Abstract:
The interior of a vessel containing pressurized fluid is protected against undesirable chemical corrosion and/or mechanical erosion caused by the fluid due, for example, to changes in the chemistry of the fluid, by an imperforate, chemically corrodable tube projecting into the interior of the vessel and having a closed inner end. A chemical corrosion through-opening in any portion of the tube permits pressurized fluid to enter and pressurize the tube interior, with fluid pressure within the tube being utilized to automatically generate a corrosion/erosion detection signal indicative of an undesirably high fluid chemical corrosivity level within the vessel.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention generally relates to protecting fluid containing vessels from chemical corrosion and/or mechanical erosion by fluid disposed therein and, in illustrated embodiments thereof, more particularly provides specially designed pressure-based chemical corrosion/mechanical erosion monitoring and protection apparatus and associated methods for such vessels.  
         [0002]     Fluid-containing vessels, such as tanks and the like, are often susceptible to internal corrosion and/or erosion damage, and corresponding premature failure when the chemical corrosivity level of the fluid which they contain increases. For example, water chemistry is known to attack boiler, water heater and chiller tank materials, with the result that the tanks, and associated fluid system materials, can prematurely deteriorate.  
         [0003]     Various proposals have previously been made for monitoring corrosion of a sacrificial member disposed in fluid contained within a vessel and automatically generating a protective corrosion detection output signal. Generation of this corrosion detection signal permits suitable maintenance to be performed prior to premature corrosion damage to the vessel. A primary disadvantage of many of these previously proposed corrosion detection systems has been their structural and/or fabricational complexity which undesirably increases their overall costs.  
         [0004]     A need thus exists for a simpler, less expensive technique for monitoring a vessel and protecting it from chemical corrosivity of fluid which it contains. It is to this need that the present invention is directed.  
       SUMMARY OF THE INVENTION  
       [0005]     In carrying out principles of the present invention, in accordance with representatively illustrated embodiments thereof, a vessel adapted to contain a quantity of pressurized fluid is provided with specially designed apparatus and associated methods which detect a predetermined, corrosivity level in the fluid (created, for example, by a change in its chemistry during operation of a system in which the vessel is incorporated) and responsively generates a corrosion/erosion detection signal.  
         [0006]     In one representative embodiment thereof, the corrosion protection apparatus comprises a sacrificial member having a hollow interior bounded by a chemically corrodable outer wall disposed within the vessel, the outer wall being configured and constructed to corrode through to the interior of said sacrificial member in response to exposure of the outer wall to a predetermined combination of fluid exposure time and fluid chemical corrosivity correlated to a predetermined amount of chemical corrosion and/or mechanical erosion by the fluid of the interior of the vessel; and a monitoring system operative to receive fluid pressure from the interior of the sacrificial member and responsively generate an output signal indicative of an unacceptably high chemical corrosivity level of fluid within the vessel. The sacrificial member may be mounted within the vessel or may otherwise be communicated with its interior, such as by being mounted in a fluid conduit communicating with the interior of the vessel to be protected.  
         [0007]     In a second representative embodiment thereof, the corrosion protection apparatus comprises at least one additional sacrificial member substantially identical to the first sacrificial member. The interiors of the sacrificial members are communicated, representatively by flexible conduits, to provide the corrosion/erosion protection apparatus with a desirable redundancy in corrosion detection.  
         [0008]     Preferably, the hollow sacrificial members used in these illustrative embodiments, which provide the vessel with chemical corrosion protection as opposed to cathodic protection against electrical-based corrosion, are non-anode members, have hollow imperforate tubular configurations with closed inner ends disposed within the vessel, have interiors which are empty prior to receiving pressurized vessel fluid therein, with a chemical corrosion-created hole in any portion of the tube wall causing pressurized fluid within the vessel to enter and pressurize the interior of the tube.  
         [0009]     The monitoring system may take a variety of alternate forms including, for example, a switch structure mechanically actuated by transmission thereto of vessel fluid pressure transmitted thereto via the interior of a chemically corroded sacrificial member and coupled to an electrical monitoring circuit operative to responsively output the corrosion detection signal, or a suitable mechanical device operative to receive a fluid pressure generated force and responsively output a mechanical corrosion/erosion detection signal.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a schematic cross-sectional view through a portion of a pressurized fluid-containing vessel having associated therewith specially designed pressure-based chemical corrosion/mechanical erosion protection apparatus embodying principles of the present invention;  
         [0011]      FIG. 2  is a schematic representation of a mechanical version of a portion of the chemical corrosion/mechanical erosion protection apparatus; and  
         [0012]      FIG. 3  is a schematic cross-sectional view through a portion of a pressurized fluid-containing vessel having associated therewith an alternate embodiment of the chemical corrosion/mechanical protection apparatus depicted in  FIG. 1 . 
     
    
     DETAILED DESCRIPTION  
       [0013]     Schematically depicted in  FIG. 1  is an illustrative vessel  10  adapted to hold a pressurized fluid  12  and having a chemically corrodable or mechanically erodable outer wall  14 . The pressurized fluid  12  may be a liquid, such as water, or a gas, and the vessel  10  may representatively, but not by way of limitation, be a metal tank of the type used in water heaters, boilers, chillers or the like.  
         [0014]     Operatively associated with the vessel  10 , and embodying principles of the present invention, is specially designed protective apparatus  16  for protecting the vessel  10  against chemical corrosion and/or mechanical erosion of the interior surface of its outer wall  14  by the fluid  12  within the vessel  10  in the event that the chemical corrosivity of the fluid  12  becomes undesirably high. The protective apparatus  16 , in the illustrative embodiment thereof shown in  FIG. 1 , includes a hollow sacrificial member  18  disposed within the interior of the vessel  10 , a pressure diaphragm assembly  20 , an electrical switch  22 , and a suitable electrical monitoring circuit  24 . While the sacrificial member  18  is representatively illustrated as being disposed within the vessel  10 , it could be otherwise communicated with the vessel&#39;s interior such as being placed in a fluid conduit (not shown) communicated with the interior of the vessel  10 . The sacrificial member  18  may thus be said to be “communicated with” the interior of the vessel in either of these two situations.  
         [0015]     The hollow sacrificial member  18 , which is shown projecting downwardly into the interior of the vessel  10 , is representatively a tube formed from a suitable chemically corrodable material such as a selected metal, and has an initially imperforate side wall  26 , a closed inner end  28 , and an open upper end  30 . When the tube  18  is initially positioned within the vessel  10 , the interior  32  of the tube  18  is empty, and is isolated from the interior of the vessel  10  by the tube side and end walls  26 , 28  which enclose the tube interior  32  and are directly exposed to the fluid  12 . While the hollow sacrificial member  18  representatively has a tubular configuration, it could alternatively have a variety of other imperforate, hollow, enclosing configurations if desired without departing from principles of the present invention.  
         [0016]     Pressure diaphragm assembly  20  has a housing  34  internally divided into upper and lower chambers  36 , 38  by a flexible diaphragm member  40 . A vertically movable actuating member  42  is engaged by the top side of the diaphragm member  40 , and a hollow tubular connection section  44  projects downwardly from the bottom side of the housing  34 . As indicated in  FIG. 1 , the connection section  44  is sealingly threaded into a corresponding opening  46  in the vessel wall  14  and is suitably secured to the open upper end  30  of the sacrificial tube  18  in a manner communicating the tube interior  32  with the lower chamber  38  of the diaphragm assembly housing  34 .  
         [0017]     The electrical switch  22  has a mechanical actuating portion  48  operatively engaged by the diaphragm assembly actuating member  42 , and switch  22  is operatively coupled to the monitoring circuit  24  by the schematically depicted leads  50 , 52 .  
         [0018]     According to a feature of the present invention, the hollow, chemically corrodable sacrificial tube  18  is configured and constructed (for example, as to its material and wall thickness) to corrode through to its interior  32  (at, for example, the illustrative side wall corrosion hole  54 ) in response to exposure of its immersed outer wall section  26 , 28  to a predetermined combination of fluid exposure time and fluid chemical corrosivity within the vessel  10  correlated to a predetermined limited amount of chemical corrosion and/or mechanical erosion by the fluid of the interior of the outer vessel wall  14 . Depending on the particular application, this predetermined, limited amount of chemical vessel corrosion and/or mechanical erosion may be very small, or may be substantial (but, of course, well short of vessel failure). By virtue of this design feature of the present invention, a corrosion through-opening will be created in the sacrificial tube  18  before an unacceptable level of chemical corrosion and/or mechanical erosion damage is caused to the interior of the vessel wall  14  by an increased chemical corrosivity level of the pressurized fluid  12 .  
         [0019]     It should be noted that the tube  18  is not designed as a sacrificial anode structure in that it functions to protect the vessel  10  against chemical corrosion and/or mechanical erosion as opposed to cathodically protecting the vessel  10  against electrically-created corrosion. The tube  18 , in a preferred embodiment thereof, may thus be referred to generally as a hollow, chemically corrodable sacrificial non-anode structure.  
         [0020]     When the inserted, initially imperforate tube  18  is subjected to the predetermined combination of fluid exposure time and fluid chemical corrosivity within the vessel  10 , the tube  18  corrodes through (for example at the depicted side wall opening  54 ), at which time pressurized fluid  12  flows through the opening  54  into the empty tube interior  32  and flowing upwardly therethrough toward the lower diaphragm chamber  38  as indicated by the arrow  56  in  FIG. 1 . The resulting fluid pressurization of the lower diaphragm chamber  38  forces the diaphragm  40  upwardly, as indicated by the arrow  58 . In turn, the forced upward movement of the diaphragm  40  upwardly moves the actuating members  42  and  48 , as indicated by the arrow  60 , to operate the electrical switch  22 . In response to the operation of the switch  22 , the monitoring circuit  24  automatically generates an appropriate corrosion/erosion detection signal  62  which may be utilized to notify maintenance personnel that the chemical corrosivity of the fluid  12  has reached an unacceptably high level so that appropriate corrective action can be taken.  
         [0021]     It is important to note that the tube  12  functions both as a chemically corrodable trigger element in the overall protective apparatus  16  and a fluid pressure transport structure. Coupled with the quite simple and relatively inexpensive other portions of the protective apparatus  16 , this advantageously provides the vessel  10  with chemical corrosion protection which is simple, inexpensive and reliable.  
         [0022]     While the fluid chemical corrosion-created opening  54  shown in  FIG. 1  is representatively positioned in the tube side wall  26  generally centrally along the tube length, a fluid chemical corrosion-created opening in any portion of the immersed tube wall  26 , 28  will completely fill and pressurize the tube interior  32  and responsively create the same automatically generated corrosion detection signal  62 . Thus, the corrosion protection function of the tube  18  is independent of both the location of the wall corrosion opening formed therein and the vertical extent of the fluid chemical corrosion to which the tube is subjected.  
         [0023]     Additionally, pressure-driven output components other than the representatively depicted electrical switch  22  and associated electrical circuit  24  could be alternatively utilized in the protective apparatus  16 , if desired, without departing from principles of the present invention.  
         [0024]     For example, as shown in  FIG. 2 , the electrical switch  22  and the electrical circuit  24  shown in  FIG. 1  could be replaced with a suitable mechanical indicating device  64  having a force input portion  66  which, when forcibly engaged by the diaphragm assembly actuating member  42 , responsively outputs a mechanical detection signal  68 . As another alternative, as later described herein, the protective components  20 , 22  shown in  FIG. 1  may be replaced with a pressure-to-electric switch operatively interposed between the open upper end  30  of the tube  18  and the monitoring circuit  24 .  
         [0025]     An alternate embodiment  16   a  of the previously described chemical corrosion/mechanical erosion protective apparatus  16  of  FIG. 1  is schematically shown in  FIG. 2 . In order to facilitate ready comparison between the apparatus  16  and the apparatus  16   a , components in the apparatus  16   a  similar to those in apparatus  16  have been given identical reference numerals to which the subscripts “a” have been added.  
         [0026]     The protective apparatus  16   a  shown in  FIG. 2  is operatively associated with a representative vessel  10   a , having a spaced pair of openings  46   a  formed in its outer wall  14   a , and includes two chemically corrodable sacrificial tubes  18   a  each substantially identical in construction and operation to the previously described tube  18 . The open upper tube ends  30   a  are secured to hollow cylindrical connection structures  70  sealingly and threadingly received in the spaced apart vessel wall openings  46   a . As shown, the interiors  32   a  of the tubes  18   a  are communicated with one another by means of flexible conduits or tubes  72 , 74 . Conduit  72  is interconnected between the left tube  18   a  and a first leg of a tee fitting  76 , and conduit  74  is interconnected between the right tube  18   a  and a second leg of the tee fitting  76 . A flexible conduit  78  is interconnected between the third leg of the tee fitting  78  and the pressure inlet  80  of a conventional pressure-to-electric switch  82  coupled, in turn, to the monitoring circuit  24   a  by leads  50   a , 52   a.    
         [0027]     Via the flexible conduits  72 ,  74  and  76 , the interiors  32   a  of both of the tubes  18   a  communicate with the pressure inlet  80  of the pressure-to-electric switch  82 . Accordingly, when a chemical corrosion through-opening is created in any portion of either of the tubes  18   a  (for example, the corrosion opening  54   a  illustratively shown in the left tube  18   a ), pressurized fluid  12   a  enters such tube, completely fills and pressurizes its interior  32   a , and flows through the flexible tubing (as indicated by the arrows  84  extending through conduits  72 , 78  from the perforated left tube  18   a ). This pressurizes the switch inlet  80  and actuates the switch  82  (either opening or closing it as the case may be) to thereby responsively cause the monitoring circuit  24   a  to output the corrosion/erosion detection signal  62   a.    
         [0028]     As previously mentioned, a fluid chemical corrosion opening formed in any portion of either of the two tubes  18   a  responsively creates the corrosion detection signal  62   a . Thus, compared to the previously described protective apparatus  16 , the protective apparatus  16   a  incorporates therein a desirable corrosion detection redundancy while at the same time providing a simple, inexpensive and reliable chemical corrosion protection for the vessel  10   a.    
         [0029]     The foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims.