Abstract:
A safety check unit for use in a liquid distribution system for preventing damage to a pump and associated components of the system in event of loss in pumping pressure. The unit provides a check component to prevent back-flow of the liquid when the pump is shut down, and provides protection against a possible vacuum condition in the system by introducing air to the system; protects against damage by a surging back-flow of liquid by opening a relief port of the unit; and protects against air in the system by use of an air relief mechanism of the unit.

Description:
FIELD OF THE INVENTION 
     This invention relates to a safety check unit for use in a liquid distribution system, having a pump for distribution of the liquid, to protect equipment of the system from damage associated with loss of pumping capability. 
     BACKGROUND OF THE INVENTION 
     In a liquid distribution system, such as a municipal water or sewage system, a pump is typically provided at least at one end of the distribution system so as to provide the pressure required for distributing the liquid throughout the system. An example of a system of concern is a municipal water system wherein water from a reservoir, for example, is pumped through a series of water mains for eventual distribution to homes, commercial establishments, industrial facilities, and the like. In such a system, it is prudent to protect the pump and associated equipment from damage which could occur if the pump, for whatever reason, suddenly loses head pressure and stops pumping. When such an event occurs, damage can be caused to the pump, distribution manifolds, piping and other equipment associated with the pump. 
     A number of conditions caused by the sudden loss of pumping pressure must be addressed within seconds of the pressure loss in order to prevent damage to the mentioned equipment. The conditions include: 1) the presence of a negative pressure (in relation to atmospheric pressure) within manifolds, pipelines, fittings, valve bodies, etc. near the pump which potentially can cause cracking or structural failure of those components; 2) a back-flowing of the liquid in the system, with an impact which potentially can cause severe structural damage to the pump, manifolds, pipeline, fittings, valve bodies etc. in the vicinity of the pump; and 3) if such conditions are not addressed properly, pockets of air which can form and which can cause problems upon start-up of the system following the loss of pumping pressure. 
     Prior art means to overcome the conditions which threaten the pump and related equipment have been cumbersome and complex, they involve many man hours for installation and they require a large amount of space in pumping station facilities. Use of a number of components, each to address a different condition described above, and installed in different locations, increases the possibility of component failure and leakage at joints connecting the piping and the components. Mismatching of size or capacity of the components does not provide the optimum protection. Extensive engineering analysis to match all of the components to each other and to the overall system is required. High labor cost and often compromised assembly of the components, under field conditions, can result in future occurrences of leaks and the like. Positioning of the various components at locations in the system, which may not be the critical location for operating in an optimum manner when loss of pressure or surge occurs, compromises the system. 
     The various devices, which previously have been provided for controlling the above-mentioned threats to the system include: 1) a check valve, which ideally is piped into the system immediately down stream of the system pump; 2) a surge relief valve, usually positioned at an end of a manifold of the system, but remote from the pump, for receiving and relieving the above-described back-flow surge resulting from the loss of pumping pressure, and 3) an air/vacuum valve, also usually provided at an end of a manifold, or other various locations in the system at a location remote from the pump, to allow air into the system when negative pressure within the system is detected, so as to prevent a vacuum condition, and to allow that air out of the system prior to or during normal operating conditions. 
     In the present disclosure of the apparatus of the invention, terms such as upstream, downstream, and the like, are used in relation to the flow of the liquid being pumped in a direction to supply the liquid under pressure from the liquid source, through the liquid distribution system to the residential, commercial, and industrial users. 
     OBJECTS OF THE INVENTION 
     It is an object of the present invention to provide a compact device which incorporates all of the functions necessary to protect a pump, and associated components of a liquid distribution system, from structural damage caused by a sudden drop in the pumping pressure of the pump. 
     It is another object of the present invention to dispose components of the device, and sensing means required for operation of each component, at an optimum location in the distribution system, and to have components configured for optimum effectiveness in overcoming detrimental conditions. 
     It is yet another object of the invention to provide a device having all of the features properly sized in relation to each other and integrated for optimum performance, and to provide a device which can be incorporated into a liquid distribution system at solely one critical point of insertion into the system. 
     It is still another object of the invention to provide a device requiring no electrical, hydraulic or other external support, and requiring no intervention of operating personnel for damage controlling operation of the device or for returning the device back to normal operating conditions following return of the pumping pressure. 
     SUMMARY OF THE INVENTION 
     The present invention is a safety check unit for use in a liquid distribution system which has a pump and a piping network downstream of the pump for distributing the pumped liquid, wherein the pump intakes a liquid at an intake pressure and outputs the liquid to the piping network at an output pressure which is greater than the intake pressure; and upon terminating pumping, the liquid in the pipe network exerts a back-pressure at the pump which is greater than the intake pressure. The unit is configured for placement in communication with the liquid distribution system downstream of the pump and includes: a liquid checking portion, for checking liquid when back-flowing from the piping network toward the pump, the liquid checking portion having an inlet port in communication with the pump, an outlet port in communication with the distribution system, an internal chamber intermediate the ports and a closing member disposed in the internal chamber for preventing back-flowing of the liquid; a surge relief portion, communicating directly with the internal chamber, for relieving liquid from the system and reducing liquid pressure in the system rapidly when the liquid pressure in the internal chamber is above a pre-selected pressure which is greater than an operating output pressure of the pump; an air input portion, communicating directly with the internal chamber, for providing air to the system when the internal chamber is at least partially void of liquid and a pressure in the void is below atmospheric pressure; and an air release portion, communicating directly with the internal chamber, for releasing air from the system at an adjustable speed when air is in the internal chamber at a pressure above atmospheric pressure. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The invention will become more readily apparent from the following description of the embodiments thereof which are shown, by way of example only, in the accompanying drawings, wherein; 
     FIG. 1 is a schematic diagram of a fluid distribution system which incorporates the device of the present invention; 
     FIG. 2 is a vertical cross-section of the device of the present invention showing components positioned as they would be during normal pumping conditions; 
     FIG. 3 is a vertical cross-section of the device of the present invention showing components positioned as they would be just following a sudden loss of pumping pressure and liquid flowing due to momentum of the liquid; 
     FIG. 4 is a vertical cross-section of the device of the present invention showing components positioned as they would be when liquid flow due to momentum has stopped; 
     FIG. 5 is a vertical cross-section of the device of the present invention showing components positioned as they would be just following an initial stage of a surging back-flow of liquid; 
     FIG. 6 is a vertical cross-section of the device of the present invention showing components positioned as they would be near the end of a surging back flow of liquid; 
     FIG. 7 is a vertical cross-section of the device of the present invention having an alternative surge pressure relief means. 
     FIG. 8 is a vertical cross-section of the device of the present invention having an alternative liquid checking portion, surge pressure relief portion, and air input/release portion; 
     FIG. 9 is a vertical cross-section of the device of the present invention having an alternative liquid checking portion, surge pressure relief portion, air input portion, and air release portion; 
     FIG. 10 is a vertical cross-section of the device of the present invention having an alternative liquid checking portion and air input/release portion; 
     FIG. 11 is a partial vertical cross-section of the device of the present invention having an alternative liquid checking portion; and 
     FIG. 12 is a vertical cross-section of the device of the present invention having an alternative liquid checking portion, surge pressure relief portion, and air input/release portion. 
    
    
     DETAILED DESCRIPTION 
     The present invention can be incorporated into any system wherein a liquid is being pumped under pressure to a distribution network, or the like, and wherein, if the pumping pressure suddenly drops, the already pumped liquid would return toward the pump under pressure as a surging back-flow. 
     Liquid systems, which should incorporate the present device, for protection of components of the system, include municipal water systems, municipal sewage systems, oil or other liquid pipeline systems, and industrial processing systems. For purposes of disclosing the present invention, one type of a municipal water system will be described. FIG. 1 shows a municipal water system having a water source  1 . Water is pumped by a water pump  2  through piping  3  to a water storage tank  4  for distribution to homes, commercial establishments, industrial facilities, and the like through distribution pipes of a municipal water distribution system  5 . In such a distribution system, the pump  2  must provide an output pressure in excess of a back pressure resulting from gravity acting on the water of the system. The amount of back pressure is dependent on the height h from the pump to the top surface of the water in storage tank  4 . It is that back pressure, which if unchecked, can cause severe damage to the pump and associated equipment of the pumping facility if a sudden drop in pumping pressure occurs. Such a sudden drop in pumping pressure can occur, for example, if electrical power to the pump is interrupted. The device of the invention, a safety check unit  6 , is preferably installed in the water distribution system immediately downstream of the pump  2  as depicted in the schematic diagram of FIG.  1 . 
     FIG. 2 shows a vertical cross-section of the safety check unit  6  of the invention. The unit is installed so as to be in direct communication with the water being pumped and is preferably installed adjacent to the pump or a short distance from the pump in a header, manifold, or piping of the system, with use of flanges  7 . A body  8  of the unit defines an internal chamber  9  through which the pumped water travels in a direction indicated by arrow  10  as it flows from inlet port  11  to outlet port  12 . The body  8  has formed therein an annular seat  13  upon which closing member  14  pivotally closes to prevent back flowing of the water when the pumping pressure is less than the back pressure of the distribution system. FIG. 2 depicts the closing member  14  in an “open” position and FIGS. 3-7 depict the closing member  14  in a “closed” or “checking” position. In the preferred embodiment of the invention the manner of operation of the closing member is by a pivotal or swinging type movement about axis  15 . Various other mechanisms for providing the checking action are possible. Other mechanisms providing checking action are piston action, poppet action, tilting disc action, spring loaded action, etc. 
     The device of the invention includes other portions, which are also in direct communication with chamber  9 . Such direct communication with that chamber provides for optimum operation of the device and greatest protection for the equipment of the pumping system. The other portions of the device include a surge relief portion  16  which communicates with chamber  9  through, relief inlet port  17 , and a combination air-vacuum portion  18  which communicates with chamber  9  through piping  19 . In other embodiments of the invention the air-vacuum portion is made up of a separate air input portion and a separate air release portion. 
     A sequence of events, which most likely occurs when pumping pressure is suddenly lost, is described with reference to FIGS. 2-6. The functions carried out by safety check unit  6 , in response to those events, are also described. 
     FIG. 2 shows safety check unit  6  in normal operation, that is, the pump is providing a liquid pressure at the outlet port  12  which is greater then the back pressure of the liquid distribution system. Therefore, liquid  20  is flowing in the direction indicated by arrow  10  from inlet port  11  to outlet port  12 . The force of the flowing liquid overcomes the gravitational force on closing member  14  and closing member  14  is in the open position. In normal operation, surge relief portion  16  is blocking the escape of liquid by way of differential piston  21  blocking channel  22  which communicates with relief port  17 . A pilot valve  23 , which is used to control the surge relief portion  16  has opening  24  closed by the pressure of spring  25 . Air/vacuum portion  18  has opening  26  closed by float assembly  27  which floats in chamber  28  in the liquid of the distribution system which fills that chamber. With safety check unit  6  having its components positioned as described, all of the pumped liquid entering inlet port  11  exits outlet port  12  for delivery to the liquid distribution system as no other outlet path is open. 
     If a pump failure occurs, the following series of events most likely would take place in the distribution system. First in the sequence of events, the supply of liquid to inlet port  11  by the pump is terminated and the entrance of liquid or air past pump  2  and into the system through inlet port  11  is in most cases blocked by the mechanism of the pump. Without the flow of liquid, closing member  14  first drops by gravity to a position on annular seat  13  as depicted in FIG.  3 . 
     Next, in the sequence of events, due to the momentum of the flowing (already pumped) liquid, a liquid column separation may occur whereby chamber  9  becomes at least partially empty of liquid and a near vacuum condition tends to occur in chamber  9 . The near vacuum condition can extend partially into the pipe or manifold downstream of outlet  12  as shown in FIG.  3 . Such a vacuum condition, which could have a damaging affect on the system, is averted by action of the air-vacuum portion  18  of the safety check unit. Opening  26  is opened by movement of float  27  downward in the now liquid-depleted chamber  28  by the force of gravity, so as to allow air into chamber  9  by way of piping  19 . Air-vacuum portion  18  allows air into the chamber  9  when no liquid is present in chamber  28  containing float  27  and pressure in a void of chamber  9  is less than atmospheric pressure. 
     Next, in the sequence of events, as the momentum of the flowing liquid diminishes, the flow of liquid stops as depicted in FIG.  4 . Closing member  14  remains against annular seat  13 , air vacuum portion  18  remains open due to float  27  being displaced from opening  26 , and surge relief portion  16  remains closed. 
     Next, in the sequence of events, the flow of liquid reverses and surges toward pump  2  as depicted in FIG.  5 . Air in the system, which entered the system in order to prevent a vacuum condition, is now released from the system by way of the air/vacuum portion  18 . Also, entrapped air from the liquid is released. Referring to FIG. 5, air-vacuum portion  18  has opening  26  in the open position since air is still present in chamber 28 and the float  27  is not floating. Air is released by the air/vacuum portion when the air is at a pressure greater than atmospheric pressure, as is the case when the liquid is back-flowing. The rate at which the air leaves the system can be restricted or regulated by throttling device  36  which is in communication with opening  26  of air/vacuum portion  18 . In addition to the float action air/vacuum valve described above, spring type, and diaphragm type mechanisms can be incorporated. Additionally, a weight loaded type air input mechanism can be incorporated. By releasing the air at a selected rate, the air helps to cushion the surging back-flow of liquid. 
     As described above, closing member  14  is closed against seat  13  initially by the force of gravity alone and then by the force of the back-flowing liquid. Following removal of air in the system, liquid enters chamber  28  and float  27  floats to close off opening  26 . The pressure in chamber  9  increases, due to the surging back-flow of liquid. To relieve the pressure of the surging back-flowing liquid, differential piston  21  of surge pressure relief portion  16  displaces upwardly as shown in FIG. 6 to allow the surging liquid pressure to be relieved through outlet port  29 . The pressure at which differential piston  21  displaces upwardly is pre-selected and is set at a value which is greater than the normal operating pressure of the pump. The differential piston  21  remains upwardly displaced until the pressure in chamber  9  is less than that set pressure. The pre-selected pressure is set by means of relief pilot valve  23 . Relief pilot valve  23  senses the pressure in chamber  9  through sensing tube  30 . During normal pumping operation of the distribution system (FIG.  2 ), differential piston  21  of the surge pressure relief portion  16  has liquid of equal pressure on faces A and B as face A communicates with chamber  9  by way of channel  22  and face B communicates with chamber  9  by way of piping  31  and  32 . However, since face A has a smaller surface area than face B, the net force on the piston is downward, thus closing off channel  22 . If the pressure in chamber  9 , which is conveyed to relief pilot valve  23  through sensing tube  30  increases, due to the surging back-flow, to a pressure above the pre-selected pressure set for relief pilot valve  23 , spring  25  is overcome by that pressure and valve opening  24  of the relief pilot valve  23  opens to the atmosphere so as to drop the pressure in piping  33  and  32  as well as the pressure against face B of differential piston  21 . The pressure against face B is then such that the net force on differential piston  21  is in the upward direction thus allowing the surging pressure to be relieved by way of channel  22  and outlet port  29 . 
     After the surging pressure is relieved and the pressure within chamber  9  becomes less than the pre-selected pressure, relief pilot valve  23  closes by action of spring  25 , liquid pressure on faces A and B of differential piston  21  becomes substantially equal again, and, due to the difference in surface areas of the faces, the piston is forced to the downward closed position again. The speed at which the piston moves to the closed position can be controlled with use of closing speed control valve  34  which meters the liquid flowing toward face B of the differential piston. Speed control valve  34  is preferably a needle valve, but can be any of various other means of regulating flow so as to better control the flow of liquid so as to prevent a secondary surge of liquid which would result from differential piston  21  closing too quickly. In order to prevent clogging of needle valve  34 , a strainer  35  is preferably disposed in piping  31  ahead of speed control valve  34 . 
     Following the closing of outlet port  29  by differential piston  21 , components of the safety check unit are disposed for normal pumping operation. When pumping is resumed, components of the safety check unit are disposed as depicted in FIG. 2, without intervention of operating personnel. 
     An important feature of the safety check unit of the invention is the common chamber with which all of the portions of the unit directly communicate. With such direct communication, each of the actions required by the different portions of the unit to protect the pump, and other components of the distribution system, takes place in a very short period of time so as to provide maximum protection to the pump and associated equipment. 
     A second embodiment of the invention provides surge pressure relief in a different manner. Referring to FIG. 7, surge pressure relief portion  37  relieves surging back-pressure of the liquid, as described above, by movement of valve  38  in an upward direction so as to open chamber  22 . During normal operation of the system, valve  38  is held in a closed position by spring means  39 . The pressure required for opening valve  38  is preselected and set by adjustment of the spring mechanism. In addition to the surge pressure relief valves described above, diaphragm operated, lever and weight, spring loaded and other type actions can be incorporated into the unit. 
     FIGS. 8-12 show the safety check unit of the invention having portions using various other mechanisms to carry out the functions of the device. 
     In FIG. 8, safety check unit  40  incorporates a spring loaded action liquid checking portion  41 , a spring loaded action surge relief portion  42  and a float action air input/air release portion  43 . 
     In FIG. 9, safety check unit  44  incorporates a poppet action liquid checking portion  45 , a spring loaded action surge relief portion  46 , a weight loaded valve action air input portion  47 , and a float action air release portion  48 . 
     In FIG. 10, safety check unit  49  incorporates a tilting disk action liquid checking portion  50 , a piston action surge relief portion  51 , and a diaphragm action air input/air release portion  52 . 
     In FIG. 11, safety check unit  53  incorporates a spring loaded action liquid checking portion  54 , a piston action surge relief portion  55  and a float action air input/air release portion  56 . 
     In FIG. 12, safety check unit  57  incorporates a piston action liquid checking portion  58 , a spring loaded action surge relief portion  59 , and a float action air input/air release portion  60 . 
     In all of the above described safety check units the liquid checking portions of each includes an internal chamber  9  which communicates directly with the surge relief portion, the air input portion, and the air release portion. 
     While specific configurations of the components have been set forth for purposes of describing embodiments of the invention, various modifications can be resorted to, in light of the above teachings, without departing from applicant,s novel contributions; therefore in determining the scope of the present invention, references shall be made to the appended claims.