions to be cleaned including the regions which would
be out of the ejection path if an existing scale removing device were used.
[0047] The present invention is not restricted to the preferred embodiment described above,
but various modifications are possible. For example, as shown in Fig. 7, it is possible
to adopt a cleaning head 100 having two cavitation nozzle tips 101. In Fig. 7, chambers
102 communicating with the nozzle tips are formed in the cleaning head 100. High-pressure
water is supplied to the nozzle tips 101 through the chamber 102 to generate cavitation
as described above. Numeral 104 indicates an image guide consisting, for example,
of an optical fiber connected to a CCD camera 105 at the forward end of the head.
[0048] In a venturi-type cleaning head 110 shown in Fig. 8, the portion corresponding to
the cylindrical flow passage 99a of Figs. 4 and 5 is formed as a throat portion 111,
so that the cavitation, shown by bubbles 112, is generated in the throat portion 111.
Thus, this cleaning head 110 can be used not only in water, but also in the air. Further,
in this cleaning head 110, the front edges are not simply obliquely chamfered, but
formed as curved portions 113.
[0049] As can be easily seen from Fig. 1, the lance 58 can move along the cylindrical main
body 52a of the lance conveying member 52 as indicated by the white arrows, so that,
when it is completely drawn back, the cleaning head at the forward end thereof is
positioned on the inner side of the end cover member 52b of the cylindrical main body.
In this condition, the scale removing device 50 is brought in and taken out of the
body portion through the hand hole 2b. Thus, when the corners of the cleaning head
110 are formed as curved portions 113 as shown in Fig. 8, there is no interference
with the hand hole 2b when the device is brought in and taken out of the body portion,
thereby achieving an improvement in terms of operational efficiency. Thus, the curved
portions 113 are best adapted to the outer peripheral configuration of the end cover
member 52b of the cylindrical main body 52a shown in Fig. 1.
[0050] Next, with reference to Figs. 9(a) through 9(d), various cleaning heads or nozzle
tips which can be applied to embodiments of the scale removing device of the present
invention to generate cavitation will be described. A cleaning head 120 shown in Fig.
9(a) includes a first member 122 having a cone-shaped flow passage 123 communicating
with a high-pressure water hose 121, a second member 124 having a cylindrical flow
passage 125 communicating with the flow passage 123, and a third member 126 having
a cone-shaped flow passage 127 communicating with the flow passage 125. Detachably
fitted into the third member 126 is a nozzle tip 129 containing a cone-shaped flow
passage 129a communicating with the flow passage 127 and a cylindrical flow passage
129b. Further, arranged in the cone-shaped flow passage 127 is a cylindrical member
or pin 128 whose forward end protrudes into the cylindrical flow passage 125. In this
cleaning head 120, high-pressure water enters the cone-shaped flow passage 123 from
the high-pressure hose 121, and is ejected into the cylindrical flow passage 125 to
generate cavitation around the pin 128. In this cleaning head 120, the nozzle tip
129, etc. are further provided in front of the flow passage 125, so that, if the cleaning
head 120 is used in the air, it is possible to generate cavitation.
[0051] Figs. 9(b) and 9(c) show other nozzle tips 130 and 135 which are of an orifice type.
In front of a cylindrical flow passage or chamber 131, there is provided a tapered,
substantially cone-shaped flow passage 132, and, at the forward end of the cone-shaped
flow passage 132, there is formed a relatively short cone-shaped flow passage 133.
It is assumed that, by reducing the length of this flow passage 133, the generation
of cavitation in the high-pressure water flowing from the left to the right in the
drawing is promoted. The nozzle tips 130 and 135 are different in outer configuration.
[0052] Fig. 9(d) shows a horn-type nozzle tip 140. High-pressure water is introduced into
a horn-shaped flow passage 141 from the right side of a nozzle tip 140, and it flows
by way of a cylindrical chamber or flow passage 142 before it leaves a cone-shaped
flow passage 143 to generate cavitation. In this embodiment, the generation of cavitation
is promoted by mounting an appropriate ultrasonic oscillator 144 to the cylindrical
flow passage 142.
[0053] Apart from the above-described preferred embodiments and modifications thereof of
the present invention, the following modifications are possible:
- (1) The ultrasonic oscillator, which is only used in the modification shown in Fig.
9(d), can be provided on the upstream side of the nozzle (a position where cavitation
is not generated yet) when promotion of cavitation is desired.
- (2) While in the above embodiments one or two nozzle tips are used, it is possible
to increase the number of nozzle tips. Further, when mounting a plurality of nozzle
tips to the same cleaning head, a combination of different types of nozzle tips is
possible.
- (3) A CCD camera and an image guide can also be provided in the cleaning heads of
the embodiments in which they are not incorporated.
INDUSTRIAL APPLICABILITY
[0054] As described above, an embodiment of the present invention may provide a scale removing
device for a steam generator of the type which includes: a body portion; a tube plate
and a plurality of tube support plates arranged horizontally in the body portion so
as to traverse the body portion; a plurality of heat-transfer tubes which extend from
the tube plate and end at the tube plate and which extend through the tube support
plates in a row-like fashion so as to define a tube lane in the body portion; and
a hand hole which is formed at a position above the tube plate and through which the
scale removing device is inserted to clean a portion centered about the tube plate,
the scale removing device comprising: a flexible lance holding a high-pressure water
hose and movable with respect to the tube plate and the heat-transfer tubes, and a
cleaning head mounted to the forward end of the flexible lance, wherein formed inside
the cleaning head are a fluid passage communicating with the high-pressure water hose,
a chamber communicating with the fluid passage, and a cavitation generating nozzle
hole communicating with the chamber, whereby, when high-pressure water is caused to
flow through the flexible lance, cavitation is generated, and an intense impact pressure
is propagated from the nozzle hole of the cleaning head over a wide range and hits
the scale in the portion centered about the tube plate, thereby making it possible
to easily remove scale which otherwise toughly adheres to a region out of the ejection
path. This is particularly advantageous when this steam generator is used in a nuclear
power plant since it helps to protect the operators from exposure to radiation and
to maintain the heat-transfer tubes in a sound state.
[0055] Further, an embodiment of a scale removing device formed in accordance with the present
invention preferably further comprises a suspension guide device horizontally arranged
on the tube plate and a lance conveying member suspended by the suspension guide device
and guided in horizontal movement through the hand hole, wherein the flexible lance
runs through the lance conveying member and is paid out from and drawn back to the
lance conveying member, and wherein the forward end portion of the cleaning head is
formed into a curved surface not interfering with the body portion wall surface defining
the hand hole, whereby there is advantageously no interference with the hand hole
when the scale removing device in which the flexible lance with the cleaning head
is accommodated in the lance conveying member is brought in and taken out through
the hand hole. Further, when the cleaning head is inserted between a number of heat-transfer
tubes closely arranged in the steam generator, the insertion is facilitated when the
forward end portion of the cleaning head is formed as a curved surface.
[0056] Further, the same effect can be obtained when the lance conveying member has a cylindrical
main body through which the flexible lance runs and when the forward end portion of
the cleaning head is configured such that when the flexible lance has been completely
drawn back, it does not protrude from the peripheral surface of the cylindrical main
body. The number of cavitation generating nozzle holes may be one or two.
[0057] Furthermore, an embodiment of the present invention may provide a scale removing
device for a steam generator including:
a body portion; a plurality of tube support plates horizontally arranged inside the
body portion so as to traverse the body portion; a plurality of heat-transfer tubes
extending in a row-like fashion through the tube support plates so as to define a
tube lane in the body portion; a pair of hand holes formed in the body portion at
a position directly above at least one of the tube support plates so as to be diametrically
opposed to each other; and flow slots formed in the portions of the tube support plates
corresponding to the tube lane, the scale removing device being inserted through the
hand holes, ascending and descending through the flow slots formed in the tube support
plates, and cleaning the portions centered about the tube support plates, the scale
removing device comprising a flexible lance holding a high-pressure water hose and
movable with respect to the tube support plates and the heat-transfer tubes, and a
cleaning head mounted to the forward end of the flexible lance, wherein formed inside
the cleaning head are a fluid passage communicating with the high-pressure water hose,
a chamber communicating with the fluid passage, and a cavitation generating nozzle
hole communicating with the chamber whereby, when high-pressure water is caused to
flow through the flexible lance, cavitation is generated, and an intense impact pressure
is propagated from the nozzle hole of the cleaning head over a wide range and hits
the scale in the portion centered about the tube plate, thereby making it possible
to easily remove toughly adhering scale. This is particularly advantageous when this
steam generator is used in a nuclear power plant since it helps to protect the operators
from exposure to radiation and to maintain the heat-transfer tubes in a sound state.
[0058] Further, the cleaning head includes a head main body portion in which the fluid passage
and the chamber communicating with the fluid passage are formed, and a nozzle tip
detachably mounted to the head main body portion, the cavitation nozzle hole being
formed in the nozzle tip, whereby, if erosion is generated in the nozzle tip as a
result of repeated use, it is possible to easily replace the nozzle tip by a new one,
thereby achieving a reduction in maintenance cost.
[0059] Further, in preferred embodiments it is possible to mount an ultrasonic oscillator
to the nozzle tip, whereby it is possible to further enhance the cavitation impact
pressure, thereby increasing the ratio at which the adhering scales are removed.
[0060] Further, the nozzle tip includes a hexahedron defining the cavitation generation
hole, thin-plate-like mounting portions extending from two opposing surfaces of the
hexahedron except for the surfaces where there are a small-diameter end and a large-diameter
end of the cavitation generation hole, and a protruding portion defining a flow passage
communicating with the small-diameter end of the cavitation generating hole, wherein
a recess of a contour corresponding to the configuration of the nozzle tip is formed
in the head main body portion, and wherein the nozzle tip can be inserted into the
recess and mounted to the head main body portion by the mounting portion, whereby
it is possible to reduce the size of the nozzle tip, making the scale removing device
suitable for insertion between closely arranged heat-transfer tubes as in the case
of a steam generator. Further, by providing a CCD camera in the forward end portion
of the cleaning head, it is possible to perform the cleaning operation while observing
an image of the portion being cleaned that is displayed on a monitor outside the steam
generator.
1. Kalk-Entfernungsvorrichtung zur Entfernung von Kalk aus einem Dampfgenerator, der
beinhaltet:
einen Korpus-Abschnitt (2); eine Rohrplatte (3) sowie eine Vielzahl von Rohr-Stützplatten
(6), die horizontal in dem Korpus-Abschnitt derart angeordnet sind, dass sie den Korpus-Abschnitt
durchqueren; eine Vielzahl von Wärmeübergangs-Rohren (5), die sich von der Rohrplatte
erstrecken und an der Rohrplatte enden, und welche sich durch die Rohrstützplatten
in reihenartiger Weise derart erstrecken, dass sie eine Rohrbahn (16) in dem Korpus-Abschnitt
definieren; und
ein Handloch (2b, 2c), welches an einer Position oberhalb der Rohrplatte ausgebildet
ist und durch welches die Kalk-Entfernungsvorrichtung zur Reinigung eines Abschnitts
eingesetzt wird, der um die Rohrplatte herum zentriert ist,
wobei die Kalkentfernungsvorrichtung umfasst:
eine flexible Lanze (58, 61), die einen Hochdruck-Wasserschlauch (91) hält und in
Bezug auf die Rohrplatte (3) und die Wärmetransfer-Rohre (5) beweglich ist, sowie
einen Reinigungskopf (60, 82), der am vorderen Ende der flexiblen Lanze (58, 81) befestigt
ist, wobei innerhalb des Reinigungskopfs (60, 82) Fluid-Durchgänge (60a), die mit
dem Hochdruck-Wasserschlauch in Wirkverbindung stehen, eine Kammer (60b), die mit
dem Fluid-Durchgang in Wirkverbindung steht, sowie ein Kavitationserzeugungs-Düsenloch
(99b), das mit der Kammer in Wirkverbindung steht, ausgebildet sind.
2. Kalk-Entfernungsvorrichtung gemäß Anspruch 1, des Weiteren umfassend eine Suspensions-Führungsvorrichtung
(51), die in ihrer Verwendung horizontal oberhalb der Rohrplatte (3) angeordnet ist,
sowie ein Lanzen-Förderelement (52), welches von der Suspensions-Führungsvorrichtung
(51) herunterhängt und in einer horizontalen Bewegung durch das Handloch (2b, 2c)
führbar ist, wobei die flexible Lanze (58, 81) durch das Lanzen-Förderelement (52)
hindurch verläuft und von dem Lanzen-Förderelement (52) wegbewegt und zu diesem zurückgezogen
wird, und wobei der vordere Endabschnitt des Reinigungskopfs (60, 82) in einer gekrümmten
Oberfläche so ausgebildet ist, dass er nicht in Wechselwirkung mit der Korpus-Abschnitt-Wandoberfläche
tritt, die das Handloch (2b, 2c) definiert, wenn er hier hindurch eingesetzt ist.
3. Kalk-Entfernungsvorrichtung gemäß Anspruch 2, wobei das Lanzen-Förderelement (42)
einen zylindrischen Hauptkorpus (52a) aufweist, durch den die flexible Lanze (58,
81) hindurch verläuft, wobei der vordere Endabschnitts des Reinigungskopfs (60, 82)
derart aufgebaut ist, dass dann, wenn die flexible Lanze vollständig zurückgezogen
wurde, dieser nicht von der umfänglichen Oberfläche des zylindrischen Hauptkörpers
hervorsteht.
4. Kalk-Entfernungsvorrichtung gemäß Anspruch 1, in der eins oder eine Vielzahl der Hohlraum-Erzeugungs-Düsenlöcher
(99b) ausgebildet ist.
5. Kalk-Entfernungsvorrichtung gemäß einem der voranstehenden Ansprüche, wobei der Reinigungskopf
(60, 82) einen Kopfkörper-Hauptabschnitt beinhaltet, in dem der Fluid-Durchgang (60a)
und die Kammer (60b), die mit dem Fluid-Durchgang in Wirkverbindung steht, ausgebildet
sind, sowie eine Düsenspitze (96) wieder entfernbar an dem Kopfkörper-Korpusabschnitt
befestigt ist und das Hohlraum-Erzeugungs-Düsenloch (99b) in der Düsenspitze ausgebildet
ist.
6. Kalk-Entfernungsvorrichtung gemäß Anspruch 5, wobei ein Ultraschall-Oszillator an
der Düsenspitze 96 befestigt ist.
7. Kalk-Entfernungsvorrichtung gemäß Anspruch 5, wobei die Düsenspitze (96) ein Hexaeder
beinhaltet, das das Hohlraum-Erzeugungsloch (99b) definiert, Befestigungsabschnitte
(96b) in der Art einer dünnen Platte, die sich von zwei gegenüberliegenden Oberflächen
des Hexaeders außer denjenigen Oberflächen, an denen das Ende mit kleinem Durchmesser
und ein Ende mit großem Durchmesser des Hohlraum-Erzeugungslochs ausgebildet sind,
erstrecken, sowie einen hervorstehenden Abschnitt (96c), der einen Strömungsdurchgang
definiert, der mit dem Ende des Hohlraum-Erzeugungslochs (99b) mit kleinem Durchmesser
in Wirkverbindung steht, wobei eine Aufnahme mit einer Kontur, die mit dem Aufbau
der Düsenspitze (96) korrespondiert, in dem Kopfkörper-Korpusabschnitt ausgebildet
ist, und wobei die Düsenspitze (96) in die Aufnahme hinein eingesetzt ist und an dem
Kopfkörper-Korpusabschnitt durch den Befestigungsabschnitt (96b) befestigt werden
kann.
8. Kalk-Entfernungsvorrichtung gemäß einem der voranstehenden Ansprüche, wobei eine CCD-Kamera
am vorderen Endabschnitt des Reinigungskopfs vorgesehen ist.
1. Dispositif de détartrage pour détartrer un générateur de vapeur du type qui inclut:
une partie de corps (2);
une plaque de tube (3) et une pluralité de plaques (6) de soutien de tube agencées
horizontalement dans la partie de corps de manière à traverser la partie de corps;
une pluralité de tubes de transfert thermique (5) qui s'étendent de la plaque de tube
et se terminent à la plaque de tube et qui s'étendent à travers les plaques de soutien
de tube en forme de rangées, de manière à définir une voie (16) de tube dans la partie
de corps; et
un trou de poing (2b, 2c) qui est formé à une position au-dessus de la plaque de tube
et à travers lequel le dispositif de détartrage doit être inséré pour nettoyer une
partie centrée autour de la plaque de tube,
le dispositif de détartrage comprenant:
une lance flexible (58, 81) maintenant un flexible d'eau à haute pression (91) et
mobile par rapport à la plaque de tube (3) et les tubes de transfert thermique (5),
et une tête de nettoyage (60, 82) montée à l'extrémité vers l'avant de la lance flexible
(58, 81), où un passage de fluide (60a) communiquant avec le flexible d'eau à haute
pression, une chambre (60b) communiquant avec le passage de fluide, et un trou de
buse (99b) de génération de cavitation communiquant avec la chambre, sont formés à
l'intérieur de la tête de nettoyage (60, 82).
2. Dispositif de détartrage selon la revendication 1, comprenant en plus un dispositif
de guidage de suspension (51), qui, en utilisation, est agencé horizontalement au-dessus
de la plaque de tube (3) et un organe (52) de transport de lance suspendu par le dispositif
de guidage de suspension (51) et pouvant être guidé dans un mouvement horizontal à
travers le trou de poing (2b, 2c), où la lance flexible (58, 81) circule à travers
l'organe (52) de transport de lance et est déroulée et renvoyée à l'organe (52) de
transport de lance, et où la partie d'extrémité vers l'avant de la tête de nettoyage
(60, 82) est formée dans une surface incurvée de manière à ne pas gêner la surface
de paroi de partie de corps définissant le trou de poing (2b, 2c), lorsqu'elle est
inséré à travers celui-ci.
3. Dispositif de détartrage selon la revendication 2, dans lequel l'organe (52) de transport
de lance a un corps principal cylindrique (52a) à travers lequel la lance flexible
(58, 81) circule et où la partie d'extrémité vers l'avant de la tête de nettoyage
(60, 82) est configurée de telle sorte que lorsque la lance flexible est renvoyée
complètement, elle ne fait pas saillie à partir de la surface périphérique du corps
principal cylindrique.
4. Dispositif de détartrage selon la revendication 1, dans lequel un ou une pluralité
desdits trous de buse (99b) de génération de cavitation sont formés.
5. Dispositif de détartrage selon l'une quelconque des revendications précédentes, dans
lequel la tête de nettoyage (60, 82) inclut une partie de corps principal de tête
dans laquelle le passage de fluide (60a) et la chambre (60b) communiquant avec le
passage de fluide sont formés, et une pointe de buse (96) monté de manière amovible
à la partie de corps principal de tête, le trou de buse (99b) de génération de cavitation
étant formé dans la pointe de buse.
6. Dispositif de détartrage selon la revendication 5, dans lequel un oscillateur ultrasonique
est monté à la pointe de buse (96).
7. Dispositif de détartrage selon la revendication 5, dans lequel la pointe de buse (96)
inclut un hexaèdre définissant le trou (99b) de génération de cavitation, des parties
de montage (96) en forme de plaques minces s'étendant à partir de deux surfaces opposées
de l'hexaèdre à l'exception des surfaces où il y a une extrémité à petit diamètre
et une extrémité à grand diamètre du trou de génération de cavitation, et une partie
protubérante (96c) définissant un passage d'écoulement communiquant avec l'extrémité
à petit diamètre du trou (99b) de génération de cavitation, où un évidement d'un contour
correspondant à la configuration de la pointe de buse (96) est formé dans la partie
de corps principal de tête, et où la pointe de buse (96) peut être insérée dans l'évidement
et montée à la partie de corps principal de tête par la partie de montage (96b).
8. Dispositif de détartrage selon l'une quelconque des revendications précédentes, dans
lequel une caméra CCD est pourvue dans la partie d'extrémité vers l'avant de la tête
de nettoyage.