Abstract:
A fire suppression sprinkler system convertible between a wet and a dry mode of operation is disclosed. The system features a field convertible valve having a bypass loop with a bypass valve for selectively configuring the valve for wet or dry mode operation. For dry mode operation, the bypass valve is open. The field convertible valve also has a system actuator, a gas control valve and a water supply shut-off valve which are open in the dry mode. In the wet mode of operation, the bypass valve is open and the gas control and water supply shut-off valves are closed. The field convertible valve operates in a latch mode controlled by the system actuator in the dry mode, and as a flapper valve in the wet mode of operation. A method of converting the mode of operation of the sprinkler system is also disclosed.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of and claims priority to pending U.S. application Ser. No. 11/565,764 filed Dec. 1, 2006. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to valves used to control water flow to fire suppression sprinkler systems and especially to valves that are useable in both wet and dry systems. 
     BACKGROUND OF THE INVENTION 
     Fire suppression sprinkler systems comprise a piping network having branches extending throughout a building or other structure through which water or other fire suppressing fluid may be conveyed to be discharged on a fire within the structure. Sprinkler heads are mounted on the piping network and positioned throughout the structure, the sprinkler heads opening in response to a fire event to effect the water discharge. The piping network is connected to a source of pressurized water. Flow of water from the source to the network is controlled by a valve. 
     One characteristic which may be used to distinguish fire suppression sprinkler systems from one another is whether the system is a “wet” system or a “dry” system. In a wet system, pressurized water is present throughout the piping network when the system is in the ready state. The water is prevented from being discharged by the sprinkler heads themselves, which remain closed unless a fire event is detected. Once a fire occurs, the sprinkler heads in the vicinity of the fire open and immediately discharge water onto the fire. The valve which controls water flow from the source to the sprinkler heads opens in response to the demand for water flow. 
     In contrast, a compressed gas, typically compressed air, fills the piping network in a dry system when the system is in the ready state. The valve which controls the flow of water to the sprinkler heads is held closed and prevents water from entering the piping network until a fire event is detected. The valve is controlled by a system actuator which is capable of sensing a drop in the air pressure within the piping network occasioned, for example, when a sprinkler head opens in response to a fire event. When the sprinkler head opens, it discharges compressed air from the network, causing the air pressure to drop within the piping network. The system actuator senses the pressure drop and opens the valve, which allows water to flow into the piping network. The water displaces the air in the system and eventually reaches the open sprinkler head, which discharges the water onto the fire. Latched clapper valves are advantageous but high air pressure in conjunction with a low differential clapper design are also feasible. 
     Wet systems are preferred unless freezing environments are expected. Water is immediately available at the sprinkler heads for discharge as soon as one or more heads opens, thus providing rapid response to suppress a fast spreading fire. Dry systems are used when the piping network is subjected to temperatures that are below the freezing point of the water or other liquid used to suppress the fire. This may occur, for example, in an unheated structure, such as a warehouse located in a temperate zone where the ambient temperature varies seasonally below freezing for extended periods. 
     The valves used in the wet system to control the flow of water from the source to the network are different from those used in the dry system. Wet system valves act as check valves and open in response to a demand for water flow, but close automatically when demand for flow ceases. In contrast, dry system valves are held closed and are opened by a system actuator that responds to one or more indications of a fire event, for example, loss of air pressure in the piping network. The valve may also be actuated directly by a pressure differential. 
     It is often desirable to have the option to operate a sprinkler system in either the wet or the dry mode as a particular situation demands. This would be advantageous, for example, in unheated warehouses in cold climates to permit faster water delivery during warm periods. Furthermore, it may also be desired to readily convert a system from the wet to the dry mode or vice versa. This would be advantageous, for example, if the use to which the structure in which the sprinkler system is positioned changes. The prior art practice for effecting such multi-mode systems is to install both a wet system valve and a dry system valve, and all of their appurtenant auxiliary valves and components, in series with one another between the water source and the piping network. Then, depending upon which sprinkler system is desired, the appropriate valves and their associated components and auxiliary valves are used, and the valves associated with the other system are bypassed or otherwise opened or closed as required to isolate them. Using two valves and all of their associated components is complex and expensive however. There is clearly a need for an alternative which allows a sprinkler system to readily be converted from wet to dry mode and back again as required in response to a particular demand. 
     SUMMARY OF THE INVENTION 
     The invention concerns a valve for controlling fluid flow. The valve comprises a chamber having an inlet and an outlet. A seat is positioned within the chamber downstream of the inlet. A closing member is positioned within the chamber and is movable into and out of engagement with the seat to control fluid flow through the chamber. A latch is positioned within the chamber. The latch is movable between a first position engaging the closing member for maintaining the closing member in engagement with the seat, and a second position disengaged from the closing member and allowing the closing member to move out of engagement with the seat. A latch actuator is mounted on the valve and is engaged with the latch for moving the latch between the first and second positions. A bypass loop is connected to providing fluid communication between the inlet upstream of the seat and the chamber downstream of the seat. A bypass valve is positioned within the bypass loop. The valve is openable and closeable for controlling the flow of fluid through the bypass loop. 
     The valve according to the invention may also comprise a gas conduit in fluid communication with the chamber downstream of the seat, and a gas control valve positioned within the gas conduit for controlling flow of gas to the chamber. 
     The invention also includes a fire suppression sprinkler system convertible for use as a wet system or a dry system. The sprinkler system comprises a source of pressurized liquid and a piping network in fluid communication with the liquid source. A plurality of sprinkler heads are mounted on the piping network for discharging the liquid in the event of a fire. A first valve is positioned in the piping network between the liquid source and the sprinkler heads for controlling flow of the liquid thereto. A bypass loop is connected to provide fluid communication between a point upstream of the first valve and downstream thereof. A bypass valve is positioned in the bypass loop for controlling flow of the liquid therethrough. The system further includes a source of pressurized gas and a gas conduit providing fluid communication between the gas source and the piping network downstream of the first valve. A gas control valve is positioned within the gas conduit. A system actuator is in fluid communication with the gas source as well as the liquid source and the first valve. The system actuator opens the first valve in response to a drop in gas pressure within the piping network when the system is operated as a dry system. However, the first valve opens in response to flow from at least one of the sprinkler heads when the system is operated as a wet system. 
     The invention also encompasses a method of converting a fire suppression sprinkler system for use as a wet system or a dry system. The method comprises:
         (a) providing a source of pressurized liquid;
           (b) providing a piping network in fluid communication with the liquid source;   (c) providing a plurality of sprinkler heads mounted on the piping network for discharging the liquid in the event of a fire;   (d) providing a first valve positioned in the piping network between the liquid source and the sprinkler heads for controlling flow of the liquid thereto;   (e) providing a bypass loop for fluid communication between a point upstream of the first valve and downstream thereof, a bypass valve being positioned in the bypass loop for controlling flow of the liquid therethrough;   (f) opening the bypass valve to convert the system into a wet system;   (g) closing the bypass valve to convert the system into a dry system;   (h) providing a source of pressurized gas;   (i) providing a gas conduit for fluid communication between the gas source and the piping network downstream of the first valve, a gas control valve being positioned within the gas conduit;   (j) opening the gas control valve to convert the system into a dry system;   (k) closing the gas control valve to convert the system into a wet system;   (l) providing a system actuator in fluid communication with the gas source, the liquid source and the first valve;   (m) providing a shut-off valve between the liquid source and the system actuator;   (n) opening the shut-off valve to convert the system to a dry system; and   (o) closing the shut-off valve to convert the system to a wet system.   
               

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a field convertible sprinkler system according to the invention; 
         FIG. 2  is a right front side perspective view of a field convertible valve according to the invention; 
         FIG. 3  is a left rear side perspective view of a field convertible valve according to the invention; 
         FIG. 4  is a longitudinal sectional view of one type of field convertible valve according to the invention; 
         FIG. 5  is a longitudinal sectional view of a field convertible valve configured to operate in a dry system mode; and 
         FIG. 6  is a longitudinal sectional view of a field convertible valve configured to operate in a wet system mode. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  shows, in schematic form, a convertible fire suppression sprinkler system  10  according to the invention. System  10  includes a piping network  12  having a plurality of sprinkler heads  14  mounted thereon. The network extends throughout a structure such as a building, warehouse, industrial complex or other facility needing fire protection. The sprinkler heads are not shown in detail, because virtually any type of sprinkler head is feasible with the system. The heads open in the event of a fire to discharge a fire suppressing fluid, typically water, to extinguish and prevent the spread of fire throughout the facility. 
     Piping network  12  is in fluid communication with a pressurized source of water  16  which supplies the fire suppressing fluid discharged from the sprinkler heads during a fire. Flow of water to the network is controlled by a valve  18 , for example, a butterfly valve, which is positioned so that it may be used to isolate the entire system for repair or replacement of components. A field convertible valve  20  according to the invention is located downstream of and in series with the butterfly valve  18 . The field convertible valve and its associated trim valves, described in detail below, allow the system  10  to be easily converted from a wet system to a dry system and vice versa. 
     A bypass loop  22  affords fluid communication around the convertible valve  10 . Two valves are positioned in the bypass loop, a check valve  24  and a bypass valve  26  such as a ball valve which may be opened or closed as desired. Bypass valve  26  is one of the trim valves used to convert between a wet and dry system, explained in detail below. 
     A compressed gas conduit  28  is in fluid communication with the piping network  12  upstream of the convertible valve  20 . The gas conduit is in fluid communication with a source of compressed gas  30 , for example, a compressor or compressed gas tanks, which supply the compressed gas to the system when it is used in the dry mode of operation. Two valves are positioned within gas conduit  28 , a check valve  32  and a gas control valve  34 . Check valve  32  is designed to allow air to flow in both directions through the conduit but will prevent the flow of water toward the gas control valve  34 . The check valve  32  is used to prevent water from contaminating components, such as the air compressor, associated with the dry mode operation of the system. Gas control valve  34  is another of the trim valves associated with convertible valve  20  used to convert between the wet and the dry modes of operation of the system  10 . A pressure detecting device  36  may also be used on the gas conduit  28 . Such devices are well known and include air pressure switches such as the EPS 40-2 marketed by System Sensor of St. Charles, Ill. 
     A system actuator  38  is also in fluid communication with the gas conduit  28 . System actuator  38  controls the operation of convertible valve  20  when the system is operated in the dry mode. To effect this control, the system actuator is in communication with the convertible valve  20  through a water conduit  40 . The system actuator is also in communication with the pressurized water supply  16  through another water conduit  42 . A shut-off valve  44  is positioned in water conduit  42  and constitutes yet another trim valve used to convert the system between the different modes of operation. 
     When the system is operated in the dry mode, control of the convertible valve  20  is effected hydraulically by the system actuator  38  as described below. There are various system actuator designs, for example, those sold by Victaulic Company such as the model 776 or 753A. Operational and structural details of various system actuators may be found in U.S. Pat. Nos. 6,293,348, 6,536,533, 6,666,277 and 6,708,771, hereby incorporated by reference herein. The system actuator  38  may also be used in conjunction with an accelerator as described in U.S. Pat. No. 6,752,217, hereby incorporated by reference herein. 
     Sprinkler systems may have equipment to allow a test of the system functionality. The test equipment comprises a test valve  46  that is in fluid communication with the piping network  12  between the butterfly valve  18  and the convertible valve  20 . The test valve  46  is in fluid communication with two conduit test branches, the wet mode branch  48  and the dry mode branch  50 . Both branches may share a common flow sensor  52  which generates a signal when water is flowing through either of the branches. A wet mode test valve  54  is located in the wet mode branch  48 . A flow restrictor device  56 , such as an orifice plate is located downstream of the wet mode test valve. The wet mode branch vents into the drain piping  45  of the system. A dry mode test valve  58  is positioned in the dry mode branch  50 . The dry mode test valve also vents to the system drain  45 . Both the dry and wet modes are in fluid communication with an alarm  60 , such as a water motor alarm, which is activated during system testing as described in detail below. 
     Sprinkler System Operation 
     With reference to  FIG. 1 , the sprinkler system  10  may be configured for dry mode operation by closing the bypass valve  26 , opening the shut-off valve  44  to charge the actuator  38 , opening the gas control valve  34 , closing the wet mode test valve  54 , opening the dry mode test valve  58 , latching the field convertible valve  20  in the closed position, setting the system actuator  38  into its ready mode and charging the system actuator and the piping network  12  with compressed air from the source  30  through the compressed air conduit  28 . The butterfly valve  18  is opened to provide water to the system from the source  16 , the water charging the field convertible valve  20  and the system actuator  38  with hydraulic pressure through water conduits  40  and  42 . 
     When a fire event is detected, one or more of the sprinkler heads  14  open, venting compressed air from the piping network  12 . The resultant drop in air pressure within the system is detected by the system actuator  38  because it is in fluid communication with the network though compressed air conduit  28 . (Compressed air from the source  30  cannot be supplied at a rate which will compensate for the drop in pressure due to opening of one or more sprinkler heads.) In response to the pressure drop in the piping network  12 , the system actuator  38  vents the water conduit  40 ,  42  to the system drain  45 . This reduces the hydraulic pressure within water conduit  40 , which releases a latch mechanism (described below) within the field convertible valve  20 . (Again, the system is designed so that water cannot be supplied from the source  16  through water conduit  42  at a rate sufficient to compensate for the reduction in hydraulic pressure within water conduits  40  and  42  occasioned by the action of system actuator  38 .) Release of the latch mechanism allows the field convertible valve  20  to open in response to upstream pressure, thereby allowing water to flow from the pressurized source  16  through the piping network  12  to be discharged by the open sprinkler head or heads  14 . 
     To test the system  11  when it is set to operate in the dry mode and in the ready condition (i.e., gas conduit  28 , system actuator  38  and piping network  12  charged with compressed air, field convertible valve  20  latched and under hydraulic pressure by system actuator  38 ), the test valve  46  is opened allowing water to flow through the dry mode test branch  50  (the wet mode test valve  54  being closed) and to the water motor alarm  60 . Water that flows through the dry mode test valve  58  is vented to the system drain  45 . 
     To configure the system  10  for wet mode operation, the bypass valve  26  is opened, the shut-off valve  44  is closed, the gas control valve  34  is closed, the dry mode test valve  58  is closed and the wet mode test valve  54  is opened. The latching mechanism of the field convertible valve  20  is not engaged, allowing the valve to operate as a check valve and open in response to a demand for water when a sprinkler head opens. Closing the gas control valve isolates the piping network  12  from the compressed gas source  30 , thereby allowing the piping network to be charged with water. Closing the shut-off valve  44  isolates the system actuator  38 , rendering it ineffective as it does not control opening of the field convertible valve  20  during wet mode operation. 
     With the opening of the bypass valve  26  the bypass loop  22  is able to allow upstream pressure surges to go around the field convertible valve  20  without opening it. This is advantageous because the valve  20  is connected to an alarm, for example, water motor alarm  60 , which is tripped when the valve opens to supply water to the piping network. Regulations require that false alarms caused by transient events such as pressure surges be avoided. To that end, the bypass loop is designed to allow flows less than about 4 gallons per minute, i.e., the valve will not open for flows under 4 gallons per minute, as such flows are not indicative of a fire event. However, the system must trigger an alarm anywhere within the range between about 4 gallons per minute and about 20 gallons per minute as such flows will be indicative of a fire event depending upon the water pressure at which the system is operated. The higher the system pressure the larger the flow required before sufficient pressure differential across the valve required to open the valve is reached. 
     In the wet ready mode, with the field convertible valve  20  closed, the butterfly valve  18  open and the piping network  12  charged with water, a fire event will cause one or more of the sprinkler heads to open, immediately discharging water onto the fire. This causes a drop in water pressure within the piping network. The flow rate demanded is greater than the bypass loop  22  can supply, and the resulting higher water pressure upstream causes the field convertible valve  20  to open, supplying water to the sprinkler heads and triggering water motor alarm  60 . 
     For testing in the wet ready mode, the test valve  46  is opened. Water flows through the wet mode test branch  48  where it encounters a flow restrictor, such as orifice  56 . The flow restrictor is designed to allow a build up of pressure within the wet mode test branch so that water will flow to the water motor alarm  60 , which provides a signal indicative of the system status. Water from the wet mode test branch is discharged into the system drain  45 . 
       FIG. 2  shows an example of a field convertible valve  20  according to the invention. Valve  20  comprises a chamber  62  which houses a closing member and latching mechanism described below. The chamber may have an access port  64  closed by a removable plate  66  to allow repairs to be effected. The chamber has in inlet  68  connectable to the pressurized water source  16  and an outlet  70  that is connectable to the piping network  12  as shown in  FIG. 1 . 
     With reference again to  FIG. 2 , the detailed configuration of the bypass loop  22  is illustrated. Bypass loop  22  provides fluid communication between the upstream and downstream sides of a seat  72  (see, for example,  FIG. 4 ), allowing the valve seat and its closing member  74  (described below) to be circumvented in wet mode operation. As shown in  FIG. 2 , bypass loop  22  has two valves controlling flow through it, the bypass valve  26  and the check valve  24 . As noted, the bypass valve  26  is opened when the field convertible valve  20  is operated in the wet mode, and closed to convert the valve  20  into the dry mode of operation. Check valve  24  prevents backflow of water from the piping network during wet mode operation of the system. This is advantageous because with variable water supplies the check valve allows transient water flux pressure to be trapped and contained in the system downstream of the valve. 
       FIG. 3  shows details of the connection of the gas conduit  28  to the field convertible valve  20 . Conduit  28  is in fluid communication with the chamber  62  downstream of the valve seat. The gas conduit also has two valves that control flow through it, the gas control valve  34  and the check valve  32 . As noted above, the gas control valve  34  is open during dry mode operation and closed to convert the valve  20  and system  10  to wet mode operation. The check valve  32  is preferably a water only check valve in that it is configured to allow gas to pass freely in either direction but will prevent water from flowing from the valve  20  toward the pressurized gas source  30 . Use of this check valve is advantageous to avoid water contamination of the system actuator  38  and the source of compressed gas  30 , which could be a compressor for example. The gas conduit  28  is connected with the system actuator  38 , and the system actuator is connected with the convertible valve  20  through the water conduit  40  as well as to the source of pressurized water  16  through the water conduit  42 . 
       FIG. 4  shows a sectional view of one example of a field convertible valve  20 , illustrating the aforementioned valve seat  72  positioned within the chamber  62  downstream of the inlet  68 . The valve closing member  74  associated with the seat is pivotally mounted within the chamber and is movable into and out of engagement with the seat to effect opening and closing of the valve. 
     The connection of the system actuator with the valve  20  affords fluid communication between the system actuator  38  and a latch actuator  76  best shown in  FIG. 4 . In this valve embodiment, the latch actuator  76  comprises a cylinder  78  that houses a piston  80  reciprocably movable within the cylinder in response to hydraulic pressure controlled by the system actuator  38  through water conduit  40 . A piston rod  82  has a first end attached to the piston and an opposite end that extends into chamber  62  where it engages a latch  84  that is pivotably mounted within the chamber. When the field convertible valve  20  is used in the dry mode, latch  84  engages the valve closing member  74  to hold it in the closed position until the latch is released. The latch is released by a drop in hydraulic pressure within the cylinder  78 . The hydraulic pressure drop is caused by the system actuator  38  reacting to a gas pressure drop within the piping network. The gas pressure drop is cause by a sprinkler head opening in response to a fire. A biasing spring  86  is positioned within the cylinder  78  to withdraw the piston rod  82  from engagement with the latch  84  when the hydraulic pressure drops in the cylinder. With the latch free to pivot, the upstream pressure acting on the valve closing member  74  can open the valve  20  by pivoting the valve closing member, permitting water flow to the piping network  12 . 
     When the field convertible valve  20  is operated in the wet mode, the cylinder  78  is isolated from the hydraulic pressure of the source  16  by the closure of shut-off valve  44  (see  FIG. 1 ) and the latch actuator is  76  is rendered non-functional. This allows the valve closing member to open in response to pressure changes within the chamber  62  as a result of a sprinkler head opening. When operated in the wet mode, the latch  84  may be biased away from the valve closing member by a biasing spring  88  so as not to interfere with the operation of the valve. 
     Note that there is a port  90  on the valve  20  which is in fluid communication with the chamber  62  through an opening  92  in the valve seat  72 . When the valve closing member  74  pivots and disengages from the seat, the opening  92  is exposed. This allows water to flow out of the valve through the port, which is in fluid communication with the water motor alarm  60 . In this manner, when used in the wet mode, an alarm is activated when the valve  20  opens. 
       FIGS. 5 and 6  illustrate another embodiment of a field convertible valve  20  according to the invention. Valve  20  of  FIG. 5  differs in the type of latch actuator used. In this embodiment, the latch actuator  76  used in the dry mode of operation comprises a sub-chamber  94  positioned adjacent to the valve chamber  62 . A flexible diaphragm  96  partitions the sub-chamber from the valve chamber. The diaphragm is attached to the pivoting latch  84  which engages the valve closing member  74  when the valve is operated in the dry mode. Hydraulic pressure within the sub-chamber  94  acting on the diaphragm  96  through the water conduit  40  maintains the latch  84  engaged with the valve closing member  74 , thereby keeping the valve closing member engaged with the valve seat. When this hydraulic pressure is relieved by action of the system actuator  38 , the latch  84  is free to pivot and allow the valve closing member to disengage from the seat, opening the valve  20  as illustrated in  FIG. 6 . Latch  84  may have a biasing spring  98  which biases it away from the valve closing member to facilitate valve opening. 
     When operated in the wet mode, the field convertible valve  20  shown in  FIGS. 5 and 6  is isolated from the compressed gas supply by the closing of gas control valve  34 . The latch actuator  76  is isolated from the pressurized water source  16  by closing the shut-off valve  44 . The system actuator  38  does not control opening of the valve  20 , which is free to open in response to a pressure difference between the upstream and downstream sides of the valve seat. The latch  84  is biased away from the valve closing member  74  to allow free pivoting motion to open and close the valve. Again, there is a port  90  and an opening  92  positioned within the valve seat and closed by the valve closing member. When the valve closing member opens, it uncovers the opening  92  and permits water to flow through port  90  which is in fluid communication with a water motor alarm which signals the opening of the field convertible valve  20 . 
     The system  10  may also include a temperature sensor  100  (see  FIG. 1 ) that warns system operators of the approach of freezing temperatures. The temperature sensor may be mounted in the building or structure where the piping network extends and could trip an alarm or provide a signal to a control panel warning when temperatures drop below a threshold above freezing to give adequate warning to convert the system from a wet to a dry system. 
     Field convertible valves according to the invention provide an efficient way to change the mode of operation of a sprinkler system from a wet mode to a dry mode and vice-versa without duplicating parts or extensive replacement of major system components.