Patent ID: 7056053

Claim:
A bolted connection for bolting together a pair of annular casings, said bolted connection comprising: a. a pair of annular casings each having at an end an annular flange including a radially-extending planar surface adapted for surface-to-surface contact with the other radially-extending flange planar surface, wherein the radially-extending flange surfaces when in contact with each other and in an unbolted condition are slidable relative to each other both radially and circumferentially relative to a casing longitudinal axis, each flange including a plurality of circumferentially spaced throughbores for receiving respective connecting bolts; b. at least one connecting bolt having a longitudinal axis and including a bolt head, a bolt shank extending through one of said pair of flange throughbores, and a threaded end for receiving a connecting nut for connecting together the planar, radially-extending casing flanges, the at least one connecting bolt having a bolt shank outer diameter that is smaller than diameters of the flange throughbores to define a first gap between the bolt shank and the flange throughbores; c. a first two-piece annular washer between the bolt head and a flange surface of one of the flanges, and a second two-piece annular washer between the connecting nut and a flange surface of the other flange, each two-piece annular washer including a first annular washer element having a planar annular face and an oppositely-facing convex annular surface, and a second annular washer element having a planar annular face and an oppositely-facing concave annular surface, wherein the respective convex and concave annular surfaces of the first and second washer elements are in contacting relationship and are slidable relative to each other, and wherein the first and second washer elements have their respective planar annular faces facing in opposite, outwardly-facing directions with the planar faces of the first two-piece annular washer facing the bolt head and in contact with the flange surface of one of the flanges and the planar faces of the second two-piece annular washer facing the connecting nut and in contact with the flange surface of the other flange; c. wherein the first washer elements that abut one of a bolt head and a connecting nut each have an inner diameter that corresponds in size with the bolt shank outer diameter, and the second washer elements that abut the flange surfaces have an inner diameter that is greater than the bolt shank outer diameter to define a second gap between the bolt shank and the second washer elements, so that upon relative radial and circumferential displacements of the contacting, radially-extending flange surfaces the first gap and the second gap allow angular movements of the connecting bolt longitudinal axis within the throughbores and relative to the flange planar surfaces, to minimize connecting bolt bending stresses upon relative radial or circumferential displacements of the radially-extending flange surfaces.