Abstract:
An orifice nozzle-type steam trap, a Venturi nozzle-type steam trap, and/or a tunnel-structured resistance tube-type steam trap are provided capable of coping with a change in the discharged amount of a drain due to, for example, a variation in the amount of steam used resulting from the operating condition of steam-based equipment, seasonal external factors and/or a variation in the working pressure difference between the inlet and outlet of a steam trap. A strainer filter can be provided that eliminates strength insufficiency due to the miniaturization of strainer screens of these nozzle-type steam traps, retains the forms of the screens, allows the screens to be easily attached to and detached from the strainers, and/or makes maintenance, such as screen cleaning, easy. The orifice nozzle-type, Venturi nozzle-type, and tunnel-structured resistance tube-type steam traps include, for example, a drainage volume adjusting mechanism which is a piping structure in which the height difference between the drain vent and the non-drain system vent of a Venturi nozzle is variable. In addition, the strainer filter includes, for example, a support body for reinforcing the rigidity of a screen attached to a strainer disposed on the inner side and/or the outer side of the screen.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part application of, and claims priority to, International Application No. PCT/JP2014/070163 (international publication WO/2015/016298) filed Jul. 31, 2014, which in turn claims priority to Japanese patent application No. JP2014-112882 filed May 30, 2014 and JP2013-161493 filed Aug. 2, 2013. All of the above applications are hereby incorporated herein by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to nozzle-type steam traps, including Venturi nozzle-type, orifice nozzle-type and/or tunnel-structured resistance tube-type steam traps for automatically and continuously discharging drain (steam condensate resulting from the condensation of steam) arising in steam-based equipment and a vapor transport piping system installed among these equipment out of the system in a variety of facilities, including factories and offices, which use steam as a heat source through a heat exchanger. 
       BACKGROUND ART 
       [0003]    A large number of steam traps are used in a variety of facilities, including factories and offices, which use steam as a heat source through a heat exchanger, in order to automatically discharge drain arising in steam-based equipment and a vapor transport piping system installed among these equipment out of the system. 
         [0004]    This is for the purpose of securing suitable temperature conditions in steam-based equipment, including heating machines, drying machines and heaters, which use high-temperature and high-pressure steam obtained with a boiler at a heat exchange unit and in a vapor transport piping system that connects the boiler and the steam-based equipment. If, for example, drain stays in steam-based equipment, the heating efficiency of the equipment degrades, thus significantly decreasing the productivity of the equipment. In addition, heating unevenness due to drain droplets can be a cause for the quality failure of products and impairs the stable operation of factories. Yet additionally, drain staying within the vapor transport piping system can be a cause for the occurrence of extremely dangerous steam hammering and may impair the safe operation of factories. This steam hammering refers to a phenomenon in which drain staying within the vapor transport piping system forms a large chunk while being washed away by a steam, and the large chunk of drain collides with curved portions of pipes and valves. The steam hammering also refers to a phenomenon in which if drain staying within the vapor transport piping system comes into contact with steam, the steam condenses all at once, the volume of the steam reduces to zero, and the drain rushes to and collides with a location where a vacuum state is formed locally. 
         [0005]    Conventionally, there have been used mechanical engineering-based mechanical steam traps (bucket-type and float-type steam traps), thermostatic steam traps (bimetal-type and bellows-type steam traps), and thermodynamic steam traps (disc-type steam traps). 
         [0006]    These mechanical steam traps including movable portions are basically drain valve mechanisms. These steam traps repeat a series of actions in which when a certain amount of drain accumulates, the drain is discharged by opening a drain valve, and then the drain valve is closed immediately. Accordingly, these steam traps suffer severe steam leakage caused by damage to movable portions due to operating delays or repetitive actions and remarkably consume steam. In addition, the intermittent drainage of a steam trap including a movable portion does not assure the stable operation of steam-based equipment. Hence, the abovementioned mechanical steam traps have been brought under review from the viewpoint of, for example, the high-efficiency and energy-saving operation and the CO 2  reduction of factories. 
         [0007]    Among other things, nozzle-type steam traps as typified by the orifice nozzle-type, Venturi nozzle-type and tunnel-structured resistance tube-type steam traps are a focus of attention. These steam traps are called fluidics-based steam traps and take advantage of the nature in which water is lower in kinetic viscosity than steam when passing through a microstructural passage and an amount of water approximately 30 times the amount of steam flows the passage. As typical examples,  FIGS. 1 to 4  illustrate conventional Venturi nozzle-type steam traps. As is evident from the figures, the steam traps are structured so as not to include any movable portions where drain passes through the microstructural passage of a Venturi nozzle  3 . Unlike the abovementioned mechanical steam traps, the Venturi nozzle-type steam traps are less liable to steam leakage and realize continuous drainage on the basis of such a drainage mechanism and a drainage structure as described above. Consequently, the fuel use of a boiler is significantly decreased, thereby enabling steam-based equipment to be stably operated. In addition, the structure free from movable portions is superior in durability and has the characteristic that maintenance and inspection are easy to carry out. Yet additionally, the structure is resistant to steam hammering and freezing and is also superior in stability and safety. 
         [0008]    For such a reason as described above, there have been recognized a large number of proposals related to the abovementioned fluidics-based steam traps, the orifice nozzle-type and Venturi nozzle-type steam traps in particular. Examples of proposals for the orifice nozzle-type steam traps include Japanese Patent Laid-Open No. 2002-310392, Japanese Patent Laid-Open No. 2004-162866, Japanese Patent Laid-Open No. 2004-190827, Japanese Patent Laid-Open No. 2004-218124, and Japanese Patent Laid-Open No. 2008-309290. Examples of proposals for the Venturi nozzle-type steam traps include U.S. Pat. No. 4,426,213, U.S. Pat. No. 4,745,943, U.S. Pat. No. 5,060,686, U.S. Pat. No. 5,123,452, U.S. Pat. No. 5,429,150, and U.S. Pat. No. 5,628,339. All of the above published applications and patents are hereby incorporated herein by reference in their entirety. 
         [0009]    In the orifice nozzle-type, Venturi nozzle-type, and tunnel-structured resistance tube-type steam traps, however, drain serves as a sealing material. Accordingly, a drain vent  10  of a Venturi nozzle  3  connecting from the inlet of a body  1  through a strainer is formed in a position lower than the position of a non-drain system vent  11  connecting to the outlet of the body and fixed, as illustrated in  FIG. 2 , in the case of, for example, Venturi nozzle-type steam traps. 
         [0010]    A method of exchanging a nozzle for another different in diameter and length has therefore been adopted in the case of the abovementioned nozzle-type steam traps, in order to cope with a change in the discharged amount of drain due to, for example, a variation in the amount of steam used resulting from seasonal external factors or the operating condition of steam-based equipment or a variation in the working pressure difference between the abovementioned inlet and outlet. Such a method has the problem, however, in which the range of the abovementioned change in the discharged amount of drain that the method can cope with is limited, in spite of the method&#39;s high workload. In contrast, a mechanism for exchanging an orifice diameter for another by means of rotation according to the amount of drain (Japanese Patent Laid-Open No. 2004-21$724) and a mechanism in which the passageway length of an orifice is variable (Japanese Patent Laid-Open No. 2002-310392) have been proposed in the case of, for example, orifice nozzle-type steam traps. 
         [0011]    That is, the abovementioned conventional nozzle-type steam traps have a first problem in which adjustments following a change in the amount of drainage are difficult to make and the range of changes to be coped with is limited. 
         [0012]    On the other hand, the abovementioned nozzle-type steam traps have the problem in which since the diameter of a nozzle that drain passes through is small, pipes are liable to become clogged with foreign matter, such as rust or dust. Accordingly, as is understood from  FIG. 3 , a foreign matter-removing device referred to as a strainer  5  provided with a screen  6  for purifying fluid itself has been placed before a nozzle (see, for example, Japanese Patent Laid-Open No. 2002-257287, Japanese Patent Laid-Open No. 2004-230305, Japanese Patent Laid-Open No. 2008-309290, U.S. Pat. No. 4,745,943, and U.S. Pat. No. 5,120,336, all of which are hereby incorporated by reference herein in their entirety). It has become increasingly clear, however, that a screen having a microscopic opening needs to be applied. For example, whereas a 60-mesh or coarser screen is used in U.S. Pat. No. 4,745,943 and U.S. Pat. No. 5,120,336, an 80 to 100-mesh screen is used in Japanese Patent Laid-Open No. 2010-156450. Rigidity degrades extremely along with the microstructuring of screens, however, thus making it extremely difficult to retain the form of a screen itself and attach/detach and clean the screen. Notwithstanding the difficulty, only one end of the nozzle side (drain outlet side) of a screen is simply fixed by a welding method, a screw-in method, or the like, in consideration of the maintenance of a strainer, such as screen cleaning. For such a problem as described above, Japanese Patent Laid-Open No. 2004-230305 discloses reinforcement with a grip or a metal plate having small holes. The patent document neither includes any descriptions with regard to the removal of foreign matter and flow rates, nor specifically proposes a solution to the above-described problem. 
         [0013]    On the other hand, a study has been made on a contrivance for removing foreign matter trapped in an orifice by adopting an up-down movable orifice, as in Japanese Patent. Laid-Open No. 2008-309290. 
         [0014]    As described above, the abovementioned nozzle-type steam traps have a second problem in which rigidity degrades along with the miniaturization of screen meshes, thus making it difficult to retain the form of a screen itself and handle the screen for attachment/detachment or cleaning. 
       CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent Laid-Open No. 2002-310392 
     Patent Literature 2: Japanese Patent Laid-Open No. 2004-162866 
     Patent Literature 3: Japanese Patent Laid-Open No. 2004-190827 
     Patent Literature 4: Japanese Patent Lard-Open No. 2004-218724 
     Patent Literature 5: Japanese Patent Laid-Open No. 2008-309290 
       [0015]    Patent Literature 6: U.S. Pat. No. 4,426,213
 
Patent Literature 7: U.S. Pat. No. 4,745,943
 
Patent Literature 8: U.S. Pat. No. 5,060,686
 
Patent Literature 9: U.S. Pat. No. 5,123,452
 
Patent Literature 10: U.S. Pat. No. 5,429,150
 
Patent Literature 11: U.S. Pat. No. 5,628,339
 
       Patent Literature 12: Japanese Patent Laid-Open No. 2002-257287 
     Patent Literature 13: Japanese Patent Laid-Open No. 2004-230305 
       [0016]    Patent Literature 14: U.S. Pat. No. 5,120,336
 
Patent Literature 15: Japanese Patent Laid-Open No. 2010-156450, all of which are hereby incorporated by reference herein in their entirety.
 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0017]    For the above-described first problem, the present invention is intended to provide an orifice nozzle-type steam trap, a Venturi nozzle-type steam trap, and a tunnel-structured resistance tube-type steam trap including a drainage volume adjusting mechanism capable of coping with a change in the discharged amount of drain due to, for example, a variation in the amount of steam used resulting from the operating condition of steam-based equipment, seasonal external factors or a variation in the working pressure difference between the inlet and outlet of a steam trap. In addition, for the second problem, the present invention is intended to provide a strainer filter that eliminates rigidity insufficiency due to the microstructuring of a strainer screen, retains the form of the screen, allows the screen to be easily attached to and detached from a strainer, and makes maintenance, such as screen cleaning, easy, and an orifice nozzle-type steam trap, a Venturi nozzle-type steam trap and a tunnel-structured resistance tube-type steam trap including the drainage volume adjusting mechanism provided with the strainer filter. Here, means for removing foreign matter from a fluid itself to purify the fluid is referred to as a screen, and a component that uses this screen to remove foreign matter from a fluid itself to purify the fluid, as in the present invention, is referred to as a filter. 
       Solution to Problem 
       [0018]    In order to solve the first problem of the related art, a nozzle-type steam trap of the present invention is provided with a drainage volume adjusting mechanism having a piping structure in which the height difference between a drain vent, through which drain is discharged into a drain reservoir disposed in the steam trap and a non-drain system vent through which drain is discharged from the drain reservoir to the outer side of a steam trap system can be varied by means of a rotational mechanism. 
         [0019]    In particular, the steam trap can be simplified and downsized by disposing the drain reservoir, the drain vent and the non-drain system vent in the upper section of a vapor transport system provided with the steam trap or by rotatably connecting a pipe provided with the drain reservoir and a pipe in which the non-drain system vent is disposed inside a cross-sectional area of the reservoir on the same axis as the above-described piping structure. 
         [0020]    On the other hand, the discharged amount of drain of the steam trap can be unlimitedly adjusted by rotatably connecting a pipe provided with the drain reservoir and a pipe in which the non-drain system vent is disposed outside a cross-sectional area of the reservoir on the same axis as the above-described piping structure. An existing nozzle-type steam trap can thus be used as is. 
         [0021]    In addition, the nozzle-type steam trap of the present invention is vertically piped and provided with a drainage volume adjusting mechanism capable of switching between a piping structure in which drain discharged from a drain vent is ejected out of a steam trap system in a free-fall state and a piping structure in which drain is ejected out of the steam trap system from a location higher than the drain vent. 
         [0022]    In order to solve the second problem of the related art, a strainer filter of the present invention includes a support body for reinforcing the rigidity of the screen disposed on the inner side and/or the outer side of a screen attached to a strainer. 
         [0023]    In particular, the strainer filter of the present invention is made of corrosion-resistant metal, the support body for reinforcing the strainer filter is made of a spring material, and the screen and the support body are joined together, coupled with each other, screwed together, engaged with each other, sewn together, or mated with each other. 
         [0024]    Alternatively, the strainer filter of the present invention is a screen made of heat-resistant fiber, the support body for reinforcing the strainer filter is made of a spring material, and the screen and the support body are joined together, coupled with each other, screwed together, engaged with each other, sewn together, or mated with each other. 
       Advantageous Effects of Invention 
       [0025]    According to a nozzle-type steam trap including the drainage volume adjusting mechanism of the present invention, it is possible to easily adjust and optimize the discharged amount of drain for a change in the discharged amount of drain due to a variation in the amount of steam used or working pressure, while maintaining advantages that orifice nozzle-type, Venturi nozzle-type and tunnel-structured resistance tube-type steam traps have, without having to exchange an orifice nozzle, a Venturi nozzle, or a tunnel-structured resistance tube for another. 
         [0026]    On the other hand, according to the strainer filter of the present invention, the form of the screen is retained and the filter can be easily attached to and detached from the strainer, thus making maintenance, such as filter cleaning, easy. In addition, the size of the strainer filter can be freely adjusted, independent of the size of the strainer. 
         [0027]    Using the falter the screen of which is reinforced with the support body in the strainers of the orifice nozzle-type, Venturi nozzle-type and tunnel-structured resistance tube-type steam traps including the drainage volume adjusting mechanism, it is possible to provide a nozzle-type steam trap significantly improved in the workability of nozzle replacement and filter replacement. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0028]      FIG. 1  shows an external view of a conventional Venturi nozzle-type steam trap, in which an arrow is meant to be a flow of steam and/or liquid. 
           [0029]      FIG. 2  shows a front view of the conventional Venturi nozzle-type steam trap from which an end cap is removed. 
           [0030]      FIG. 3  is a cross-sectional view taken by cutting the steam trap parallel to the page on a dashed line a in  FIG. 1 . 
           [0031]      FIG. 4  is a cross-sectional view taken by cutting the steam trap vertically to the page on a dashed line b in  FIG. 2 . 
           [0032]      FIG. 5  illustrates a first embodiment of the present invention, where (a) of  FIG. 5  is a cross-sectional view and (b) of  FIG. 5  is a side view of a Venturi nozzle-type steam trap in which a drainage volume adjusting component is introduced using a union. 
           [0033]      FIG. 6  illustrates second and third embodiments of the present invention and is a front view of a Venturi nozzle-type steam trap which is configured by introducing a drainage volume adjusting component in a conventional Venturi nozzle-type steam trap using a union and from which an end cap is removed. 
           [0034]      FIG. 7  illustrates the second and third embodiments of the present invention and is a cross-sectional view taken by cutting the steam trap vertically to the page on a dashed line c in  FIG. 6 . 
           [0035]      FIG. 8  illustrates the second embodiment of the present invention which is a Venturi nozzle-type steam trap characterized by disposing a pass-through slot serving as a non-drain system vent in the drainage volume adjusting component of  FIG. 6 . (a) of  FIG. 8  is a cross-sectional view taken by cutting the steam trap vertically to the page on a dashed line d in  FIG. 7 , whereas (b) of  FIG. 8  is a side view of the steam trap, in a case where the non-drain system vent is located in the uppermost section of the drainage volume adjusting′ component. 
           [0036]      FIG. 9  illustrates the second embodiment of the present invention which is a Venturi nozzle-type steam trap characterized by disposing a pass-through slot serving as a non-drain system vent in the drainage volume adjusting component of  FIG. 6 . (a) of  FIG. 9  is a cross-sectional view taken by cutting the steam trap vertically to the page on a dashed line d in  FIG. 7 , whereas (b) of  FIG. 9  is a side view of the steam trap, in a case where the non-drain system vent is located in the lowermost section of the drainage volume adjusting component. 
           [0037]      FIG. 10  illustrates the third embodiment of the present invention in which a partition serving as a non-drain system vent is disposed in the drainage volume adjusting component and positioned horizontally. 
           [0038]      FIG. 11  illustrates the third embodiment of the present invention in which a partition serving as a non-drain system vent is disposed in the drainage volume adjusting component and positioned at an angle. 
           [0039]      FIG. 12  illustrates a fourth embodiment of the present invention in which a rotatable U-tube is disposed in order to adjust the discharged amount of drain, and is an external view from which an end cap is removed. 
           [0040]      FIG. 13  illustrates a fifth embodiment of the present invention in which a drain reservoir, the drain vent of a Venturi nozzle, and a non-drain system vent are rotatably disposed in the upper section of a vapor transport system, in order to adjust the discharged amount of drain, and is an external view from which an end cap is removed. 
           [0041]      FIG. 14  illustrates the fifth embodiment of the present invention and is a cross-sectional view taken by cutting  FIG. 13  parallel to the page. 
           [0042]      FIG. 15  illustrates a sixth embodiment of the present invention in which a cock and a drain pondage adjusting tube are disposed within the steam trap, in order to adjust the discharged amount of drain, where (a) of  FIG. 15  is an external view of the steam trap, whereas (b) of  FIG. 15  is a cross-sectional view taken by cutting a body  1  parallel to the page. 
           [0043]      FIG. 16  illustrates a first embodiment of a strainer filter of the present invention. 
           [0044]      FIG. 17  illustrates a second embodiment of the strainer filter of the present invention. 
           [0045]      FIG. 18  illustrates a third embodiment of the strainer filter of the present invention. 
           [0046]      FIG. 19  illustrates a fourth embodiment of the strainer filter of the present invention. 
           [0047]      FIG. 20  illustrates one embodiment of a Venturi nozzle-type steam trap of the present invention including a drainage volume adjusting mechanism provided with a strainer filter, and is an example in which the strainer filter of the present invention illustrated in  FIG. 16  is applied to a Venturi nozzle-type steam trap including the drainage volume adjusting mechanism of the present invention illustrated in  FIGS. 13 and 14 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0048]    Hereinafter, embodiments of the present invention will be described by citing a Venturi nozzle-type steam trap as a typical example, while referring to the accompanying drawings. The present invention is also applied, however, to orifice nozzle-type and tunnel-structured resistance tube-type steam traps capable of continuous drainage. In addition, the present invention is not limitative, except as set forth in the technical scope defined by the appended claims. 
         [0049]    (a) of  FIG. 5  is a cross-sectional view of a Venturi nozzle-type steam trap according to a first embodiment of the present invention. As is evident from the figure, a drainage volume adjusting component  15  in which the position of a non-drain system vent  11  is continuously variable with respect to a drain vent  10  of a Venturi nozzle  3  is disposed in the steam trap using a union  14 . As is evident from the cross-sectional view ((a) of  FIG. 5 ) and the side view ((b) of  FIG. 5 ), this steam trap is fabricated by forming the non-drain system vent  11  inside an cross-sectional area of a drain reservoir  12  and connecting a pipe including the drain reservoir  12  and a pipe provided with the non-drain system vent  11  by means of a union, a flange or the like rotatable on the same axis. Accordingly, the height difference between the drain vent  10  and the non-drain system vent  11  can be controlled freely. It is therefore possible to adjust and optimize the discharged amount of drain for a change in the discharged amount of drain due to the amount of steam used or the variation of working pressure, without having to exchange an orifice nozzle, a Venturi nozzle, or a tunnel-structured resistance tube for another. In addition, the steam trap of the present embodiment has the advantage of being simple and small. 
         [0050]      FIGS. 6 to 9  illustrate a Venturi nozzle-type steam trap according to a second embodiment of the present invention. This steam trap is characterized by additionally attaching a drainage volume adjusting component  15  to the conventional Venturi nozzle-type steam trap illustrated in  FIG. 2 . The drain vents  10  of the Venturi nozzles illustrated in  FIGS. 2 and 6  are the same, but the non-drain system vent  11  illustrated in  FIG. 2  serves as an intra-drain reservoir conduction port  13  (conventional non-drain system vent  11 ) for circulating drain throughout the reservoir  12  in  FIGS. 6 to 9 . In addition, the non-drain system vent  11  illustrated in  FIG. 2  is disposed in the drainage volume adjusting component  15  in  FIGS. 6 to 9 . This drainage volume adjusting component  15  is connected to the body  1  on the same axis using a rotatable union, flange or the like, so that the height difference between the drain vent  10  and the non-drain system vent  11  is continuously variable. 
         [0051]    As is evident, from  FIGS. 7 to 9 , the conventional non-drain system vent  11  serves as the intra-drain reservoir conduction port  13  for connecting drain reservoirs  12  in two places, and therefore, the tolerable capacity of the drain reservoirs  12  increases. Thus, it is possible to widen the range of application with regard to a variation in the amount of steam used, a variation in the working pressure difference or the like that differs depending on facilities. In addition, the second embodiment has the advantage of being able to use a conventional Venturi nozzle-type steam trap as is. Here, a case is illustrated in which the drain vent  10  and the intra-drain reservoir conduction port  13  are formed at the same height. The positions to dispose these constituent parts in depend on the situation of facilities, however. This is because drain pondage serving as a sealing material is determined by the position of the intra-drain reservoir conduction port  13 ′ of the Venturi nozzle-type steam trap as the result of additionally installing the drainage volume adjusting component  15 , as is evident from the cross-sectional view of  FIG. 7  taken by cutting the steam trap vertically to the page on the dashed line c of  FIG. 6 . Accordingly, the intra-drain reservoir conduction port  13  may be disposed according to a variation in the amount of steam used, a variation in the working pressure difference, or the like that differs depending on facilities. 
         [0052]    Then, as illustrated in (a) of  FIG. 8  and (a) of  FIG. 9  which are cross-sectional views taken by cutting the steam trap vertically to the page on the dashed line d of  FIG. 7 , the drainage volume adjusting mechanism in the second embodiment can also adjust the discharged amount of drain in completely the same way as in the first embodiment. 
         [0053]      FIGS. 10 and 11  illustrate a third embodiment of the present invention. This steam trap is characterized by additionally attaching a drainage volume adjusting component  15  in which the non-drain system vent  11  is formed using a partition, in contrast to the drainage volume adjusting component  15  in which such a non-drain system vent  11  as illustrated in  FIGS. 8 and 9  is formed as a pass-through slot. This steam trap features a modified shape of the non-drain system vent  11 . The non-drain system vent  11  may have any shapes, as long as the vent serves the same function. 
         [0054]      FIG. 12  illustrates a fourth embodiment in which the drainage volume adjusting mechanism of the present invention is also additionally attached to the conventional Venturi nozzle-type steam trap.  FIG. 12  illustrates a case in which a drain pondage adjusting U-tube  16  is connected to the vapor transport piping system by means of a rotatable union.  14 , flange or the like and an elbow  17  or the like. In this case, the non-drain system vent  11  illustrated in  FIG. 2  is used as the intra-drain reservoir conduction port  13  for connecting drain reservoirs  12  in two places and serves as the drain vent  10  illustrated in  FIG. 2 . In addition, the role of the non-drain system vent  11  of the Venturi nozzle-type steam trap illustrated in  FIG. 2  functions at the uppermost end  11  of the abovementioned U-tube  16  in the present embodiment. That is, this steam trap is a typical example of disposing the non-drain system vent outside the cross-sectional area of a pipe provided with the drain reservoirs. The height difference between the intra-drain reservoir conduction port  13  and the non-drain system vent  11  can be continuously varied by rotating the abovementioned U-tube  16  using the union  14 . According to this method, the amount of pondage can be set almost unlimitedly by designing the length, thickness, shape and the like of the U-tube, thereby making it possible to cope with the situation of every facility. 
         [0055]      FIGS. 13 and 14  illustrate a fifth embodiment of the present invention. This steam trap also uses a component including a rotatable non-drain system vent  11  as a drainage volume adjusting mechanism. The steam trap is characterized, however, in that the reservoir  12 , the drain vent  10  of the Venturi nozzle, and the non-drain system vent  11  are disposed in the upper section of a vapor transport system provided with the steam trap. Also in this case, the body  1  in which the Venturi nozzle  3  is placed in a position lower than the non-drain system vent  11  is connected to the vapor transport piping system by means of a rotatable union, flange or the like and the height difference between the drain vent  10  and the non-drain system vent  11  is continuously controlled by means of rotation to adjust the discharged amount of drain. This embodiment also has the advantage of being able to simplify and downsize the steam trap. 
         [0056]    On the other hand, the sixth embodiment illustrated in  FIG. 15  realizes the advantage of being able to almost unlimitedly change the discharged amount of drain offered by the fourth embodiment by means of a completely different drainage volume adjusting mechanism. As is evident from (a) of  FIG. 15 , the sixth embodiment is first characterized in that the steam trap is vertically positioned, and thus, the steam trap corresponds to the body  1  and is connected to the vapor transport system using the elbows  17 . The interior of the body  1  of (a) of  FIG. 15  is characterized in that the drain pondage adjusting tube  19  is disposed so that the non-drain system vent  11  is higher than the drain vent  10 , as illustrated in the cross-sectional view of (b) of  FIG. 15 , and that a drainage volume adjusting mechanism capable of switching between a piping system in which drain free-falls and a piping system in which drain is transported to the drain pondage adjusting tube  19  using a cock  18  is incorporated. That is, the sixth embodiment is characterized in that the steam trap is vertically piped to enable switching between a piping structure in which drain discharged from the drain vent  10  is ejected out of the steam trap system in a free-fall state and a piping structure in which the drain is ejected out of the steam trap system from the non-drain system vent  11  higher than the drain vent  10 . 
         [0057]    Incidentally, such a steam trap as described above is used under severe environmental conditions, and therefore, deterioration-resistant stainless steel has conventionally been recommended for use as the material of the steam trap. Corrosion resistance may have to be taken into consideration, however, depending on a facilities environment. In that case, it is preferable to use austenitic stainless steel (for example, SUS304 or SUS316) or austenitic-ferritic stainless steel (for example, SUS329J3L, SUS329J4L, SAF2507, SAF2707HD or DP28W) superior in corrosion resistance. Workability and cost have to be also taken into consideration, however, to select from these materials, and therefore, SUS304, SUS316, SUS329J3L and SUS329J4L are particularly suitable. 
         [0058]    Subsequently, embodiments of the strainer filter of the present invention will also be described by citing a Venturi nozzle-type steam trap as a typical example, while referring to the accompanying drawings. The strainer filter can also be applied, however, to any steam traps, in addition to orifice nozzle-type and tunnel-structured resistance tube-type steam traps. 
         [0059]    The diameter of a Venturi nozzle  3  is generally selected from approximately 0.1 mm to 15 mm nozzle diameters in an elaborate manner, according to the operating and environmental conditions of an apparatus. Accordingly, in order for the nozzle not to become clogged with rust or dust within piping, a screen having a mesh opening smaller than at least the nozzle diameter is required. This requirement can be fulfilled with an approximately 300-mesh to 2-mesh (in the case of ASTM standards) screen. 
         [0060]    If an 80-mesh size is exceeded, however, the rigidity of even a metallic screen degrades remarkably. For example, if a cylindrical screen  6  is directly attached to such a Y-shaped strainer  5  as illustrated in  FIGS. 1 to 3 , the screen becomes deformed during operation. In the case where strainer maintenance for reasons of, for example, the clogging of the screen is performed, such deformation easily takes place when the screen is attached or detached. In addition, the screen, if not carefully cleaned, easily becomes deformed or broken. On the other hand, applying a screen made of heat-resistant fiber is advantageous from the view point of cost and molding workability. The screen is not usable, however, since the screen larks rigidity irrespective of its mesh size. 
         [0061]    Hence, the abovementioned problem is eliminated by reinforcing the screen with a rigid support body as illustrated in, for example,  FIGS. 16 to 19 . In addition, the size of the screen can be freely adjusted in conformity with the size of the strainer  5 . Although  FIGS. 16 to 19  illustrate a filter in which a support body  21  is reinforced, from inside of a screen  20 , the support body  21  may be reinforced from outside of the screen  20 . 
         [0062]    The material of such a screen  20  as mentioned above is not limited. Since the screen is used in high-temperature steam containing impurities, such as rust, however, it is preferable to use metal, such as iron, nickel, chromium, titanium, zinc, copper, aluminum, or an alloy thereof, in consideration of heat resistance, joining properties, rigidity, corrosion resistance, and the like. Incorporating the abovementioned support body  21  enables use of a heat-resistant fiber superior in cost and workability. Glass fiber, aramid fiber, polyether ether ketone, or the like is preferably used as this heat-resistant fiber. Among these materials, stainless steel, such as SUS304 or SUS316, is most preferred from the viewpoint of corrosion resistance, molding workability, cost, and the like. The screen can have a mesh structure, including a woven mesh, a punched mesh, an electroformed mesh, an etched mesh and a non-woven fiber mesh, according to the material. In addition, the aperture shape of the screen is not limited in particular, but may be a circle, an ellipse, a quadrangle, a rhomboid, or the like. 
         [0063]    The material of the support body  21  for reinforcing the screen  20  is not limited in particular, either. Like the screen, however, it is preferable to use metal, such as iron, nickel, chromium, titanium, zinc, copper, aluminum, or an alloy thereof, in consideration of heat resistance, joining properties, rigidity, corrosion resistance, and the like. Stainless steel is suitable in particular. As illustrated in  FIG. 7 , such a structure of the support body  21  as to offer the performance advantages of springs is most preferable in solving the problems of a conventional screen. 
         [0064]    The above-described screen  20  and support body  21  are integrated with each other by means of joining together, coupling with each other, screwing together, engaging with each other, sewing together, or mating with each other, though the method of integration differs depending of a material used. Welding is preferred if metallic materials are integrated with each other. If the screen is made of synthetic resin, the screen and the support body can be joined together by means of thermal fusion bonding. 
         [0065]    The screen and the support body may be joined together using an adhesive agent. A heat-resistant adhesive agent is required, however, as in the case of the screen and the support body described earlier. A polyimide-based adhesive agent, for example is preferably used. 
         [0066]      FIG. 20  illustrates one embodiment to which a strainer filter of the present invention is specifically applied. This embodiment has been implemented by applying the strainer filter to a nozzle-type steam trap including a drainage volume adjusting mechanism capable of adjusting and optimizing the discharged amount of drain without the need for exchanging the Venturi nozzle  3  for another.  FIG. 20  is a cross-sectional view of the steam trap. As is evident from the figure, the steam trap has an extremely simple structure in which the position of the non-drain system vent  11  can be moved up and down by means of rotation using a union  14  to adjust the discharged amount of drain. In addition, a filter  22  for preventing the clogging of the Venturi nozzle  3  can be easily attached to the steam trap, and the rigidity of a screen is reinforced with a support body. The screen therefore does not become damaged. Yet additionally, such reinforcement enables the screen to be easily cleaned, and the size of the filter can be changed freely. 
       INDUSTRIAL APPLICABILITY 
       [0067]    A nozzle-type steam trap of the present invention including a drainage volume adjusting mechanism characterized by a piping structure in which the height difference between a drain vent and a non-drain system vent is variable and a strainer filter suited for the steam trap have been described with respect to the discharge of drain in the steam piping system of equipment including a boiler and the like. From the viewpoint of the discharge of condensate liquids in gas flow piping, however, the steam trap and the strainer filter can be applied to not only water vapor systems but also gas piping systems of all sorts. 
       REFERENCE SIGNS LIST 
       [0000]    
       
         
           
               1 : Body 
               2 : Gasket 
               3 : Venturi nozzle 
               4 : End cap 
               5 : Strainer 
               6 : Screen 
               7 : Strainer end cap 
               8 : Steam plug 
               9 : Nameplate 
               10 : Drain vent of Venturi nozzle 
               11 : Non-drain system vent 
               12 : Drain reservoir 
               13 : Intra-drain reservoir conduction port 
               14 : Union 
               15 : Drain pondage adjusting component 
               16 : Drain pondage adjusting U-tube 
               17 : Elbow 
               18 : Cock 
               19 : Drain pondage adjusting tube 
               20 : Screen 
               21 : Support body 
               22 : Strainer filter 
               30 : Inlet of steam and/or liquid 
               40 : Outlet of steam and/or liquid