Butterfly valve

A method of fabricating a butterfly valve comprising a substantially cylindrical casing (20) having an inner circumferential surface formed with an annular valve seat (A), a pair of stem bores (25A, 25B) formed through said casing (20) at diametrically opposite locations thereof, valve stem means (33A, 33B) rotatably extending through said pair of stem bores (25A, 25B), a valve disk (44), stem mount means (46A, 46B) on said valve disk (44) attaching said valve disk (44) to the valve stem means (33A, 33B), the valve disk (44) having an outer peripheral edge portion opposed in its entirety to the valve seat (A) when the valve disk (44) is in its closed position, an annular groove (52) in the outer peripheral portion of said valve disk (44), and an annular valve seal (51) partially fitted in said annual groove (52), a resin injection channel (53) with which the annular groove (52) is in communication, said valve seal (51) being radially deformed and anchored in the annular groove (52) by first resin (58) injected into the groove (52) through the resin injection channel (53) at a predetermined pressure so that the valve seal (51) is pressed uniformly against the valve seat (A) when the valve disk (44) is in its closed position, wherein the method is characterized in that,

• (a) prior to introducing the valve disk (44) into the casing (20) and inserting the valve stem means (33A, 33B) through the stem bores (25A, 25B) of the casing (20), a dummy stem (64) having a diameter equal to the diameter of the valve stem means (33A, 33B) is inserted through the stem bores (25A, 25B),
• (b) a bearing ring (31A, 31B) is fitted on the dummy stem (64) and placed in each stem bore (25A, 25B),
• (c) the dummy stem (64) is adjusted to a predetermined position relative to the casing (20) with a clearance formed between the bearing ring (31A, 31B) and the stem bore (25A, 25B),
• (d) the clearance is filled with second resin (32A, 32B) injected under pressure so that the bearing ring (31A, 31B) is anchored in place upon curing of the second resin (32A, 32B),
• (e) the dummy stem (64) is removed from the anchored bearing ring (31A, 31B),
• (f) the valve disk (44) is introduced into the casing (20),
• (g) the valve stem means (33A, 33B) is inserted through the anchored bearing ring (31A, 31B) so as to be received by the stem mount means (46A, 46B) of the valve disk (44),
• (h) the valve disk (44) is adjusted to a predetermined position relative to the valve seat (A) with a second clearance formed between the valve stem means (31A, 31B) and the stem mount means, and
• (i) the second clearance is filled with third resin (48A, 48B) injected under pressure so that the valve stem means (31A, 31B) is anchored onto the stem mount means (46A, 46B) upon curing of the third resin (48A, 48B).