Cast convoluted piping flange

Published: 02nd November 2010
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A convoluted flange ring for a flange coupler in a piping system the flange ring having an annular bolting disk with an outer rim and an inner rim forming a U-shaped cross section, with the bolting disk having a transitional thickness for improved stress management, the thickness of the bolting disk increasing from the outer rim to the inner rim.

To prevent deformations in the flange rim of the lighter weight prior art convoluted flange from being transmitted as stresses to the pipe weldment, the outer periphery of the U-shaped rim contacts the abutting face of the opposing flange. This contact provides strength for mechanical support of the pipe connection without excessively stressing the pipe at or above the weld to a flared stub end fitting for seating the flange rim. This method of managing stresses in the prior art flange restricts the type of seals that can be used and requires great precision in selecting a seal according to proper thickness.

Conventional flanges are cast and ordinarily are relatively thick to prevent warpage on bolting. Because cast flanges are relatively inexpensive to produce, various systems have been devised to construct convoluted flanges with a cast metal flange rim. U.S. Pat. No. 4,458,924 of Schlicht, issued Jul. 10, 1984 entitled, "Bimetal Flange Connector" describes one such flange with a ductile iron convoluted flange rim. While the weight of the bimetal flange is reduced over conventional flanges, the process of fabricating the bimetal flange is more complicated and costly than conventional cast or forged flanges.

This inventor has constructed useful cast convoluted flanges that have the advantages of the Shultz flange without the requirement that the periphery of the flange rim contact the opposing flange face. However, to provide for the structural integrity for the physical connection to the connected flange, the cast convoluted flange is of greater thickness, thereby compromising the advantages of lighter weight and reduced material requirement characteristic of a convoluted flange. Furthermore, the added thickness results in a build-up of stresses transmitted to the pipe weldment making this design less than an ideal solution.

It is an object of this invention to provide a light-weight convoluted flange that is designed and configured to provide all of the advantages of a convoluted flange in an inexpensive casting or forging with controlled management of stresses. The objective is accomplished by using transitional changes in thickness of the flange member. The improved convoluted flange has greater flexibility and allows the flange bolts to compress a seal interposed between the compression faces with the desired force to effect proper sealing without transmitting excess stresses to the flange stub or pipe weldment.

Another object of this invention is to provide a flange assembly that includes a trapped flange seal and utilizes a convoluted flange member, preferably of the type that includes controlled management of stress. The trapped seal flange assembly is particularly useful for piping systems carrying abrasive slurries and eliminates turbulence that abrades the inside surface of the pipe. The trapped seal is also desirable for systems where it is necessary to minimize contact of the medium in the pipe with the seal, particularly a seal that may otherwise extrude into the piping passage on tightening of the flange bolts.

Another object of this invention is to provide a flange assembly where the flange rim through which the tightening bolts pass is rotatable on the pipe end for ease of alignment with the holes on the opposed flange to which it connects, and where the flange rim has a convoluted design that does not require the outer lip from contacting the opposed flange, thereby allowing for use of a greater variety of flange seals.

The improved convoluted flange assembly of this invention is designed for inexpensive fabrication by casting, forging, cold rolling or a variety of other forming methods suitable for the size, material and use of the flange. The flange has performance characteristics that exceed equivalent, heavier flat flanges with substantial savings in materials, manufacturing costs and other expenses associated with handling and shipping of goods in quantity. Although designed as a metal flange for use with welded pipe, the flange can be adapted to threaded pipe or even plastic fittings formed by different plastic molding processes.

The flange achieves its light-weight flexibility and superior stress distribution characteristics by a flange rim or bolting ring having a convoluted cross sectional configuration of varying thickness. At strategic places in the cross section of the U-shaped flange rim, the thickness is transitionally increased to generate uniform mechanical stresses in critical areas of the flange on tightening of the interconnection bolts. Stress management is accomplished without the necessity of the outer perimeter of the flange rim contacting the face of the opposed flange fitting. In this manner, the requirement for seals of precise thickness is not necessary to achieve the desired degree of sealing.

The improved convoluted flange assembly in one embodiment includes a trapped flange seal allowing use of an alignment ring to closely align segments of abutting pipe for elimination of fluid turbulence within the pipe. Although the use of an alignment ring has been incorporated in prior art piping systems designed and constructed by this inventor, the improvement of the trapped seal construction is a novel improvement that insures that the flange seal will not extrude into the piping passage.

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