Patent Publication Number: US-11045673-B2

Title: Methods and system for filling a suppressant container

Description:
PRIORITY DATA &amp; INCORPORATION BY REFERENCE 
     This application is an international application claiming the benefit of priority to U.S. Provisional Application No. 62/404,438 filed Oct. 5, 2016, which application is incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This invention relates generally to fire suppression systems and their suppressant supply systems. More specifically, the present invention is directed to methods and systems for providing a container of liquid suppressant at an operative pressure for a firefighting suppression systems. 
     BACKGROUND OF THE INVENTION 
     Known firefighting suppression systems employ a liquid suppressant that is vaporized to extinguish a fire. The vaporized suppressant extinguishes the fire principally by heat absorption. One suppressant that is used in these known suppression systems is 3M™ Novec™ 1230 Fire Protection Fluid (“Novec 1230”) from 3M (having American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) designation FK-5-1-12). Novec 1230 is liquid at room temperature which facilitates ease in handling, storage and transfer. In order to use the Novec 1230 in these known firefighting suppression systems, the Novec 1230 is stored within one or more container assemblies as a super-pressurized suppressant to 25 bar (360 psi.) at 20 degrees Celsius using nitrogen gas. The containers for these known systems can vary in size, for example, from about 5 liters to 180 liters. In use, the containers are connected to system piping for distribution of the suppressant through the pipework as a fluid and then discharged as a gas through one or more nozzles. 
     Suppression systems can be installed in offshore platforms, data processing centers, tape storage facilities and many other facilities. It is desirable to transport the Novec 1230 in its liquid form to the site of the suppression system and then pressurize the suppressant onsite with nitrogen gas within a system container assembly. A known method of filling and pressurizing the containers, i.e., “charging” is to first add the liquid Novec (by weight) to the container then pressurize the container to an operative head space pressure of 25 Bar with nitrogen gas and then to agitate the container in a mechanized mixing process. Agitation causes some of the nitrogen to dissolve into the liquid Novec 1230, which causes the pressure to drop in the container. The known method includes repeatedly adding nitrogen gas and agitating the container until the desired head space pressure is back to 25 Bar and no longer drops. At this point in the process, it is believed that the Novec 1230 is sufficiently saturated with nitrogen so that the container head space pressure becomes stable. Given the size and the weight of some of the containers, the mechanized mixing process uses a mechanical mixer to turn, shake and flip or invert the container. A known mechanical mixer is a large and heavy mechanical mixing inverter having its own support frame requiring sufficient pneumatic and electrical supply sources and space in which to safely position, handle, secure and manipulate the heaviest of containers. Accordingly, a shortcoming of existing solutions for onsite filling is the need for mechanized mixing to handle the containers and sufficiently mix the Novec 1230 and nitrogen gas within service or operational limits for proper system operation. 
     There is a continuing need for methods and systems to fill and pressurize container assemblies for firefighting suppression systems without the logistic complexity and requirements of mechanized mixing used in the conventional charging operations. Adding to the problems in the currently known filling process is the difficulty in measuring the amount of nitrogen by weight that is required to saturate the Novec 1230 and pressurize the container. The weighing process is difficult because very accurate weighing scales are required. Scales capable of such accuracy can be easily damaged and are therefore not ideal for onsite filling where they would be subject to shock during transportation, etc. Moreover, the gas pressure during the fill process can cause the liquid suppressant to move within the container, which can generate undesirable excessive fluctuations in the weigh scale read out. 
     DISCLOSURE OF THE INVENTION 
     Preferred methods and systems are provided for a container of saturated liquid suppressant, preferably Novec 1230, at an operative pressure for a firefighting suppression system. The preferred method and systems provide for a charged container in which the need for mechanized mixing is eliminated. By eliminating mechanized mixing from the filling process, the preferred systems and methods can provide for a filled and pressurized container within a commercially comparable and more preferably an advantageous time period. 
     One preferred method of filling and pressurizing a container with firefighting liquid suppressant includes providing a pressurized receiving container containing nitrogen gas at a predetermined pressure; and adding an amount of firefighting liquid suppressant to the pressurized receiving container. Preferred embodiments of the fill method include first filling the receiving container with nitrogen and adding liquid suppressant to the container last. 
     In another preferred aspect, a system is provided for filling and pressurizing a container with firefighting liquid suppressant. The preferred system includes a receiving container defining an internal volume; a supply of nitrogen gas coupled to the receiving container for positively pressurizing the internal volume of the container to an internal pressure; a supply of liquid suppressant; and a transfer pump coupled to the receiving container and the supply of liquid suppressant for transferring the liquid suppressant to the receiving container against the internal pressure to define a head space pressure and more preferably a nominal operating head space pressure. By monitoring the head space pressure in the container, the need for a weigh scale at the receiving container can be eliminated. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
       The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate exemplary embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain the features of the invention. 
         FIG. 1  is a flow chart of a first embodiment of a preferred method of filling and pressurizing a container with liquid suppressant and nitrogen gas. 
         FIG. 2  is a flow chart of a second embodiment of a preferred method of filling and pressurizing a container with liquid suppressant and nitrogen gas. 
         FIG. 3  is a schematic view of a preferred system for carrying out the methods of  FIGS. 1-2 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Shown in  FIG. 1  is a preferred method  10  for filling and pressurizing a receiving container with firefighting liquid suppressant, in this instance Novec 1230, extinguishing agent from 3M, for storage or installation in a firefighting suppressant system (not shown). The preferred method includes a first step  12  of filling a receiving container with nitrogen gas to a predetermined pressure to provide a pressurized receiving container of nitrogen gas. A second step  14  of the preferred method includes filling, adding or transferring to the receiving container a liquid suppressant to a desired or required fill density. The fill density preferably fills the container with an amount of liquid suppressant sufficient to operate the firefighting suppressant system to effectively address a fire. A preferred fill density of liquid suppressant for filling a receiving container preferably ranges from about 0.5 to about 0.85 kilogram per liter (kg/L) and more preferably ranges from about 0.5 to about 1 kilogram per liter (kg/L). The preferred second step  14  includes filling the receiving container with an amount of firefighting liquid suppressant that can be saturated by the nitrogen  14   a  within the container and define an operating head space pressure  14   a  within the container. As used herein, “operating head space pressure” or “operational head space pressure” is defined as the final stabilized pressure within the container above the liquid suppressant preferably at ambient temperature that is sufficient for storage of the pressurized liquid and operation in a firefighting suppressant system. A preferred operating head space pressure is at least 25 bar (363 psi.), preferably less than 45 bar (653 psi.) and more preferably is 25 bar. Preferably, the operating head space pressure varies directly with the ambient temperature and is preferably a nominal pressure that can vary within a defined range. As used herein, the ambient temperature preferably ranges from 20 degrees Celsius to 25 degrees Celsius and can range from 21-23 degrees Celsius and is more preferably 21 degrees Celsius. Preferably, the operating head space pressure is at least 25 bar (363 psi.), preferably less than 45 bar (653 psi.) and more preferably ranges between 22 psi. and 28 psi. to define a nominal operating head space pressure of 25 bar at the preferred ambient temperature of 21 degrees Celsius. The ambient temperature can be higher or lower depending upon the operation or storage conditions and the nominal operating head space pressure can vary accordingly. For example, where the ambient temperature is above 25 degrees Celsius, the nominal operating head space pressure can range from 26 bar to 30 bar for temperatures that may range from 30 degrees Celsius to 55 degrees Celsius. Where the ambient temperature is below 20 degrees Celsius, the nominal operating head space pressure can range from 20 bar to 25 bar for temperatures that may range from −20 degrees Celsius to less than 20 degrees Celsius. With the first and second steps  12 ,  14  completed, the pressurized container can be stored for future use of otherwise installed in a preferred concluding step  16  of the preferred method for use in the firefighting suppressant system. 
     The predetermined pressure of nitrogen in the first pressurizing step  12  defines the amount of nitrogen delivered to the receiving container that is preferably sufficient to saturate the liquid suppressant subsequently fed into the container and establish the desired operating head space pressure within the container after completing the filling step  14 . The inventors have determined that by initially filling the receiving container with an adequate amount of nitrogen and then subsequently filling the pressurized container with liquid suppressant, the receiving container can be filled to an operational fill density and head space pressure without the need for a mechanized mixing process thereby overcoming the disadvantage of previously known charging methods. The inventors have determined that the preferred methods described herein provide for stable head space pressure over two or more days. By eliminating the need for mechanized mixing, the time to fill and pressurize a container is reduced or at least comparable to convention charging methods. 
     Shown in  FIG. 2  is another preferred embodiment  100  of the filling method. The preferred method  100  includes predetermining the pressure of the nitrogen  105  prior to the step of pressurize the receiving container with nitrogen  112 . The preferred step of predetermining the nitrogen pressure  105  includes calculating the weight of nitrogen to be supplied to the receiving container based upon the internal volume of the receiving container, the total weight of the liquid suppressant to be supplied to the container in the second step  114  and the operational head space pressure. The predetermining step  105  preferably includes converting the calculated nitrogen weight to a total pressure value to define the amount of nitrogen to be delivered to the receiving container in the pressurizing step  112 . Moreover, the predetermined pressure of nitrogen is preferably calculated at the ambient temperature for the receiving container in which the container is stored or operated. 
     The preferred method of filling  114  includes the step  114   a  of monitoring the head space pressure throughout the process step of filling the container with liquid suppressant. More specifically, the preferred process includes continually or intermittently determining or monitoring the head space pressure during the step of filling with liquid suppressant. In the course of filling the container with liquid suppressant, the head space pressure can vary until the operating pressure value is achieved and stabilized. If the measured head space pressure is below the operating head space pressure value, for example, below 25 bar, the filling step  114  is repeated or continued to fill the receiving container with liquid suppressant. If the head space pressure is at or within an acceptable range of the operating head space pressure, the filling step  114  is completed and the receiving container can be stored or place into service  116  to conclude the filling process  100 . Again the preferred filling method  100  is performed and completed without mechanical agitation of the receiving container. In the preferred filling method  100 , the head space pressures preferably never exceeds 45 bar and in the end, the preferred nominal operating head space pressure is preferably at least 25 bar at 21 degrees Celsius. 
     The preferred second step of transferring the liquid suppressant to fill the receiving container  14 ,  114  preferably transfers the liquid suppressant from a liquid suppressant supply of a known initial weight. The filling step  14 ,  114  can include monitoring the weight loss of the liquid supply to reach a predetermined weight value and indicate that the desired amount of liquid suppressant has been transferred from the supply to the receiving container. 
     Shown in  FIG. 3  is a preferred system  300  for carrying out the previously described processes  10 ,  100  for filling and pressurizing a container with firefighting liquid suppressant. The preferred system  300  includes a receiving container  302  defining an internal volume to be filled and pressurized with nitrogen gas and liquid suppressant in a manner as described herein. The container  302  is preferably configured for both storage and connection to a firefighting system that employs a pressurized liquid suppressant. Accordingly, the preferred system is configured for installation and/or set up for liquid suppressant filling and pressurization at the site of the firefighting system or suppressant storage. 
     The preferred system  300  also includes a supply of nitrogen gas  304  coupled to the receiving container  302  for positively pressurizing the internal volume of the container  302  to a preferably predetermined internal pressure. The system  300  also includes a supply of liquid suppressant  306  and a transfer pump  308  coupled to each of the receiving container  302  and the supply of liquid suppressant  306  for transferring the liquid suppressant to the receiving container  302  against the internal pressure to define a head space pressure in the space  302   a  above the liquid within the receiving container  302  and more preferably establish a preferred nominal operating head space pressure. In a preferred embodiment of the transfer pump  308 , liquid suppressant is transferred to the receiving container  302  against a head space pressure that exceeds 25 bar and more preferably against a head space pressure that ranges from 25-45 bar and that can more preferably transfer against a head space pressure that is greater than 45 bar. 
     In preferred embodiments of the systems and methods described herein, the preferred liquid suppressant employed is in this instance Novec 1230 extinguishing agent from 3M. The liquid suppressant can be a newly supplied material or recycled, for example, from the firefighting system validated to be in accordance with the original specification of the liquid suppressant. Moreover, the preferred supply of liquid suppressant  306  is a supply container having a fixed volume of liquid suppressant. For example, the supply of liquid suppressant  306  is embodied as a fifty-five gallon drum of suppressant. The transfer pump  308  pulls or draws the liquid suppressant from the supply container  306 . As previously described, preferred embodiments of the filling method include measuring the weight loss in the liquid suppressant supply to determine the amount of liquid suppressant transferred to the receiving container. The preferred system  300  can include a weigh scale to measure the loss in weight of the liquid suppressant supply container  306  during transfer of liquid suppressant to the receiving container  302 . 
     The system  300  includes multiple fittings for isolating any one of the interconnected receiving container  302 , the liquid suppressant supply  306 , the transfer pump  308  or the nitrogen supply  304 . For example, fluid control from the transfer pump  308  is preferably controlled by shut-off valves, such as for example, a first ball valve  314   a  on the outlet side of the transfer pump  308 . The nitrogen gas source  304  preferably include a shut-off valve  314   b  to control the flow and pressure of nitrogen gas to the container  302 . The receiving container  302  is preferably embodied as a known storage cylinder assembly or container. The interconnections between system components can be made with appropriate pipe or hose connections and embodied in a central manifold. 
     The preferred system  300  can be used in the preferred methods of filling previously described. In one exemplary filling operation of the preferred method  100 , a nitrogen gas pressure is determined based upon the size of the receiving container  302 , the target fill weight of the liquid suppressant and the ambient temperature for saturation of the liquid suppressant and the establishing the operational head space pressure. The first nitrogen source  304  is connected to the receiving container  302  and the receiving container is pressurized to the predetermined nitrogen pressure. The nitrogen source  304  is then disconnected. 
     The transfer pump  308  is then started to transfer of liquid suppressant to the receiver container  302 . In one preferred method of operation, the first ball valve  314   a  is closed and the transfer pump  308  is operated to build up a discharge pressure of 55 bar in the transfer piping on the outlet side of the pump  308  before or above the receiving container  302 . When the discharge pressure reaches the desired level, the first ball valve  314   a  is opened for filling of the container  302 . During the liquid suppressant transfer, the pressure inside the container is monitored using an appropriate gauge or sensor (not shown), such as for example a diaphragm pressure transducer, to determine the head space pressure in the receiver container  302 . Additionally or alternatively, the system piping can include pressure sensors or gauge to monitor the pressure along the system piping. The change in weight of the liquid suppressant source  306  can be measured and monitored during transfer. Suppressant transfer continues until the target fill weight is reached in the receiver container  302  and the head space pressure measures in the preferred range of 25 bar to less than 45 bar and more preferably is 25 bar. The head space pressure in the receiving container could be up to 35 bar or greater. However it has been shown that over a period of a few days, the liquid suppressant will continue to dissolve the nitrogen and the head space pressure will drop to a desired operational level. Thus, the charging process is completed without mechanized mixing. 
     While the present invention has been disclosed with reference to certain embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the present invention, as defined in the appended claims. Accordingly, it is intended that the present invention not be limited to the described embodiments, but that it has the full scope defined by the language of the following claims, and equivalents thereof.