Abstract:
A system having a flame rod assembly for operation in a high temperature pilot burner. The assembly is designed for operation in temperatures from about −40 to 1100 degrees C. The system may operate in inclement weather involving high speed winds and significant amounts of moisture and rain to hurricane storm force levels and rates. The system incorporates an electrical apparatus which may provide flame sensing and ignition via the flame rod assembly incorporating a quick drying insulator around a rod of the assembly to ensure proper operation of the electrical apparatus.

Description:
[0001]    The present application is a continuation-in-part of U.S. patent application Ser. No. 12/905,309, filed Oct. 15, 2010, and entitled “A Rapidly Self-Drying Rectifying Flame Rod”. U.S. patent application Ser. No. 12/905,309, filed Oct. 15, 2010, is hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    The present disclosure pertains to flame sensing and ignition and particularly to precipitation resistant mechanisms for sensing and igniting pilots. 
       SUMMARY 
       [0003]    The disclosure reveals a system having a flame rod assembly for operation in a high temperature pilot burner. The assembly is designed for operation in temperatures from about −40 to 1100 degrees C. The system may operate in inclement weather involving high speed winds and significant amounts of moisture and rain. The system incorporates an electrical apparatus which may provide flame sensing and ignition via the flame rod assembly incorporating a quick drying insulator around the rod. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0004]      FIG. 1  is a diagram of a pilot for an industrial process flare assembly; 
           [0005]      FIG. 2  is a diagram of an illustrative example of a flame rod assembly for a detection and ignition mechanism; 
           [0006]      FIGS. 3   a  and  3   b  are diagrams of configurations of a flame rod assembly for a pilot burner; and 
           [0007]      FIG. 4  is a diagram of still another configuration of a flame rod assembly. 
       
    
    
     DESCRIPTION 
       [0008]    An industrial process flare may need a computerized electronic management system to continuously monitor the existence of its pilot flame. This may be to ensure that the flare will ignite when the need arises. As electronic management technology advances, a closed loop feedback time cycle required may decrease. However, related art flame monitoring technology is currently not necessarily providing adequate response times. 
         [0009]    Ionization flame rod technology may indicate an existence of a flame virtually instantaneously. Because of extreme environmental conditions, a product is needed for use in flare pilot applications. The product may utilize several characteristics to overcome various challenges. A location of the flame rod may ensure that it will work continuously in high wind speed environments. A hermetic seal and a particular profile of a rod insulator may keep heavy rain and moisture from causing a failure of the flame rod. A signal cable connected to the rod at the insulator should be of the type that can withstand high temperatures. The materials and manufacturing processes may allow the resultant flame rod product to withstand very high temperatures during an operational life. Also, such product may be rapidly self-drying. These considerations may differentiate the present flame rod product from other flame rod technology in terms of reliability and service life, thus giving a holder of the present flare rod product a competitive advantage in the flare and flare pilot market. 
         [0010]    The present product may contain a limited number of parts. The flame rod and its threaded connections may be either cast or machined from a steel or stainless steel alloy (selected as required for service). The insulator may be made of any suitable insulating material, such as ceramic. The insulator material may be cast with a specific geometry and attached to a flame rod at the end connections via a high temperature coupling with brazing or welding. “Brazing” or “welding” may be referred to as “brazing” herein. “High temperature” brazing may withstand temperatures at least up to 1100 degrees Celsius (C.) (2012 degrees F.). The brazing process may satisfy specifications for integrity and temperature requirements. Results of high temperature brazing may withstand temperatures equal to or greater than about 815 degrees C. (1500 degrees F.). The high temperature brazing process may involve a use of alloys incorporating materials such as chromium, nickel, and other like materials. Ordinary or low temperature brazing may involve a use of materials such as copper, silver, and the like. 
         [0011]    A signal cable attached to the flame rod may have a high temperature rating sufficient for the operating conditions. An example flame rod product may meet geometrical requirements as revealed in  FIG. 2 . The metallic materials may be machined or cast from suitable steel or stainless steel alloys. The alloys may incorporate, but are not necessarily limited to, ASTM 304, ASTM 310, ASTM 316, Inconel™, Kanthol (or Kanthal), hastaloy (or Hastelloy™), and so forth. 
         [0012]    An ignition/flame rod for a flare may provide flame ignition through sparking and detection through ionization detection in a pilot for a flare system. The product may be exposed to extreme temperatures (i.e., −40 to 1100 degrees C.). The product may be mounted several hundred of feet above the ground in the air, or mounted close to the ground, or somewhere in between. The product needs to withstand the extreme temperatures without having its performance affected. The product should be robust enough to have at least five years of life without issues, which may be the typical lifecycle of a refinery between service times. Detection should be reliable at a six-sigma level and be without false positives. 
         [0013]    In sum, certain aspects of the present product may incorporate self drying capabilities, a temperature resistance up to 1100 Celsius degrees, and a combination of detection and ignition capabilities. Particularly, the ceramic insulator may have self-drying capabilities. Likewise, the flame rod may have self-drying capabilities. 
         [0014]    The flame rod may be made of a high temperature, high performance (HP) alloy, to withstand the severe temperatures produced both by the pilot flame and by the flare flame. The rod may be connected to a longer rod or tubing made of a high temperature resistant alloy. An electrical signal may be transmitted through a naked rod/tubing to a wire several feet below and then to an electric box. The electric box may provide a carrier voltage for ionized gas detection from the pilot flame through a flame relay and another voltage for sparking through a high voltage transformer. A switch may allow an electrical passage selectively between the two devices. The switch box may be placed at a ground level. Two ceramic insulators may provide protection against short circuiting and may be placed in the upper part of the unit, where the naked rod is the distance between the two ceramic assemblies ( FIG. 4 ). The distance may, for example, be several feet. The tip of the rod may be inserted in the pilot tip above the gas spud. 
         [0015]    A ceramic insulator assembly may be provided. A flame rod may be purchased and inserted in the ceramic insulator. High temperature alloy tubing or a rod may be attached to the bottom end of the insulator assembly with a coupling. The second ceramic insulator assembly may be inserted in the high temperature alloy tubing or rod. A wire may be attached to the bottom part of the assembly and run all the way to the switch box. The switch box may be placed at grade, or where the customer specifies, and it may be connected to the electric power source. 
         [0016]      FIG. 1  is a diagram of a pilot  11  for an industrial process flare assembly  12 . Flare  12  may have a tube or stack  13 . On top of tube  13  may be a nozzle  16  upon which a flare main flame  17  of flare  12  can arise and burn. In examples of application, a gas flare or flare stack may be used to eliminate fluids such as combustible waste, process gas or other material at oil wells, gas wells, rigs, refineries, chemical plants, refinery process units, chemical process units and so on. A present concern is to continuously monitor the existence of the flame of the pilot  11  for flare  12 . Flare  12  might not necessarily always have a flame  17  if there is no fluid or material to burn; however, flare  12  should be ready to burn with a flame  17  at virtually any time. Such readiness may require a pilot  11  proximate to flare  12 . 
         [0017]    The present approach and apparatus may be used for assuring that a flame from pilot  11  is present for flare  12 . Pilot  11  may incorporate a pilot burner  21  which provides the flame which is present for flare  12  in case the flare needs to be ignited to obtain a flame  17  to burn off gas or whatever is provided via tube or stack  13 . A tube  22  may provide an air and fuel mixture for sustaining the flame of the burner  21  of pilot  11 . A tube  23  with screen and/or deflector  24  may provide a flame front generator (FFG) for igniting the pilot burner  21  in situations where the flame of the pilot burner  21  has ceased. A tube  25  may be connected to tube  22 . Tube  25  may provide high energy (capacitance discharge) ignition up stream of the fuel air mixture delivery to burner  21  from tube  22 . Tubes  23  and  25  may provide alternate forms of ignition for the pilot burner  21 . In burner  21 , there may be a thermocouple and line  26  which may determine whether or not burner  21  is operating with a measurement of temperature at the burner. Thermocouple and line  26  may be connected to a temperature indicator  64 . A concern may be a slow indication of temperature change at burner  21 . The slow indication may imply that if the pilot flame at burner  21  goes out, there may be a delay for the burner  21  assembly to cool down sufficiently to reveal an absence of the pilot  11  flame, and then for an ignition of the pilot flame to occur. Heat from the pilot main flame  17  may inadvertently heat the thermocouple  26  when the pilot flame is extinguished causing a false positive indication of the presence of flame at the pilot burner  21 . 
         [0018]    A high temperature cable  37  may be attached to the end of a rod  39  with a crimp connection, screw connection, braze or weld. Cable  37  may be to go through pipe or conduit  36  to an electrical switch mechanism  38 . 
         [0019]    Rod  32  may be regarded as a multi-mode device. In one mode, rod  32  may be a part of an ionization device for detecting whether the pilot burner  21  flame is on or not. The detecting may be nearly instantaneous. In another mode, rod  32  may be part of an ignition device for igniting the gas/air mixture to pilot burner  21  in an event that the flame in the pilot burner has been extinguished. An operating carrier voltage to rod  32  in an ionization or detection mode may, for instance, be in a range from 100 to 200 volts. The noted operating detection voltage range is an illustrative example but may be of other ranges. The operating voltage to rod  32  in an ignition mode may be in a range from 10 to 20 thousand volts. The noted operating ignition voltage range is an illustrative example but may be of other ranges. Switch mechanism  38  may provide a selected voltage to rod  32  via rod  39  and cable  37 . Rods  32  and  39  in some approaches as may instead be a one-piece rod. 
         [0020]    Insulator  34  may be for high voltage isolation (i.e., up to 20,000 volts) of rod  32  from various items in the environment. The rod  39  portion in insulator  34  may be hermetically sealed from the environment. Insulator  34  may have a corrugated shape or other advantageous shape on its external portion to prevent the various items, such as heavy rain, from causing electrical shorts or failures. Insulator  34  may be positioned relative to flame  17  and/or flame  21  so as to be dried almost instantly. Insulator  34  may be fabricated from other suitable insulating materials besides ceramic. 
         [0021]    A structure  82  may hold and support tube  22 , tube  23 , tube  25 , tube  36  and thermocouple line  26 . 
         [0022]    When a flame is emitted by pilot burner  21 , the combustion process may create and move a field of ionized gas  81  as a part of the burner flame. An effect of an ionized gas field  81  in the flame may result in an electrical voltage or potential occurring between the metal burner  21  and flame rod  32 , as rod  32  may be situated through an opening  79  of burner  21  to be in the ionized gas field  81 . The voltage may be conveyed over a carrier signal emitted by a flame rod signal amplifier  42 . The signal may be conveyed from rod  32  via coupling  33 , rod  39 , coupling  35 , cable  37 , switch  38  and line  43  to amplifier  42  for conditioning into a useful signal at an output  44 . Amplifier  42  and burner  21  may be connected to a common ground  63 . 
         [0023]    Output  44  may indicate whether there is a flame in the pilot burner  21 . If there is no flame, then output  44  via a processor  45  may cause electrical box  38  to send a very high voltage from voltage source  46  via line  47  to rod  32  in form of a spark to ignite the fuel/air mixture from tube  22  so as to re-light the pilot burner  21 . Voltage source  46  and burner  21  may be connected to the common ground  63 . 
         [0024]    Switch  38 , processor  45 , signal amplifier  42  and high voltage source  48  may assembled together as illustrated or alternately constructed together into a single electrical device. Alternately, switch  38 , processor  45 , signal amplifier  42  and high voltage source  46  may be constructed in any combination of combined devices. 
         [0025]      FIG. 2  is a diagram of a flame rod assembly  31  for the detection and ignition mechanism. The mechanism may quickly detect pilot  11  flame failure and provide a prompt ignition of the pilot  11  burner  21  flame. The flame rod may be two components  32  and  39 . Rod  32  may be a flame rod portion which is of a cast and/or machined stainless steel alloy. Coupling  33  may connect rod  32  to an insulator  34 . An end  51  of rod  32  and an end  52  of rod  39  may be threaded and be screwed into threaded counterparts in both ends of coupler  33 . Coupler  33  may be of a cast and/or machined stainless steel alloy. Insulator  34  may be composed of ceramic or other similar appropriate material. Coupling  33  may be attached to insulator  34  with a compression, a brazed, high temperature sealed connection. At a base of insulator  34  may be a stainless steel coupling  35  brazed to the insulator. Coupling  35  may be attached with a weld, braze or threaded ends, to a conduit or pipe  36 , as shown in  FIG. 1 . An end  54  of rod  39  and an upper portion of coupling  35  may be threaded for connection to each other. The lower portion of coupling  35  at end  55  may be threaded for connection to pipe or conduit  36  ( FIG. 1 ). Even though the flame rod is shown to be two rods or pieces  32  and  39  connected together by being threaded into coupling  33 , rods  32  and  39  may alternatively be a one piece rod. In either rod structural approach, rod or rod portion  32  may have a significant portion of its unconnected end situated in the pilot burner  21  via opening  79  ( FIG. 1 ). 
         [0026]      FIG. 2  further shows example dimensions of assembly  31 . Dimension  56  of ⅜ inch may be a diameter of rod portions  32  and  39 . Length  57  of rod portion  32  may be 5 and ½ inches. Length  58  of insulator  34  may be approximately 6 inches or more. Diameter dimension  59  of coupling  33  may be approximately 1 inch. A length dimension  61  of coupling  33  may be approximately ¾ inch. A length dimension  62  of coupling  35  may be 2 inches. These dimensions may instead be of other magnitude values. 
         [0027]      FIG. 3   a  is a diagram of a configuration of a stainless steel flame rod  65  assembly situated in a pilot burner  66 . A ceramic insulator  67  may be situated on flame rod  65  with compression fittings  68  and  69  brazed to or compressed against and sealing to the ceramic at the ends of insulator  67 . A high temperature cable  71  may be connected to rod  65  at fitting  69 . A mounting bracket  72  may be secured around ceramic insulator  67 . 
         [0028]      FIG. 3   b  is a diagram of another configuration of a flame rod  65  assembly. Fittings  68  and  69  may be brazed to the ends of ceramic insulator  67  to secure it to rod  65 . Rod  65  may be bent for another kind of a burner. Rod  65  may have an insulator  73  on a portion of the rod near the burner. A ring-like bracket  74  on insulator  73  may be welded or brazed to a pilot tip. 
         [0029]      FIG. 4  is a diagram of still another configuration of a flame rod  65  assembly. There may be a conducting rod or cable  76  connected to flame rod  65  with a coupling  77 . A ceramic insulator  67  may be around rod  65  and secured with compression fittings  68  and  69  brazed to the ceramic insulator  67 . To the left of fitting  68  in the Figure, there may be a significant length of un-insulated rod  65  until another ceramic insulator  78  is provided on rod  65  beginning at another NPT compression fitting  69  brazed or otherwise sealed to insulator  78 . At the other end of insulator  78  may be another fitting  68  brazed or otherwise sealed to the ceramic insulator  78 . Mounting brackets  72  may be secured around insulators  67  and  78 . Rod  65  may extend from insulator  78  and have a curve for a particular kind of burner. A ceramic insulator  73  may be formed on rod  65  close to the end of the rod. A ring-like bracket  74  formed on insulator  73  may be rested against, welded or brazed to a pilot tip. 
         [0030]    With reference to  FIGS. 1-4 , insulators  34 ,  67  and  78  may become wet from exposure to environmental elements such as precipitation. Insulators  34 ,  67  and  78  may have a length, shape and design so as to minimize the possibility of electrical short circuiting from the flame detection/ignition rods  32 ,  39 ,  65 ,  71  and  76  to grounded supports  35  and  72 . Insulators  34 ,  65  and  78  may also be positioned relative to the burner flame  21  and/or the main flare flame  17  such that radiant heat from either or both flame  21  and flame  17  will rapidly (nearly instantaneously) dry a wet insulator  34 ,  67  or  78  thereby eliminating a possible short circuit. A short circuit may otherwise render the ignition and flame detection capabilities of the present system inoperable. 
         [0031]    The position the insulators  34 ,  67  and  78  from the flare  12  and burner  21  may vary relative to the size of the flare flame  17  and/or the burner  21  flame. However, if the flare flame  17  is extinguished, for instance in a case where there is no material available for burn-off, then the burner  21  flame needs to be sufficiently large or hot enough to keep the insulator dry at virtually all times even for a short period when the burner  21  flame may be accidentally or intentionally be extinguished for some reason. In case of such extinguishment, the insulator should be sufficiently hot enough to maintain a dry condition in a worse case environment of precipitation for a period of time long enough (e.g., thermal inertia) until burner  21  can be relit with a flame. 
         [0032]    The length of the insulators  34 ,  67  and  78  should be sufficiently long enough and thick enough to prevent arcing between the rod and, for example a grounded component such as a support strap, during a conveyance of a high voltage via the rod during an igniting of burner  21 . The needed length, thickness and/or diameter of the insulators may depend on the magnitude of the ignition voltage. Also, the dimensions (e.g., diameter, thickness and length) of the insulators should be sufficient so that leakage of ionization signals for indicating a presence or non-presence of a burner  21  flame is sufficiently small so that the signals are strong enough at the recipient end for detection. The material content of the insulator should also have a very small conductance factor. Ceramic may be an example of such insulator material. 
         [0033]    The shape of insulators  34 ,  67  and  78  may aid in reduction of the effects of precipitation on the insulators. An example design may incorporate a corrugated external surface on the insulators. The shape of the insulators may be selected from a variety of designs. Further, the insulators may have straight and/or curved configurations. Other design factors of the insulators may be implemented. 
         [0034]    In sum, the factors of insulators  34 ,  67  and  78  such as position relative to and distance from flare  12  and/or burner  21 , insulator temperature, length, thickness, diameter, material content, shape, configuration and other factors may be interdependent (e.g., in terms of quantification) in that, for example, a strong factor may compensate for a weak factor. The design and layout of the flare  12  and burner  21  may indicate factors needed for effective insulators. The location and environment of the flare and burner may indicate considerations such as cold, humid, hot, dry, windy, calm and other conditions, which may dictate needed specifics for insulators. 
         [0035]    In the present specification, some of the matter may be of a hypothetical or prophetic nature although stated in another manner or tense. 
         [0036]    Although the present system and/or approach has been described with respect to at least one illustrative example, many variations and modifications will become apparent to those skilled in the art upon reading the specification. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the related art to include all such variations and modifications.