Patent Publication Number: US-4927476-A

Title: Method for making a reinforced thermosetting resin structure with integral flanged nozzle

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates in general to a method of attaching flanged nozzles comprised of fiber reinforced thermosetting resin plastic materials to structures of similar composition, including, in its more specific aspects, to a novel, improved method for the attachment of flanged nozzles to fiber reinforced thermosetting resin pipe headers. 
     BACKGROUND OF THE INVENTION 
     A wide range of industries utilize pipe and vessels comprised of fiber reinforced thermosetting resin material. Such materials are commonly known in the trade as fiberglass reinforced plastic (&#34;FRP&#34;) materials, as glass reinforced plastic (&#34;GRP&#34;) materials, or simply as reinforced thermosetting plastic (&#34;RTP&#34;) materials, although the reinforcing fibers are often composed of materials other than glass, such as polyester, carbon, mixed boron, kelvar, etc. For convenience, the term reinforced thermosetting plastic, or the abbreviation &#34;RTP,&#34; will be used herein, however, it is to be understood that the present invention is applicable to each of the above described materials, and to materials with similar molding and forming characteristics, through a range of variation in resin or resin-like formulations and reinforcing materials. Reinforced thermosetting plastic RTP materials are selected for service because of the need for materials which are corrosion resistant and which have adequate strength. Typical uses for corrosion resistant RTP equipment include pipe headers and drying towers (as used in chlorine manufacture), generators (as used in chlorine dioxide units), process reactors and piping (such as for fertilizer plants and chemical plants), scrubbers, coolers and vaporizers (as used in sulfuric acid plants), evaporators, waste tanks, recovery tanks (as used in mining or chemical manufacturing), cells, tanks, and recovery units (as in tin, lead, copper, or other metal extraction plating or purification units), washer hoods and bleach towers (as used in wood pulping), or as in chimney liners (as used in power plants and incinerators), petroleum processing, water treatment plants, and a variety of other uses. 
     Reference will on occasion be made below to the joint or to the juncture between a main pipe header or corresponding structure and a branch pipe part or similar structure. This is done simply for the sake of convenience and clarity and is not intended to limit the scope of my invention which is, in general, applicable to fabrication of any structure having angularly intersecting fluid containing portions. Also, directions of up, down, top, bottom, etc. are used for convenience and may correspond to illustrations provided, however, it is to be understood that the present invention provides a method and apparatus equally applicable to attachment of parts at any desired branch pipe part orientation. In illustrations herein, nozzles may be shown in a direction that is perpendicular to the longitudinal axis of a main pipe part, however, the method of the present invention is adaptable to nozzle attachment at any desired angle by creating a suitable mold shape and by including an angle in the mold support means designed for positioning the mold and preformed branch part at the proper angle relative to the main pipe part. In addition, it is to be noted that the terms interior and exterior are used only for convenience in providing an explanatyion of the present invention. Such use is for illustrative purposes and in no way limits the scope of the present invention. There are applications where nozzles are desired on the &#34;interior&#34; rather than the &#34;exterior,&#34; and where the method of fabrication taught by the present invention is particularly useful. Examples include but are not limited to applications such as &#34;through hull&#34; fittings for boats, ships, marine bulkhead applications, and aircraft of composite or resin-like materials of construction, or the like. 
     In structures of the character under consideration, a problem arises at the junctures between the main pipe part and an attached nozzle. Unlike metal pipe parts, attachments of RTP parts cannot simply be welded together and still provide adequate strength and corrosive resistance at such juncture or corner. In many different types of service, there is a need for improved corrosion resistance in equipment of RTP construction. In particular, there exists a need for improved corrosion resistance at joints and at nozzle connection points in RTP equipment. 
     In vessels constructed according to presently practiced methods, it is common for the initial failure point in RTP vessels and pipe systems to be the point of attachment, or joint, between the vessel and a nozzle which has been attached during fabrication. 
     In the fabrication of RTP equipment there are various methods known for attachment of nozzles to pipes or vessels. A traditional method of fabrication is known as the &#34;tee insert&#34; connection. The header is prepared by cutting a hole therein, the nozzle placed against the header or vessel and the parts joined by using a secondary overlay wrap of resin impregnated glass cloth. 
     In a similar, but slightly improved method, edges of parts to be joined are beveled so that bevels on the nozzle and on the vessel match. These matched surfaces are coated with resin and then fitted together. There are a number of disadvantages to this method. It is fairly difficult to achieve an exact fit between the parts unless the beveled angle can be precisely manufactured. Since manufacturing of such joints is usually done by manual grinding of the end of the nozzle and of the edge of the hole in the pipe or vessel, it is a normal result of such method of manufacture that voids are created which require filling. The filler is subject to corrosion and erosion and the result is low corrosion resistance in the joint between the two pipe parts. Also, the joint is sharp and angular. Thus, during fluid flow, turbulence is created, which tends to increase corrosion attack. 
     Attempts have been made to improve the quality of joints created by the mating of matched mitered parts. For example, U.S. Pat. No. 3,873,391 shows, in FIGS. 3 and 4, a method of attachment wherein predesigned complementary metered edges are fitted together and secured by means of cement, and thereafter a liquid mixture coating of elastomer resins are applied to the external surfaces of the preformed pipe subsections adjacent to the joint. Thus, the strength of the joint is enhanced. However, in such methods, the corrosion resistance of the joint is not improved. 
     In larger vessels, typically larger than eighteen inches (18&#34;) diameter, it is feasible to put a resin rich interior overlay on the joint created by the method described above. Although such an overlay is a considerable improvement over the method used on smaller diameter pipes, the overlay protrudes from the finished surface of the vessel or pipe part. The overlay therefore creates turbulence in fluid flow and exacerbates corrosion and erosion at the joint. Although the service life of such an &#34;inside overlay&#34; joint is greatly improved over a joint without the inside overlay, the result is still a joint which is quite susceptible to corrosion attack when compared to a smooth molded surface in the vessel or piping system. 
     In the case of nozzle attachment to pipe or vessels having a diameter of approximately eighteen inches (18&#34;) or smaller, it is usually not possible to include a corrosion barrier overlay on the inside of such joint. Thus, the corrosion barrier is interrupted at the joint. Further, corrosion and erosion of joint materials exposes the reinforcement fibers, thus, the entire joint may fail. 
     Changes in fluid flow direction at nozzle attachment points result in a variety of shear, tensile, and torsion forces due to the hydraulic and fluid dynamic action on the joint. Where RTP parts are joined, one failure mode is for the bond joining the overlay to the primary laminate to fail, resulting in the overlay becoming separated from the primary parts. This phenomenon is known as peeling. Another failure mode is for corrosion and erosion of an initial resin rich layer to expose the reinforcing fibers, allowing further corrosive and erosive attack and thus weakening the joint. 
     In other known methods for manufacture of FRP vessels, pipe headers, and pipe parts, &#34;stub molds&#34; are mounted directly on the primary mandrel used for producing the main pipe part or vessel. A rounded fillet is created at the juncture of the mandrel and the stub mold by using wax. Resin impregnated fiber is laid down over both the stub mold and the mandrel, and the result is a smooth, rounded corner. Although this results in an equally corrosion resistant and servicable joint as the present invention, it has several disadvantages. The stub mold method results in increased costs, primarily increased utilization time for tooling, and lower productivity of shop labor. Moreover, it is difficult if not impossible to provide a flanged nozzle by this method. 
     Methods similar to the &#34;stub mold&#34; method have been used for the manufacture of fiber reinforced plastic pipe parts, such as pipe tees. Descriptions may be found in the U.S. Pat. No. 4,601,496, or in earlier variations as shown in U.S. Pat. No. 4,106,797 and U.S. Pat. No. 3,765,979. Fundamental to each of these methods is the simultaneous use of a mandrel on each axis; i.e., a mandrel for the main part and another mandrel for the branch part. A solid one-piece, two-axis, expendable mandrel is disclosed in U.S. Pat. No. 4,601,496, in FIG. 1. 
     BRIEF SUMMARY OF THE INVENTION 
     I have now invented and am disclosing herein a novel method of fabricating a pipe header with flanged nozzles which solves the problems posed in the preceding paragraphs by insuring that the wanted corrosion resistant and strength properties are obtained at the juncture where the nozzle intersects the main pipe part. 
     My invention provides a new way to attach a branch pipe section to a main RTP pipe section. The main pipe section is prepared by chamfering the exterior of the pipe section adjacent to a through branch opening in the pipe section. Further, the exterior surface of the main pipe part is roughened adjacent to the sloping chamfered surface. The branch pipe section or nozzle is also prepared by chamfering and roughening the exterior of the stub end of the nozzle. Then, a smooth mold member having a branch locating portion, a flange portion and a transition portion is positioned inside the main pipe section so as to locate the branch pipe section. A mold member is constructed so that the flange portion provides a surface which is tangential to the interior of the main pipe part, and so that the branch locating portion provides a surface which is tangential to the interior of the branch pipe part, and so that a smooth transition portion is provided between the branch locating surfaces and the flange portion surfaces. 
     The branch pipe section or nozzle is then positioned around the branch locating portion of the mold in a tight fitting relationship, and positioned so as to locate the nozzle at a desired position relative to the main pipe part. 
     Once the mold and the nozzle or branch pipe part are positioned, a quantity of resin material is applied to wet the mold, and more particularly to wet the transition portion of the mold, the adjacent parts of the main pipe section, and the adjacent parts of the branch pipe section. The initial resin rich layer is completed by including a veil type reinforcing cloth application, fully wetted out in accordance with standard fabrication techniques. Usually, this initial resin rich layer is allowed to cure before proceeding with additional laminates, so that the initial layer is not compressed, decreasing the ratio of resin to reinforcing material, and thus thereby decreasing the corrosion resistance. However, initial layer(s) of chopped strand mat are normally used to complete the base layer of resinous matrix. After the base layer has cured, support means for the nozzle and mold are disengaged, and the mold is removed. Additional layers of resin saturated glass are then laminated over the base layer to complete the desired corrosion resistance and strength properties of the joint. Alternately, the entire joint can be completed with the mold in place. 
     OBJECTS OF THE INVENTION 
     Fiberglass industrial equipment is normally manufactured with an inner resin rich corrosion barrier. This corrosion barrier is most effective when it is smooth and uninterrupted along the interior surface. Therefore, it is particularly advantageous to form fiberglass vessels, pipes, and headers on a smooth mold so as to provide maximum corrosion resistance. Thus, a method to achieve such a result when attaching flanged nozzles is particularly desirable. 
     It is an object of the present invention to attach nozzles to a main pipe part, or to a vessel or other structure, with a continuous and uninterrupted corrosion barrier, thereby eliminating or minimizing the possibility of corrosion attack. 
     It is another object of this invention to product a joint where the continuous and uninterrupted corrosion barrier is smooth and flush with both the main pipe part or vessel and the nozzle, which overcomes or reduces the above referenced drawbacks of the prior known methods of nozzle construction. 
     It is yet another object of this invention to produce a joint which decreases fluid flow turbulence and stress fatiguing. 
     It is a feature of the present invention that a new primary laminate is formed to join the existing primary laminates in a preformed nozzle and in a main pipe part or vessel. 
     It is a feature of the present invention that a mold is required along only one axis of the finished pipe section or vessel during the nozzle attachment process. 
     It is a further feature that the one-axis mold method of the present invention is simple and provides lower manufacturing costs when compared to known methods. 
     It is an advantage of this invention that a joint is produced where there are no voids in the joint requiring filler or putty. 
     It is an advantage of this invention that a joint is produced where there are no voids in the joint requiring filler or putty. 
     It is an advantage of the present invention that a smooth interior joint surface is created, thus minimizing the possibility of corrosion. 
     Several advantages of my novel pipe header structures have been identified above. Yet another important advantage of my invention, alluded to above, is that there are no internal or external mechanical splices or overlaps between the sections of the structure. This is important because inside splices are disruptive to fluid flow, and both the external and internal overlays are expensive. 
     Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The invention may be more clearly understood by reference to the accompanying drawings thereof, wherein: 
     FIG. 1 is a vertical, sectional view showing a main pipe section or header, with a flanged nozzle installed thereon by presently known methods. 
     FIG. 2 is a partial, vertical, sectional view of a point of nozzle attachment, similar to FIG. 1, showing a nozzle installed on a pipe header utilizing an external overlay, as presently known in the art. 
     FIG. 3 is a partial, vertical, sectional view of a point of nozzle attachment, enlarged so that details of a mitered joint and interior and exterior overlay as presently known in the art are clearly seen, taken along line 3--3 of FIG. 1. 
     FIG. 4 is a perspective view of a pipe header or main pipe section, to which it is desired to attach a flanged nozzle in accord with the present invention. 
     FIG. 5 is a perspective view of a pipe header or main pipe section to which it is desired to attach a flanged nozzle, showing surface preparation on the pipe header or main pipe section in accord with the present invention. 
     FIG. 6 is a perspective view of a pipe header or main pipe section, showing a preformed flanged nozzle being positioned at the desired point of attachment by utilization of a mold and of support means in accord with the present invention. 
     FIG. 7 is a vertical, sectional view taken in the longitudinal direction of a pipe header or main pipe section, showing a preformed flanged nozzle being positioned at the desired point of attachment by utilization of a mold and of support means in accord with the present invention. 
     FIG. 8 is vertical, cross-sectional view of a pipe header or main pipe section, showing a preformed flanged nozzle being positioned at the desired point of attachment, taken along the line 8--8 of FIG. 7. 
     FIG. 9 is a vertical sectional view of a point of nozzle attachment showing placement of the base layer of resinous matrix in accord with the present invention. 
     FIG. 10 is a vertical sectional view of a point of nozzle attachment showing a completed joint with resinous laminates applied in accord with the present invention. 
     FIG. 11 is a vertical, sectional view of a point of nozzle attachment showing a completed joint with resinous laminates applied in accord with an alternate embodiment of the present invention. 
     FIG. 12 is a vertical sectional view of a point of nozzle attachment showing placement of further layer(s) of resinous matrix to the joint while the mold is still in place, as may be practiced in yet another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It is necessary in a variety of reinforced thermosetting plastic &#34;RTP&#34; structures, and particularly in pipe headers, to attach flanged nozzles thereto. By way of background, a typical method of attachment for flanged nozzles as known in the art is shown in FIG. 1. A main pipe header or main pipe section 2 has an interior wall surface 10, a corrosion barrier laminate 6, a structural laminate 4, and an external wall surface 8. A preformed branch nozzle section 12 is provided for attachment to pipe section 2. Preformed nozzle 12 has an interior wall surface 20, a corrosion barrier laminate 16, a structural laminate 14, and an exterior wall surface 18. The preformed flanged nozzle section 12 also has a flange end 13 and a stub end 15. On the flange end 13 can be seen the flange face 38 and apertures 36 for bolt placement. To join the preformed flanged nozzle to the pipe header, it is common practice to create a mitered surface 26 on the stub end 15 of the preformed flange nozzle 12. An aperture is created in the main pipe section 2, and the edges of the main pipe section adjacent to the aperture are shaped to be complementary to mitered surface 26 on the preformed nozzle. Resinous material is applied to the surfaces to be joined, and the complementary mitered surfaces sections are fitted together. It is common that such method of manufacture results in creation of voids which must be filled by use of resinous filler or putty 28. In most instances, an exterior overlay 21 is applied around the periphery of the joint, covering adjoining surface 23 on the main pipe section 2, and adjoining surface 25 on the preformed flanged nozzle 12. The external overlay 21 also has an exterior surface 22. Although the external overlay 21 improves the strength of the joint, it does not improve the corrosion resistance of the joint against fluids contained in the header. Further, a common failure mode of such joints is for vibration or fluid pressure leaking through the joint to force the resinous matrix of the overlay 21 to be separated from nozzle 12 and from pipe section 2, at the joining surfaces 23 and 25 respectively, a phenomenon known as &#34;peeling&#34;. 
     In vessels typically larger than eighteen inches (18&#34;) diameter, it is feasible to put a resin rich interior overlay 30 inside the joint. The overlay 30 protrudes from the pipe section interior wall finished surface 10. It also protrudes from the interior finished wall surface 20 of the preformed flanged nozzle. Deposits may also form at the joint 34 between the interior overlay 30 and the flanged nozzle section, as well as at the joint 32 between the interior overlay and the main pipe section. Thus, the overlay 30 creates turbulence in the flowing fluid, and exacerbates corrosion and erosion at the point of nozzle attachment. 
     FIG. 2 shows a sectional view along a longitudinal direction of a main pipe section. However, FIG. 2 illustrates the joint typically constructed for main pipe sections with less than eighteen inches (18&#34;) diameter where it is impractical or impossible to include an interior overlay in the joint. In such smaller vessels, the corrosion barrier is completely interrupted at the joint, thus exposing putty 28. The erosion of the putty or filler material 28 may expose ends of reinforcing fibers, weakening or eroding them, causing the joint to ultimately fail. 
     FIG. 3 is a partial vertical sectional view similar to the view shown in FIG. 1. However FIG. 3 is taken along the longitudinal direction of the main pipe section, along the line 3--3 of FIG. 1, rather than along the cross sectional direction that is illustrated in FIG. 1. FIG. 3 further illustrates the use of an interior overlay 30 to prevent corrosion or erosion at a mitered joint. It can be clearly seen in FIG. 3 that the abrupt direction changes created by use of such an interior overlay create an irregular surface that interrupts smooth fluid flow. Although the use of such an interior overlay 30 is a clear improvement over the unprotected mitered joint illustrated in FIG. 2, such fabrication technique fails to provide smooth interior surfaces for fluid flow, and fails to eliminate protruding surfaces which can initiate corrosion and erosion in pipe section. 
     The present invention involves a novel and improved apparatus and method to attach RTP nozzles to RTP vessels or pipe sections. While the illustrated embodiments of the invention show main pipe parts and branch nozzles of cylindrical configuration, such is not intended to limit the invention to the particular configuration or to limit it to a specific size or shape. The method of the present invention, and apparatus therefore is uniquely capable of providing a way of joining various RTP parts, by creating a mold shaped for the particular configuration of parts which are to be joined. 
     Attention is now directed to FIG. 4, a perspective view of a main pipe header or main pipe section to which it is desired to attach a flanged nozzle by the method of and use of the apparatus of the present invention. The main pipe section 40 has a pipe wall 41 with an interior wall surface 44 and an exterior wall surface 46. The pipe wall 41 is further composed of a corrosion barrier laminate 43 and a structural laminate 42. The main pipe section 40 has a through branch outlet or aperture therein defined by a wall edge portion 48 of the main pipe section. The wall edge portion 48 has an exterior or top edge surface portion 50 and an interior or bottom edge surface portion 52. 
     FIG. 5 is a perspective view of the same main pipe section as illustrated in FIG. 4, however preparation of the header 40 for attachment of a nozzle in accordance with the present invention has been performed. Exterior surface 46 of the main pipe section has a roughened area 58 from the bottom wall edge surface portion 52 to a roughened surface limit at line 60. The surface of the main pipe section must be roughened to create a good adhering surface to enhance bonding efficiency for application of further resinous laminates. Roughening is also required since the usual technique for RTP pipe fabrication includes use of a wax in the final exterior coat, to promote proper curing of air inhibited resin compositions. This roughening is generally accomplished by lightly sanding the surface of the header to remove the top wax layer. The roughening and sanding operation must create a surface free of moisture, dirt, waxes, or other contaminants. Final roughening of surface preparation must occur within a few hours, preferably not more than twenty four (24) hours, prior to application of the initial resin coat. The roughened surface 58 extends from the bottom edge surface portion 52 of the main pipe section adjacent to the through branch outlet or aperture all the way out to roughened surface limit at line 60. Beginning at line 56, the exterior surface portion of the main pipe section is removed and a chamfered edge is created from line 56 to the bottom edge surface portion 52. It will be seen in later drawings that the effect of chamfering around the aperture is to create a sharp angle alpha (α) between the sloping surface 54 and the interior surface 44 of the main pipe section 40. Angle alpha is usually in the range of 45° or less, and preferably 30° or less, and when required, may be 20° or less. At bottom wall edge 52, the apex of this sharp angle, the interior pipe wall 44, meets sloping surface 54. In practice, the exact edge 52 may not be preserved during the grinding operation, and a new edge, 52&#39;, may be formed, however only edge 52 is shown in the accompanying drawings. 
     FIG. 6 illustrates the same main pipe section as previously illustrated in FIG. 5, however in FIG. 6 a preformed flanged nozzle 80 has been positioned on mold 70. In fabrication of a flanged nozzle in accord with the present invention, mold 70 is positioned and supported by means which will be subsequently discussed. In normal shop operation, the fabricator secures bracket 98 to the flanged nozzle 80. Bracket 98 has a housing 100 and wings 106. The housing is slidably engaged with support rod means 95 and can be positioned at the desired height on support rod 95, normally near the top end 6 of rod 95. An internally threaded portion or hub 102 of housing 100 threadably engages a threaded allen bolt 104 such that an allen wrench (not shown) can be inserted in allen bolt 104 to rotate the allen bolt so that the allen bolt is compressed against support rod 95 to secure bracket 98 against rod 95. The objective is to provide means to position bracket 98 so that the interior edge surface portion 90 of the preformed flanged nozzle 80 can be positioned at the desired height on mold 70. It will become obvious as the invention is practiced that other means for retaining the preformed nozzle at the desired height will be acceptable and will achieve equivalent results. For instance, support rod 95 could be threaded, and housing 100 could have an internally threaded rim. Thus, as housing 100 is rotated the position of the preformed flanged nozzle would be adjusted. Further, it can be readily seen that various means of securing bracket 98 to a preformed part such as a preformed flanged nozzle 80 can be utilized without departing from the scope of the present invention. In the present embodiment of the invention, bolt 108 is placed through aperture 94 in flanged nozzle 80 and through a corresponding aperture (not shown) in wing 106, and threaded end of bolt 108 is threadably engaged to nut 110 to secure flanged nozzle 80 against bracket 98. As shown in FIG. 7, a washer 112 can also be utilized with bolt 108 and nut 110. 
     Before turning to the next figure, the details of mold 70 must be further explained. A proper fitting mold is essential to practice of the present invention. It is generally necessary to make a new mold each time a new nozzle shape or size is desired, and each time a new header diameter or vessel configuration is required. For instance, nozzles could be constructed for rectangular, triangular, elliptical or other unusual shapes for through branch outlets from a main pipe section or header, or from a tank or container. Essential features of the mold are that it provide a smooth transition from the main part to the branch part. Thus, the mold surface should have a flange portion with a point of tangency with the interior wall 44 of the main pipe part 40, and a branch locating portion which has a point of tangency with the interior wall of the preformed nozzle 80 being attached. This point of tangency should, as a minimum, exist at the edge of the main pipe section and at the edge of the nozzle being attached, at the point where the respective parts no longer cover the mold surface. There should be a smooth transition portion between the flange portion and the branch locating position. By utilizing a mold as taught by the present invention, it is possible to provide a smooth transition from the interior of the main pipe section to the interior of the branch nozzle on pipe section, eliminating sharp angles in the attachment, and eliminating flow disturbances caused by interior overlays. 
     The mold must define a smooth transition curve from the point of tangency at the interior wall 44 of the main pipe part 40 to the point of tangency of the mold with the interior wall of the branch nozzle. The shape of the curve defining this transition may be a circular curve, a compound curve, or may be defined by parabolic or other mathematical expression. Although nozzle attachment is illustrated herein with a branch nozzle at a ninety (90°) degree angle from the main pipe section, or &#34;tee&#34; fitting, it is to be understood that the present invention is equally applicable to other angles of attachment, such as a forty five (45°) degree angle or &#34;wye&#34; fittings, or at various other angles. Attachment of nozzles at various angles can be accomplished by use of individually prepared molds which define a smooth transition curve from the main pipe section to the branch nozzle, and by a support rod means 95 (see No. 95 of FIG. 7) which is modified so that the rod changes direction near the main pipe section to a direction generally coaxial with the desired angle of the branch nozzle to be attached. Further, the function of a support rod means 95 could be alternately accomplished by use of a multiple legged device, such as a tripod, by use of a simple jack or by other suitable means. And, where an interior support surface portion of the main pipe is not readily accessible, or in the case of articles other than pipe sections, external legs or braces, or suction cupt means against the structure itself, could be used for support rod means components. However, the support rod means depicted herein has been found to be quite helpful in allowing the mold and nozzle to be manipulated and positioned from the outside of the main pipe section, rather than requiring workmen to manipulate apparatus in the interior of the main pipe section. This feature is extremely helpful when attaching nozzles to long pipe header sections, and when adding nozzles to small diameter pipe sections where it is difficult or impossible for workers to enter the pipe section. Also, to facilitate mold position and recovery, a string or cord 136 can be attached to the mold. 
     Molds can be prepared from a variety of suitable materials, however, the following method has been utilized with success: 
     (a) Prepare a male mold from metal pipe parts, by attaching pipe sections of appropriate diameter. Build up weldment or fillet sufficient to provide a desired transition curve shape, and complete by grinding and polishing the weldment or fillet to provide a smooth, uniform surface. 
     (b) Use the just completed metal male mold to build a corresponding female mold of suitable RTP materials. 
     (c) Form the working male mold from the just completed female RTP mold by use of a silicone elastomer molding compound, such as RTU-HS from the Dow Chemical Company. A silicone rubber moldmaking compound such as Dow Corning 3112 RTV Silicone Rubber with Dow Corning No. 1 catalyst, available from the Dow Corning Corporation, Midland, Mich., is equally useful. 
     In forming the mold, precise manufacturing tolerences are required so that the size and shape of the mold exactly matches the size and shape of relevant portions of the preformed main pipe section and the interior size and shape of relevant portions of the preformed nozzle. The mold is pressed against the interior wall of the main pipe section in a tight fit relation so as to seal the joint between the interior wall of the main pipe section and the mold. Further, the mold must be insertable in the preformed nozzle to be attached so that there is a tight fitting relationship between the nozzle and the mold. As a snug, tight fitting relationship is desired between the nozzle and the mold, it is not unusual to resort to use of lubricants, such as soapy water, or to simultaneous cooling of the mold and heating of the nozzle, to allow placement of the nozzle over the mold at the desired location. 
     Turning now to FIG. 7, a mold 70 and flanged nozzle 80 are depicted in vertical cross section along the longitudinal axis of a main pipe header 40. The main pipe header can be seen to have an interior wall 44, a corrosion barrier laminate 43, a structural laminate 42, and an exterior wall 46. The exterior surface of the main pipe section 40 has been prepared as shown in FIG. 5 and FIG. 6. The roughened exterior surface 58 extends to line 56 where a sloping or chamfered surface 54 begins. The chamfered surface 54 ends at the bottom wall edge portion 52 of the main pipe section. The main pipe section also has an interior edge surface portion 45. Mold 70 is composed of two major sections, a branch locating portion 71 which extends to locate the branched nozzle or pipe section, and a flange portion 72 for sealing against the interior wall 44 of the pipe section 40 and for providing surface sufficient to support the mold against the interior wall 44. The mold flange portion 72 has further important details, including locating portion 73 which seals the mold against the interior pipe section wall 44, and a pair of flanged portion outer ends 78 in the longitudinal direction. The locating portion 73 fits tightly against the main pipe section interior edge surface portion 45 of the main pipe section interior wall. A junction 62 is defined between the flanged portion outer ends 78 in the longitudinal direction and the main pipe interior section wall 44. Mold flange portion 72 also has a bottom surface 79. 
     The mold is supported by means of a support plate or ring 116 having an inner wall 120 which defines an aperture for passage therethrough of support sleeve 122 which is slidably engaged to support rod 95. Mole support sleeve 122 can be slidably adjusted from outside the main pipe header so that the mold can be secured in a tight fitting relation to the interior pipe wall 44. With a properly fabricated working mold and a properly positioned mold, support sleeve 122 can be adjusted so that bottom support flange 124 of sliding support sleeve 122 compresses support ring 116 along compressing surface 130 of the support ring, against mold 70, along compressing surface 118 of support ring, achieving a seal between mold 70 and main pipe section 40 at the bottom wall edge surface portion 52. A smooth transition between the mold flange portion 72 and the mold transition surface 74 at the bottom wall edge surface portion 52 insures that a smooth interior surface of the finished joint can be created. The sliding mold support sleeve 122 is positioned and secured in the same manner as the support bracket 98 previously described. An internally threaded portion or hub 102 of sliding support sleeve housing 126 threadably engages a threaded allen bolt 128 such that an allen wrench (not shown) can be inserted at allen bolt 128 to rotate the allen bolt so that the allen bolt is compressed against support rod 95 to secure the sliding support sleeve 122 against rod 95. The objective is to provide a means to securely position sliding support sleeve 122 at the desired height on support rod 95. It will become obvious as the invention is practiced that other means for retaining the mold at the desired height will be acceptable and will achieve equivalent results. For example, if support rod 95 were threaded, the support sleeve 122 could be internally threaded and rotatably adjusted to secure the mold 70 at the desired position. 
     The preformed flanged nozzle is positioned and secured by use of bracket 98 as earlier described in the discussion of FIG. 6. The preformed flanged nozzle 80 has a flange end 82 and a stub end 83. Stub end 83 has an external surface 84, a portion of which adjacent to the joint must be roughened in the manner previously described for the exterior of the main pipe section. Beginning at point 86, the stub end 83 of the flanged nozzle 80 must be chamfered or ground down to create a smooth sloping surface 88 which extends to the bottom wall edge surface portion 90. At the bottom wall edge surface portion 90, the interior wall 85 of the nozzle stub end 83 intersects sloping chamfered surface 88. Thus, the sloping surface 88 and the nozzle interior 85 define an angle beta (β) having an apex at the interior edge surface portion 90. Angle beta is usually in the range of 45° or less, and preferably 30° or less, and when required, may be 20° or less. The nozzle interior 85 further has an interior surface edge portion 89 which contacts the branch locating portion of mold 70 in a tightly fitting relationship. 
     Further, the branch locating portion 71 of mold 70 has a top end 76. The branch locating portion 71 also has an inner wall surface 77 which defines an opening of sufficient size for passage of support rod means through the mold. Where the mold branch locating portion top end 76 joins the flanged nozzle interior wall 85, a peripheral joint 66 is defined which extends completely around the interior wall 85 of the nozzle. It is preferable in practice of this invention to have contact of the branch locating portion 71 of the mold along the interior wall 85 of nozzle 80 from joint 66 to point of intersection between chamfered surface 88 and the interior wall 85 at the nozzle bottom wall edge surface portion 90. This contacting area of the mold branch locating portion is known as the mold branch locating portion outer surface 75. 
     It can also be seen in FIG. 7 that the mold is configured to provide an aperture therein for passage therethrough of support rod means 95. Also, support rod means 95 may also include at the bottom end 97 a protective block 140 of wood or other suitable material, and carpet remnant 142 so that the interior wall surface 44 of header, and in particular the interior surface support portion 138 main pipe section 40 is not damaged during the nozzle attachment process. 
     FIG. 8 shows a vertical cross-sectional view of a main pipe header with a mold in place and a flanged nozzle being attached in accordance with the present invention. The view is taken along line 8--8 of FIG. 7. Here, the flanged portion 72 of mold 70 can be seen to provide a smooth curve contoured to match the interior curvature of the main pipe header 40. This smooth portion of the mold exterior has a flange portion locating portion 73 which is fabricated to provide and when in the operating position is secured in a tight fitting relationship with the interior wall 44 of the main pipe section. Mold flange portion 72 extends outward to a mold flange portion outer edge 64 at either end of the mold when viewed in a cross-sectional direction. 
     Turning now to FIG. 9, application of a base layer of resinous matrix 150 can be seen. Exposed portions of mold 70 and the adjacent areas of pipe header 40 and of nozzle 80, respectively the sloping chamfered surface 54 on the main pipe header 40, and the sloping chamfered surface 88 on the flanged nozzle 80, are wetted with resin. The resin wetted surfaces are coated with one or more layers of resin impregnated C-veil fiber or equivalent depending upon the chemical service environment. The base layer also normally includes at least two layers of one and one-half (11/2) oz. chopped strand mat, however, actual base layer requirements may vary depending upon resins and reinforcing materials used in the particular application. The fresh resin layer(s) are worked with brush and/or rollers to fully wet the reinforcing fibers and to remove trapped or entrained air bubbles. After the base layer or layers of resin and reinforcing fiber matrix cures, the mold 70 top support bracket 98, and support post 95 are removed. Then, additional layers of resin saturated glass reinforcement are laminated on the base layer of resinous matrix 150 which has just been applied. 
     Turning to FIG. 10, a completed flanged nozzle fabricated according to the present invention can be seen. FIG. 10 is a vertical sectional view of a portion of a joint between a main pipe section and a flanged nozzle along the longitudinal axis along the main pipe section. Most striking in this view is the smooth transition provided between the main pipe vessel and the flanged nozzle. The new resinous matrix 150 provides a transition surface portion of new resinous laminate which has a smooth surface which is tangential with the main pipe header interior wall 44 at point 52, and provides a smooth curved transition to point 90 where it is tangential to the interior pipe surface 85 of flanged nozzle 80. Further, it can be seen that in addition to providing a smooth surface for fluid flow, there are no crevices for deposits to form or to serve as initiation points for corrosive processes. In addition to a first resin layer 150, a further corrosion barrier 152 is laminated over the joint, and then a structural laminate 154 is provided. The base resin rich corrosion barrier 150 and the additional corrosion barrier 152 can be varied in thickness to suit the application. Although initial layer 150 and corrosion barrier 152 are shown discretely for purposes of illustrating the fabrication procedure, the present method results in a single uniform resin rich corrosion barrier containing both layer 150 and layer 152, which may become virtually indistinguishable. Similarly, the structural laminate 154 can be varied as necessary to provide the strength for the particular application requirements. Although both corrosion and appearance concerns are normally less important on the vessel exterior, in the present invention an overlap of resin 156 is provided beyond initial chamfered point 56. This overlap area may be varied in width and extends out to a junction 164 where the new exterior laminate ends and the external pipe wall 58 begins. A final resinous layer must extend out to meet the unroughened exterior header pipe wall 46. Similarly, an overlap area 158 is provided so that the new structural laminate overlaps the external roughened nozzle surface. This overlap will extend to the junction of the new laminate with the existing nozzle exterior laminate at point 160. Further, it can be seen in the most preferred embodiment that a smooth transition 162 is provided between the nozzle and the new structural laminate and a smooth transition 166 is provided between the main pipe section and the new structural laminate. 
     Turning now to FIG. 11, an alternative method of completion can been seen where resin overlap area on the nozzle 158 may be somewhat thicker than as described in FIG. 10. Also, the end of the new structural laminate at point 170 immediately turns to a ridge 172 of new structural resinous material, rather than a smooth transition as may otherwise be provided as shown in FIG. 10. Similarly, at the main pipe section, the end of the new structural laminate at point 174 immediately turns to a ridge 176 of new structural resinous material. 
     Turning now to FIG. 12, this vertical sectional view shows an alternative method of completion of this resinous joint wherein the mold 70 is left in place after the first layer or layers of resin cure and the entire joint is completed with the mold 70 still in place. Although this results in less efficient use of the mold and tooling in situations where multiple nozzles are being fabricated, it still results in a workable flanged nozzle attachment. 
     The present invention is illustrated by the following example. It will be understood, however, that the invention is not limited to the specific details of this example. 
     EXAMPLE 
     A flanged pipe nozzle, six inch (6&#34;) nominal diameter, made from fiber reinforced thermosetting resin material, was attached to a twenty (20&#34;) inch diameter pipe header of fiber reinforced thermosetting resin material according to the method of the present invention. The header and the preformed-formed flanged were made from a chlorendic polyester type resin, available from Ashland Chemical as Hetron-197. The preformed nozzle had a side wall thickness of one-half (1/2) inch. The nozzle stub end was ground and chamfered to produce a sharp angle between the sloping chamfered surface and the interior nozzle wall. The pipe header was prepared by cutting a through branch opening or aperture therein and grinding the exterior periphery of the header adjacent to the through branch opening or aperture. The grinding operation produced a sharp angle between the sloping exterior chamfered surface and the inside wall of the header. A mold and mold support means was arranged to a predetermined position in the through branch opening and the preformed flanged nozzle positioned and secured thereon. 
     The exposed portions of the mold and the adjacent areas of the pipe header and of the nozzle were wetted with a premium quality corrosion resistant grade chlorendic polyester resin, available from Ashland Chemical Company as Hetron-197. Hetron-197 resins are cured through use of a catalyst with optional promoter. Commonly utilized are a benzoyl peroxide (BPO) catalyst with dimethyl analine (DMA) promoter, or methyl ethyl ketone peroxide (MEKP) catalyst with cobalt napthenate promoter. However, it will be readily appreciated by those skilled in the art that the specific resin type is only important in regard to the corrosion resistance required for the material to be contained. A variety of resins, including but not limited to polyester, halogenated polyester, vinyl ester, epoxy type, isophthalic, furan, bisphenol-A fumarate, or other resins can be utilized to achieve the desired surface contour with the structural and corrosion resistant advantages of the present invention, without departing from the scope of the present invention. 
     The wetted surfaces were then coated with two (2) layers of resin impregnated veil weave glass cloth approximately ten (10) mils thick each. Veil weave known as C-veil, a glass fiber, or Nexus™ veil, a polyester fiber by Burlington Industries are equally applicable, the choice being dependent upon the chemical service environment. Nexus™ surfacing veil is available from Burlington Formed Fabrics, a division of Burlington Industries, N.Y., N.Y., and is found in apertured and non-apertured styles varying in weight from 1.05 to 1.3 ounces per square yard (ozs./sq. yd.), and thickness ranging from 0.011 to 0.014 inches. Veil is very fine and provides a finished resinous matrix of approximately 90% resin and 10% glass. Four layers of one and one-half (1-1/2) oz./yd 2  chopped strand mat, Certainteed #M-113, saturated with a chlorendic polyester resin, Ashland Chemical Company #Hetron-197, were then used to complete the base layer. After the base layer of resin and glass was cured, the mold, top support bracket, and support post were removed. Then additional layers of resin saturated glass reinforcement were laminated on over the base layer, first to complete a corrosion barrier, then to complete a structural laminate. Application of resinous matrix laminates is continued until a desired thickness of material is achieved. Fiber reinforcement utilized in the resinous matrix can be by means of fiber cloth, cloth tape, woven rovings, strands, mat, veil, or any combination of the like. The fiber reinforced resinous matrix must be built up upon the mold or upon the base layer until the outside dimensions approximate the outside dimensions desired in dimensions approximate the outside dimensions desired in the finished product. 
     The foregoing description of the preferred embodiments of the invention have been presented for purposes of illustration and description and for providing an understanding of the invention. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The particular embodiments were chosen and described in some detail to best explain the principles of the invention and its practical application to thereby enable others skilled in the relevant art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Changes and modifications from the specifically described embodiments can be carried out without departing from the scope of the invention. It is intended that the invention be defined by the appended claims.