Tube shields having a thermal protective layer

Abstract

A tube shield, and method of manufacturing the tube shield, having a support structure with an external surface, an internal surface, and an edge, and a thermal protective layer on at least one surface of the shield support structure. The thermal protective layer is composed of a filler, one or more emissivity agent, and either an inorganic adhesive or a binder that is colloidal silica, colloidal alumina, or combinations thereof. A colorant, a surfactant, and/or a stabilizer may be incorporated into the thermal protective layer.

1 . A tube shield for protecting an external surface of a tube having a tube wall, comprising:
 a support structure having an internal surface and an external surface,   said internal surface formed to encompass the tube and be disposed adjacent the tube wall; and   a thermal protective layer disposed on at least one surface of said shield support structure, wherein said thermal protective layer has   a. from about 5% to about 40% of an inorganic adhesive, from about 45% to about 92% of a filler, and from about 1% to about 20% of one or more emissivity agents; or   b. from about 5% to about 60% of colloidal silica, colloidal alumina, or combinations thereof; from about 23% to about 79% of a filler; and from about 1% to about 20% of one or more emissivity agents.   
   
   
       2 . The tube shield of  claim 1 , wherein:
 said support structure is an elongated half-circle shell conformed to mate with a second tube shield to receive the tube therebetween; and   said support structure further comprises an edge surface running along a periphery of said internal and external surfaces and extending therebetween.   
   
   
       3 . The tube shield of  claim 1 , wherein:
 said thermal protective layer is   disposed on said external surface of said support structure;   disposed on said internal surface of said support structure;   disposed on said external surface and on said internal surface; or   disposed substantially on all surfaces of said support structure.   
   
   
       4 . The tube shield of  claim 1 , wherein:
 said support structure comprises a metallic substrate or a ceramic substrate.   
   
   
       5 . The tube shield of  claim 4 , wherein:
 said metallic substrate is taken from the group consisting of steel, low carbon steel, stainless steel, cast iron, iron, aluminum, and alloys, and combinations thereof.   
   
   
       6 . The tube shield of  claim 1 , wherein:
 said thermal protective layer further comprises   from about 1.0% to about 5.0% of a stabilizer;   from about 1.0% to about 5.0% of a stabilizer taken from the group consisting of bentonite, kaolin, magnesium alumina silica clay, tabular alumina, and stabilized zirconium oxide;   up to about 1.0% of a surfactant;   a colorant; or   combinations thereof.   
   
   
       7 . The tube shield of  claim 1 , wherein:
 said inorganic adhesive is taken from the group consisting of an alkali/alkaline earth metal silicate taken from the group consisting of sodium silicate, potassium silicate, calcium silicate, and magnesium silicate;   said filler is taken from the group consisting of silicon dioxide, aluminum oxide, titanium dioxide, magnesium oxide, calcium oxide, and boron oxide;   said one or more emissivity agents are taken from the group consisting of silicon hexaboride, boron carbide, silicon tetraboride, silicon carbide, molybdenum disilicide, tungsten disilicide, zirconium diboride, cupric chromite, and metallic oxides;   said emissivity agents are a metal oxide taken from the group consisting of iron oxide, magnesium oxide, manganese oxide, chromium oxide, and derivatives thereof; or combinations thereof.   
   
   
       8 . The tube shield of  claim 1 , wherein:
 said thermal protective layer contains   a. from about 5% to about 40% of an inorganic adhesive, the inorganic adhesive is taken from the group consisting of an alkali/alkaline earth metal silicate taken from the group consisting of sodium silicate, potassium silicate, calcium silicate, and magnesium silicate; from about 45% to about 92% of a filler, the filler taken from the group consisting of silicon dioxide, aluminum oxide, titanium dioxide, magnesium oxide, calcium oxide, and boron oxide; and from about 1% to about 20% of one or more emissivity agents taken from the group consisting of silicon hexaboride, boron carbide, silicon tetraboride, silicon carbide, molybdenum disilicide, tungsten disilicide, zirconium diboride, cupric chromite, and metallic oxides;   b. from about 5% to about 60% of colloidal silica, colloidal alumina, or combinations thereof; from about 23% to about 79% of a filler taken from the group consisting of silicon dioxide, aluminum oxide, titanium dioxide, magnesium oxide, calcium oxide, and boron oxide; and from about 1% to about 20% of one or more emissivity agents taken from the group consisting of silicon hexaboride, boron carbide, silicon tetraboride, silicon carbide, molybdenum disilicide, tungsten disilicide, zirconium diboride, cupric chromite, and metallic oxides;   c. from about 5% to about 40% of an inorganic adhesive, the inorganic adhesive taken from the group consisting of an alkali/alkaline earth metal silicate taken from the group consisting of sodium silicate, potassium silicate, calcium silicate, and magnesium silicate; from about 45% to about 92% of a filler, the filler taken from the group consisting of silicon dioxide, aluminum oxide, titanium dioxide, magnesium oxide, calcium oxide, and boron oxide; and from about 1% to about 20% of one or more emissivity agents taken from the group consisting of silicon hexaboride, boron carbide, silicon tetraboride, silicon carbide, molybdenum disilicide, tungsten disilicide, zirconium diboride, cupric chromite, and metallic oxides; and from about 1% to about 5% of a stabilizer taken from the group consisting of bentonite, kaolin, magnesium alumina silica clay, tabular alumina, and stabilized zirconium oxide; or   d. from about 5% to about 60% of colloidal silica, colloidal alumina, or combinations thereof; from about 23% to about 79% of a filler taken from the group consisting of silicon dioxide, aluminum oxide, titanium dioxide, magnesium oxide, calcium oxide, and boron oxide; and from about 1% to about 20% of one or more emissivity agents taken from the group consisting of silicon hexaboride, boron carbide, silicon tetraboride, silicon carbide, molybdenum disilicide, tungsten disilicide, zirconium diboride, cupric chromite, and metallic oxides; and from about 1% to about 5.0% of a stabilizer taken from the group consisting of bentonite, kaolin, magnesium alumina silica clay, tabular alumina, and stabilized zirconium oxide.   
   
   
       9 . The tube shield of  claim 1 , further comprising:
 a brace disposed to secure said tube shield in place, said strap having a support structure with the thermal protective layer disposed thereon.   
   
   
       10 . The tube shield of  claim 1 , wherein:
 said support structure formed into an elongated half-circle shell is bent to form an inner or an outer elbow to accommodate a turn in the tube and coupled with a second tube shield bent to form an opposing inner or outer elbow to encapsulate the turn in the tube.   
   
   
       11 . The tube shield of  claim 1 , having
 from about 2% to about 20% of a first emissivity agent taken from the group consisting of, boron carbide, silicon carbide powder, silicon tetraboride, molybdenum disilicide, tungsten disilicide, zirconium diboride, cupric chromite, and metal oxides; and from about 0.5% to about 3.5% of a second emissivity agent taken from the grouped consisting of silicon hexaboride.   
   
   
       12 . A method of manufacturing a tube shield having a thermal protective layer, comprising:
 providing a support structure having an exposed surface;   wherein the exposed surface is on interior surface, or on an exterior surface, or on combinations thereof;   mixing a thermal protective coating containing
 a. from about 6% to about 40% of an inorganic adhesive, from about 23% to about 56% of a filler, from about 0.5% to about 15% of one or more emissivity agents, and from about 18% to about 50% water, or 
 b. from about 15% to about 60% of colloidal silica, colloidal alumina, or combinations thereof; from about 23% to about 55% of a filler, from about 0.5% to about 15% of one or more emissivity agents, and from about 10% to 50% water; and 
   applying the mixed thermal protective coating to the exposed surface using a spray gun to form a thermal protective layer from about 2 mils (5 microns) to about 10 mils (254 microns) thick.   
   
   
       13 . The method of  claim 12 , further comprising:
 the thermal protective layer further comprises   from about 0.5 percent to about 2.4 percent of a stabilizer;   up to about 1.0% of a surfactant;   from about 0.5 percent to about 2.4 percent of a stabilizer taken from the group consisting of bentonite, kaolin, magnesium alumina silica clay, tabular alumina, and stabilized zirconium oxide;   a colorant; or   combinations thereof.   
   
   
       14 . The method of  claim 12 , wherein:
 the inorganic adhesive is taken from the group consisting of an alkali/alkaline earth metal silicate taken from the group consisting of sodium silicate, potassium silicate, calcium silicate, and magnesium silicate;   the filler is taken from the group consisting of silicon dioxide, aluminum oxide, titanium dioxide, magnesium oxide, calcium oxide, and boron oxide;   the one or more emissivity agents are taken from the group consisting of silicon hexaboride, boron carbide, silicon tetraboride, silicon carbide, molybdenum disilicide, tungsten disilicide, zirconium diboride, cupric chromite, and metallic oxides;   the emissivity agents are a metal oxide taken from the group consisting of iron oxide, magnesium oxide, manganese oxide, chromium oxide, and derivatives thereof; or   combinations thereof.   
   
   
       15 . The method of  claim 12 , wherein:
 the spray gun is taken from the group consisting of an high volume low pressure spray gun or an airless spray gun.   
   
   
       16 . The method of  claim 12 , further comprising:
 agitating the solution of thermal protective coating prior to applying.   
   
   
       17 . The method of  claim 12 , further comprising:
 rotating the direction of spray to facilitate an even thickness.   
   
   
       18 . The method of  claim 12 , further comprising:
 allowing the thermal protective layer to air dry from about two to about four hours.   
   
   
       19 . The method of  claim 12 , wherein:
 the support structure comprises a metallic substrate or a ceramic substrate.   
   
   
       20 . The method of  claim 12 , further comprising:
 preparing the exposed surface first by   cleaning, grit blasting, or combinations thereof.