Patent Publication Number: US-11384404-B2

Title: Lance with blowout preventer, oxygen flow reducer and improved ignition system

Description:
RELATED APPLICATION 
     The present application is related to and claims priority from U.S. 
     Provisional Application No. 62/830,063 filed Apr. 5, 2019, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention is related to the general field of discharge ports on ladles, furnaces and tundishes, and more specifically to a thermal lance for unplugging a clogged molten metal vessel discharge port. 
     BACKGROUND 
     Discharge ports in molten metal dispensing systems at times can fail to open specifically upon an initial opening attempt, either through the clogging of the nozzle or tap hole fill material or hardened metal in the dispensing port, thereby inhibiting the flow of motel metal out of the vessel. The inventor of the instant application has developed several solutions over the years to assist in unclogging the plugged discharge port, including the inventions disclosed in U.S. Pat. Nos. 4,450,986; 4,746,037; 4,787,142; 4,877,161; 5,544,695; 7,537,723 and 7,563,407, the disclosures of which are incorporated herein by reference in their entirety. 
     In U.S. Pat. No. 4,450,986, a telescoping lance assembly includes a cylindrical housing that encloses a free-floating hollow metal tube. High pressure oxygen (on the order of 100 psi) is ported through the housing to propel the tube upwardly into the obstruction and to sustain burning as the combustible material is ignited. The tube is partially filled with magnesium wires or low carbon steel wires as the primary combustible material. 
     In U.S. Pat. No. 4,746,037, the telescoping lance assembly includes a flared bottom and a combustible collar at the top. The flared bottom is wider than the opening in a bushing located at the top of the housing to keep the tube from falling out of the housing. The tube is filled with magnesium wires or low carbon steel wires intertwined with steel wool to allow oxygen flow and to provide high surface area for combustion. The combustible collar includes a cardboard sheath wrapped around a low temperature blasting fuse and the exposed ends of the wires and steel wool. This construction provides a reliable ignition. 
     U.S. Pat. No. 4,877,161 discloses an improved lance assembly with a double telescoping mode to provide greater extension into a deep discharge port without the need for elongating the housing. The lance assembly includes a cylindrical housing with a port to admit pressurized oxygen. Inside the housing is either one or two free floating tubes. The tube (when single) or the uppermost tube (when dual) contains combustible magnesium or low carbon steel wires as the combustible material. The tube is crimped into the wires at the top and bottom of the tube to prevent the wires from moving forward or backward inside the tube. The tips of the wire extend out of the top end of the tube and they may be capped with an igniter covered by tape. 
     In another prior art lance assembly, the telescoping tube is made of stainless steel to provide a lower rate of consumption than the more combustible material of the thermal lance inside of it. The tube may have a flared base or a base flange to keep it centered in the housing, and the housing may include a bushing near the top end to prevent the tube from completely exiting the housing. The combustible material of the lance is a combination of thin cylindrical rod made of low carbon sheet metal that is roll-formed into a cylindrical rod that allows oxygen to flow axially through the rod. Rods of this type, and the process of making them, are described in U.S. Pat. No. 4,787,142. They are used as electrodes in exothermal cutting of metal and are commonly called burning bars or slice rods. They can be obtained from welding supply distributors under the brand name ARCAIR. The axial oxygen flow and increased surface area as compared to a solid bar or a hollow tubular bar provide for a rapid ignition and for burning in the presence of high temperature and oxygen flow. 
     The rod is surrounded by a low carbon steel sheath to provide greater rigidity and more mass of combustible low carbon steel. The sheath has an inner bore slightly greater than the outer diameter of the rod and an outer diameter less than the inner diameter of the stainless steel tube. The rod extends about ¾ inch to 1½ inches beyond the end of the sheath and several inches out of the opposite end. One end of the sheath is welded to the rod where the longer end of the rod extends such that the rod and sheath move together as a combustible lance within the telescoping tube. The top end of the tube can be crimped and filled with a steel wool (not shown) and can include a low temperature blasting fuse. This lance design provides greater combustible mass and more rigidity than the prior lances filled with steel or magnesium wires. 
     U.S. Pat. No. 7,563,407 discloses an improved thermal lance tip on a lance assembly. The lance assembly includes an outer low carbon steel sheath having an inner diameter. An inner rod is disposed in a sheath having an internal bore and a thin cylindrical rod that is roll-formed from low carbon steel sheet. The rod is sized for conforming fit in the bore of the tube and has a length dimension that is longer than the length of the tube. The rod is inserted into the bore of the tube and allowed to move axially within the tube under propulsion of the pressurized oxygen to allow the rod to be burned at a rate independent of the burn rate of the sheath. One or more apertures in the tube restrict the flow of oxygen until the rod is ignited. An  0  ring located near the fuse protector of the lance housing keeps the lance from moving during routine handling and storage. 
     The existing thermal lances can, at times, be difficult to ignite. A need exists for an improved thermal lance that facilitates ignition. 
     SUMMARY OF THE INVENTION 
     A telescoping thermal lance assembly is disclosed for use in unplugging a vessel discharge port. The telescoping thermal lance assembly includes a housing with an upper end that has an opening. An oxygen inlet port is located on the housing spaced apart from the open end. The oxygen inlet port is configured to connect to a supply of pressurized oxygen. 
     A cylindrical extension tube is disposed within the housing and extends partially out through the opening in the upper end of the housing. The extension tube has an open top and a closed bottom opposite the open top with a sidewall extending between the open top and the closed bottom. The extension tube has an inner diameter defining a cylindrical interior cavity, and an aperture extending through the sidewall or the closed bottom for permitting a flow of oxygen to enter into the interior cavity. The extension tube is slidingly disposed within the housing and configured to slide at least partially out of the opening in the upper end of the housing when a supply of pressurized oxygen is channeled into the inlet port. 
     The assembly includes an elongated cylindrical hollow lance tube made from a combustible material. The lance tube has an axial length with first and second ends. The lance tube has a cylindrical sidewall defined by an outer wall having an outer diameter and an inner wall having an inner diameter. The sidewall has a wall thickness between the outer and inner walls. The lance tube has a longitudinal axis. The lance tube being is slidingly disposed within the interior cavity of the extension tube and configured to slide at least partially out of the open top of the extension tube when a supply of pressurized oxygen is channeled into the aperture. 
     A slice rod is located within the inner wall of the lance tube. The slice rod being formed from low carbon steel. 
     A cap is attached to the open top of the extension tube, spaced apart from the tip of the lance tube. The space below the cap and above the tip of the lance tube defines an igniter section. 
     A tubular blow-out preventer sleeve is located in the igniter section above the tip of the lance tube and inside the extension tube. The sleeve has an outer diameter less than the inner diameter of the extension tube, and a wall thickness that is wider than any gap between the outer diameter of the lance tube and the inner diameter of the extension tube. 
     In one embodiment the sleeve has a bottom that rests against an upper edge of the lance tube. 
     The sleeve preferably has a wall thickness of at least 1/64 inch. 
     The sleeve is preferably made from a combustible material. In an embodiment, the combustible material is low carbon steel. 
     There is preferably steel wool located in the igniter section. 
     The cap preferably includes a hole and a fuse extends from outside the cap through the hole into the igniter section. 
     The telescoping thermal lance assembly may include a plurality of wires inserted into an upper end of the slice rod in close proximity to the cap. The wires being made from low carbon steel. The wires extend into oxygen passageways in the slice rod and protrude from the upper end of the slice rod so as to temporarily inhibit oxygen flow into the igniter section. 
     The foregoing and other features of the invention and advantages of the present invention will become more apparent in light of the following detailed description of the preferred embodiments, as illustrated in the accompanying figures. As will be realized, the invention is capable of modifications in various respects, all without departing from the invention. Accordingly, the drawings and the description are to be regarded as illustrative in nature, and not as restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For the purpose of the illustrating the invention, the drawings show a form of the invention which is presently preferred. However, it should be understood that this invention is not limited to the precise arrangements and instrumentalities shown in the drawings. 
         FIG. 1  is a side view of an inner lance assembly according to the present invention. 
         FIG. 2  is a cross sectional view of a thermal lance assembly including the inner lance assembly of  FIG. 1  and a blowout preventer according to the present invention. 
         FIG. 3  is an enlarged view of the top of the thermal lance assembly of  FIG. 2 . 
     
    
    
     DISCLOSURE OF THE INVENTION 
     The present invention relates to an improved thermal lance for unplugging a vessel discharge port, for example, in a refractory lined ladle. As shown in  FIG. 1 , an inner lance assembly  10  includes a tubular thermal lance tube  14  with a lance rod  12 , commonly called a burning bar or slice rod, disposed within the lance tube  14 . The inner lance assembly  10  is located within an axially displaceable extension tube  16  which is located within the interior of a housing  1  to form a telescoping thermal lance assembly. The extension tube  16  may have a flared base or a base flange  15  ( FIG. 2 ) to keep it centered in the housing  1 , and the housing may include a bushing  19  near the top end to prevent the extension tube  16  from completely exiting the housing  1 . The bottom of the tube  16  has an aperture  17  to allow oxygen to flow into the tube. 
     As noted above, the inner lance assembly  10  (lance tube  14  and lance rod  12 ) and tube  16  are disposed within the outer housing  1 . A conduit  18  communicates pressurized oxygen to the interior of the housing  1 . When the apparatus is placed in line with an obstructed discharge port and an oxygen supply is opened, the oxygen flows through the conduit  18  and into the housing  1  raising the axially displaceable extension tube  16  toward the obstruction in the discharge port. Oxygen flows around and into the interior or the raised tube  16  through aperture  15  to facilitate rapid burning upon ignition in the vicinity of the obstruction, as is well known in the field. 
     As extension tube  16  telescopes out of housing  1 , lance tube  14  telescopes out of the tube  16 . In addition, lance rod  12  telescopes out of lance tube  14 . The telescoping extension tube  16  is preferably made of stainless steel or other high carbon steel to provide a lower rate of consumption than the more combustible material of the thermal rod  12  and lance tube  14  which are located inside extension tube  16 . As tube  16  slides upward, the base flange  15  contacts the bushing  19  at the uppermost end of the housing  1  thereby preventing the extension tube  16  from exiting the housing  1 . 
     As discussed above, the combustible lance assembly  10  includes tube  14  and lance rod  12 , both made of low carbon steel formed into a cylindrical rod that has substantial mass and surface area, yet allows oxygen to flow axially between and through the lance tube  14  and rod  12 . The axial oxygen flow and increased surface area provide rapid ignition and burning in the presence of high temperature molten metal and oxygen flow. 
     Referring to  FIG. 3 , the lance tube  14  is shown within the extension tube  16 . (The housing  1  is not shown in this figure for simplicity.) A tip  30  of the lance tube  14  is located below the top of the extension tube  16 . The tip of the lance tube  14  may be formed with one or more protrusions extending upward (in the illustrated embodiment) from the end of the lance tube  14 . The protrusions facilitate ignition of the thermal lance assembly. The details on the lance tube and the protrusions are described in U.S. Pat. No. 11,187,461 titled “Tip Protrusions On Lance Ignition Tube”, filed concurrently herewith, the disclosure of which is incorporated herein by reference in its entirety. A cap or bullet tip  60  is preferably attached to the top of the extension tube  16 . An igniter section  50  is defined between the tip  30  of the lance tube  14  and the bottom of bullet tip  60 . Steel wool (not shown in  FIG. 3 ) or other porous combustible material is located in the igniter section  50 . It is also contemplated that volatile material, including liquids, solids, or semi-solids could be added to the igniter section  50  to facilitate ignition. The outer diameter of the lance tube  14  is less than the inner diameter of the extension tube  16 , thus leaving a gap between the lance tube  14  and the extension tube  16  defining a passageway 40 through which oxygen can flow. The lance tube  14  includes an inner bore 22 containing the slice or lance rod  12  which is also designed for oxygen to flow through to the igniter section  50 . Slice rods, and the process of making them, are described in U.S. Pat. No. 4,787,142. 
     The bullet tip  60  includes a hole  62 . A low temperature blasting fuse  64  preferably extends through the hole  62  into the igniter section  50 . The fuse  64  protrudes out from the cap as shown to facilitate lighting. 
     In order to temporarily reduce the oxygen flow during ignition, a plurality of fine wires  66  are inserted into the slice rod or burning bar  12 . The wires are preferably made of low carbon steel and configured to ignite when exposed to the burning fuse  64  and steel wool. The wires  66  are inserted in a short distance, preferably approximately ½ inch into the oxygen passageways in the slice rod or burning bar and protrude out of the slice rod approximately ¼ inch so as to be in close proximity to the fuse  64 . As should be apparent, the wires  66  work in conjunction with the steel wool or other combustible material in the igniter section  50  to provide additional ignition sites and reduce oxygen flow to further improve ignition reliability. 
     It has been determined that sometimes the heat and pressure during combustion can cause the side wall of the extension tube  16  above the lance tube  14  to blowout. Accordingly, the present invention incorporates a tubular blow-out preventer sleeve  70  in the igniter section  50  above the tip  30  of the lance tube  14  inside the extension tube  16 . The sleeve  70  is preferably made from stainless steel, carbon steel or combustible material, with an outer diameter slightly less than the inner diameter of the extension tube  16  so that it can slip snugly in. The sleeve  70  preferably has a wall thickness of about 1/64 inch, thereby providing the ignition zone  50  with increased protection against blowout. 
     The incorporation of the preventer sleeve  70  not only adds lateral strength to the extension tube  16 , but also prevents inadvertent compression of the steel wool during shipping. The inventor has determined that shipping can sometimes cause the lance tube  14  to move toward the cap  60  compressing the steel wool. This can lead to a gap forming between the fuse  64  and the steel wool which can lead to reduced ability of the steel wool igniting. Similarly, it is sometimes necessary to test the ability of the thermal lance assembly to extend. In those cases the user applies pressurized oxygen to test the sliding of the tubes without lighting the fuse. This can cause the lance tube  14  to compress the steel wool. 
     The present invention overcomes those issues by providing a stiffened ring of combustible material in the ignition section  50  to inhibit or prevent relative movement between the lance tube  14  and the cap  60 . 
     As used herein, the term “engage” is intended to both direct physical engagement through one or more components as well as operative engagement. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The term “connected” is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening. 
     All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments of the invention and does not impose a limitation on the scope of the invention unless otherwise claimed. The various embodiments and elements can be interchanged or combined in any suitable manner as necessary. 
     The use of directions, such as forward, rearward, top and bottom, upper and lower are with reference to the embodiments shown in the drawings and, thus, should not be taken as restrictive. Reversing or flipping the embodiments in the drawings would, of course, result in consistent reversal or flipping of the terminology. 
     No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. There is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention, as defined in the appended claims. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalent.