Patent Publication Number: US-10330309-B2

Title: Boiler

Description:
TECHNICAL FIELD 
     The present invention relates to a suspended boiler, and particularly relates to a boiler provided with a mechanism capable of reducing the seismic response of equipment provided inside the boiler. 
     BACKGROUND ART 
     With boilers, the boiler main body is suspended by a steel support frame so that thermal expansion of the boiler main body during operation is not obstructed. Accordingly, when an earthquake occurs, the boiler main body exhibits pendulum motion inside the steel support frame like that of a hanging bell. As such, seismic damping devices are provided to restrict relative displacement between the boiler main body and the steel support frame. 
     For example, Patent Document 1 proposes a boiler seismic damping device including elastoplastic elements between a back stay provided outward of the boiler main body and a steel support frame suspension supporting the boiler main body; wherein the elastoplastic elements are divided into a plurality of groups. 
     CITATION LIST 
     Patent Document 
     Patent Document 1: Japanese Unexamined Patent Application Publication No. H05-340502A 
     SUMMARY OF INVENTION 
     Technical Problems 
     When earthquakes occur, not only does relative displacement between the boiler main body and the steel support frame occur, but, also, relative displacement between the boiler drum constituting the outer shell of the boiler main body and equipment provided inside the boiler drum occurs (hereinafter, the equipment provided inside the boiler drum is referred to as an “internal element”) Note that, typically, this internal element is piping. However, while seismic damping devices in the related art, including the device recited in Patent Document 1, address the relative displacement between the boiler main body and the steel support frame, there are no examples that address reducing the seismic response of the internal elements. 
     Thus, an object of the present invention is to provide a suspended boiler capable of reducing the seismic response of an internal element provided inside a boiler drum. 
     Solution to Problem 
     A boiler according to an aspect of the present invention includes a boiler main body; and a steel support frame suspending and supporting the boiler main body. In such a boiler, the boiler main body includes a furnace wall composed of water pipes and plate-like fins arranged in an alternating manner; an internal element housed inside the furnace wall; and a buffering mechanism that interferes with the internal element and attenuates vibration energy when relative displacement, of the internal element with respect to the furnace wall, occurs that exceeds a predetermined value. 
     According to the aspect of the present invention, the buffering mechanism is provided that attenuates vibration energy when relative displacement of the internal element with respect to the furnace wall occurs that exceeds a predetermined value. As a result, the seismic response of the internal element can be reduced. 
     It is preferable that a load on the buffering mechanism of the present invention, caused by the interference resulting from the relative displacement in a main vibration direction of the internal element, is transmitted to the fins. 
     Additionally, in the boiler according to the present invention, the buffering mechanism may include an energy attenuating body that compresses to plastically deform due to the interference. 
     In cases where an energy attenuating body and a frame supporting the energy attenuating body and fixed to the furnace wall are provided as the buffering mechanism, it is preferable that the frame is fixed to the fins of the furnace wall. This frame may have energy attenuating capacity to compress to plastically deform due to the interference. 
     Additionally, it is preferable that a honeycomb structure is used as the energy attenuating body; and an axial line of this honeycomb structure may be disposed along the main vibration direction. 
     It is preferable that a pair of the buffering mechanism is provided, on both a forward side and a return side of the main vibration direction. 
     In the boiler according to the aspect of the present invention, the buffering mechanism includes a damping element fixed to the furnace wall, in which bending and shearing occurs; and an interference body fixed to the internal element, with which the damping element interferes. 
     It is preferable that a pair of the interference body is provided, on both a forward side and a return side of the main vibration direction. 
     Advantageous Effects of Invention 
     According to an aspect of the present invention, a buffering mechanism is provided that attenuates vibration energy when relative displacement of the internal element with respect to the furnace wall occurs that exceeds a predetermined value. As a result, a suspended boiler is provided whereby the seismic response of the internal element can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a drawing illustrating a schematic configuration of a suspended boiler according to an embodiment of the present invention. 
         FIGS. 2A and 2B  are drawings illustrating a buffering mechanism according to a first embodiment.  FIG. 2A  is a partial cross-sectional plan view, and  FIG. 2B  is a side view. 
         FIGS. 3A, 3B and 3C  are drawings explaining operations and effects of the buffering mechanism according to the first embodiment when the first embodiment is subjected to earthquake ground motion. 
         FIGS. 4A and 4B  are drawings illustrating an example of a preferable energy attenuating body according to the first embodiment. 
         FIG. 5A to 5D  are drawings illustrating a process through which the energy attenuating body illustrated in  FIGS. 4A and 4B  plastically deforms. 
         FIGS. 6A and 6B  are drawings illustrating a modified example of the energy attenuating body illustrated in  FIGS. 4A and 4B . 
         FIGS. 7A to 7D  are partial cross-sectional plan views illustrating a buffering mechanism according to a second embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The present invention will be described below in detail on the basis of embodiments illustrated in the attached drawings. 
     First Embodiment 
     As illustrated in  FIGS. 1, 2A, and 2B , a suspended boiler  1  according to the present embodiment includes a boiler main body  3  and a steel support frame  5  surrounding the boiler main body  3 , wherein the boiler main body  3  is suspended from the steel support frame  5  by hanging members  7 . Note that only a portion of the steel support frame  5  is illustrated in  FIG. 1 , but the steel support frame  5  is formed from a combination of a plurality of pillars  5 A extending in a vertical direction, a plurality of beams  5 B extending in a horizontal direction, and the like. 
     The boiler main body  3  includes a boiler drum  10  and an internal element  4  provided inside the boiler drum  10  and constituted primarily of piping. The present embodiment includes a buffering mechanism  20  that reduces the seismic response of the internal element  4  using the relationship between the internal element  4  and a furnace wall  11  of the boiler drum  10 . 
     The furnace wall  11  is a membrane wall and, as illustrated in  FIG. 2 , is composed of water pipes  15  and plate-like fins  16  arranged in an alternating manner and joined by welding. Accordingly, an inner surface  12  and an outer surface  13  of the furnace wall  11  have uneven forms in which a portion of the outer peripheral surface shape of the water pipes  15  and the surface of the fins  16  repeat in an alternating manner. The furnace wall  11  is provided with the water pipes  15  primarily to prevent overheating, and recover and effectively use heat. These purposes are achieved by passing water and/or steam through the water pipes  15 . Accordingly, from the perspective of maintaining the functions of the boiler  1 , it can be said that, in the furnace wall  11 , the water pipes  15  are more important constituents than the fins  16 . 
     As illustrated in  FIGS. 2A and 2B , the buffering mechanism  20  is fixed to the furnace wall  11  of the boiler drum  10 . The furnace wall  11  includes an inner surface  12  facing the internal element  4  and an outer surface  13  opposite the inner surface  12 , and, in the furnace wall  11 , the buffering mechanism  20  is fixed to the inner surface  12  side. 
     In the structural design of the boiler  1 , the buffering mechanism  20  is provided within a range of a clearance C set between the internal element  4  and the furnace wall  11  constituted by the water pipes  15  and the fins  16 . 
     The buffering mechanism  20  includes a frame  21  that has a gate-shaped cross section, and an energy attenuating body  25  that is attached to the frame  21 . When the internal element  4  interferes with the energy attenuating body  25 , the energy attenuating body  25  attenuates the energy caused by this interference. 
     The frame  21  is made from, for example, grooved steel that has a gate-shaped cross-section, and includes a web  22  and a pair of flanges  23 ,  23  connected to both ends of the web  22 . The flanges  23 ,  23  straddle the water pipes  15  of the furnace wall  11  and are fixed to the fins  16  by welding, for example. Thus, the buffering mechanism  20  is fixed so that the load is not transmitted directly to the water pipes  15 . 
     The energy attenuating body  25  is fixed to the web  22  of the frame  21  by welding, for example. 
     The energy attenuating body  25  plastically deforms upon interference by the internal element  4  when earthquake ground motion occurs and the internal element  4  shakes greater than expected. As a result, the energy attenuating body  25  attenuates the kinetic energy and reduces the seismic response. In order to achieve this, the energy attenuating body  25  is provided with mechanical characteristics whereby the energy attenuating body  25  yields prior to the internal element  4  and/or the furnace wall  11  becoming damaged when the internal element  4  interferes with the energy attenuating body  25 . 
     Note that, due to the structure of the boiler main body  3 , shaking in the direction of the solid white arrow A in  FIGS. 2A and 2B  is expected to be greater than shaking in the direction orthogonal thereto when earthquake ground motion occurs. As such, the direction of the solid white arrow A is defined as the main vibration direction A. 
     Additionally, the frame  21  and the energy attenuating body  25  of the buffering mechanism  20  are formed from the same heat-resistant steel as the internal element  4  and the furnace wall  11 . 
     Next, operations and effects of the buffering mechanism  20  when the boiler  1  provided with the buffering mechanism  20  is subjected to earthquake ground motion are described while referencing  FIGS. 3A and 3B . 
     When earthquake ground motion is received and the internal element  4  becomes relatively displaced from the normal state illustrated in  FIG. 3A  so as to approach and ultimately interfere with and impact the energy attenuating body  25 , the energy attenuating body  25  compresses to plastically deform as illustrated in  FIG. 3B , and attenuates the energy resulting from the earthquake ground motion. The internal element  4  separates from the energy attenuating body  25  once due to the swing-back of the earthquake ground motion, but then interferes again with the energy attenuating body  25 . The amount of displacement of the internal element  4  at this time is greater than the previous relative displacement. Accordingly, the energy attenuating body  25  compresses more than at the previous interference in order to attenuate the earthquake ground motion energy. 
     The energy attenuating body  25  repeats this behavior and, as a result, reduces the seismic response of the internal element  4  while exhibiting the load-displacement relationship illustrated in  FIG. 3C . 
     In the buffering mechanism  20 , while the energy attenuating body  25  attenuates the energy, the load is borne by the frame  21 . As such, the load is transmitted to the furnace wall  11  to which the frame  21  is fixed. It is desirable that the functions of the furnace wall  11  are not lost due to the load. In order to meet this demand, in the present embodiment, the frame  21  is fixed to the fins  16  and, as a result, the load is borne by the fins  16  and is not directly transmitted to the water pipes  15 . As described above, the water pipes  15  can be said to be responsible for the functions of the boiler  1  and, as such, the frame  21  straddles the water pipes  15 , and the flanges  23 ,  23  are attached to the fins  16 . As a result, even if the fins  16  become damaged, the functions of the boiler  1  will be ensured. 
     As described above, according to the present embodiment, the buffering mechanism  20  that attenuates energy within the clearance C is provided. As such, the seismic response of the internal element  4  can be reduced and seismic response reduction effects of the overall steel support frame  5  of the boiler  1  can be obtained due to the energy attenuating effects. 
     Furthermore, according to the present embodiment, a structure is used in which the load from the buffering mechanism  20  is borne by the fins  16  and is not directly transmitted to the water pipes  15 . As such, the functions of the boiler  1  can be ensured. 
     In the preceding, a description of a single buffering mechanism  20  was given. However, depending on the load expected to result from the earthquake ground motion, a plurality of buffering mechanisms  20  may be installed in the plan direction and the height direction. That is, an appropriate number of buffering mechanisms  20  may be installed at locations considered to be most effective from the perspective of the vibration mode of the internal element  4 . In general, it is preferable that the buffering mechanism  20  be installed at locations where the vibration mode of the internal element  4  is the largest. 
     In the preceding, a configuration is described in which the web  22  and the flanges  23 ,  23  do not contact the water pipes  15  in order to avoid damaging the water pipes  15 . However, provided that the functions of the water pipes  15  can be maintained, the web  22  and the flanges  23 ,  23  may contact the water pipes  15 . However, in this case as well, it is assumed that the load will be primarily borne by the fins  16 . 
     Additionally, in the preceding, a configuration was described in which the energy attenuating body  25  of the buffering mechanism  20  plastically deforms, but the frame  21  may also plastically deform simultaneously or in a delayed manner in order to attenuate the energy. 
     Next, though optional so long as the effects described above can be obtained, a preferable example of the energy attenuating body used in the present embodiment is described in detail while referencing  FIGS. 4A and 4B . Note that, in  FIGS. 4A and 4B , constituents that are the same as those in  FIGS. 2A and 2B  are marked with the same reference signs as in  FIGS. 2A and 2B . 
     A honeycomb core  26  illustrated in  FIG. 4B  is proposed as a preferable example of the energy attenuating body. 
     As illustrated in  FIG. 4B , the honeycomb core  26  has a structure formed by assembling a plurality of hexagonal cells  27 , for example. A hexagonal through-hole  28  penetrating along an axial line L of the cell  27  is formed in each cell  27 , and this through-hole  28  is open to both ends of the cell  27 . 
     As illustrated in  FIGS. 4A and 4B , the energy attenuating body made from the honeycomb core  26  is fixed to the frame  21  such that a compression direction of the honeycomb core  26  when the internal element  4  interferes with the honeycomb core  26  matches the axial line L direction. 
     The honeycomb core  26  compress and deforms when the internal element  4  interferes and, as a result, attenuates the energy resulting from the impact force of the internal element  4 . An example of these changes will be described while referencing  FIGS. 5A to 5D . 
     Due to interference of the internal element  4 , the honeycomb core  26  deforms and compresses from an initial state indicated by the dashed lines in  FIG. 5A , and ultimately reaches a completely collapsed state illustrated in  FIG. 5B . At this point, the honeycomb core  26  has lost energy attenuating capacity. Thereafter, if a large relative displacement of the internal element  4  occurs, as illustrated in  FIG. 5C , the frame  21  plastically deforms instead of the honeycomb core  26 , and the entire buffering mechanism  20  takes responsibility for attenuating the energy.  FIG. 5D  is a load-displacement line diagram illustrating the changes depicted in  FIGS. 5A to 5C . Note that (a), (b), and (c) in  FIG. 5D  correspond to the states depicted in  FIGS. 5A, 5B, and 5C , respectively. 
     As with the energy attenuating body  25 , the honeycomb core  26  as the energy attenuating body is also provided with mechanical characteristics whereby the honeycomb core  26  yields prior to the internal element  4  and the furnace wall  11  becoming damaged, and an appropriate number of buffering mechanisms  20  provided with the honeycomb core  26  may be installed at locations considered to be most effective from the perspective of the vibration mode of the internal element  4 . Specifically, as illustrated in  FIG. 6A , a plurality of buffering mechanisms  20  can be provided at intervals or, as illustrated in  FIG. 6B , a buffering mechanism  20  having a dimension spanning three of the fins  16  can be provided. 
     Second Embodiment 
     Next, a second embodiment of the present invention will be described while referencing  FIGS. 7A to 7D . Note that the same reference signs as used in  FIGS. 2A and 2B  are used in  FIGS. 7A to 7D  for configurations that are the same as in the first embodiment. 
     A buffering mechanism  30  according to the second embodiment utilizes a damping structure that is subjected to bending and shearing, and is configured to be capable of attenuating energy resulting from reciprocating vibration caused by earthquake ground motion. 
     As illustrated in  FIGS. 7A and 7B , the buffering mechanism  30  is provided on a first end portion in the horizontal (width) direction H of the internal element  4  closest to the furnace wall  11 , on a lower end portion in the vertical (up-down) direction V. The buffering mechanism  30  includes a main damping element  31  provided on the furnace wall  11  side, and a damper bearing  35  provided on the internal element  4  side and that interferes with the main damping element  31  when vibration occurs in the main vibration direction A that exceeds a predetermined value. 
     The main damping element  31  includes a first arm  32  extending perpendicularly from the furnace wall  11 , and a second arm  33  extending parallel to the furnace wall  11 . A first end (fixed end) side of the first arm  32  is fixed to a fin  16  of the furnace wall  11 , and a second end (free end) side of the first arm  32  is fixed to a first end (fixed end) side of the second arm  33 . 
     The first arm  32  of the main damping element  31  is located at a position separated exactly a first predetermined distance from an end portion in the horizontal direction H of the internal element  4 ; and the second arm  33  of the main damping element  31  is located at a position separated exactly a second predetermined distance from the lower end portion in the vertical direction V of the internal element  4 . 
     The damper bearing  35  is a member made from, for example, grooved steel that has a gate-shaped cross-section, and is attached to a bottom surface  4 A of the internal element  4 . The damper bearing  35  includes a fixing portion  36  fixed to the bottom surface  4 A, and a pair of stoppers  37 A and  37 B hanging from both ends in the width direction of the fixing portion  36 . Note that here, the “width direction” matches the direction in which the earthquake ground motion occurs. Here, the fixing portion  36  and the stoppers  37 A and  37 B are made from rectangular plates, but this is just an example and, provided that the desired goals can be achieved, the form is not limited thereto. 
     The damper bearing  35  includes an insertion gap  38  between the stoppers  37 A and  37 B, and the second arm  33  of the main damping element  31  is inserted into this insertion gap  38 . A width W 38  of the insertion gap  38  is configured to be greater than a thickness T of the internal element  4  and, at stationary times, the internal element  4  is separated from the stoppers  37 A and  37 B. 
     Next, operations and effects of the buffering mechanism  30  when the boiler  1  provided with the buffering mechanism  30  is subjected to earthquake ground motion are described. 
     When the subjected to earthquake ground motion and the internal element  4  relatively displaces from a normal state, the stopper  37 A of the damper bearing  35  approaches and ultimately interferes with the second arm  33 . Upon interference, the second arm  33  of the main damping element  31  is subjected to bending and shearing, plastically deforms, and attenuates the energy of the earthquake ground motion. The second arm  33  separates once from the stopper  37 A due to the swing-back of the earthquake ground motion and, this time, interferes with the stopper  37 B. The amount of displacement of the internal element  4  at this time is greater than the previous relative displacement. Accordingly, the second arm  33  is subjected to bending and shearing, plastically deforms, and compresses more than at the previous interference in order to attenuate the earthquake ground motion energy. 
     The second arm  33  of the main damping element  31  repeats this behavior and, as a result, reduces the seismic response of the internal element  4  while exhibiting the load-displacement relationship illustrated in  FIG. 7D . Note that, as illustrated in  FIG. 7C , the structure of the first arm  32  can be made smaller by providing a reinforcing arm  34  that reinforces the first arm  32  between the first arm  32  and the fin  16 . 
     In this configuration, the second arm  33  is primarily responsible for plastically deforming and attenuating the energy. However, as described in the first embodiment, a configuration is possible in which the support member, namely the first arm  32  of  FIGS. 7A and 7B , the first arm  32  of  FIG. 7C , the reinforcing arm  34 , and the stoppers  37 A and  37 B are plasticized. 
     With the buffering mechanism  30  according to the second embodiment, as with the buffering mechanism  20  of the first embodiment, the seismic response of the internal element  4  can be reduced and seismic response reduction effects of the overall steel support frame  5  of the boiler  1  can be obtained due to the energy attenuating effects. Additionally, a structure is used in which the load from the buffering mechanism  30  is borne by the fins  16  and is not directly transmitted to the water pipes  15 . As such, the functions of the boiler  1  can be ensured. 
     In addition, in the second embodiment, the pair of stoppers  37 A and  37 B are provided at an interval in the main vibration direction A, thereby making it possible to attenuate energy on both the forward side and the return side of the reciprocating vibration. Moreover, in cases where reciprocating vibration occurs repeatedly, such as with earthquake ground motion, a greater amount of energy is attenuated and greater seismic response reduction effects are obtained. 
     Additionally, the buffering mechanism  20  of the first embodiment is required to be installed between the internal element  4  and the furnace wall  11  and, as such, the installation position may be limited by the space between the internal element  4  and the furnace wall  11 . In contrast, the buffering mechanism  30  of the second embodiment can be provided on the bottom surface  4 A of the internal element  4  and, as such, is mostly free of limitations on the installation position. Additionally, with the buffering mechanism  20 , the compression amount (deformation amount) of the energy attenuating body  25  is required to be smaller than the space between the internal element  4  and the furnace wall  11 . However, with the buffering mechanism  20  in which the damper bearing  35  is provided on the bottom surface  4 A of the internal element  4 , this limitation does not exist and, as a result, the deformation amount can be increased. 
     Two preferable embodiments of the present invention have been described. However, as long as there is no departure from the spirit and scope of the present invention, configurations described in the above embodiments can be selected as desired, or can be changed to other configurations as necessary. 
     REFERENCE SIGNS LIST 
     
         
           1  Boiler 
           3  Boiler main body 
           4  Internal element 
           4 A Bottom surface 
           5  Steel support frame 
           7  Hanging member 
           10  Boiler drum 
           11  Furnace wall 
           12  Inner surface 
           13  Outer surface 
           15  Water pipe 
           16  Fin 
           20  Buffering mechanism 
           21  Frame 
           22  Web 
           23  Flange 
           25  Energy attenuating body 
           26  Honeycomb core 
           27  Cell 
           28  Through-hole 
           30  Buffering mechanism 
           31  Main damping element 
           32  First arm 
           33  Second arm 
           34  Reinforcing arm 
           36  Fixing portion 
           37 A,  37 B Stopper 
           38  Insertion gap 
         C Clearance