Fire extinguishers – Fluid systems – Distributing systems
Reexamination Certificate
2002-09-12
2004-06-22
Hwu, Davis (Department: 3752)
Fire extinguishers
Fluid systems
Distributing systems
C169S016000, C169S018000, C169S022000, C169S042000
Reexamination Certificate
active
06752217
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an accelerator for use in a dry, pressurized-gas, liquid extinguent sprinkler fire control and suppression system. The dry accelerator of the present invention is applicable for use in a dry type fire control and suppression sprinkler system, in which the piping between the source of the pressurized liquid extinguent, typically water, and individual sprinkler heads is normally pressurized with a gas, typically air, and is void of liquid until the system becomes actuated. The dry accelerator of the present invention is utilizable for all dry type sprinkler systems regardless of system operating gas pressure.
BACKGROUND OF THE INVENTION
Fire control and suppression sprinkler systems generally include a plurality of individual sprinkler heads which are usually ceiling mounted about the area to be protected. The sprinkler heads are normally maintained in a closed condition and include a thermally responsive sensing member to determine when a fire condition has occurred. Upon actuation of the thermally responsive member, the sprinkler head is opened, permitting pressurized water at each of the individual sprinkler heads to freely flow therethrough for extinguishing the fire. The individual sprinkler heads are spaced apart from each other by distances determined by the type of protection they are intended to provide (e.g., light or ordinary hazard conditions) and the ratings of the individual sprinklers, as determined by industry accepted rating agencies such as Underwriters Laboratories, Inc., Factory Mutual Research Corp. and/or the National Fire Protection Association. It should be well appreciated that once the sprinkler heads have been thermally activated there should be minimal delay for the water flow through the sprinkler head at its maximum intended volume.
In order to minimize the delay between thermal actuation and proper dispensing of water by the sprinkler head, the piping that connects the sprinkler heads to the water source is, in many instances, at all times filled with water. This is known as a wet system, with the water being immediately available at the sprinkler head upon its thermal actuation. However, there are many situations in which the sprinkler system is installed in an unheated area, such as warehouses. In those situations, if a wet system is used, and in particular, since the water is not flowing within the piping system over long periods of time, there is a danger of the water within the pipes freezing. This will not only deleteriously affect the operation of the sprinkler system should the sprinkler heads be thermally actuated while there may be ice blockage within the pipes but, such freezing, if extensive, can result in the bursting of the pipes, thereby destroying the sprinkler system. Accordingly, in those situations, it is the conventional practice to have the piping devoid of any water during its non-activated condition. This is known as a dry fire protection system.
While all fire protection sprinkler systems generally include a check valve for isolating the sprinkler system piping from the pressurized water source during the non-activated condition, the design of such check valves for a dry type fire control sprinkler system has presented various problems. The check valve, which is interposed between the system piping and pressurized water source, includes a clapper which, when it is in its closed operative condition, prevents the flow of the pressurized water into the sprinkler system piping. The sprinkler piping in the dry fire protection system normally contains air or some other inert gas-(e.g., nitrogen) under pressure. The pressurized air, which is also present within the sprinkler system piping, is presented to the check valve. Should one or more of the sprinkler heads be thermally activated to its open condition, the pressure of the air within the sprinkler system piping and check valve will then drop. The check valve must be appropriately responsive to this drop in pressure, normally in opposition to the system water pressure also present in the check valve, to move the clapper to its open condition. When this occurs, it is desirable to have a rapid expulsion of the pressurized air within the check valve and the sprinkler system piping to permit the rapid flow of the pressurized water through the open check valve into the sprinkler system piping and through the individual sprinkler heads to rapidly extinguish the fire.
The check valves intended for dry-type fire control sprinkler systems have typically controlled the clapper movement by the water and the air pressure applied to its opposite sides. Such fire check valves include an air seal which opposes the pressurized water seal. To appropriately apply the system air pressure over the surface of the clapper air seal, a priming water level is oftentimes maintained within the check valve. During normal conditions, when no sprinkler heads have been activated, the two seals will be at an equilibrium, thereby maintaining the clapper in its closed condition.
In order to increase the speed of check valve operation upon a drop off of the system air pressure, occasioned by the activation of one or more sprinkler heads, the system air pressure is normally applied to the clapper air seal over a substantially greater area than the water pressure is applied to the clapper water seal. This is known as a high differential type check valve. A problem of such valves is that should there be a reduction in the system water pressure after the clapper has opened, there is a tendency for the clapper to re-close, particularly since the pressure against the opposite (air) side of the clapper has thereby been increased due to the column of water that has flowed therethrough. Since the pressure applied against the air seal of the clapper will now be increased by the column of water extending upwards from the re-closed check valve, a greater water pressure would now be required to move the clapper to its open condition. Such disadvantageous re-closure is referred to as a water columning effect. This could result in failure of the check valve to subsequently open should one or more of the sprinkler heads be thermally activated.
In order to avoid the re-closure of the clapper, prior art dry system check valves have generally been provided with a mechanical latch to maintain the clapper in its open condition once it has been activated. The inclusion of such a mechanical latch, while serving to prevent re-closure, however, disadvantageously requires the entire sprinkler system to be shut down and the interior of the high differential type actuator accessed to release the latch and re-close the clapper after the fire has been extinguished. Thus prior dry system check valves have typically required the main supply of water to be shut off, the water drained from the system and then the high differential check valve opened to manually unlatch and reset the clapper. Recognizing the disadvantage of having to manually access the interior of the check valve, a mechanism is shown in U.S. Pat. Nos. 5,295,503 and 5,439,028, which include a reset linkage mechanism that is attached to the check valve and is actuated by the rotation of an externally accessible handle. As can be well appreciated such a mechanism adds to the size, cost and complexity of the check valve.
Traditionally, dry pipe valves used in sprinkler systems employ pressurized air in order to keep water from entering the sprinkler system. Although this pressurized air is given a mechanical advantage over the water pressure, typically of from about 5-8:1, typical air pressures in dry sprinkler systems are from 30 psi to 50 psi. Displacement of this volume of air from the piping of the sprinkler system will delay the operation of the sprinkler control valve, as well as slow the rate of water entry into the sprinkler system once the control valve is actuated.
Traditional accelerators operate by sensing a rapid decay of sprinkler system air pressure, caused by sprinkler head activation. Upon the detection of th
Hwu Davis
Synnestvedt & Lechner LLP
Victaulic Company of America
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