Abstract:
A building sprinkler system includes a pump that feeds a plurality of sprinkler heads. A driver is operatively connected to the pump for driving the pump. A speed control is responsive to suction pressure at a suction side of the pump. The speed control is configured to reduce driver speed when the suction pressure falls below a set threshold pressure value to maintain the suction pressure above the set threshold pressure value.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application No. 60/989,613, filed Nov. 21, 2007, the details of which are hereby incorporated by reference as if fully set forth herein. 
     
    
     TECHNICAL FIELD 
       [0002]    This application relates to sprinkler systems and more particularly to a sprinkler system fire pump and fire pump driver with speed control. 
       BACKGROUND 
       [0003]    Building (or other facility) sprinkler systems provide pressurized liquid (e.g., water) to extinguish fire. A pump is used to provide the water pressure. The pump may be powered by an electric motor or other type of pump driver, such as an internal combustion engine. 
         [0004]    Such sprinkler systems are often designed for a defined flow rate and pressure. For a given engine/pump combination, the discharge line pressure for the pump is dependent on the fluid flow rate through the system and the pressure of the water being supplied to the pump (also called suction pressure). The suction pressure may have a wide range between high and low pressures and will characteristically decrease with increased fluid flow rate. In some instances, there is a concern that if the suction pressure falls below atmospheric pressure, ground water can infiltrate the suction line which can contaminate the drinking water supply. Furthermore, low or negative suction pressure can lead to damage such as pipe collapse due to external forces acting on the pipe. 
       SUMMARY 
       [0005]    In an aspect, a building sprinkler system includes a pump that feeds a plurality of sprinkler heads. A driver is operatively connected to the pump for driving the pump. A speed control is responsive to suction pressure at a suction side of the pump. The speed control is configured to reduce driver speed when the suction pressure falls below a set threshold pressure value to maintain the suction pressure above the set threshold pressure value. 
         [0006]    In another aspect, a method of controlling a pump driver of a building sprinkler system is provided. The method includes operating the pump driver connected to a pump thereby delivering fluid from a building fluid source. Speed of the pump driver is controlled based on pressure at a suction side of the pump. 
         [0007]    In another aspect, a speed control system for controlling speed of a pump driver operatively connected to a pump of a building sprinkler system is provided. The speed control system includes a throttle for controlling pump driver speed. An actuator includes a throttle linkage connected to the throttle. The actuator is controlled in response to pressure at a suction side of the pump. The actuator is configured to move the throttle lever when the suction pressure falls below a set threshold pressure value. 
         [0008]    Various advantages and features of the invention will be apparent from the following description of particular embodiments. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]      FIG. 1  is a partial, perspective view of an embodiment of a sprinkler system; 
           [0010]      FIG. 2  is a diagrammatic, partial view of the sprinkler system of  FIG. 1 ; 
           [0011]      FIG. 3  illustrates an embodiment of a method of controlling the sprinkler system of  FIG. 1 ; 
           [0012]      FIG. 4  is a diagrammatic view of another embodiment of a sprinkler system; 
           [0013]      FIG. 5  is a side, section view of an embodiment of a valve assembly for use in the sprinkler system of  FIG. 4 ; 
           [0014]      FIG. 6  is a side, section view of another embodiment of a valve assembly for use in the sprinkler system of  FIG. 4 ; 
           [0015]      FIG. 7  is diagrammatic, partial view of another embodiment of a sprinkler system; and 
           [0016]      FIGS. 8 and 9  are illustrative, exemplary plots of system and pump performance curves. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Referring to  FIG. 1 , a sprinkler system, generally referred to as element  10 , includes an engine or motor, in this instance, an internal combustion engine  12  coupled to a pump  14 . The pump  14  moves water from a pump inlet  16 , through an outlet pipe  18  and to sprinkler heads  17  of a fluid delivery system  19 . The pump  14  is operated by the internal combustion engine  12 , which can be a diesel engine. The engine  12 , however, could be another type of internal combustion engine or an electric motor. The engine  12  drives a shaft  20  that operates the pump  14 . The RPM of the engine  12  and thereby shaft  20  is controlled by a throttle controller  22 . 
         [0018]    Referring to  FIG. 2 , a pressure sensor  24  is connected to the suction side of the pump  14 . The pressure sensor  24  provides a signal that is indicative of suction pressure at the pump inlet  16 . The throttle controller  22  receives the signal from the pressure sensor  24  and determines (e.g., using a processor and memory) whether the suction pressure is below a set value (e.g., selected from a pressure between about 5 psi and about 30 psi). In some embodiments, the set pressure value is selectable by an operator from a range of pressure values, for example, using a user input (e.g., a dial, keypad, button, etc.). In one embodiment, a second, lower set pressure value (e.g., at or below about 5 psi) may be used for determining if the engine  12  is to be shut down. 
         [0019]      FIG. 3  illustrates a method  26  for controlling the engine  12  of the sprinkler system  10 . At step  28 , with the engine  12  already activated, liquid is pumped from the pump inlet  16 , through the outlet pipe  18  and toward the sprinkler heads. At step  30 , the pressure sensor  24  sends a signal indicative of pressure at the suction side of the pump  14 . The throttle controller  22  determines whether the detected pressure is below the set pressure value at step  32  using the signal from the pressure sensor  24 . If the detected pressure is determined to be above the set pressure value, then the throttle controller  22  does not command a reduction in engine speed. If the detected pressure is determined to be below the set pressure value, the throttle controller  22  determines the magnitude of the difference between the detected pressure and the set pressure value at step  34 . At step  36 , the throttle controller  22  determines a reduction in engine speed based on PID (proportional-integral-derivative) logic. The PID logic may include gain settings that determine the level of damping to reach the desired reduction in engine speed. The gain settings can also help control the time it takes to reach the desired reduction in engine speed and how much overshoot and oscillation around the throttle setting will occur. 
         [0020]    At step  38 , the throttle controller  22  reduces the throttle of the engine  12  thereby reducing the engine speed. The throttle controller  22  continues to monitor the signal from the pressure sensor  24 . If the throttle controller  22  determines at step  39  that the pressure at the suction side of the pump  14  has increased above the set pressure value, the throttle controller  22  increases the speed of the engine  12 , for example, back to its normal operating throttle at step  40 . If the throttle controller  22  determines at step  39  that the pressure at the suction side of the pump  14  remains below the set pressure value, the throttle controller determines whether the engine throttle is at a minimum throttle at step  42 . If the engine throttle is not at a minimum, the throttle controller  22  may again decrease the throttle of the engine  12  and monitor the signal from the pressure sensor  24 . In some embodiments, represented by the dashed line, the method  26  may repeat steps  34  and  36 . If the engine throttle is at a minimum throttle and the pressure at the suction side of the pump remains below the set pressure value, the throttle controller  22  shuts down the engine  12  at step  44  and signal to an alarm, for example, to alert an operator. 
         [0021]    In some embodiments, the throttle controller  22  includes a deadband range that prevents continuous throttle setting changes, for example, due to relatively small pressure changes detected by the throttle controller  22  using the pressure sensor  24 . Instead, the pressure detected at the suction side of the pump using the pressure sensor  24  will have to decrease below or above the deadband range before the throttle controller  22  will command a reduction or increase in the engine&#39;s throttle setting. 
         [0022]    While the above discussion focuses on an electronic throttle control system, a mechanical throttle control system may be used. Referring to  FIG. 4 , a throttle control system  50  includes a throttle control actuator assembly  52  including a cylinder  54 . An end block  56  closes and seals an end of the cylinder  54  and an end block  58  closes and seals an opposite end of the cylinder. A slidable piston  60  is received in the cylinder  54  and a compression spring  62  extends from end block  56  to the piston. The spring  62  biases the piston  60  against a shoulder  64  of end block  58 , which corresponds to a full throttle position. 
         [0023]    Within the end block  58  is a fluid receiving chamber  66 . A piston rod  68 , integral with a piston head  70  of the piston  60 , extends axially through chamber  66  and beyond the end block  58 . The piston rod  68  connects to a throttle linkage  72 , the length of the throttle linkage being adjustable to facilitate proper setting of the full throttle position. The piston rod  68  may be sealed by an o-ring  74  thereby preventing fluid leakage past the piston rod. 
         [0024]    A fluid dampening reservoir  76  is attached to the end block  56  via an orifice  78  thereby fluidly communicating with the cylinder  54  through fluid channel  80  within the end block  56 . Orifice  78  is used to dampen fluid pressure surges that may otherwise be transmitted directly to the dampening reservoir  76 . 
         [0025]    Fluid pressure is received within the fluid receiving chamber  66 , from fluid line  82 , that acts upon the piston  60 . This fluid pressure can cause movement of the piston  60  to compress the spring  62  thereby rotating a throttle lever  84  counterclockwise due to the linkage  72  thereby slowing the throttle of engine  12 . 
         [0026]    Fluid pressure to the fluid receiving chamber  66  is controlled, at least in part, by a valve assembly  86 . The valve assembly  86  receives fluid pressure from the discharge side of the pump  14  through line  88  and fluid pressure from the suction side of the pump through line  90 . 
         [0027]    Referring now to  FIG. 5 , the valve assembly  86  includes an upper housing member  92 , a mid housing member  94  and a lower housing member  96  that are fastened together by fasteners  98  to form a valve body  100 . A valve stem  102  is located in the valve body  100  and is connected to an upper valve disc  104  that connects the valve stem to a flexible diaphragm  106  and a lower valve disc  108 . The flexible diaphragm  106  spans a vented chamber  109  including vent  110  and is located between the upper and mid housing members  92  and  94  to provide a seal member therebetween. A compression spring  111  is used to apply a biasing force against the upper valve disc  104 . 
         [0028]    As noted above, the valve assembly  86  utilizes hydraulic pressure from the discharge and suction sides of the pump  14  to operate. A pump discharge chamber  112  is connected to the line  88  that receives fluid pressure from the discharge side of the pump  14 . A suction supply chamber  114  is connected to the line  90  that receives fluid pressure from the suction side of the pump  14 . A control circuit chamber  116  is connected to the fluid line  82  that leads to the fluid receiving chamber  66  of the throttle control actuator assembly  52 . 
         [0029]    During normal operation which is illustrated by  FIG. 5 , hydraulic pressure within the suction supply chamber  114  overcomes both the bias force applied by the spring  111  and an opposing force applied by hydraulic pressure within the pump discharge chamber  112  in order to seat the lower valve disc  108  against a sealing surface  118 , which prevents flow of water into the control circuit chamber  116 . The hydraulic pressure within the suction supply chamber  114  overcomes both the bias force applied by the spring  111  and the opposing force applied by hydraulic pressure within the pump discharge chamber  112  because an area of the diaphragm  106  exposed to the hydraulic pressure within the suction supply chamber  114  is much greater than an area of the lower valve disc  108  exposed to the hydraulic pressure within the pump discharge chamber  112 . Thus, it takes a much lower hydraulic pressure within the suction supply chamber  114  to seat the lower valve disc  108  against the sealing surface  118  than it does for the hydraulic pressure within the pump discharge chamber  112  (in combination with the spring force) to unseat the lower valve disc from the sealing surface. A sealing member  120  (e.g., an o-ring) prevents pressurized fluid from moving past the valve stem  102 . 
         [0030]    When the hydraulic pressure at the suction side of the pump  14  drops below a set value (e.g., a pressure between about 5 psi and 30 psi), the hydraulic pressure in the suction supply chamber  114  is no longer sufficient to seat the lower valve disc  108  against the sealing surface  118  and the hydraulic pressure in the pump discharge chamber  112  and the spring force unseat the lower valve disc thereby allowing pressurized fluid to flow from chamber  112  into the circuit control chamber  116 . Referring briefly to  FIG. 6 , an adjustment device  122  may be used to adjust the bias force applied to unseat the lower valve disc  108  from the sealing surface  118 . The adjustment device  122  includes a spring  123  that allows for adjustment of the set pressure value. 
         [0031]    Referring back to  FIG. 4 , hydraulic pressure is received by the valve assembly  86  from both the pump discharge  18  ( FIG. 1 ) through line  88  and the pump inlet  16  through line  90 . The valve assembly  86  is normally closed during normal operating conditions as described above. If the pressure on the suction side of the pump  14  falls below the set pressure value, the valve assembly  86  opens thereby permitting fluid to flow through line  82 , a control line  124 , through orifice  128  and into a drain  130 . As fluid flows into the orifice  128 , a controlled back pressure is formed in control line  124  and in line  82  communicating with the fluid receiving chamber  66  in the throttle control actuator assembly  52 . Thus the pressure acting upon the piston  60  is substantially reduced below the pump discharge pressure (which may be in the range of 110 to 240 psi, such as about 170 psi), but the pressure acting upon the piston varies as the pressure in the suction supply chamber  114  varies when the lower valve disc  108  unseats from the surface  118 . 
         [0032]    At start up and/or during normal steady state operating conditions, the throttle lever  84  and the throttle control actuator assembly  52  are positioned as illustrated in  FIG. 4  with the compression spring  62  biasing the piston  60  toward its extended position. In this configuration, the throttle lever  84  is in its full throttle position whereby the pump  14  is providing a set water flow rate and working pressure at rated operating speed throughout the sprinkler system. As the system is operating, the pump discharge chamber  112  receives pressure from the pump discharge  18  and the suction supply chamber  114  receives pressure from the pump inlet  16 . So long as the pressure within the pump inlet  16  is above the set pressure value (e.g., between about 5 and about 30 psi), the valve assembly  86  remains closed and the throttle lever position is unchanged. 
         [0033]    In the event that the pressure at the suction side of the pump  14  goes below the set pressure value, the valve assembly  86  opens as described above thereby permitting fluid flow from chamber  112  to chamber  116  and subsequently into line  82 . Fluid also flows into the control line  124 , through orifice  128  and into drain  130 . The orifice  128  acts to restrict fluid flow trough the control line  124  thereby causing a controlled back pressure throughout the control line and into the fluid receiving chamber  66  of the throttle control actuator assembly  52 . As the pressure at the suction side of the pump  14  varies causing the lower valve disc  108  to move up and down, the back pressure caused by the orifice  128  also varies causing the piston  60  to extend and retract thereby retarding and advancing the throttle lever  84 . Once the pressure at the suction side of the pump  14  rises above the set pressure value, the valve assembly  86  closes thereby preventing or reducing further fluid flow into line  82 . Fluid flow through orifice  128  continues such that pressure within the control line  124  and line  82  decays to a pressure below that needed to overcome the bias provided by spring  62 . The spring  62  then biases the piston  60  in its extended position with the throttle lever  84  in its normal operating position. 
         [0034]    The fluid dampening reservoir  76  may be used to dampen rapid fluid pressure fluctuations that may occur between the valve assembly  86  and the fluid receiving chamber  66 . System  50  can further include line  140  and hose  142  that can be used to dump pressure within the system. 
         [0035]    Referring to  FIG. 7 , throttle control system  200  includes a suction pressure sensor assembly  202  that monitors the suction pressure at pump inlet  16  and an actuator pressure sensor assembly  204  that monitors pressure in chamber  66  of the throttle control actuator assembly  52  (see  FIG. 4 ). For example, the cylinder pressure sensor assembly  204  may include a pressure sensor located at any of the chamber  66 , line  82  or line  124  of  FIG. 4  for detecting pressure at the chamber  66 . If the pressure detected by the actuator pressure sensor assembly  204  rises above a set pressure value (e.g., 75 psi) as the pump throttle is decreased and if pressure detected by the suction pressure sensor assembly  202  is below another set value (e.g., 10 psi), then an engine shut down signal is provided that causes the engine  12  to shut down. An exhaust valve  206  is provided to direct controlled backpressure to a drain (for example, drain  142  of  FIG. 4 ). 
         [0036]      FIGS. 8 and 9  illustrate exemplary plots  154  and  160  of system and pump performance curves. This discussion of  FIGS. 8 and 9  is for illustrative purposes and is not meant to be limiting. The pump performance curves  154  and  162  plot the pump&#39;s capacity versus pressure and is determined through tests conducted by the pump manufacturer. This typical pump performance curve  162  is plotted for a constant speed (RPM). The system resistance curve  164  plots the change in flow due to elevation considerations and frictional losses. The system resistance curve  164  is typically developed by the user (or other entity) based upon the conditions of service, such as physical layout, process conditions and fluid characteristics. The pumping system operates at point O where the pump performance curve  162  and the system resistance curve  164  intersect. A suction supply curve  166  plots the suction pressure versus change in flow. The suction supply curve  166  is often supplied by a municipality. The curves  162 ,  164  and  166  represent normal operating conditions. The operating suction pressure can be determined where a vertical line drawn through point O intersects the suction supply curve  166  at point S. 
         [0037]    Referring first to  FIG. 8 , in some instances, the operating point O may force the suction pressure at point S below a specified limit  167 . The throttle of engine  12  is decreased, which causes the pump performance curve  162  to move down (see dotted line  162 ′) As can be seen, moving the pump performance curve  162  down results in shifting the operating point to the left to point O′, thereby increasing the suction pressure higher along curve  166  (see point S′). The throttle is decreased until the operating point O′ is shifted to the left with a resulting shift in S′ that reaches the specified suction pressure limit  167 . 
         [0038]    In some instances, referring to  FIG. 9 , there may be a decrease in suction pressure, for example, due to sudden increased demand, which causes the suction supply curve  166  to move down (see dotted line  166 ′), thereby lowering the suction pressure at the operating point O. As described above, if the suction pressure decreases below the set pressure value (e.g., selected from a value between about 5 psi and about 30 psi), the throttle of the engine  12  is decreased, which causes the pump performance curve  162  to move down (see dotted line  162 ′). As can be seen, moving the pump performance curve  162  down results in shifting the operating point to the left to point O′, thereby maintaining or even increasing the suction pressure (see point S′). 
         [0039]    The above-described engine throttle control systems are used to maintain a minimum suction pressure. Maintaining a minimum suction pressure can reduce or inhibit undesirable infiltration of ground water into the system, which can then enter the drinking water supply. Additionally, maintaining a minimum suction pressure can reduce or inhibit the effect of external forces on the pipes, which can potentially lead to pipe leakage or collapse. Additionally, the throttle control systems can shut down the engine if the suction pressure does not rise to or above the set pressure value despite a reduction in engine throttle. 
         [0040]    It is to be clearly understood that the above description is intended by way of illustration and example only and is not intended to be taken by way of limitation, and that changes and modifications are possible. Accordingly, other embodiments are contemplated and modifications and changes could be made without departing from the scope of this application.