Hitco, Inc.

George D Lee

Donald M Hatch

Controlled buoyancy of underwater pipe installations, typically subsea risers, is achieved by securing to the pipe at least two buoyancy members each comprising a plurality of rigid hollow tubular members arranged side-by-side to form a group which is enclosed in a rigid liquid-tight shell. Advantageously, the tubular members have flat sides lying in planes which are radial with respect to the pipe when the buoyancy member is in place, and adjacent pairs of the tubular members are in flush side-wall-to-side-wall contact. Superior results are obtained when the tubular members are pultrusions of polymeric material and the shells are continuous layers of fiber-filled polymeric material.

Underwater riser buoyancy

An underwater panel comprises a three-dimensional structure for housing sound absorbing material therein, the structure being waterproof and extremely rigid in construction to prevent compression of the sound absorbing material in an environment of relatively high water pressure while at the same time being relatively highly sound transmissive so as to readily pass energy waves from the surrounding water into the sound absorbing material. The panel comprises an integrally woven and resin impregnated fabric which is relatively highly sound transmissive and which has a pair of waterproof opposite faces joined by a pair of intermediate ribs. A plurality of generally planar stiffening elements which are highly sound transmissive and which may be made from resin impregnated fabrics are inserted into the fabric so as to extend between the opposite faces and provide substantial resistance to compression of the panel due to the pressure of the surrounding water. These stiffening elements which are either disposed adjacent single ribs or within pockets formed by parallel pairs of ribs combine with the ribs to define spaces between the opposite faces in which highly sound absorbent material resides.

Structural sound absorbing panel for underwater use and methods of

Buoyancy members in the form of a segment of a hollow cylinder are produced by providing a cylindrical mold having two longitudinally extending flanges spaced apart by not more than 180.degree.; forming a layer of fiber-filled uncured polymeric material on the surface of the mold between the flanges, with the layer being continuous, extending over the surfaces of the flanges and including an overhang at the edge of each flange; assembling on the uncured layer a plurality of rigid elongated tubular elements disposed in side-by-side relationship with the assembly of tubular elements filling the angular space between the portions of the layer carried by the flanges; bending the overhand portions of the layer to overlie the corresponding outer edges of the assembly of tubular elements; applying at least one flexible reenforcing member transversely across the assembly of tubular elements with the reenforcing member extending across the flanges and being held under tension; applying a layer of fiber-filled uncured polymeric material over the exposed surfaces of the assembly of tubular elements until the assembly of tubular elements is completely enclosed in a shell of the fiber-filled uncured polymeric material; and curing the polymeric material. The buoyancy members are particularly useful to control the overall buoyancy of subsea risers.

Method for making buoyancy members

Acoustical panels are comprised of woven fabrics which have at least one face ply portion woven of warp and fill yarns comprising yarns of non-fugitive and fugitive material. The fabric is woven relatively densely to facilitate handling and use thereof in fabrication of the acoustical panel. The substantial disintegration of the fugitive strands of yarn at the completion of the fabrication process provides a selected porosity in the face portion of the woven fabric for controlled transmission of sound waves into the interior of the panel. In a preferred method of making an acoustical panel, the fabric is woven of yarns comprising a mixture of non-fugitive and fugitive material. After installation of porous acoustical elements into pockets formed in the face portion and insertion of mandrels into flutes formed within the fabric, the fabric is impregnated with resin, cured, and the mandrels removed. The formed panel is then heated to a temperature sufficient to burn out the fugitive yarns without affecting the non-fugitive yarns to provide the face portion with a desired porosity to sound waves.

Method of making woven acoustical panel

A multi-ply woven article has elements positioned within pockets formed by double plies of the article to provide the article with desirable acoustical properties as well as considerable strength and rigidity. The double plies may comprise a generally parallel pair of rib plies which extend between the opposite faces of the article in generally zig zag fashion to form a plurality of intermediate rib portions, or a pair of generally parallel, spaced apart face plies forming each of the opposite faces of the article, or both. Some of the pockets formed by the double plies are filled with acoustical elements having a selected number of holes of appropriate size so as to pass sound waves therethrough at a controlled rate, while still other pockets are filled with non-acoustical elements which are generally impervious to sound waves. By appropriate location of the acoustical and non-acoustical elements the article is effectively provided with a plurality of chambers which trap and dissipate sound wave energy entering from outside the article.

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Monterey Park, CA, United States of America

George D Lee