Abstract:
Embodiments of the present invention provide a non-electric pump. Gas pressure, typically steam or compressed air, is used to move a liquid, typically steam condensate, from a low pressure source to a high pressure destination. A tank fills with liquid from the source. Once full, the motive pressure is admitted to the tank and the pressure forces the liquid to the destination. When the tank is empty, the motive valve shuts and a vent valve opens to vent off the motive gas. A balanced trap plunger with an unattached float linkage provides for improved pump efficiency.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to pumps, and more specifically, to a steam powered pump with improved efficiency. 
       BACKGROUND 
       [0002]    Steam-powered pumps have been used for years in a variety of industrial applications, such as heating and hot water distribution, to name a few. Such systems produce condensate as a byproduct. Condensate generated from latent water vapor must be collected and discarded to avoid damage to the heating/cooling unit and to prevent this contaminant from entering the surrounding environment. 
         [0003]    Pumps used in prior art condensate recovery systems collect the condensate in a vessel, and then introduces a high-pressure working fluid—such as steam—into the vessel by operating a change-over valve. The pressure of the high-pressure working fluid discharges the condensate from the inside of the vessel. To insure high-efficiency operation of the pump, it is necessary to collect as much condensate as possible within the vessel and to properly switch the change-over valve. One such prior art pump is disclosed in U.S. Pat. No. 5,655,888 to Yumoto, and is incorporated herein by reference, to the extent not inconsistent with the present disclosure. As efficient pump mechanisms improve the ability to return condensate to the boiler, and improve efficiency of the overall system, it is therefore desirable to have a steam-powered pump with improved efficiency and operating characteristics. 
       SUMMARY 
       [0004]    Embodiments of the present invention provide a non-electric pump. Instead, gas pressure (typically steam or compressed air) is used to move a liquid (typically steam condensate) from a low pressure source to a high pressure destination. The gas pressure, called motive pressure, must be greater than the pressure of the destination. Check valves are used to permit the liquid to only flow from source to destination. Pumps according to embodiments of the present invention are cyclic devices. A tank fills with liquid from the source. Once full, the motive pressure is admitted to the tank and the pressure forces the liquid to the destination. When the tank is empty, the motive valve shuts and a vent valve opens to vent off the motive gas. Once the tank pressure is relieved the liquid from the source can enter—repeating the cycle. 
         [0005]    A bi-stable overcenter type of mechanism is used to actuate the motive and vent valves, which have opposite action. These valves need to actuate quickly, essentially “snap acting” to prevent the motive and vent valves from being open (even partially) at the same time. The work done by the float as it rises is stored in springs that act on the overcenter links. As the float forces the links to travel over center, the spring energy forces the links to quickly change position, thereby actuating the valves. 
         [0006]    Embodiments of the present invention can also serve as a steam trap. Steam traps are used in steam systems to isolate the steam from the condensate. In a steam heated process, such as an air heater for example, steam will heat the air in some type of heat exchanger. In the process the steam, having released its latent heat, will condense to a liquid. This condensate must be drained out of the heat exchanger to make room for more steam to enter. A steam trap is a type of valve that opens to allow the condensate to pass through, but it closes once steam enters the trap, as it is efficient to preserve steam in the heat exchanger to provide heat to the external source. Steam traps come in many shapes and sizes and they use one of several different physical principles to open to liquids but close to gases. A typical type of trap in the air heating process above would use float connected to a valve (similar to a toilet tank valve). Liquid entering the valve causes the float to rise and open the valve. Once the liquid drained away, gravity causes the float to lower thus closing the valve. This float trap mechanism is included in embodiments of the present invention. 
         [0007]    A typical valve has a plunger that fits into a seat. The force required to open the valve is calculated by multiplying the seat area by the pressure difference between the inlet and outlet. This force increases linearly as the pressure differential increases. The force increases as the square of the seat diameter. The flow capacity of the valve also increases as the square of the seat diameter. It is desirable with a valve to maximize both flow capacity and maximum operating differential pressure. However, with the aforementioned valve type, there is a tradeoff, and either the maximum operating differential pressure or the flow capacity will be constrained. 
         [0008]    Embodiments of the present invention overcome this problem by utilizing a balanced valve. The valve seat has two sealing faces that close simultaneously. Preferably, the diameter of the faces is very closely controlled, with one diameter being slightly larger than the other, in one embodiment having a 0.015 inch to 0.030 inch difference. The inlet pressure acts simultaneously on both the upper and lower surfaces of the valve plunger. The net force is greatly reduced since it is controlled by the difference in area of the two seating diameters. This seat design can provide 3 to 4 times the flow area of a typical pump/trap seat. Furthermore, the balanced valve is biased in the open position by a spring, and the linkage that closes the valve is not mechanically connected to the valve, but is instead unattached. The combination of the bias spring, and the unattached linkage provide for improved efficiency, since as the linkage rises, it does not have to overcome the force required to open the valve. By combining a vapor powered pump packaged with a steam trap that utilizes a balanced design, embodiments of the present invention provide the advantage of a higher pumping capacity for a given pump size. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    In the drawings accompanying the description that follows, often both reference numerals and legends (labels, text descriptions) may be used to identify elements. If legends are provided, they are intended merely as an aid to the reader, and should not in any way be interpreted as limiting. 
           [0010]      FIG. 1  is an outside isometric view of an embodiment of the present invention. 
           [0011]      FIG. 2  is a cross-sectional view of an embodiment of the present invention with the float in the low position. 
           [0012]      FIG. 3  is a cross-sectional view of an embodiment of the present invention with the float in a middle position. 
           [0013]      FIG. 4  is a cross-sectional view of an embodiment of the present invention with the float in the high position. 
           [0014]      FIG. 5  is a side cross-sectional view illustrating the motive and vent valve linkages. 
           [0015]      FIG. 6  is a detailed view of the steam trap valve. 
           [0016]      FIG. 7  is a block diagram of an example usage of an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]      FIG. 1  is an outside isometric view of an embodiment of a pump  100  in accordance with the present invention. As will be explained, pump  100  has two modes of operation: In one mode, it operates as a steam trap, and in another mode, it operates as a pump. For the purposes of this disclosure, reference  100  is referred to as a “pump,” even though it can also provide the mode of operation as a trap. Pump  100  is comprised of tank  101  that holds liquid and/or steam. Liquid enters the pump via input check valve  102 . The input check valve  102  allows liquid to flow only in one direction (unidirectionally), which is into the tank. Input check valve  102  prevents liquid from exiting the tank. During the pumping operation, liquid is output via output check valve  104 . Output check valve  104  is unidirectional, and only allows liquid to exit the tank, and does not allow liquid to enter the tank. Optionally, a sight glass  110  is used to allow visual verification of pump operation. When the pump is operating normally, an operator can observe a changing liquid level in the sight glass. Sight glass shutoff valves  112  and  114  allow for servicing and replacement of the sight glass during maintenance of the pump  100 . Cover  105  houses motive valve inlet  106  and vent valve outlet  108 , which provide entry and exit for the steam that powers pump  100 . 
         [0018]      FIG. 2  is a cross-sectional view of pump  100  with the float  130  in the low position. In one embodiment, float  130  is comprised of metal, such as aluminum, and may be hollow, or filled with a buoyant material such as foam. The float  130  is connected to float arm  132 . Float arm  132  is connected to operating rod  148 , which is mechanically linked to trap plunger rod  136  via adjustment fitting  133 . The adjustment fitting  133  allows the travel limits of the plunger rod  136  to be adjusted via threads on the adjustment fitting  133 . The float is in the low position when the level of liquid in tank  100  is low enough to allow the float to fall to is minimum height. This causes the trap plunger rod  136  to push the trap plunger  132  into the trap valve seat  140 , thereby preventing any liquid or steam from escaping out of the trap body  144 . Trap body  144  therefore serves as a liquid discharge port when the pump  100  is in operation. There is a gasket sealing the pump mechanism cover ( 105 ) to the tank ( 101 ) and another gasket sealing the trap body ( 144 ) to the tank ( 101 ). The float arm  132  and valve actuation linkages are attached to pump frame  134 . Pump frame  134  is secured to cover  105 . The valve actuation linkage comprises operating rod  148 , link  150 , and pivot arm  156 , as well as valve actuator weldment  158 . Therefore, operating rod  148  controls the operation of motive and vent valves that are present in cover  105 . Operating rod  148  is connected to link  150 . Upper trip pin  152  and lower trip pin  154  establish travel limits for link  150 . Link  150  is attached to pivot arm  156 . As liquid enters the tank  101  via liquid inlet port  146  the float  130  will rise, and as it nears the top of its travel, the valves in the cover  105  will be actuated. There are two valves in the cover, a motive valve (not shown in this view) and a vent valve  160 . Both valves are actuated via the valve actuator weldment  158 . 
         [0019]      FIG. 3  is a cross-sectional view of pump  100  of the present invention with the float in a middle position. The liquid being pumped (typically water) is at level L 1 , which causes float  130  to raise as compared with the low position indicated in  FIG. 2 . As the float is elevated, plunger rod  136  travels upward, spring  142  forces plunger  138  upward, thereby allowing liquid to exit the tank  101  via trap body  144 . Link  150  and pivot arm  156  position valve actuator weldment  158  such that vent valve  160  is opened, so that gas can escape from the tank  101  to make room for incoming liquid. 
         [0020]      FIG. 4  is a cross-sectional view of pump  100  with the float  130  in the high position. The liquid, having risen to level L 2  causes operating arm  148  to move link  150  and pivot arm  156  such that valve actuator weldment  158  simultaneously closes vent valve  160 , and opens the motive valve (not shown in this FIG., refer to  FIG. 5 ). Once the motive valve opens, high-pressure steam enters tank  100  and as plunger  138  is in a raised position, liquid is forced out of trap body  144 . In one embodiment, plunger rod  136  is not mechanically attached to plunger  138 . Pump frame  134  serves as a travel limit for plunger  138 . In this way, as float  130  approaches its upper travel limit, it is not affected by the weight of the plunger  138 . In the high position, plunger rod  136  moves independently of plunger  138 . By reducing the amount of force the float must overcome in order to raise, pump efficiency is improved. 
         [0021]    As the high-pressure steam enters the tank  101  via the opened motive valve, the liquid is expelled via trap body  144 , and the float lowers until it reaches the low position (shown in  FIG. 2 ). When the tank  101  is sufficiently empty such that the float  130  is in the low position, the motive valve closes simultaneously as the vent valve  160  opens, and the plunger  138  is pushed into the closed position, preventing liquid from escaping via trap body  144 . This cycle then repeats, and the pumping operation continues. 
         [0022]      FIG. 5  is a side cross-sectional view (as viewed from direction A in  FIG. 4 ) illustrating the motive and vent valve linkages. In this view, motive valve  170  and vent valve  160  are visible. Valve actuator weldment  158  is configured to open one valve, and simultaneously close the other valve, depending on the position of the float (see  FIGS. 2-4 ). When the valve actuator weldment  158  is in its lowest position, vent valve  160  is opened, and motive valve  170  is closed. As valve actuator weldment approaches its highest position, motive valve plunger  172  travels upward, and pushes ball  174 , which allows steam to enter the tank  101 . Simultaneously, valve actuator closes vent valve  160 . This causes pressure to build in the tank, which expels liquid from the tank via trap body  144 . As the float lowers, motive valve  170  closes. Since the tank is still pressurized from the steam, liquid continues to be expelled from trap body  144  until the float reaches the low position. At that point, valve actuator weldment  158  will be low enough to allow vent valve  160  to open, and plunger  138  seals the trap body  144 . This allows the tank to fill, and the cycle repeats. 
         [0023]    The following table summarizes the state of the trap plunger  138  based on the various float positions during the filling of the tank. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 FLOAT POSITION 
                 TRAP 
               
               
                   
                   
               
             
             
               
                   
                 LOW 
                 CLOSED 
               
               
                   
                 MIDDLE 
                 OPENED 
               
               
                   
                 HIGH 
                 OPENED 
               
               
                   
                   
               
             
          
         
       
     
         [0024]    The following table summarizes the state of the valves based on the direction of the float. When the float is rising, the apparatus is in a filling mode, and the motive valve is closed and the vent valve is opened. When the float is falling, the apparatus is in a pumping mode, and the motive valve is opened and the vent valve is closed. 
         [0000]    
       
         
               
               
               
             
           
               
                   
               
               
                 FLOAT 
                   
                   
               
               
                 DIRECTION 
                 MOTIVE VALVE 
                 VENT VALVE 
               
               
                   
               
             
             
               
                 RISING 
                 CLOSED 
                 OPENED 
               
               
                 FALLING 
                 OPENED 
                 CLOSED 
               
               
                   
               
             
          
         
       
     
         [0025]      FIG. 6  is a detailed view of the steam trap valve. Plunger  138  has rod receptacle  186 , which is a hollowed area for receiving and guiding the plunger. In one embodiment, plunger rod  136  is unattached (not physically connected with a fastener) to plunger  138 , and is disposed within rod receptacle  186 . Spring  142  biases the plunger  138  into an open position, such that when the float rises, which in turn causes plunger to  136  to raise, the spring  142  causes plunger  138  to move upward, which opens the trap valve, allowing liquid to flow through radial passages  180 , and exit the apparatus via trap body ( 144  of  FIG. 2 ). 
         [0026]    The plunger  136  is disposed with valve seat  140 . In this detailed view, it can be seen that the plunger  138  is comprised of a first portion and a second portion. The first portion has a diameter D 1  and the second portion has a diameter D 2 . In this case, diameter D 2  is slightly larger than diameter D 1 . This causes two separate sealing edges, first sealing edge  182 , and second sealing edge  184  that form between the plunger  138  and the valve seat  140 . The inlet pressure acts simultaneously on both the upper surface  188  and lower surface  190  of the plunger  138 . The net force is greatly reduced since it is controlled by the difference in area of the two seating diameters, D 1  and D 2 . This allows a fairly large seat diameter, providing the advantage of higher throughput, without the typical disadvantage of the increased force required to operate the plunger, which can reduce pump efficiency. 
         [0027]      FIG. 7  is a block diagram of an example usage of an embodiment of the present invention. A hot water heating system  200  is shown, which comprises pump  100  of an embodiment of the present invention. Boiler  208  provides steam to heat exchanger  204  via steam line  210 . Cold water line  202  supplies cold water to heat exchanger  204 . As a result of heat exchange, hot water exits the heat exchanger  204  via hot water line  206 . The steam exits heat exchanger via steam output line  212 . Since the temperature drops as a result of the heat exchange, there is a mixture of steam and condensate in the steam output line  212 . The steam output line is connected to the input valve ( 102  of  FIG. 1 ) of the pump. As condensate fills the pump  100 , it is pumped out via condensate line  214 , which is connected to the output ( 104  of  FIG. 1 ) of pump  100 , and returns the condensate to boiler  208 . Motive gas line  216  provides power to the pump, and vent gas line  218  allows steam to be returned, thereby keeping the steam in a closed system. 
         [0028]    The pump  100  automatically switches between trap mode and pump mode depending on the operation conditions of system  200 . For example, when the demand for hot water is high, the steam control valve  213  is opened sufficiently to provide enough pressure such that pumping may not be necessary. In this case, pump  100  operates as a steam trap. The float then moves only between the low and middle positions (see.  FIG. 2  and  FIG. 3 ). When moving to the middle position, the trap plunger  138  opens, and condensate will exit via trap body  144 , so long as pressure within tank  101  is sufficient to do so. The steam trap within the pump  100  prevents steam from entering the condensate line  214 . However, as there is sufficient pressure to force liquid from the pump  100 , the motive gas is not supplying force to the pump  100 , since the float never reaches the high position ( FIG. 4 ). 
         [0029]    Once hot water demand drops to a low level, steam control valve  213  is partially closed, which results in a drop in steam pressure. Now, the pressure is no longer sufficient to move the condensate back to the boiler. In this case, the tank within pump  100  starts to fill with condensate, until the float reaches the high position (see  FIG. 4 ), and the motive valve of the pump opens, and gas from the motive gas line allows the pumping operation to begin. Therefore, pump  100  switches between trap mode and pump mode automatically, without the need for user intervention. 
         [0030]    Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, certain equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (assemblies, devices, circuits, etc.) the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiments of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several embodiments, such feature may be combined with one or more features of the other embodiments as may be desired and advantageous for any given or particular application.