Graphite spiral packing for stuffing box and method for manufacturing the same

In a valve having a stem which projects axially into a stuffing box and which includes a packing gland which is secured in place to retain an annular body of packing material in the stuffing box to a selected depth in an annular space about the valve stem,

• the improvement wherein said annular body of packing comprises:
• a longitudinally elongated spiral of packing material, this spiral being of substantially uniform transverse cross-sectional shape and constituted by a plurality of helical turns;
• said spiral comprising a plurality of axially pre-compressed, radially adjoining layers of graphite, compession-crumpled into a united structure consisting substantially entirely of graphite;
• said spiral being sufficiently radially flexible as to permit a length of said spiral, constituted by more than one helical turn thereof, to be conformingly telescopically selectively received on any valve stem having a diameter which falls within a predetermined range of diameters including ones both larger and smaller than a medial diameter;
• said plurality of layers of radially adjoining layers of graphite, compression molded into a united structure, being constituted of a plurality of layers of flexible foamed graphite tape which in transversally corrugated with respect to the length of such tape;
• said radially adjoining layers of graphite, compression-crumpled into a united structure having multiple zig-zag interlocking folds extending along the lengths of such layers;
• and
• said layers of said united structure being so compressed that they are about one-half the width of said layers of said flexible foamed graphite tape;
• said spiral being sufficiently long to constitute in one piece sufficient packing to fill said stuffing box to said depth when said packing gland is secured on said valve.

A method for providing a multi-layer spiral of a plastically deformable material, comprising:

• providing a mandrel having a generally cylindrical outer peripheral surface;
• disposing a spacer of multiple-turn helical form on said mandrel so that the spacer surrounds said mandrel and has an inner peripheral surface thereof juxtaposed with the outer peripheral surface of the mandrel;
• axially spreading said spacer so as to provide an inter-turn space extending helically about said spacer;
• laying a plurality of lengths of plastically deformable material, one upon another in layers in radial superposition, into said inter-turn space, so that said lengths extend along said space throughout more than one helical turn;
• while radially confining said space and said spacer with an outer body, applying compressive force to said spacer at opposite ends thereof so as to compression-crumple said layers into a united structure;
• and
• removing said united structure from said spacer.