Patent Publication Number: US-2005121210-A1

Title: Cascaded inert gas purging system

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This is a continuation-in-part of application Ser. No. 09/710,271 filed Nov. 10, 2000. 
    
    
     BACKGROUND OF THE INVENTION  
      The present invention relates to systems used for protecting electronic, mechanical, hydraulic or other components from the effects of harsh environments that may exist in industrial facilities.  
      The importance of controlling and monitoring production processes using for example, electronic, mechanical, electromechanical, hydraulic devices and instrumentation requires that, at times, the electronic instrumentation be located in the production environment. This places the electronic instrumentation in surroundings that may be harsh and can often have a detrimental effect on the electronic components that such components may not be capable of withstanding. For example, electronic devices may be placed in a plant process environment that normally sustains saturation humidity that, over time, can severely damage and incapacitate the electronic components, if not properly protected.  
      Another problem occurs during plant cleaning or disinfection, which may require that the plant equipment used be cleaned with high pressure hot water. Water pressures greater than 600 psi may be used to plant clean equipment. Such cleaning can be detrimental to the electronic monitoring and control systems situated nearby. Such water pressures can easily penetrate most common rated electronic enclosures resulting in damage to the electronic circuitry contained within.  
      To overcome the problem, electronic components have been placed in hermetically sealed chambers that are designed to be waterproof. This technique is described in U.S. Pat. No. 6,075,204 to Celauro et al. This waterproof enclosure has proven successful under severely harsh conditions by preventing condensation from forming inside the enclosure as the outside temperature decreases, thereby eliminating damage to the electronics within. However, this system does not make a direct provision for the hermetically isolated satellite sensors connected to the system. Thus, the sensors are still subjected to the same harsh environment, unless the sensors are independently purged with a dry gas.  
      U.S. Pat. No. 5,603,892 to Grilletto et al. provides a gas purged electronics enclosure in which a control system is used to open and close valves to purge a contaminant-free gas through the electronics enclosure. In addition, a getter material is used as a scavenger to ensure the removal of contaminants. This patent describes a system that has only one enclosure for housing electronic components.  
      While purge systems are known, the prior art does not provide a suitable and economical solution for protecting electronic and other devices that may be located in various places throughout a process environment and which may be interconnected. What is needed is an integrated system that is capable of protecting these multiple interconnected devices.  
     SUMMARY OF THE INVENTION  
      The present invention provides a system that protects electronic and other components from the outside environment by means of continuously cascading a flowing pressurized gas through the system to prevent harsh environmental conditions from adversely effecting system components&#39; and the components ability to monitor a plurality of plant operations.  
      The present invention is an integral cascaded distributed purge system used to protect interconnected electronic components, although the system is not limited to such electronic components. The system is particularly useful in industrial applications where the surrounding environment can adversely affect electronic components. For example, in a food plant, cleaning procedures require that hot water, strong caustic detergents and steam be used to wash down equipment. This creates an atmosphere where moisture can inadvertently enter into a sealed enclosure, ultimately leading to electronic failures. By installing the distributed purge gas system of the present invention, electronic devices located at different points in a process are protected by an integrated system that continuously purges pressurized gas through the system. This is accomplished in an efficient and cost effective manner, i.e. through already existing interconnecting cabling and fixtures.  
      The system is capable of providing protection to the entire system of separately housed electronic devices from a single highly reliable source.  
      Accordingly, the present invention is a system for protecting electronic or other components from contamination, which includes a tightly controlled, multi-tiered distribution means; a pressurized gas in fluid communication with the distribution means; a plurality of apparatus for enclosing electronic devices connected to the distribution means, with each apparatus connected to the distribution means by a conduit having a first end and a second end, wherein the first end is connected to the distribution means and the second end is connected to the apparatus.  
      The present invention also includes: 
          i) A system for protecting a data component from contamination, comprising: sensing means constructed and arranged for communication with a process component to be sensed and for transmitting a signal representing the sensed process component; distribution means for distributing a pressurized fluid to the sensing means; connecting means for connecting said distribution means with said sensing means and having a first end and a second end, said first end being connected to said distribution means for communication therewith, and said second end being connected to said sensing means for communication therewith; and regulating means in communication with said sensing means for regulating the fluid pressure from said distribution means to be greater at the sensing means than a pressure of the environment external to said system.     ii) A method for protecting a data component from contamination in a processing environment, comprising enclosing the data component in an enclosure; supplying pressurized fluid to said enclosure; maintaining a positive pressure of said pressurized fluid; and venting said pressurized fluid as necessary to maintain the positive pressure selected.     iii) A method for protecting data components in a processing environment, comprising: providing a pressure differential between the data components and the processing environment; controlling the pressure differential for a pressure at the data components to exceed a pressure at the processing environment for preventing the processing environment from contacting the data components; and regulating the pressure differential between the data components and the processing environment to remain continuous at a select pressure.     iv) A method for protecting a data component from an external environment, comprising: providing a fluid with a first pressure at the data component; enclosing the fluid at the data component; maintaining the first pressure of the fluid at the data component for providing a fluid wall at the data component; separating the data component from the external environment with the fluid wall; and venting the fluid pressure of the fluid to maintain the fluid wall at a select pressure.       

    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      For a more complete understanding of the present invention, reference may be had to the detailed description of the preferred embodiments taken in conjunction with drawings, of which:  
       FIG. 1  is a schematic representation of a preferred embodiment of a distribution purge system of the present invention.  
       FIG. 2  is a schematic representation of another embodiment of a distributed purge system of the present invention.  
       FIG. 3  is a schematic representation of a check valve that functions as a flow control means in a preferred embodiment of the present invention.  
       FIG. 4  is a schematic representation of an apparatus for enclosing, for example, devices to be sensed or sensing devices according to the present invention.  
       FIG. 5  is a schematic representation of gas flow elements of the system of the present invention.  
       FIG. 5A  shows an alternate arrangement for certain features of  FIG. 5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The present invention prevents moisture and contaminants from the surrounding process environment from contacting for example, electronic or mechanical components, or data gathering devices situated in the environment. The term “contaminants” as used herein means moisture, particulate matter or any other substance which may adversely impact the components and their operation.  
      In  FIG. 1 , electronic components are protected in a distributed or cascaded purge gas system of the present invention shown generally at  10 , where pressurized gas is directed to flow from  12  into a distribution means such as distribution manifold  20 . The manifold  20  distributes the pressurized gas through a conduit, such as cable or conduit  40 , to apparatuses  22 ,  23 ,  24 ,  25  and  26  (“ 22 - 26 ”), which house the electronic or mechanical components at different locations along the process. The components are constructed to generate signals representing data sensed at locations in a plant or processing environment. The manifold includes electric components (not shown) for the system. These components are constructed and arranged as transceivers, i.e. to receive sensor signals from the apparatus  22 - 26  via the conduit  40  and in turn generate a data signal to another remote location reporting on the production environment being sensed and monitored.  
      Alternatively, each of the apparatus  22 - 26  can be used for different sensory functions, i.e., the sensing of temperature, pressure, humidity, flow, level, noise, etc. of other devices or systems being monitored or controlled by the system  10 . Each manifold  20  in combination with the apparatus  22 - 26  are referred to herein as a hub network  14 . A hub network  14  preferably includes one manifold  20 , at least one of the apparatus  22 - 26  and the conduit  40  connecting the manifold and apparatus selected. However, for most processing environments, a plurality of apparatus will be connected to the manifold  20 . See for example,  FIG. 2 . The system  10  may include a plurality of the hub networks  14  for a single plant facility. Where a plurality of hub networks  14  are used, the manifolds  20  will be preferably arranged in parallel.  
      Each apparatus  22 - 26  is designed with a pressure or flow control means such as check valve  30 . The valve  30  allows the manifold  20  and therefore the system  10  to purge pressurized gas through each apparatus serially or in parallel by continuously (if necessary) venting or bleeding a portion of the pressurized gas through the check valve to maintain the system  10  at a desired pressure. The valve  30  is set to open and release the pressurized gas at a predetermined pressure. The check valve  30  continuously controls the pressurized gas at a preferred pressure to be about 1 to 2 psi above the next level in the flow cascade and at the least, to maintain a pressure within the system  10  above that of the plant environment so that moisture, for example, is prevented from entering the apparatus  22 - 26  in the system  10 . In effect, a pressurized wall of a fluid, preferably a gas, is used and controlled to prevent ingress of the external environment into the system  10 . In the case of the last apparatus in the flow cascade (exhaust to atmosphere), the check valve  30  will typically hold the internal pressure of the final apparatus at about 0.5 to 1 psi above the surrounding external environment.  
       FIG. 2  represents another embodiment of a distributed purge system of the present invention shown generally at  100 . Pressurized gas is supplied from supply tank  50  and directed to filter  58  for removal of contaminants and moisture. The pressure of the pressurized gas is decreased through a series of pressure regulating valves  52  and  54 . By way of example, pressurized gas from the supply tank  50  may be at about 45 psi. The pressure is reduced to 35 psi by pressure regulating valve  52  and then reduced further to 30 psi by pressure regulating valve  54 .  
      The supply tank  50  may contain liquid nitrogen (LN) for use with the system  100 . Alternatively, a supply tank  51  contains compressed dry air, which air can be sourced from the immediate facility in which the system  100  is operating. A solid state membrane air dryer can be used which provides (−)40° F. dewpoint air; which is a very dry air.  
      The compressed dry air can be introduced from the tank  51  to the system  100  through either line  51   a  or  51   b . The selection of line  51   a  or  51   b  will be determined by whether or not the compressed dry air is to be introduced upstream or downstream of the pressure regulating valve  52 . Regardless of which of the lines  51   a ,  51   b  is used, it is preferred to introduce the compressed dry air from the tank  51  upstream of the filter  58  to take advantage of filtering the air to be introduced into the system  100 .  
      Differential flow control module  56  modulates the pressure of its effluent pressurized gas to control the flow of the pressurized gas into the distribution manifold  20 . For example, pressurized gas at about 30 psi may be continuously modulated at about 2 psi at the effluent of the flow control module  56 . The pressurized gas  12  is shown flowing continuously through conduit  40  into the apparatuses  22 - 26 , such as for example, apparatus  22 , and being exhausted through check valve  30 , which is shown in greater detail in  FIG. 3 .  
      The apparatuses  22 - 26  are shown with sensing means  34 , which is a part of the respective one of the apparatus  22 - 26 . The sensing means  34  can optionally be constructed and arranged within each apparatus. The sensing means is in communication with a process, system or apparatus (not shown) of the host facility by connector  35 . Where a plurality of the hub networks  14  are used, the sensing means  34  are preferably arranged in series.  
      The control module  56  is provided for each manifold  20  and preferably for each hub network  14 . The module  56  preferably includes a needle valve and a constant differential relay.  
      Integration of more than one apparatus  22 - 26  to a distribution manifold  20  increases the efficiency and cost effectiveness of the systems  10 , 100 . The carefully controlled pressurized gas-sharing arrangement minimizes the number of separate pressurized gas supply sources that are needed by doing away with the closed system arrangement used in the prior art, where each electronic device is housed in its own system, thereby greatly increasing complexity and material costs. The system  10 , 100  of the present invention easily and capably maintains pressure in the system by controlling, via cascade, the flow of the pressurized gas through a multitude of apparatuses  22 - 26  that house electronic devices in the system by utilizing “cracking” or relief pressures of the check valves  30  installed in each apparatus to apportion the flow.  
      While the system  100  in  FIG. 2  depicts a single distribution means, it should be understood that the present invention can be readily configured with an infinite number of hub networks  14 , such as shown in  FIG. 1 , without compromising the effectiveness or efficiency of the system.  
      While apparatuses  22 - 26  are shown in  FIG. 1 , it should be understood that the present invention will provide protection for one or a plurality of cascaded levels of purged enclosures. This protection is achieved from the present system also utilizing the existing cascaded electrical connectivity of the distributed electronics system to distribute the purge gas.  
      The distribution means may be any suitable device that is capable of distributing pressurized gas  12  to each apparatus  22 - 26 , which house an electronic device. The apparatus  22 - 26  however, may each alternatively be connected to or in communication with an electronic device, rather than actually house the electronic device. In such an arrangement, the cascade effect of maintaining pressure is still employed to protect the system  10 ,  100 .  
      Preferably, the distribution manifold  20  is hermetically sealed to reduce the possibility of contaminants from entering the system  10 , 100  and to maintain a positive pressure within the system. It should be noted that the hermetic seal by itself may not be sufficient in preventing moisture, i.e. steam or condensate, or other contaminants from entering or forming in the distribution manifold  20 . By continuously purging the system with pressurized gas, the gas in the system is constantly changing, thus decreasing the chance of moisture or contaminant collection and formation. A pressure control device, such as check valve  32  shown in  FIG. 2 , may be connected to the distribution manifold  20  to assist in adjusting the pressure of gas in the manifold  20 . Non-limiting examples of the distribution manifold  20  include boxes, enclosures, electrical panels, manifolds, pipes, tubes, electrical cables and conduits, and intermediate storage canisters or tanks.  
      Preferably, pressurized gas  12  can be any inert gas source. For the purposes of the present invention, the term “inert gases” is intended to mean any gas that will not react with, and in the environment created within, the apparatus or system. For example, nitrogen, helium, compressed dry air or instrumentation air of relatively high purity with minimal moisture content, are some of the many inert gases that may be used with the system  10 , 100  of the present invention. Preferably, the pressurized gas is superdried compressed air having a dewpoint of about −40° F.  
      A flow control check valve  30  shown in  FIG. 3  is an example of a device that is capable of providing flow control by modulating pressure from upstream in the system. Pressurized gas  12  flows into the flow control valve  30  from the electronics or other enclosure, first passing through fixed restriction zone  62 , then into the variable restriction zone  64 . The variable restriction zone  64  is shown as a spring mechanism, which opens the check valve when the pressure exceeds a predetermined value. The pressurized gas then passes through a second fixed restriction zone  66  for exiting the flow control valve  30 . However, a device that can control the flow of a pressurized gas may be used. Particularly preferred is a ball and spring type valve device, or diaphragm actuated check valve. The flow control check valve  30  may be located at an exterior surface of each of the apparatus  22 - 26  for allowing gas to continuously exit the respective apparatus  22 - 26  and hence, the system  10 ,  100 .  
      Referring again to  FIGS. 1 and 2 , the system  10 , 100  of the present invention may have a plurality of manifolds  20  for housing electronic components from the outside environment. The manifold for enclosing the electronic components preferably includes: an enclosure preferably formed of a continuous sidewall having an opening at one end thereof to provide access to an interior of manifold  20  in the interior of the enclosure. Electronic components are disposed at an interior of the enclosure, which interior is in a fluid communication with the conduit  40  and also provided with the check valve  32 . At a preferred embodiment, the access opening for the enclosure is provided with a substantially tamper proof cover for the opening to prevent access to the internal components and contamination thereof. Complete replacement or turnover of all gas within the entire system occurs three to ten times per hour for optimum protection of the system.  
      The apparatus shown in  FIG. 4  shows an example of an apparatus  22  for enclosing or communicating with the electronic or mechanical devices in the plant. Pressurized gas  72  is distributed to apparatus  22  via cable  40 , which is connected to apparatus  22  by receptacle  36 . Pressurized gas  72  circulates within a housing  70  of the apparatus  22 . Upon reaching the predetermined pressure, pressurized gas  74  exits housing  70  through flow control check valve  30  and exhausts to the atmosphere  76 . The apparatus  22 - 26  may include its own integral sensor  75  or such sensor  75  may be disposed at a remote location and connected to the apparatus  22  by another cable or conduit similar to that of conduit  40 . A flow control check valve  30  may also be used with the sensor  75  disposed at the remote location.  
      As also shown in  FIG. 5 , the pressurized gas flows through conduit  40  into their respective apparatus  22 - 26 . Each apparatus is connected to the distribution means or manifold  20  via its own conduit  40 . The conduit  40  used for this purpose must be capable of handling pressurized gas flow. Generally, the conduit  40  will additionally be used to contain electrical cables and wires. For example, any form of tubing may be used, such as pipes, plastics, cables, or the like, which are suitable conduits. Preferably, each conduit  40  has a first end such as receptacle  33  that is connected to the manifold  20  and a second end such as receptacle  36  that connects to the respective one of the apparatus  22 - 26  at a mating receptacle  37 . The receptacles  33 ,  36 ,  37  are preferably impervious to water and do not allow the gas to escape the system. A passageway  38  extends through the conduit  40  preferably between contact pins  39  of the receptacle  33 .  
      In another embodiment of the conduit  40  as shown in  FIG. 5A , a tube  41  extends through the passageway  38  or core of the conduit. Th tube  41  provides passage for the pressurized gas between and among the elements of the system. In a preferred embodiment of the present invention, modified part P/N FS 4.4-0.5/14.5 microstyle DC receptacles available from Turck, Inc. are used. In the preferred embodiment, the receptacles are multi-pin male connectors, which are mated to molded female connectors having shielded or jacketed cables for connection of the electronic circuitry internal to the enclosure to a central computer or other external electronics.  
      Should a conduit  40  leak or be severed, such condition will not diminish or compromise the effectiveness of the system  10 ,  100 . The pressure of the system will be compensated for by the valve  32  at manifold  20  closing off to maintain pressure. In such a situation, the slight reduction in pressure will trigger an alarm in the system for appropriate corrective action to be taken.  
      Referring again to  FIGS. 2, 3 , and  5 A, flow and pressure profiles for the present system  10 ,  100  can be realized by the construction, control and disposition of the system in the corresponding facility or plant. In particular, pressure control points are preferably realized at regulating valves  52  and  54 , as well as check valve  32  and variable restriction zone  64 . Flow control points for the present system  10 ,  100  are realized at flow control module  56  and fixed restriction zones  62 ,  66 . In addition, the conduit  40  is also provided with flow control points by virtue of the tube  41  as discussed with respect to  FIG. 5A . The flow and pressure profiles provide for a steady, continuous flow of the pressurizing fluid through the components at each level of the cascade in the system  10 ,  100 .  
      Although the system of the present invention is typically used in wet, humid environments, it should be understood that the system may be used in any environment, wherein it is desirable to prevent moisture and contaminants from contacting an electronic, mechanical, etc., apparatus.  
      The present invention has been described with particular reference to the preferred embodiments thereof. It will be understood that variations and modifications may be made therein without departing from the spirit and scope of the present invention as defined in the appended claims.