DK3128280T3

DK3128280T3 - Apparatus for introducing impact forces into a heating surface and method for mounting an anvil

Info

Publication number: DK3128280T3
Application number: DK16182753.0T
Authority: DK
Inventors: Torsten Pfeffer; Frank Miunske
Original assignee: Steinmueller Babcock Env Gmbh
Priority date: 2015-08-07
Filing date: 2016-08-04
Publication date: 2018-10-22
Also published as: DE102015010307B4; EP3128280B1; EP3128280A1; DE102015010307A1

Description

The invention relates to a device for applying impact forces to a heating surface, the heating surface comprising converging and diverging manifolds (also referred to as collectors and distributors), the device being provided for removing deposits on the heating surface of an anvil connected to the converging and diverging manifolds, wherein impact forces act on the anvil so as to oscillate or resonate said heating surface. A steam boiler having steam boiler heating surfaces, which each comprise a converging and diverging manifold, is known from EP 0 716 282 A1. In such steam boilers the heat transfer from the flue gas to the heat transfer medium is degraded by ash deposits on the heating surfaces. These deposits can be removed by a mechanical impact, such as disclosed in EP 0 716 282 A1, wherein the mechanical impact is transferred from an impact element to an anvil which is connected to the heating surface. Impact mechanisms for exerting mechanical impacts on the heating surfaces are further known from WO 2012/069702 A1, from EP 0 254 379 A1 and from US 3,835,817 A. Another design for introducing impact pulses into a membrane wall is known from EP 2 454 146 A1.

It has been proposed to mount the anvil at the lower end of the heating surface on the rimmed end base of the heating surface manifold, wherein the welded closing element of mostly cylindrical pressure containers is referred to as end base. The whole heating surface is oscillated by an impact pulse in axial direction of the heating surface manifold on the end base or on the anvil mounted to the end base, whereby deposits can be efficiently removed. In this process, the high impact forces result in accelerations of up to 300 times of the gravitational acceleration.

Because of the reasons mentioned above, the anvil has to be made from a mechanically highly resistant material, and the anvil must be firmly connected to the heating surface. Particularly martensitic materials, such as X20CrMoC11-1, are used for this porpose, wherein such materials show remarkably high hardness and, accordingly, are resistant to ductile deformation by the impact mechanism.

In this case the particular problem is a durable and firm connection between the anvil and the heating surface or the end base on the heating surface. The latter usually consists of ferritic materials, such as 16Mo3, which either cannot be welded to a martensitic material or can be welded only with difficulties. Accordingly, an additional austenitic or ferritic-austenitic intermediate plate is welded in between for affixing the anvil, wherein the intermediate plate can be welded to a ferritic as well as to a martensitic material. In this case, e.g. 10CrMo9-10 is used.

In these complex welding designs, a particular long and complicated, and thus expensive, heat treatment is necessary, so as to avoid embrittlement of the welds. In operation such embrittlement would lead to very fast failure of the weld, whereby the anvil could be detached from the heating surface. Thereby, the heating surface could potentially be damaged by the direct impact of the impact element on the unprotected surface of the end base.

In case the anvil should detach from the heating surface during operation, it is particularly difficult to mount a new anvil. Due to the assembly situation of the heating surfaces, the space in the region of the anvil is very restricted, with the result that welding the new anvil and heat treatment of the new welds become particularly difficult.

Accordingly, the object of the present invention is to fix an anvil to a heating surface in a more simple and economic way, and to reduce the danger of detachment of the anvil from the heating surface at the same time.

According to the invention, said object is achieved by a device for introducing impact forces into a heating surface, wherein an intermediate ring is attached to the front face of the converging or diverging manifolds of the heating surface by force-fittingly and/or form-fittingly mounting a mounting portion of the anvil.

Due to the force-fitting and/or form-fitting connection between the anvil and the intermediate ring, said intermediate plate made of a ferritic-austenitic material may be dispensed off, and as well a bonded connection thereof to the anvil may be dispensed off, and accordingly, a complicated heat treatment of the welds is not necessary.

Thus, the assembly time necessary for the connection of the anvil and the heating surface is substantially reduced. Furthermore, it is now possible to simply replace the anvil during maintenance. Should the anvil be damaged in operation, the old intermediate ring may be detached, and a new intermediate ring may be attached by welding without an additional heat treatment. Alternatively, a new intermediate ring could be welded to the old intermediate ring.

Preferably, the intermediate ring comprises a first thread (e.g. female thread), and the mounting portion of the anvil comprises a second thread (e.g. male thread), which engage when the mounting portion is attached to the intermediate ring. Thus, either the mounting portion may be screwed into the intermediate ring, or the intermediate ring is screwed into the mounting portion.

Preferably, the mounting portion of the anvil may be connected to the intermediate ring also by means of an interference fit so as to provide a force-fitting connection.

Furthermore, it is preferable, that the length of the mounting portion is less than the width of the intermediate ring, whereby, after final assembly of the anvil, a gap remains between the side of the mounting portion facing towards the con-verging/diverging manifold and the side of the converging/diverging manifold facing towards the anvil. Thus, the end base receives less mechanical load when the impact mechanism impacts on the anvil. The central region of the end base is not stressed by impact forces, whereby also no bending stress is introduced into the end base. Thereby, the life span of the end base is substantially increased, and the risk of a damage in this region is substantially reduced.

Preferably, the geometry of the end base generally corresponds to the geometry of the intermediate ring. Thus, the impact force is transferred to the end base via the ring. The end base is mechanically stressed only in the outer region, and the force is directly transferred to the tube material of the converging/diverging manifold of the heating surface.

Preferably, the intermediate ring is made of the same ferritic material as the heating surface, so as to provide a resilient bonded connection in form of a weld after the welding process, while the anvil itself is made from another material, preferably from a martensitic material, which has higher hardness compared to the ferritic material, since the anvil is exposed to the stress from the impact mechanism.

Furthermore, the converging/diverging manifold generally has the form of a cylinder, wherein the rotational symmetry axis of the intermediate ring is the same as the rotational symmetry axis of the converging/diverging manifold, so as to provide a directed introduction of the impact forces into the tube material of the converging/diverging manifold.

Preferably, a bore is provided through the intermediate ring and extends into the mounting portion of the anvil, wherein a lock pin is punched into the bore in a mounted condition of the anvil, so as to secure the anvil against detachment.

The head portion of the anvil, which receives the impact force, may be formed as a hexagon or generally as a polygon, apart from being formed as a circle, so as to provide for engagement of a large open end wrench directly with the anvil.

Preferably, the anvil can be provided with one or more tool mounts extending outwardly for engaging a tool when the anvil and the intermediate ring are assembled. In this context, a pressure compensation bore is provided preferably at the anvil, wherein the pressure compensation bore extends from the bottom of the anvil to a tool mount. This bore facilitates a pressure compensation between the surrounding and the region between the end base and the intermediate ring.

Furthermore, the invention is related to a method for mounting an anvil for introducing impact forces into a heating surface on a converging or diverging manifold of the heating surface, wherein the method comprises the following steps: attaching an intermediate ring to the front face of the converging/diverging manifold; mounting a mounting portion of the anvil to the intermediate ring by form-fit and/or force-fit.

Further advantageous embodiments of the invention are defined in the dependent claims.

In the following, the invention shall be explained with reference to the attached figures.

Fig. 1 shows an exploded side view of a section of the heating surface together with a first embodiment of the device according to the invention, wherein the anvil is screwed into the intermediate ring:

Fig. 2 shows a perspective view of the embodiment according to Fig. 1 in a condition mounted to the heating surface;

Fig. 3 shows an exploded perspective drawing of the embodiment according to Fig. 1 in a condition not mounted to the heating surface;

Fig. 3A shows a detailed view of the section of the intermediate ring of the embodiment according to Fig. 1;

Fig. 4 shows a perspective view of the drawing according to Fig. 3;

Fig. 5 shows a proposed connection of the anvil to the heating surface by means of a weld design having a ferritic-austenitic intermediate plate;

Fig. 6 shows the introduction of a force into the end base of the heating surface, wherein the embodiment according to Fig. 1 of the device is mounted, and wherein the intermediate ring, the manifold and the weld are shown as a sectional or part-sectional drawing;

Fig.7 shows a second embodiment of the device according to the invention, wherein the intermediate ring, the manifold and the weld are shown as a sectional or part-sectional drawing, respectively, and wherein the intermediate ring is screwed into the anvil;

Fig. 8 shows a third embodiment of the device according to the invention, wherein the intermediate ring, the manifold and the weld are shown as a sectional or part-sectional drawing, respectively, and wherein the anvil is connected to the intermediate ring via interference fit.

Figures 1 - 4 show a device 1 for introducing impact forces into a heating surface 2 according to a first embodiment. The device comprises an anvil 3 and an intermediate ring 4. The anvil preferably consists of a martensitic material, such as X20CrMoV11-1 having exceptional hardness, and the anvil comprises an impact plate 5 on one end for receiving impact forces which are produced by an impact mechanism which is not shown. Impact mechanisms for removing deposits on heating surfaces of steam boilers are known to the skilled person from the prior art and, accordingly, will not be described in detail for this reason.

According to a preferred embodiment, the impact plate 5 has a circular impact surface and comprises lateral tool mounts 5a. According to other embodiments, the impact plate may also be formed as a hexagon or, generally, as a polygon, so as to facilitate engagement of a large open end wrench directly with the anvil.

Furthermore, the anvil comprises a mounting portion 6 having a first thread (in this case male thread 6a), wherein the mounting portion is located at the opposite end, and wherein the impact plate 5 and the mounting portion are formed as one piece according to the invention. Preferably, the mounting portion 6 is cylindrical, and its radius is smaller than the radius of the impact plate 5.

Preferably, the intermediate ring 4 is manufactured from the same ferritic material as the heating surface 2, whereby it is possible to weld the intermediate ring 4 to the heating surface 2 without any heat treatment, and wherein the intermediate ring has an outer radius corresponding to the radius of the impact plate 5. The intermediate ring 4 comprises a second thread (in this case female thread 4b on the inside of the intermediate ring 4), wherein said second thread is provided for engagement with the first thread on the mounting portion 6 for fixing the mounting portion 6 of the anvil 3 to the intermediate ring 4. In the embodiment shown in Figures 1 - 4, the anvil 3 is screwed into the intermediate ring 4c by means of the female thread 4b and the male thread 6b.

The heating surface 2 is a superheater heating surface having a flow return or reversing manifold 7 and another converging/diverging manifold which is not shown in detail. Preferably, the manifold 7 is a cylindrical hollow structure which is closed by a welded end base 8 on at least of its ends. Even though the device 1 according to the invention will be described in the following referring to a manifold 7, the device according to the invention may also be employed with different heating surfaces having converging/diverging manifolds which are to be cleaned by impacts. The heating surface 2 further comprises tubes 10 and 11 which are provided for discharging and introducing steam into or from the manifold 7, respectively, as shown by arrows in Fig. 2. The heating surface preferably consists of a ferritic material, such as 16Mo3.

Mounting the device 1 on the heating surface 2 is carried out by welding the intermediate ring 4 to the end base 8 (see weld 9 in Fig. 2) and by screwing the mounting portion 6 of the anvil 3 into the intermediate ring 4. Thereby, the anvil 3 is form-fittingly connected to the intermediate ring 4.

Preferably, the screw connection is furthermore firmly tightened with a tightening torque of 400 Nm to 1500 Nm, preferably 800 Nm, so as to additionally obtain a connection by force-fit. The tightening torque is introduced into the anvil 3 by engaging a tool (not shown) with one of the tool mounts 5a, and by rotating the anvil 3 with respect to the intermediate ring 4 until the desired tightening torque is achieved.

After the tightening torque has been achieved, a bore 4a is formed in the intermediate ring 4 in a radial direction of the intermediate ring 4, wherein the bore extends through the threads 4b/6b into the anvil. Thereafter, a lock pin 12 is punched into the bore and is welded to the intermediate ring 4 on the outside. In this way untightening of the screw connection between the anvil and the intermediate ring due to the particular high stress during the impacts of the impact mechanism can be additionally avoided.

In case the anvil 3 is damaged during operation of the steam boiler, the anvil 3 may be separated from the intermediate ring 4 during the next down time for maintenance. This can be done either by untightening the screw connection, wherein the lock pin 12 is removed by drilling out the pin or by cutting the anvil 3 from the intermediate ring 4. A new intermediate ring 4 may be welded either to the old intermediate ring or to the end base 8. In case the new intermediate ring is fixed to the old intermediate ring, no modification of the pressure portion of the heating surface 2 occurs, which is economically reasonable, particularly with respect to the fact that inspections with respect to the end base 8 may be avoided which are otherwise necessary.

Another advantage of the solution according to the invention results from the avoidance of mechanical loads on the end base 8 when the impact mechanism hits the anvil, as shown in connection with Figures 5 and 6. First, Fig. 5 shows the above mentioned proposed anvil fixture wherein an austenitic or ferritic-austenitic intermediate plate 13 is welded to an anvil plate 14 and to an end base 8 of a manifold, and wherein the welds are subjected to a complicated heat treatment afterwards. In the embodiment according to the invention, where the intermediate plate has been substituted by the intermediate ring, the impact force is now transferred into the end base 8 via the intermediate ring 4 (see Fig. 6). In this case, however, the end base 8 is mechanically stressed only in its outer region, and the force is transferred directly into the tube material of the manifold 7 of the heating surface 2 via a ring area (see arrows 15). The central region 16 of the end base 8 is not stressed by impacts since, after mounting the anvil 3, a gap 17 remains between the side of the mounting portion 6 facing towards the end base 8 and the side of the end base 8 facing towards the anvil 3, wherein further no bending stresses are introduced into the end base 8. As a result, the life span of the end base 8 is remarkably higher, and the risk of damage in this region is remarkably reduced. As can be seen from Fig. 6, the intermediate ring 4 and the end base 8 preferably have a chamfer for the weld.

Furthermore, it can be seen in Fig. 6 that a pressure compensation bore 3a is provided in the anvil 3, wherein the pressure compensation bore extends from a bottom of the mounting portion 6 through the same and to one of the tool mounts 5a. The bore 3a is provided for pressure compensation of the gap 17 (i.e. the region between the end base 8 and the intermediate ring 4) with respect to the surroundings. This shall prevent an increase in pressure and detachment of the intermediate ring caused thereby during the welding process and in operation. A second embodiment of the device 1 according to the invention is shown in Fig. 7. The second embodiment differs from the embodiment of Fig. 1 in that the function of the intermediate ring 4 and of the mounting portion 6 with respect to mounting the anvil to the intermediate ring is inverted. According to the second embodiment, the mounting portion 6 of the anvil is formed as a ring having an inner thread 6c, and the intermediate ring 4 comprises a male thread 4c. This allows to screw the intermediate ring 4 into the anvil 3. Compared to the first embodiment, the dimensions of the intermediate ring 4 are the same in the second embodiment, while the impact plate 5 and the mounting portion 6 have correspondingly larger dimensions. Compared to the anvil plate 14 shown in Fig. 5, an impact plate 5 having a remarkably larger diameter results in this embodiment, which is advantageous. Thus, striking of the impact mechanism becomes easier (even for the case that the heating surface 2 might be displaced or inclined). Otherwise, reference is made to the description of the first embodiment. Also in this embodiment, a pressure compensation bore 3a starting from the bottom of the anvil 3 can be provided.

Fig. 8 shows another embodiment, i.e. a third embodiment, where a force-fitting connection is provided as an interference fit instead of the threaded connection of the intermediate ring 4 and the mounting portion 6. In this case - instead of the threads according to the first embodiment - a positive interference of the radius of the disk, which forms the mounting portion 6, is provided on the mounting portion 6, and the intermediate ring 4 is manufactured with a defined tolerance. However, it is also possible to manufacture the intermediate ring 4 having a negative interference and to manufacture the disk with a defined tolerance. In both cases, the fitting force would be the same. In order to mount the anvil 3 according to the third embodiment, either the anvil 3 or the intermediate ring 4 is heated or cooled down so as to obtain a temperature difference between the anvil 3 and the intermediate ring 4. A common mobile gas burner may be used for heating, wherein the intermediate ring 4 is heated to a temperature in a region of 100 °C to 300 °C and the intermediate ring expands correspondingly. The temperature difference could be provided in the same way by cooling the anvil 3 in a non-mounted condition by dry ice. In this case, the latter could be embedded in dry ice and could be cooled to e.g. about -75 °C. While the temperature difference prevails (i.e. while the anvil 3 and the intermediate ring 4 have a different temperature), the mounting portion 6 is inserted into the intermediate ring 4. Finally, the temperature difference between the anvil 3 and the intermediate ring 4 is compensated, whereby the anvil and the intermediate ring remain in interference fit as a result. Also, in this embodiment, a pressure compensation bore 3a may be provided which extends through the mounting portion 6 to the tool mount 5a.

Even though the third embodiment has been described above with an interference fit for the arrangement according to the first embodiment of Figures 1 - 4 (i.e. where the mounting portion is inserted into the intermediate ring), according to another embodiment, an interference fit could be provided also for the arrangement according to the second embodiment of Fig. 7 (i.e. in the arrangement where the intermediate ring is inserted into the mounting portion). In this case -instead of the threads according to the second embodiment - either the mounting portion 6 is manufactured with a negative interference (and the intermediate ring 4 is manufactured with a defined tolerance) or the intermediate ring 4 is manufactured with a positive interference (and the mounting portion 6 is manufactured with a defined tolerance). Thereafter, the temperature difference is obtained in the same way as has been described above with respect to the third embodiment, and then the intermediate ring 4 is inserted into the anvil 3. In this case, e.g. the intermediate ring 4 can be cooled in a unmounted condition and can be inserted into the anvil, wherein thereafter, i.e. after the temperature is balanced, the intermediate ring having an interference fit with the anvil is welded to the end base 8. Alternatively, the intermediate ring 4 can be welded to the end base 8 in a first step, and in a second step the anvil 3 is heated by means of a burner (and is accordingly expanded) and is then mounted on the intermediate ring 4 which is welded to the end base 8, wherein, after the temperature difference is balanced, detachment of the anvil is avoided by means of the clamping force of the interference fit.

In the same way as in the first embodiment, detachment of the mounted anvil 3 is additionally prevented in the further embodiments by providing a radial bore 4a through the intermediate ring 4 into the mounting portion 6 (see Fig. 7) or through the mounting portion 6 into the intermediate ring 4 (see Fig. 8) and by inserting a lock pin 12 thereafter.

It may be summarized that the device according to the invention provides the following advantages: o A complicated welded design can be avoided o No heat treatment is necessary o An assembly of the device is substantially faster and, accordingly, more economic o Maintenance is easy, re-assembly on site is fast and easily possible o No modification of the pressure portion of the heating surface 2 is neces sary in case of re-assembly o Higher life span compared to prior art mounting o The impact plate 5 can be dimensioned with a substantially larger diameter compared to the anvil plate 14. Thus the striking of the impact mechanism is facilitated in case the heating surface 2 is displaced or inclined.

In the following, the method for mounting the anvil 3 for introducing impact forces into the heating surface 2 on the converging/diverging manifold of the heating surface according to the invention is summarized: • attaching the intermediate ring 4 to the front face of the converging/diverging manifold 7 of the heating surface 2; • mounting the mounting portion 6 of the anvil to the intermediate ring 4 by form-fit and/or force-fit, wherein, as an example, either screwing the mounting portion 6, which comprises a male thread 6b, into the intermediate ring 4, which comprises a female thread 4b, is carried out, or cooling the anvil 3, inserting the mounting portion 6 into the intermediate ring 4 in a cooled condition and heating the anvil 3 in interference fit with the intermediate ring 4 is carried out. • forming the bore 4a through the intermediate ring and into the mounting portion; and • punching in the lock pin 12.

It is obvious for the person skilled in the art that, even though according to a preferred embodiment, first the intermediate ring 4 is welded to the end base 8 and then the anvil 3 is attached to the intermediate ring 4 via force-fit and/or formfit, the sequence of those steps could be changed. As an example, the intermediate ring 4 and the anvil 3 could be attached via force-fit and/or form-fit first, and then the exposed site of the intermediate ring could be welded to the end base 8.

List of reference signs 1 device 2 heating surface 3 anvil 3a pressure compensation bore 4 intermediate ring 4a bore 4b female thread 4c male thread 5 impact plate 5a tool mounts 6 mounting portion 6b male thread 6c female thread 7 manifold 8 end base 9 weld 10, 11 tubes 12 lock pin 13 intermediate plate 14 anvil plate 15 force arrows 16 central region of the end base 17 gap

Claims

A collector / distributor (7) for a heating surface (2) with an anvil (3) for the introduction of impact forces into the heating surface (2) for the removal of deposits on the heating surface, whereby the impact forces act on the anvil to cause the heating surface to oscillate, characterized by an intermediate ring (4) is provided on the front side of the collector / distributor (7) for force and / or form-fitting attachment of a fastening section (6) to the anvil (3), that the collector / distributor (7) on the front side has a welded flange bottom (8) and the middle ring (4) is welded on the front side of flange bottom (8).

Collector / distributor (7) according to claim 1, characterized in that the intermediate ring (4) has a first thread (4b) and the fastening section (6) a second thread (6b) which engages in the fastening of the fastening section (6) at each other at the intermediate ring (4).

Collector / distributor (7) according to claim 2, characterized in that the intermediate ring (4) has an inner thread (4b) and the fastening section (6) of the anvil has an external thread (6b) and the fastening section (6) is screwed into the intermediate ring (4), or that the intermediate ring (4) has an external thread (4c) and the fastening section (6) of the anvil an internal thread (6c) and the intermediate ring (4) is screwed into the fastening section.

Collector / distributor (7) according to claim 1, characterized in that the fastening section (6) is fixed to the intermediate ring (4) by pressing fit.

Collector / distributor (7) according to one of the preceding claims, characterized in that the length of the fastening section (6) is less than the width of the intermediate ring (4).

Collector / distributor (7) according to one of the preceding claims, characterized in that the geometry of the flange bottom (8) corresponds substantially to the geometry of the intermediate ring (4) and / or that the intermediate ring (4) is made of a ferritic material like the heating surface (2) while the anvil (3) is made of a different, preferably martensitic, material of higher hardness than the ferritic material.

Collector / distributor (7) according to one of the preceding claims, characterized in that the collector / distributor (7) is essentially in the form of a cylinder and the axis of rotation of the intermediate ring (4) is the same as the axis of rotation of the collector / distributor.

Collector / distributor (7) according to one of the preceding claims, characterized in that a bore (4a) is provided through the intermediate ring and into the fastening section (6) of the anvil (3) and in which a locking pin (12) is applied. ) into the mounting state of the anvil, and / or that the anvil (3) has one or more tool receiving devices (5a) extending radially outward, the anvil having at least one pressure equalizing bore (3a) extending from the bottom of the anvil (3) for a tool pickup device (5a).

Collector / distributor (7) according to one of the preceding claims, characterized in that the anvil (3) has a main part for the impact force acquisition and which is manufactured as a circle, hexagon or polygon.

A method of mounting an anvil (3) for introducing impact forces into a heating surface (2) of a collector or distributor (7) on the heating surface, characterized by placing an intermediate ring (4) on the front side of the collector / distributor (7). , whereby the collector / distributor (7) on the front side has a welded flange bottom (8) and the intermediate ring (4) is welded on the front side of the flange bottom (8), and form-closing and / or force-closing mounting of a fastening section (6) of the anvil on the intermediate ring (4) ).

Method for mounting an anvil (3) according to claim 10, characterized by screwing in the fastening section (6), which has an external thread (6b), in the intermediate ring (4) provided with an internal thread (4b), or screwing in the fastening section (6) provided with an internal thread (6) in the intermediate ring (4) provided with an external thread (4c).

Method for mounting an anvil according to claim 10, characterized by heating or cooling either the anvil (3) or the intermediate ring (4) to provide a temperature difference between the anvil (3) and the intermediate ring (4), insertion of the fastening section (6) in the intermediate ring (4) or insertion of the intermediate ring (4) in the attachment section (6), while the anvil and intermediate ring are different tempered, and compensate for the temperature difference between the anvil and intermediate ring in the press fit.

A method of mounting an anvil (3) according to any one of claims 10-12, whereby, after mounting of the fastening section (6) on the intermediate ring (4), a slot (17) is left between the collector / distributor side facing the fastening section (6). ) and the side facing the anvil (3) of the collector / distributor, since the length of the attachment section (6) is less than the width of the intermediate ring (4).

Method for mounting an anvil according to one of claims 10-13, characterized by inserting a bore (4a) into the intermediate ring (4) and in the fastening section (6), inserting a securing pin (12) into the bore (4a).