Abstract:
A control system for a pumping apparatus consisting of an engine-driven primary pump includes an intake pressure regulating system for maintaining the intake pressure above a preset low value, a discharge pressure regulating system for maintaining the discharge pressure below a preset maximum value, and a master controller for monitoring, recording, and controlling the intake and discharge pressure regulating systems and other components of the system. The discharge pressure regulating system includes a pump governor which varies the engine RPM and operates a relief valve in response to fluctuations in discharge pressure. The intake pressure regulating system includes a reserve tank that is automatically maintained at a preset level which determines the minimum intake pressure of the system. The system may also include a priming pump, foam tanks, foam pumps, bottled nonflammable gas, and an air compressor.

Description:
BACKGROUND 
     1. Field of the Invention 
     This invention relates to the art of pump control systems. 
     More particularly, the invention relates to a system for controlling and monitoring all the functions of a mobile fire pump apparatus having an electronically-controlled engine. 
     In a further and more specific aspect, the instant invention concerns a comprehensive electronic system for controlling the flow of fluids through an engine-driven fire pump. 
     2. Description of the Prior Art 
     Over the years, various systems have been devised for controlling engine-driven fire pumps. For instance, U.S. Pat. Nos. 3,786,689 and 4,189,005 to McLoughlin, as well as U.S. Pat. No. 5,888,052 to McLoughlin et al., disclose apparatus for controlling the pressure output from engine-driven centrifugal fire pumps. Likewise, U.S. Patent Application Publication No. 2005/0061373 to McLaughlin et al. discloses a system for regulating the fluid intake pressure of a pumping system, while U.S. Pat. No. 7,040,868 and U.S. Patent Publication No. 2005/7,040,868, both to McLoughlin et al., disclose systems for controlling pumping speed during discharge pressure fluctuations. Each of the aforementioned systems is somewhat limited in that it is designed primarily for the control of a single parameter (i.e. discharge pressure, intake pressure, or pump speed). None is a comprehensive system for simultaneously monitoring all the aspects of both fluid flow and engine performance. Furthermore, each of these systems is designed to control the flow of a single fluid (typically water) and does not include means for controlling the flow of any supplementary fluids, such as firefighting foam, which may be added to the discharge. 
     Accordingly, there exists a need for a comprehensive control system for simultaneously monitoring and controlling all the functions of an engine-driven mobile pumping apparatus. 
     SUMMARY OF THE INVENTION 
     Briefly, to achieve the desired objects of the instant invention in accordance with the preferred embodiments thereof, a system is provided for simultaneously monitoring and controlling all the functions of an engine-driven mobile pumping apparatus. Specifically, the system includes an engine-driven primary pump, an intake system for delivering liquid to the pump, and a discharge system for dispensing liquid from the pump. The intake system includes a supply line that is coupleable to both a reserve tank and a pressurized source, as well as an intake pressure sensor for monitoring the pressure upstream of the pump and an intake pressure regulating system for maintaining the intake pressure above a preset low inlet pressure P LOW . The discharge system includes at least one hose terminating in a discharge nozzle, a discharge pressure sensor for monitoring the pressure downstream of the pump, and a discharge pressure regulating system for maintaining the discharge pressure below a preset maximum discharge pressure P MAX  The intake and discharge regulating systems are controlled by a master processor that also monitors and records various other conditions of the system such engine speed, voltage, current, temperature, and sends information about these conditions to the vehicle&#39;s control display and/or warning systems. 
     In a preferred embodiment of the invention, the intake system includes a first conduit coupleable to the pressurized source, a second conduit coupleable to an inlet opening in the reserve tank, and a third conduit coupleable to an outlet opening in the reserve tank. The intake pressure regulating system includes control valves in the first, second, and third conduits. 
     The discharge system in this embodiment includes a discharge valve in the at least one discharge hose, and a pressure relief valve upstream of the primary pump. 
     The system is programmed such that at start up, only the valve in the third conduit is open, so that the initial intake pressure is proportional to the level of water in the reserve tank. If the discharge pressure is lower than a preset minimum level P MIN , a priming pump is actuated until P MIN  is reached. When P MIN  is reached, the priming pump switches off, but the valve in the third conduit remains open, and the other two valves stay shut until the discharge pressure sensor detects that that a preset desired output pressure P D  (typically somewhere between 100 and 150 psi) has been reached. At this point, if there is a pressurized source available, the valve in the third conduit is closed, and the valve in the first conduit is opened, so that water for the pump is supplied from the pressurized tank rather than from the reserve tank. Also, if the liquid level in the tank is below a preset minimum, the valve in the second conduit opens, allowing a portion of the liquid in the pressurized source to be diverted into the tank. As soon as the liquid level rises to its desired level, the valve in the second conduit closes again. 
     From this point onward, the system is maintained at more or less steady state by the engine governor, which responds to changes in discharge pressure by varying the RPM of the engine and/or actuating the relief valve, as needed. If the intake pressure suddenly drops below a preset low value P LOW , the valve in the third conduit reopens, allowing liquid from the tank to enter the system at a pressure proportional to the water level. When the intake pressure goes back over P LOW , this valve closes and the valve in the first conduit second conduit reopens, allowing the tank to be refilled. 
     Other components of the system include foam pumps for dispensing various firefighting foams, an air compressor for delivering rescue air to the firefighters, and a tank of compressed nitrogen or other non-flammable gases. Operation of all of these components is controlled by the master processor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and further and more specific objects and inventions of the instant invention will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment thereof taken in conjunction with the drawings, in which: 
         FIG. 1  is a schematic drawing of a control system according to the present invention; 
         FIG. 2  is a control block diagram of the system; and 
         FIGS. 3   a - i  are graphs showing the operation of various elements of the system over time. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning to the drawings in which like reference characters indicate corresponding elements throughout the several views, attention is first directed to  FIG. 1 , which shows a schematic diagram of the control system  10  for a mobile pumping apparatus such as a fire truck (not shown). A gasoline or diesel engine  12  is mechanically coupled to a main centrifugal pump  14  having a supply line  16  which is coupleable to multiple fluid sources such as, for instance, a truck-mounted water tank  18  and a fire hydrant  20 . Various arrangements may be used for coupling the supply line  16  to the water tank  18  and the hydrant  20 , but in the illustrated embodiment, the terminal end of the supply line  16  is connected to an inlet manifold  21  that connects to a first hose  22  leading to the hydrant  20  and a second hose  23  leading to an inlet opening  24  in the water tank  18 . The second hose  23  includes a one-way check valve  25  preventing water from the tank  18  from flowing out towards the hydrant  20 . In addition, a third hose  26  leads from an outlet opening  27  in the tank  18  to the inlet manifold  21 . 
     The discharge line  30  of the pump  14  is coupled to a discharge manifold  31  having a plurality of openings  32   a, b  . . . n, each of which may accommodate a fluid conduit  33   a, b  . . . n that is coupled to a mixing manifold  34   a, b  . . . n which allows water from the discharge line  30  to mix with additives such as foams, compressed gas, and air from various sources before finally being discharged through a fire hose  36   a, b , . . . n terminating in a nozzle  38 . 
     More specifically, the additives may include a Class A foam concentrate suitable for fighting wildfires and structural fires, and a Class B foam concentrate for extinguishing flammable liquid fires. In the illustrated embodiment, the Class A foam concentrate is stored in a first foam tank  40  and pumped by a first foam pump  42  into a first foam manifold  44  that accommodates a first set of foam conduits  46   a, b  . . . n leading to the mixing manifolds  34   a, b  . . . n. A first foam valve  47  is provided in each conduit  46   a, b  . . . n for controlling the amount of class A foam dispensed into the associated mixing manifold  34   a, b  . . . n. Similarly, the Class B foam concentrate is stored in a second foam tank  48  and pumped by a second foam pump  50  into a second foam manifold  52  that accommodates a second set of foam conduits  54   a, b  . . . n leading to the mixing manifolds  34   a, b  . . . n. A second foam valve  55  is provided in each conduit  54   a, b  . . . n for controlling the amount of class B foam dispensed into the associated mixing manifold  34   a, b  . . . n. 
     The system also includes an air compressor  58  driven by a water motor or hydraulic turbine  66  in the discharge line of the main centrifugal pump  14 . The compressor  58  receives ambient air through an air cleaner  68 , compresses it, and injects the pressurized air into a gas manifold  56 , which is coupled to the mixing manifolds  34   a, b  . . . n via gas conduits  62  a, b, n. The flow of this compressed air, which may be used to resuscitate firefighters or others overcome by smoke inhalation, is regulated by an air control valve  70  in an air conduit  85  leading to the gas manifold  56 . 
     In addition, the system includes a pressurized gas tank  60  for delivering an inert or chemical fire-extinguishing gas to the gas manifold  56 . A gas flow valve  63  is provided for regulating the flow between the gas tank  60  and the gas manifold  56 . Each mixing manifold  34   a, b  . . . n preferably contains a set of mixing plates (not shown), including a first mixing plate positioned downstream of the conduits,  46   a, b  . . . n, and  54   a, b  . . . n leading from the foam tanks  40 ,  48 , and a second mixing plate positioned downstream of the gas conduits  62   a, b  . . . n. The purpose of these plates is to induce turbulence in the water flowing through the manifolds  34   a, b  . . . n, thus allowing more efficient mixing than would be possible with purely laminar flow. 
     The control system  10  of the present system comprises a system of valves for regulating flow though the various supply and discharge lines so that the pressure of the fluid or fluids discharged from the nozzle  38  remains safe at all times, regardless of fluctuations in intake pressure, engine rpm, and various other factors. On the intake side of the pump  14 , the system includes a first control valve A located between the intake manifold  21  and the tank inlet opening  24 , a second control valve B located between the intake manifold and the fire hydrant  22 , and a third control valve C located between the tank outlet opening  27  and the supply line inlet opening  28 . On the discharge side of the pump  14 , the system includes a pressure relief valve D located in the discharge line  30  of the pump  14 , and a discharge valve E associated with the nozzle  42 , as well as the foam and gas control valves  47 ,  55 , and  63  mentioned earlier. 
     The control system  10  also provides continuous monitoring of parameters such as flow and pressure at various points throughout the system. Specifically, flow monitoring is achieved by a liquid flow meter  72  located in the fire hose  36 . Pressure is monitored by transducers  74 ,  76 ,  78 ,  79 ,  80 ,  82 , and  84  on or in the intake manifold  21 , discharge line  30 , hose  32 , compressor outlet line  85 , gas tank  60 , and foam lines  86  and  87 , respectively. The level of liquid in the water tank  18  and foam in foam tanks  40  and  48  is monitored by level sensors  88 ,  90 , and  92 , respectively. Also included, although not illustrated, are various sensors and/or meters for monitoring conditions such as engine speed, voltage, current, temperature, and so forth. 
     Signals from the monitoring devices  72 ,  74 ,  76 ,  78 ,  80 ,  82 ,  84 ,  88 ,  90 ,  92 , and others are input to a master processor  94 , which in turn outputs to the pump governor  96 , engine control module  96 , generator  98 , foam pump motors  99 ,  101 , control and warning displays  100 ,  102 , pump switches  104 , and drivers  106 ,  108  for the various valves as shown in  FIG. 2 . In addition, the master processor  94  sends and receives signals from one or both of a transmitter  110  that allows the discharge valve E to be operated remotely and a nozzle control module  112  that allows manual control by a firefighter carrying the hose. It also monitors voltage and current outputs from the generator  98  (which may be powered either by its own separate engine, not shown, or by power takeoff from the main engine  12 ), and sends information about these outputs to the vehicle warning and/or display systems  100 ,  102 . 
     The master processor  94  also includes a recording system (not shown) for recording all the operations of the vehicle and its systems. The system may be queried after an incident for details about the operating times and functions of various components. 
     Sequential operation of various valves and other components of the system will now be described with continued reference to  FIGS. 1 and 2 , as well as additional reference to  FIGS. 3   a - i . Initially, all the valves in the system are closed, the water level in the tank  18  is at a preset level L between full and ¾ths full, and the primary pump  14  is off. At time t 1 , the primary pump  14  is switched on, the tank outlet valve C is opened, and the pump discharge pressure transducer  76  begins to monitor the discharge pressure of the pump. If the transducer  76  detects that the actual discharge pressure P A  is below a preset minimum value P MIN , a small electric motor  114  driving a secondary (priming) pump  116  is switched on, and remains in operation until time t 2 , when P MIN  is reached. At this point, the priming pump  116  switches off. Valve C stays open, and valves A and B stay closed until t 3 , when the pump discharge pressure transducer  76  detects that a preset desired output pressure P D  (typically somewhere between 100 and 150 psi) has been reached, signifying that the nozzle discharge valve E can be opened, and the firefighters may begin spraying at the fire. In addition, the rate of flow F A  is monitored by the flow meter  72 , and maintained at an optimum flow rate F OP . 
     If there is no fire hydrant or pressurized water source available at this point, the system continues to operate in this fashion until the water tank  18  is empty. However, if a pressurized source  20  is available, valves A and B are opened and valve C is closed as soon as P A =P D , allowing water from the pressurized source  20  to flow into the water tank  18 . At t 4 , when the level sensor  86  associated with the water tank  18  detects that the water level has returned to its initial value L, valve A closes so that all the water from the pressurized source  20  flows directly into the pump  14 . 
     After t 4 , the system is maintained more or less at steady state by the pressure governor  96 , which reacts to changes in the discharge pressure P A  by actuating the pressure relief valve D and varying the RPM of the engine  12 . Operation of the governor  96  is described in greater detail in U.S. Pat. Nos. 3,786,869 and 4,189,005 to McLoughlin, as well as U.S. Pat. No. 5,888,052 to McLoughlin et al., the contents of all of which are incorporated by reference herein. 
     In most situations, the operation of the governor  96  is sufficient to keep the system running safely and smoothly, and to maintain the discharge pressure and flow rates within their desired ranges. One exception, however, is when the intake pressure suddenly drops to a very low level, such as when the fire hydrant runs out of water, or when the hose between the hydrant and the pump is run over or develops a leak, or is damaged in some other way. This can cause cavitation of the pump, and may endanger the firefighters on the hose lines. Accordingly, the system includes an intake pressure control mode that is activated whenever the pressure sensed by the intake pressure transducer  74  falls below a preset level P LOW  (typically somewhere between 2 psi and 7 psi), as shown at t 5  in  FIG. 3   i . When this occurs, the tank discharge valve C reopens, thus increasing the intake pressure by an amount proportional to the level of water in the tank. If, when the discharge valve C closes again at t 6 , the level of water in the water tank L is below the preset level L, then the hydrant-to-tank valve A opens as shown at t 6  in  FIG. 3   a , and remains open until the desired water level L is reached, as shown at t 7  in  FIG. 3   e.    
     The graphs shown in  FIGS. 3   a - e  have been greatly simplified for purposes of illustration. For instance, Valves A, B, C, and E, have all been shown to have only two states—fully open and fully closed. In reality, more complex valves having partially open and closed positions could also be used, in which case the changes in system pressure and flow would be more gradual than those shown here, but the basic principles of the invention would remain the same. 
     Various modifications and variations to the embodiments herein chosen for purposes of illustration will readily occur to those skilled in the art. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope of thereof, which is assessed only be a fair interpretation of the following claims.