Patent Application
20130098640
The present invention is directed to anti-corrosion protection in a fire protection system and, in particular, to anti-corrosion in a wet pipe fire sprinkler system.
Wet pipe fire protection systems must be occasionally drained for maintenance, system upgrade, and the like. According to many fire protection codes, it is necessary to place the system back into operation daily, even if the maintenance or upgrade takes multiple days. Also, it is usually necessary to be able to place the system back into operation within a relatively short defined period that is usually measured in terms of a few minutes. This draining and refilling with water tends to create corrosion in the piping of the wet pipe fire sprinkler system. This is caused, at least in part, from the high oxygen content air that is introduced into the system upon refilling the system with water. Such corrosion can lead to system failure resulting in expensive repairs.
A wet pipe fire protection sprinkler system and method of operating a wet pipe fire sprinkler system, according to an aspect of the invention, includes providing a sprinkler system having a pipe network, a source of water for the pipe network, at least one sprinkler head connected with the pipe network and a drain valve for draining the pipe network. An inert gas source, such as a nitrogen gas source, is connected with the pipe network. Inert gas is supplied from the inert gas source to the pipe network. Water is supplied to the pipe network, thereby substantially filling the pipe network with water and compressing the inert gas in the pipe network.
At least some of the compressed gas may be vented from the pipe network. The compressed gas may be vented under particular circumstances, such as air pressure being above a particular pressure level, or for a particular time duration, or the like. Oxygen rich air may be prevented from entering the pipe network when emptying water from the pipe network.
Gas may be discharged from the pipe network after supplying inert gas and prior to said filling the system with water. The supplying and discharging of inert gas from said inert gas source to said pipe network may be repeated before supplying water to the pipe network, thereby increasing concentration of inert gas in the pipe network. The discharging of gas from the pipe network may include opening the drain valve.
The pipe network may include a riser, a generally horizontal main, at least one generally horizontal branch line connected to the main with the sprinkler head(s) being at the branch line. The venting may be performed at the main or branch line(s).
A venting assembly may be provided that is operable to vent air under particular circumstances, such as air pressure being above a particular pressure level. The pressure level may be fixed or adjustable. A gauge may be provided for setting an adjustable pressure level. The venting assembly may include an air vent and an airflow regulator. The air vent is connected with the pipe network and discharges to the airflow regulator. The air vent may further include a redundant air vent, with the air vent discharging to the airflow regulator through the redundant air vent. The airflow regulator may be in the form of a pressure relief valve, a back-pressure regulator, or a check valve. A sampling port may be provided for sampling air that is discharged from the airflow regulator.
Water may be drained from the pipe network by connecting the inert gas source to the pipe network and supplying inert gas to the pipe network during the draining in order to resist oxygen rich gas from entering the pipe network, such as through the drain valve.
A venting assembly is provided, according to another aspect of the invention, for use with a fire protection sprinkler system having a pipe network, a source of water for the pipe network, at least one sprinkler head connected with the pipe network and a drain valve for draining the pipe network. The sprinkler system may further include an inert gas source connected with the pipe network. The venting assembly includes an air vent and an airflow regulator. The air vent is adapted to be connected with the pipe network and adapted to vent gas, but not water. The airflow regulator is adapted to be connected with the air vent and is adapted to control gas flow to and/or from the air vent. The venting assembly may include a redundant air vent, with the air vent discharging to the airflow regulator through the redundant air vent. The airflow regulator may be in the form of a pressure relief valve, a back-pressure regulator or a check valve. A sampling port may be provided at the airflow regulator.
A method of operating a wet pipe fire protection sprinkler system having a pipe network, a source of water for said pipe network, at least one sprinkler head connected with said pipe network and an inert gas source connected with said pipe network, according to an aspect of the invention, includes supplying inert gas from the inert gas source to the pipe network and supplying water to the pipe network, thereby substantially filling the pipe network with water and compressing the gas in the pipe network.
At least some of the compressed gas may be vented from the pipe network. The venting may include venting the compressed gas when gas pressure is above a particular pressure level. The pressure level may be fixed or adjustable. Gas that is vented may be sampled and analyzed. Oxygen rich air may be prevented from entering the pipe network when emptying water from the pipe network.
The method may further include discharging gas from the pipe network after supplying inert gas and prior to supplying water and repeating the supplying inert gas and discharging gas from the inert gas source to the pipe network prior to supplying water to the pipe network thereby increasing concentration of inert gas in the pipe network.
The pipe network may include a main drain valve for draining water from the piping network and wherein the discharging gas from the pipe network includes opening the main drain valve. The pipe network may include a riser and at least one generally horizontal branch line connected with the riser with the sprinkler head(s) being at the branch line. The venting assembly is at the riser or a branch line. The pipe network may be a multiple-zone piping network, including a drain line connected between the drain valve and each of the zones. Each of the zones further includes a horizontal branch line, a fill valve connecting the branch line with the riser, a zone drain valve connecting the horizontal branch line with the drain line and a venting assembly at the branch line.
The inert gas source may be connected with at least one of the zones while others of the zones remain in operation to provide fire protection. The connecting of the inert gas source with at least one of the zones may include (i) closing the fill valve and opening the zone drain valve for that zone to drain that zone, (ii) closing the main drain valve, and (iii) applying inert gas from the gas source to the branch line of that zone. The inert gas may be applied through the drain line. The method may further include (iv) discharging gas from the branch line and repeating (iii) and (iv) until a satisfactory reduction in oxygen is achieved.
The inert gas source may be connected to the pipe network and inert gas supplied to the pipe network during draining of water in order to resist oxygen rich gas from entering said pipe network during the draining.
These and other objects, advantages and features of this invention will become apparent upon review of the following specification in conjunction with the drawings.
Referring now to the drawings and the illustrative embodiments depicted therein, a wet pipe fire protection sprinkler system 10 includes a pipe network 12, a source of water for the pipe network, such as a supply valve 14, one or more sprinkler heads 16 connected with the pipe network, a drain valve 18 for draining the pipe network and a source of inert gas, such as a nitrogen source 20 connected with the pipe network (
Wet pipe fire sprinkler system 10 further includes a venting assembly 32 for selectively venting air from pipe network 12. In the illustrative embodiment, venting assembly 32 vents air and not water from the pipe network in order to remove at least some of the air from the pipe network when the pipe network is filled with water in the manner described in U.S. patent application Ser. No. 12/615,738, filed on Nov. 10, 2009, entitled AUTOMATIC AIR VENT FOR FIRE SUPPRESSION WET PIPE SYSTEM AND METHOD OF VENTING A FIRE SUPPRESSION WET PIPE SYSTEM, the disclosure of which is hereby incorporated herein by reference. Venting assembly 32 further prevents substantial air from entering pipe network 12 when the pipe network is drained of water in a manner that will be explained in more detail below. This avoids oxygen rich air from entering the pipe network at venting assembly 32 in response to a relative vacuum drawn on pipe network 12 by the draining of water, thereby displacing high nitrogen air in the pipe network. Venting assembly 32 may further be configured to vent air from the pipe network only under particular circumstances, such as air pressure in the pipe network being above a particular set point pressure level, thereby facilitating an inerting process, to be described in detail below, which may be carried out below the set point pressure level of the venting assembly. However, the venting may be based on other circumstances, such as based upon timing using a time-operated valve.
Pipe network 12 includes a generally vertical riser 24 to which drain valve 18 and supply valve 14 are connected and one or more generally horizontal mains 26 extending from riser 24. Drain valve 18, supply valve 14 and nitrogen source 20 may be conveniently located in a riser room 25 that is readily available to maintenance personnel. Pipe network 12 further includes a plurality of generally horizontal branch lines 28 connected with main 26, either above the main, such as through a riser nipple 30 or laterally from the side of the main. Sprinkler heads 16 extend from a branch line 28 via a drop 29.
In the illustrated embodiment, venting assembly 32 is connected with pipe network 12 at main 26 distally from the portion of the main that is connected with riser 24. This ensures that the main is vented. However, venting assembly 32 could be connected with a branch line 28. The venting assembly does not always need to be the highest point in pipe network 12. Venting assembly 32 does not need to be conveniently located in riser room 25 because its operation, once configured, is automatic so it does not need to be readily accessible to maintenance personnel.
In the illustrated embodiment, venting assembly 32 is made up of an air vent 34 and an airflow regulator 35 (
Venting assembly 32 may further include a redundant air vent 46 that provides redundant operation in case of failure of primary air vent 34. Such redundancy avoids water from being discharged to back-pressure regulator 36 and to the environment upon failure of the primary air vent where it may cause damage before the failure is discovered. Such redundant air vent is as disclosed in U.S. patent application Ser. No. 12/615,738, filed on Nov. 10, 2009, entitled AUTOMATIC AIR VENT FOR FIRE SUPPRESSION WET PIPE SYSTEM AND METHOD OF VENTING A FIRE SUPPRESSION WET PIPE SYSTEM, the disclosure of which is hereby incorporated herein by reference. In particular, primary air vent 34 discharges to redundant air valve 46 which, in turn, discharges to back pressure regulator 36.
Alternatively, airflow regulator 35 can be made up of a pressure relief valve. A pressure relief valve functions in a similar manner to a back-pressure regulator, except that its set point is fixed at the factory and cannot be field adjusted. Alternatively, the airflow regulator can be in the form of a check valve which allows air to be discharged from air vent 34 to atmosphere, but prevents high oxygen content atmospheric air from being drawn through air vent 34 to main 26 when the pipe network is drained of water. Back-pressure regulator 36 and the alternative pressure relief valve are commercially available from multiple sources, such as Norgren Company of Littleton, Colo., USA.
Airflow regulator 35 operates by allowing air vented by air vent 34 to be discharged to atmosphere. However, airflow regulator 35 prevents atmospheric air, which is oxygen rich, from flowing through air vent 34 into pipe network 12, such as when it is being drained. In the illustrated embodiment in which airflow regulator 35 is made up of a back-pressure regulator or a pressure relief valve, airflow regulator 35 functions by opening above a set point pressure and closing below that set point pressure. Air vent 34 functions by opening in the presence of air alone (or other gaseous mixture) and closing in the presence of water. In this embodiment, venting assembly 32 will be open to vent gas from main 26 during filling of the fire sprinkler system with water which raises the pressure of the gas in pipe network 12 above the set point of the back-pressure regulator. Once substantially all of the gas is vented, the presence of water at air vent 34 will close the air vent resulting in closing of the back-pressure regulator. Then, when the fire sprinkler system is being emptied of water, the air pressure within main 26 will decrease as a result of water being drained, as would be understood by the skilled artisan, thereby maintaining airflow regulator 35 closed to prevent drawing in a substantial amount of high oxygen content atmospheric air. This will prevent substantial amounts of oxygen rich atmospheric air from entering pipe network 12 during draining of sprinkler system 10 of water.
The wet pipe fire sprinkler system operates as follows. When system 10 is initially set up or undergoes extensive maintenance, an inerting process 50 is carried out with nitrogen or other inert gas (
It is then determined if the nitrogen concentration is at a desired level (62). If it is not, drain valve 18 is opened (64). After a delay (66) to allow pressure in pipe network 12 to drop to atmospheric pressure, the drain valve is again closed and steps 58 through 62 repeated until it is determined at 62 that the concentration of nitrogen in the pipe network is high enough. It should be understood that steps 60 and 62 are optional and may be eliminated once process 50 has been performed one or more times. Once it is determined at 62 that the nitrogen concentration is sufficient, source valve 14 is then opened (68) to admit water to the pipe network. The relatively high pressure of the water, such as between approximately 76 PSIG and 150 PSIG, compresses the nitrogen rich air in pipe network 12 to a fraction of its volume and raises the pressure of the air above the set point of back-pressure regulator 36. This causes back-pressure regulator 36 to discharge the nitrogen rich air until essentially all, or a substantial portion, of the air is depleted from the system at which time air vent 34 closes in the presence of water. Back-pressure regulator 36 then closes to prevent high oxygen rich air from entering the pipe network when it is subsequently drained of water.
Once inerting process 50 is carried out, wet pipe sprinkler system 10 may be able to be drained and refilled using a drain and refill process 80 without the need to repeat inerting process 50. Drain and refill process 80 begins (82) with system 10 filled with water either using inerting process 50 or by a conventional process. Nitrogen source 20 is connected with riser 24 and the nitrogen pressure adjusted (84), such as by adjusting air maintenance device 21. Nitrogen valve 22 is opened (86) in order to allow nitrogen gas to flow into the riser. Drain valve 18 is opened (88) to drain water from the pipe network. When the pressure in the riser falls below the nitrogen pressure, nitrogen gas will enter the riser to resist high oxygen rich air from entering the riser through drain valve 18 in response to a vacuum that occurs as the piping network is emptied of water. The airflow regulator of venting assembly 32 will prevent a substantial amount of oxygen rich air from entering main 26 through air vent 34. Once any maintenance is performed at 90 the pipe network can be refilled with water at 92. Any air in pipe network 12 will be discharged through venting assembly 32 in the manner previously described.
By varying the purity of the source of nitrogen gas, the fill pressure and the number of times that steps 58 through 62 are repeated, the concentration of nitrogen can be established at a desired level. For example, by choosing a nitrogen source of concentration between 98% and 99.9% and by filling and purging the piping network at approximately 50 PSIG for four (4) cycles, a concentration of nitrogen of between 97.8% and 99.7% can be theoretically achieved in system 10. A fewer number of cycles will result in a lower concentration of nitrogen and vice versa.
Inerting of sprinkler system 10 with nitrogen or other inert gas tends to result in an inert-rich gas present in branch lines 28 and riser nipples 30 because oxygen rich air that may enter during the draining of the system tends to stay relatively close to drain valve 18 and not enter the branch lines or riser nipples. Depending on fire protection system design, venting assembly 32 may be positioned at main 26 or at one or more branch lines 28. Also, venting assembly 32 should be positioned away from the nitrogen source connection to pipe network 12. Although illustrated as connected with riser 24, nitrogen source 20 can be connected at other portions of the pipe network.
The wet pipe fire protection sprinkler system and method of operation disclosed herein provides many advantages as would be understood by the skilled artisan. The filing of pipe network 12 with water either during or after it is filled with high nitrogen air tends to reduce corrosion in pipe network 12. This is because most air is removed from the pipe network and the amount that remains is low in oxygen. It is further believed that only a small amount of oxygen is supplied with the water. Because corrosion is believed to begin primarily at the water/air interface in a wet pipe fire sprinkler system and little oxygen is present in the high nitrogen environment, corrosion formation is inhibited.
Moreover, a high nitrogen, or other inert gas, wet pipe fire protection sprinkler system may be provided in certain embodiments without the need to apply a vacuum to the system after draining in order to remove high oxygen air. This reduces the amount of time required to place the system back into operation after being taken down for maintenance. Maximum time of restoration is often dictated by code requirements and may be very short. Also, the elimination of a vacuum on the system avoids potential damage to valve seals, and the like, which allows a greater variety of components to be used in the fire sprinkler system.
Variations will be apparent to the skilled artisan. For example, although illustrated with a single riser and main, it should be understood that multiple risers and/or mains may be used particularly with multiple story buildings, as disclosed in commonly assigned International Patent Application Publication No. WO 2010/030567 A1 entitled FIRE PROTECTION SYSTEMS HAVING REDUCED CORROSION, the disclosure of which is hereby incorporated herein by reference. Also, while water source 14 may be city water mains, it may, alternatively, include a water reuse tank, as also disclosed in such international patent application publication. Such water reuse tank reduces the size of the nitrogen source by conserving water that is relatively high in dissolved nitrogen and relatively low in dissolved oxygen.
In an alternative embodiment, a multiple-zone fire protection sprinkler system 110 that is illustrated for use with a multiple story building, but could, likewise, be used in a large protected space on a single story, includes a main supply valve 114 connected with a combination supply riser 124 that feeds a plurality of zones 148, each having a branch line 128 and a venting assembly 132 at a distal end of the branch line with respect to the riser (
In operation, one or more of the zones 148 can be accessed, such as for maintenance, while the other zones remain in operation, by closing the supply valve 150 for that zone(s) and opening the zone drain valve 152 for that zone(s). After the water is drained, main drain valve 118 is closed and nitrogen source 120 is operated to apply nitrogen to drain riser 154. When the zone(s) is filled with nitrogen gas, the nitrogen source is cut off and drain valve 118 is opened to allow the zone to relax to atmospheric pressure, as provided in procedure 50 (
Thus, it can be seen that multiple zone fire protection sprinkler system 110 can be inerted one or more zones at a time while leaving other zones in service. Only one nitrogen source and gas injection port are required and they can be located in a riser room 125.
An alternative venting assembly 332 may be provided for each zone to provide an alternative technique for venting the gas to atmosphere between inerting steps (
In another alternative embodiment, a multiple zone fire protection sprinkler system 210 includes a plurality of zones 248, each including at least one branch line 228 connected with a zone supply valve 252 with a supply riser 224 and through a zone drain valve 250 to a drain riser 254. Each zone includes a venting assembly 232, similar to venting assembly 132 or 332, at a distal end of the branch line. A venting assembly 232 may also be provided for riser 224. System 210 is similar to system 110, except that supply valves 252 and drain valves 250 are electrically controlled, such as from a control panel or programmable controller (not shown). Also, system 210 may include a main supply valve 214 and drain valve 218, either or both of Which may be electrically controlled. In this fashion, the inerting of zones 248 may be carried out either remotely or automatically thereby avoiding the need for a technician to visit the zone(s) being emptied and refilled. Other modifications will be apparent to the skilled artisan.
Changes and modifications in the specifically described embodiments can be carried out without departing from the principles of the invention which is intended to be limited only by the scope of the appended claims, as interpreted according to the principles of patent law including the doctrine of equivalents.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US11/40003 | 6/10/2011 | WO | 00 | 12/20/2012 |
| Number | Date | Country | |
|---|---|---|---|
| 61357297 | Jun 2010 | US |
