Abstract:
A steam trap comprises a housing defining a flow passage extending between an inlet and an outlet. A cap fitted to the housing has a stop face. In addition, the housing and the cap define a trap chamber. A movable valve element is located in the trap chamber. The steam trap further comprises a first temperature sensor having an inlet sensing portion in the flow path between the inlet and valve element. A second temperature sensor has an outlet sensing portion in the flow path between the valve element and the outlet.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to steam traps used in steam distribution systems. 
     Steam traps, which are essentially automatic valves used to discharge condensate, are widely used in steam distribution systems. In operation, flash steam within the trap chamber of such devices functions to keep the valve closed. As the trap cools, the steam condenses and fluid pressure in the inlet passage forces the valve element off its seat. Condensate then passes through the trap, which eventually causes the valve element to again engage the seat. 
     Attempts have been made to verify the proper operation of steam traps by measuring temperature of incoming and outgoing fluid. In this regard, external piping connections having thermocouple sensors have been attached in line with the inlet and outlet of the thermocouple housing. By analyzing the time-varying pattern of temperature readings, it can be determined on a real-time basis whether the thermocouple is operating properly. Such external connections, however, add to the overall “footprint” of the piping network and may not be possible in situations where space is limited or is otherwise tight. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect, the present invention provides a steam trap comprising a housing defining a flow passage extending between an inlet and an outlet. A cap fitted to the housing has a stop face. In addition, the housing and the cap define a trap chamber. A movable valve element is located in the trap chamber. 
     The steam trap further comprises a first temperature sensor having an inlet sensing portion in the flow path between the inlet and the valve element. A second temperature sensor has an outlet sensing portion in the flow path between the valve element and the outlet. 
     In accordance with some exemplary embodiments, the inlet may have a first internally threaded portion and a first smooth bore portion. Similarly, the outlet may have a second internally threaded portion and a second smooth bore portion. First and second sensing ports respectively intersecting the first smooth bore portion and the second smooth bore portion may also be provided. 
     Preferably, the first and second sensing ports may each have internally threaded portions for engagement by attachment portions of the first and second temperature sensors, respectively. The sensing portions of the temperature sensors may extend axially from the respective attachment portions. It will often be desirable for the temperature sensors to be thermocouples. 
     Embodiments are contemplated in which an end of the inlet sensing portion of the first temperature sensor is located past a centerline axis of the inlet. An end of the outlet sensing portion of the second temperature sensor may be located substantially at a centerline axis of the outlet. 
     In some exemplary embodiments, the housing may comprise a unitary trap body. Alternatively, the housing may comprise a body portion and a separate connector portion, the connector portion defining both the inlet and the outlet. 
     In accordance with another aspect, the present invention provides a steam trap comprising a housing defining a flow passage extending between an inlet and an outlet. A movable valve element is operative to selectively allow flow between the inlet and the outlet. A first sensing port having a first internally threaded portion is located at the inlet of the housing and extends transverse to a flow direction at the inlet. A second sensing port having a second internally threaded portion is located at the outlet and extends transverse to a flow direction at the outlet. 
     A further aspect of the present invention provides a steam trap comprising a housing comprising a body portion and a separate connector portion together defining a flow passage extending between an inlet and an outlet each located at the connector portion. A movable valve element is operative to selectively allow flow between the inlet and the outlet. A first temperature sensor has an inlet sensing portion in the flow path between the inlet and the valve element. A second temperature sensor has an outlet sensing portion in the flow path between the valve element and the outlet. 
     Further aspects and features of the present invention are provided by various combinations and subcombinations of the elements disclosed herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a steam trap constructed in accordance with an embodiment of the present invention; 
         FIG. 2  is cross-sectional view of the steam trap of  FIG. 1 ; 
         FIG. 3  is an elevational view of the inlet of the steam trap of  FIG. 1 ; 
         FIG. 4  is an elevational view of the outlet of the steam trap of  FIG. 1 ; 
         FIG. 5  is a perspective view of an alternative embodiment of a steam trap constructed in accordance with the present invention utilizing a steam trap body portion and a universal connector portion; 
         FIG. 6  is a cross-section view of the universal connector portion of the steam trap of  FIG. 5 ; and 
         FIG. 7  is a cross-sectional view of the steam trap body portion of the steam trap of  FIG. 5 . 
     
    
    
     Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only and is not intended as limiting the broader aspects of the present invention, such broader aspects being embodied in the exemplary constructions. 
       FIG. 1  illustrates an embodiment of a novel steam trap  10  constructed in accordance with the present invention. Steam trap  10  has a trap body  12  to which a cap assembly  14  is attached. Referring now also to  FIG. 2 , trap body  12  defines an inlet  16  and an outlet  18  through which the condensate flows. 
     In this embodiment, inlet  16  defines an internally threaded portion  20  upstream of a smooth bore portion  22 . As one skilled in the art will appreciate, threaded portion  20  permits connection to a pipeline via threaded coupling. Similarly, outlet  18  has an internally threaded portion  24  downstream of a smooth bore portion  26 . 
     Inlet  16  is in fluid communication with an internal inlet passage  28 , whereas outlet  18  is in fluid communication with at least one internal outlet passage  30 . Inlet passage  28  and outlet passage  30  emerge at a seating face  32  located at the end of a spigot  34 . Cap assembly  14  includes a cap  36  having internal threads engaging outer threads on spigot  34 . As can be seen most clearly in  FIG. 1 , cap  36  preferably defines a series of flats  38  about its periphery for engagement by a wrench. 
     Along with seating face  32 , cap  36  defines a trap chamber  40  in which a valve element in the form of a metal disc  42  is located. Disc  42  is movable upwardly and downwardly within chamber  40 , its movement being limited by seating face  32  and an opposed stop face  44  on the interior of cap  36 . Typically, body  12  and cap  36  are made from metal such as stainless steel. 
     In the illustrated embodiment, cap assembly  14  further includes a ceramic disc  46  juxtaposed to the top surface  48  of cap  36  to reduce heat loss that may otherwise occur through the cap. As shown, cap  36  includes a vertical pin  50  which is received in a central bore defined in ceramic disc  46 . Preferably, the pin and bore are dimensioned to form a tight fit between these two components. As a result, ceramic disc  46  will be maintained securely in proximity to top surface  48  of cap  36 , without rotating. In addition, a cover  52 , which may be stamped from thin metal, is fitted over ceramic disc  46  and secured to pin  50  such as by a small spot weld. 
     In operation, condensate reaches trap  10  at inlet  16 . The condensate flows through inlet passage  28 , lifting disc  42  off of seating face  32 . The condensate continues through outlet passage  30  and leaves trap  10  through outlet  18 . As steam approaches the trap, the temperature of the condensate increases. 
     When the hot condensate passes between disc  42  and seating face  32 , a portion of it evaporates and forms flash steam. The resulting expansion causes an increase in volume of the flowing mixture of flash steam and condensate, thus increasing the velocity. This causes a local reduction in pressure between disc  42  and seating face  32 , which pushes disc  42  into engagement with seating face  32 . A steam bubble within chamber  40  retains disc  42  against seating face  32 , thus resisting the pressure in the upstream pipeline. Loss of heat causes the bubble to collapse, resulting in cycling of steam trap  10 . 
     Proper operation of steam trap will thus cause periodic variations in temperature both upstream and downstream of disc  42 . As noted above, prior efforts to monitor these temperatures has involved attaching external piping connections in line with the inlet and outlet of the trap body. In addition to increasing the overall footprint of piping near the steam trap, such an arrangement places the sensing elements away from the valve disc. Accordingly, the response detected at this location may not always coincide with the internal steam trap temperature. 
     The present invention, in contrast, provides a construction wherein the temperature sensing elements are located within the installation “footprint” of the steam trap itself, and closer to the movable disc inside. Referring now particularly to  FIG. 2 , sensing ports  54  and  56  are associated with inlet  16  and outlet  18 , respectively. In particular, port  54  extends through the wall of body  12  so as to intersect smooth bore portion  22  in a direction transverse to the direction of fluid flow. Similarly, port  56  intersects smooth bore portion  26  in a direction transverse to the direction of fluid flow. In this embodiment, both of ports  54  and  56  are internally threaded. 
     A suitable temperature sensor is inserted through port  54  such that its sensing element will be in the flow path of the incoming fluid. In this embodiment, for example, a thermocouple sensor  58  is received in port  54 . Sensor  58  includes an attachment portion  60  having external threads which engage the internal threads of port  54 . A sensing portion  62  extends from attachment portion  60  such that its tip will be in the fluid flow path. As can be clearly seen in  FIG. 3 , the end of sensing portion  62  is, in this case, situated past (and above) the centerline CL of inlet  16  to be in alignment with the opening to inlet passage  28 . A lead wire  64  extends away from attachment portion  60  for connection to appropriate monitoring equipment. 
     In similar fashion, a suitable temperature sensor is inserted through port  56  such that its sensing element will be in the flow path of the outgoing fluid. For example, the illustrated embodiment provides a thermocouple sensor  66  which is received in port  56 . Sensor  66  includes an attachment portion  68  having external threads which engage the internal threads of port  56 . A sensing portion  70  extends from attachment portion  68  such that its tip will be in the fluid flow path. As shown in  FIG. 4 , the end of sensing portion  70  is situated approximately at the centerline CL of outlet  18  in this case. A lead wire  72  extends away from attachment portion  68  for connection to appropriate monitoring equipment. 
       FIG. 5  illustrates a steam trap  80  constructed in accordance with an alternative embodiment of the present invention. Steam trap  80  is constructed in two main portions—a steam trap body portion  82  and a universal connector portion  84 —that are fixed together. Connector portion  84  (which may also be referred to as a “connector block”) permits steam traps of different capacities to be utilized with a single connection envelope in a steam distribution system. 
     Referring now to  FIG. 6 , connector portion  84  defines an inlet  86  and an outlet  88 . In this embodiment, inlet  86  defines an internally threaded portion  90  upstream of a smooth bore portion  92 . Similarly, outlet  88  has an internally threaded portion  94  downstream of a smooth bore portion  96 . Inlet  86  and outlet  88  are in fluid communication with inlet passage  98  and outlet passage  100 , respectively. 
     Sensing ports  102  and  104  are associated with inlet  86  and outlet  88 , respectively. In particular, port  104  extends through the wall of block portion  84  so as to intersect outlet passage  100  in a direction transverse to the direction of fluid flow. Similarly, port  102  intersects smooth bore portion  92  in a direction transverse to the direction of fluid flow. As shown, both of ports  102  and  104  may be internally threaded. Suitable temperature sensors, such as those described above in connection with the previous embodiment, are inserted through ports  102  and  104  such that their sensing tips will be at the appropriate location. 
     In the illustrated embodiment, connector portion  84  further includes holes  106  and  108  for receipt of suitable fasteners. Bolts  110  and  112  ( FIG. 5 ) may extend through holes  106  and  108  to threadably engage bores  114  and  116  in body portion  82  ( FIG. 7 ). As a result, body portion  82  and connector portion  84  will be securely connected together. 
     The construction of body portion  82  may be most easily explained with reference to  FIG. 7 . As shown, body portion  82  has an attachment flange  118  at which bores  114  and  116  are located. An L-structure  120  defines an inlet passage  122  and at least one outlet passage  124 . As one skilled in the art will appreciate, inlet passage  122  is in fluid communication with inlet passage  98  of block portion  84 . Similarly, outlet passage  124  is in fluid communication with outlet passage  100 . 
     A cap assembly  126  (similar to cap assembly  14  in its construction) is attached to L-structure  120 . A movable disc  128  is located in the space between L-structure  120  and cap  126  to move in and out of engagement with a seating face. O-rings  130  and  132 , or other suitable seals, may be provided to seal the interface between body portion  82  and connector portion  84 . 
     It can thus be seen that the present invention provides a novel steam trap having integrated temperature sensors. While preferred embodiments of the invention have been shown and described, modifications and variations may be made thereto by those of skill in the art without departing from the spirit and scope of the present invention. It should also be understood that aspects of those embodiments may be interchangeable in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only and is not intended to be limitative of the invention described herein.