Dry pipe valve for fire protection sprinkler system

A differential-type dry pipe valve for a fire protection sprinkler system has a ratio of effective air sealing area to service water sealing area that is smaller than a ratio of service water pressure to system air pressure at which the fire protection sprinkler system is actuated.

TECHNICAL FIELD

This invention relates to dry pipe automatic fire protection sprinkler systems.

BACKGROUND

Dry pipe automatic fire protection sprinkler systems are typically employed for the purpose of providing automatic sprinkler protection in unheated occupancies and structures that may be exposed to freezing temperatures. The dry pipe sprinkler system is connected to a public or private water main providing a reliable supply of water, and typically includes an indicating type of water flow valve, e.g. a water gong or other alarm flow valve, a fire department connection and a dry pipe valve. The dry pipe system is used primarily in unheated warehouses and the like where water-filled pipes cannot be used, so the dry pipe valve must be protected against freezing by locating it in a heated portion of the structure, e.g. in the warehouse office or in a heated enclosure provided for the purpose, to protect the dry pipe valve from freezing.

The sprinkler portion of a dry pipe sprinkler system has an arrangement of piping similar to a wet pipe sprinkler system. However, rather than water, the dry pipe sprinkler system contains air or nitrogen under pressure above the dry pipe valve. The air pressure restrains the water in the supply main at the dry pipe valve by holding the valve in closed position until one or more sprinklers open, e.g., in the presence of fire. The loss of air pressure allows the dry pipe valve to open, permitting flow of water through the valve into the arrangement of piping and on to the open sprinkler at the location of a fire.

Many dry pipe valves are of the differential-type, single clapper construction. These center differential pressure valves are designed with a dry system seat and a water supply seat concentrically located with their axes at an equal distance from the center of the clapper hinge pin. As seen from the following equation, the differential ratio is the relationship of the air seat area divided by the water seat area:
DF=(AD/WD)2*L2/L1
AD=√{square root over (DF*WD2)}
where:AD=system (air) valve seat mean diameterWD=supply (water) seat mean diameterDF=differential, i.e., the ratio between the system water pressure and system air pressure (where 5.5 to 6.0 is the industry standard)L1=distance between the center of the hinge or pivot and the center of air pressure (i.e., the air valve seat axis)L2=distance between the center of the hinge or pivot and the center of water pressure (i.e., the water valve seat axis)

In the case of a typical ratio of 5.5 (the industry standard), a 6-inch diameter water supply thus requires a 14-inch diameter air valve seat. This valve design is very reliable and made from relatively few parts; however, this relationship also results in a valve that is relatively large and heavy, and therefore difficult to install. An alternative design for achieving a relatively lower weight is a mechanical latching dry valve. This type of dry pipe valve is relatively smaller in size, but it requires more components, and it is often more difficult to maintain because of the relatively greater number of parts located within its auxiliary chamber.

SUMMARY

According to one aspect of the invention, a differential-type dry pipe valve for a fire protection sprinkler system has a ratio of effective air sealing area to service water sealing area that is smaller than a ratio of service water pressure to system air pressure at which the fire protection sprinkler system is actuated.

According to another aspect of the invention, a dry pipe valve for a fire protection sprinkler system has a water valve seat and an air valve seat, the water valve seat being off-center relative to said air valve seat.

According to still another aspect of the invention, a differential-type dry pipe valve for a fire protection sprinkler system comprises a valve body defining an inlet and an outlet, a water-side chamber in communication with the inlet and an air-side chamber in communication with the outlet, and, therebetween, an air valve seat having an air valve axis and a water valve seat having a water valve axis. A clapper is mounted to pivot about a pivot axis closely adjacent the air valve seat between a first, clapper-closed position for resisting flow of water through the water valve seat and a second, clapper-open position for permitting flow of water through the water valve seat toward the air-side chamber. An air valve seal is mounted for sealing engagement with the air valve seat with the clapper in the first, clapper-closed position, and a water valve seal is mounted for sealing engagement with the water valve seat with the clapper in the first, clapper-closed position. In one embodiment, the air valve seat is centered a first radial distance from the pivot axis and the water valve seat is spaced a second radial distance from the pivot axis, the first radial distance being greater than the second radial distance. In another embodiment, the air valve seat and the water valve seat are asymmetrically arranged.

Preferred embodiments of this aspect of the invention may include one or more of the following additional features. The clapper is held in the first, clapper-closed position by air pressure maintained in the air-side chamber and the fire protection sprinkler system, and the clapper is urged from the first, clapper-closed position toward the second, clapper-open position by water pressure from the water-side chamber upon reduction of air pressure in the air-side chamber and the fire protection sprinkler system. Preferably, reduction of air pressure in the air-side chamber and fire protection sprinkler system results from opening of one or more fire protection sprinklers of the fire protection sprinkler system. The air valve seal and/or the water valve seal is mounted to the clapper. The dry pipe valve further comprises a latch member adapted, in a first latch member position, to permit movement of the clapper from its first, clapper-closed position toward its second, clapper-open position and to resist return movement of the clapper from its second, clapper-open position toward its first, clapper-closed position. Preferably, the latch member is mounted to the body for movement between the first latch member position resisting return movement of the clapper toward its first, clapper-closed position and a second latch member position permitting return movement of the clapper from its second, clapper-open position toward its first, clapper-closed position. More preferably, the latch member comprises an actuator disposed outside the body for movement of the latch member from the first latch member position resisting return movement of the clapper toward its first, clapper-closed position toward the second latch member position permitting return movement of the clapper toward its first, clapper-closed position. The air valve seal has a first surface disposed for sealing engagement with the air valve seat and an opposite, second surface exposed for application of sealing pressure to the air valve seal upon the air valve seat. The water valve seal has a first surface disposed for sealing engagement with the water valve seat and an opposite, second surface exposed for application of sealing pressure to the water valve seal upon the water valve seat. The dry pipe valve comprises a single clapper. The clapper, in its first, clapper-closed position, defines an atmospheric region generally between the air valve seat and the water valve seat. Preferably, the atmospheric region defined by the clapper generally between the air valve seat and the water valve seat is asymmetrical about the air valve axis. The first radial distance of the air valve seat center from the pivot axis is less than about 1.8 times the second radial distance of the water valve seat center from the pivot axis.

Objectives of the invention include providing a dry pipe valve of simple construction, with few moving parts, compact size, and lighter weight, compared to prior art dry pipe valves of similar specification.

DETAILED DESCRIPTION

Referring toFIGS. 1–5, a differential-type dry pipe valve10of the invention, for use in an automatic fire protection sprinkler system, has a body12defining an inlet14and an outlet16, and a valve access port18(FIG. 4) secured by a cover20. The body12further defines a water-side chamber22in communication with inlet14, and an air-side chamber24in communication with the outlet16. Referring also toFIGS. 6–9, a seat body28, defining a passageway27surrounded by an air valve seat30and a water valve seat32, is disposed in an aperture26defined by the body12between the water-side chamber22and the air-side chamber24. Referring in addition toFIGS. 10–14, a single clapper34is mounted between ears36,37of the seat body28to pivot about an axis, C (FIG. 2), which is closely adjacent and tangential to the air valve seat30. Referring finally toFIGS. 15–19andFIGS. 20–23, a clapper diaphragm38, mounted to the clapper34by clapper diaphragm retaining plate39, defines an air valve seal40and a water valve seal42. In closed position of the clapper34, the surface41of air valve seal40sealingly engages upon the air valve seat30, and the surface43of water valve seal42engages sealingly upon the water valve seat32, both in a water-tight manner, to resist leakage of water from the water-side chamber22toward the air-side chamber24. The region44cooperatively defined by the seat body28and the clapper diaphragm retaining plate39, generally between the air valve seat30and seal40and the water valve seat32and seal42, is maintained at ambient pressure, and water leakage past water valve seat32and seal42is released through drain port46.

Referring now in particular toFIGS. 7 and 16, in the differential-type dry pipe valve10of the invention, the axis, W, of the supply (water) pressure (i.e., the axis of the water valve seat32and water valve seal42) is positioned relatively closer to the pivot axis, C, of the clapper, as compared to the center axis, A, of the system (air) pressure (i.e. the axis of the air valve seat30and air valve seal32). The setback of the pivot, C, from the air valve seat30is also reduced. This arrangement provides a mechanical advantage to the system (air) pressure due to the non-concentric locations of the dry system seat30and the water supply seat32, and the resulting force from the hinge connection of the seating body28and clapper assembly56helping to hold the clapper34and clapper diaphragm38in sealing engagement against the seats. As a result of this construction, with the water valve seat32off-center from the air valve seat30, the differential of system water pressure to system air pressure at which the dry pipe valve10of the invention operates (i.e., opens) can be maintained within the industry standard of 5.5 (+/−0.3) with a dry pipe valve having a significantly smaller clapper and valve, as compared to prior art differential-type dry pipe valves of corresponding specification, e.g. weight reduction of up to 50% has been achieved in dry pipe valves10of the invention.

As seen in the following equations, for a 6-inch diameter valve, the diameter of the air valve seat30is reduced to 10.6 inches, as compared to 14 inches according to the prior art concentric seat designs:
DF=(AD/WD)2*L2/L1
AD=√{square root over (DF*WD2*L2/L1)}
WD=6; DF=5.5; L2=3;L1=AD/2
AD=√{square root over (DF*WD2*3/(AD/2))}
AD=3√{square root over (5.5*62*6)}
AD=10.6 inches
The result is a differential-type dry pipe valve for a fire protection sprinkler system of advantageous construction in which the ratio of effective air sealing area to service water sealing area is smaller than the ratio of service water pressure to system air pressure at which the fire protection sprinkler system is actuated.

Referring again toFIG. 2, as the clapper34moves from its closed position towards its open position, e.g. upon reduction of air pressure in the air-side chamber24due to opening of one or more sprinkler heads in response to a fire condition, pivot arm50associated with latch assembly52is deflected upward by the clapper34, allowing the clapper to pass. The pivot arm50then rotates back toward its initial position (e.g., under force of gravity) to engage with the underside of the clapper assembly56(i.e., clapper34and retaining plate39, with diaphragm38secured therebetween) to hold the valve open for flow of water into the system of fire sprinkler piping, e.g. as shown inFIG. 2). When the fire situation is secured, water flow to the dry pipe valve10is discontinued. The clapper assembly56, including the clapper34, can then be allowed to return to its closed position, with the seals40,42of the clapper diaphragm38disposed in sealing engagement with the seats30,32of the seat casting28, by applying downward pressure to the actuator53of clapper latch assembly52located outside the body12, overcoming the force (arrow, S) of spring54, to rotate the pivot arm50(arrow, P) to clear the outer end of the clapper assembly56, allowing it to fall back toward the closed position. The spring54then returns the clapper latch assembly52, and pivot arm50returns by gravity, to the respective standby positions.

Referring now in particular toFIGS. 18 and 19, the air valve seal40and the water valve seal42defined by the clapper diaphragm38are configured at rest with self-sealing, self-aligning, flexible cantilevered lips60,62, respectively. The seal lips have first surfaces41,43, respectively, deflected by engagement upon the corresponding seat30,32, and opposite, second surfaces61,63exposed for application of seal-assisting pressure. In the case of the water valve seal42, pressure is applied upon surface63by water in the water-side chamber22, and in the case of the air seal40, pressure is applied upon surface61by air or by water in the air-side chamber24, to facilitate sealing. The clapper diaphragm38is typically formed of a soft rubber or polymeric material, e.g. EPDM, having a durometer of about 60 to 70. Where this relatively soft seal material is employed, the clapper34is typically provided with an outer lip surface70(FIG. 16) for supporting the air valve seal40against extrusion or leakage under pressure. The surface70may be smoothly curved or stepped, or where the clapper diaphragm is formed of a relatively harder material, it may be found unnecessary.

Referring now toFIG. 24, a typical dry pipe fire protection sprinkler system100equipped with a differential-type dry pipe valve10of the invention will now be described. A dry pipe fire protection sprinkler system100is typically employed for protection of a warehouse or other structure102located in a geographical region subject to temperatures below freezing and having unheated areas104that must be protected against fire. The system100is connected to a reliable external source of water, e.g. a city main106, through a fire main108, riser110, and check valve112. The dry pipe valve10is preferably located within an enclosure113provided with heat, or in a heated office area114, to protect against freezing. The dry pipe valve outlet16is connected to a system of piping116, with spaced fire sprinkler heads118,119extending throughout the structure102.

To protect against freezing, the portions of the system of piping within at least the unheated portion of the structure are filled with air or other gas, e.g., nitrogen, under sufficient pressure to maintain the dry pipe valve10in closed position against the water supply pressure, as discussed above. In the presence of a fire condition, one or more of the sprinklers118,119is caused to open automatically in response to local fire temperature. The resulting reduction of air pressure within the system of piping (and within the air-side chamber of the dry pipe valve) allows the dry pipe valve to open, permitting flow of water through the system of piping to the open sprinkler(s)118,119. A water motor gong122mounted to an outer wall of the structure provides an external notice of flow of water to the sprinklers.

Once the fire has been extinguished, water flow into the fire protection system100is discontinued, e.g. at post indicator valve120. The clapper assembly56in dry pipe valve10is then allowed to return to its closed position by depressing actuator53of latch assembly52to rotate pivot arm50and release the clapper assembly. After any open sprinkler has been replaced, the system of piping116is recharged, and water flow to the inlet14of the dry pipe valve10is restored.

A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, referring toFIGS. 1 and 2, the body12defines a water inlet port48that permits a predetermined volume of water to be delivered into the air-side chamber24to cover the clapper34. This priming has, in the past, been found advantageous for facilitating sealing and lubrication of the air valve seal40, but may not be necessary in all instances, e.g., due to improvements in formulation of sealing materials.