초록 ▼

A system for preventing manway cover gasket over-compression utilizes machined surfaces on the top of eye bolt lugs on the side of a manway nozzle, machined compression stops on the periphery of the cover, and a specified distance between the top of the eye bolt lug and the manway nozzle edge to eng

A system for preventing manway cover gasket over-compression utilizes machined surfaces on the top of eye bolt lugs on the side of a manway nozzle, machined compression stops on the periphery of the cover, and a specified distance between the top of the eye bolt lug and the manway nozzle edge to engage the stops at a predetermined amount of gasket compression. Force is distributed over an increased contact surface area between the manway cover and the bolt lugs to ensure that deformation occurs preferentially in the eye bolts before any other component in the manway cover system.

대표청구항 ▼

1. A manway cover system for a railway tank car, comprising: a nozzle having a top edge defining an opening in the tank car;a manway cover received on the nozzle;a plurality of bolt lugs on a vertical side surface of the nozzle, each bolt lug having a top surface;a plurality of slots in a peripheral

1. A manway cover system for a railway tank car, comprising: a nozzle having a top edge defining an opening in the tank car;a manway cover received on the nozzle;a plurality of bolt lugs on a vertical side surface of the nozzle, each bolt lug having a top surface;a plurality of slots in a peripheral edge of the manway cover for receiving bolts to tighten the manway cover on the nozzle, each of the plurality of slots defined by two ears defining opposite sides of the respective slot;at least one projection extending downward from an edge of the manway cover having a horizontal bottom surface adapted to contact the top surface of at least one respective bolt lug;a plurality of bolts attached to respective bolt lugs in a pivoting relationship; anda gasket received between the nozzle and the manway cover; whereinthe top surface of each of said plurality of bolt lugs is at the same distance from the top edge of the nozzle, and wherein contact between the horizontal bottom surface of the projection on the manway cover and the top surface of the at least one bolt lug prevents over-compression of the gasket from tightening the bolts. 2. The manway cover system according to claim 1, comprising projections extending downward from each ear of the manway cover, each projection having a horizontal bottom surface machined to meet a respective machined top surface of a respective bolt lug at a predetermined amount of compression of the gasket. 3. The manway cover system according to claim 1, wherein the gasket has an uncompressed thickness in a range of 0.125 inch to 0.375 inches and the distance between the top surface of each bolt lug and the bottom top edge of the nozzle is in a range of 0.7 inch to 1.0 inch. 4. The manway cover system according to claim 2, wherein a distance from the machined horizontal bottom surface of each projection extending downward from the edge of the manway cover and the machined top surface of each respective bolt lug is 25% to 60% of the uncompressed thickness of the gasket. 5. The manway cover system according to claim 1, wherein the gasket is compressed 25% to 60% when the cover is closed on the nozzle and the bottom surface of the projection extending from the manway cover abuts the top of the bolt lug. 6. The manway cover system according to claim 1, wherein an area on the horizontal bottom surface of each projection extending downwardly from the edge of the manway cover contacting a respective top surface of each respective bolt lug when the cover is closed on the nozzle is at least as large as a cross sectional area of the bolt received in the respective slot. 7. The manway cover system according to claim 1, wherein the cover and nozzle remain outside a plastic deformation regime when a torque of 200 ft·lb is applied to all bolts closing the cover on the nozzle. 8. The manway cover system according to claim 2, wherein an axial pressure developed on the nozzle proximate the bolt lug is no more than 10% greater than a pressure developed at any other point on the top edge of the nozzle. 9. A manway cover for use with a manway cover and nozzle system for a railway tank car, the cover being received on a tank car nozzle defining an opening in the tank car, the cover attached to the nozzle with a plurality of bolts attached to a plurality of respective bolt lugs attached to a vertical sidewall of the nozzle, and a gasket being interposed between a top edge of the nozzle and the cover, the cover comprising: a circumferential slot in the cover receiving the top edge of the nozzle;a plurality of slots in a peripheral edge of the cover receiving the bolts to tighten the manway cover on the nozzle, each of said plurality of slots defined by two ears defining opposite sides of the slot; anda projection extending downwardly from the sides of each slot, having a machined horizontal bottom surface, said machined horizontal bottom surface adapted to contact a machined top surface of the bolt lug at a predetermined amount of compression of the gasket. 10. The manway cover according to claim 9, wherein the cover, including the projection extending downwardly from the sides of the slots, is a cast part. 11. The manway cover according to claim 9, wherein the predetermined amount of compression of the gasket is in a range of 25% to 60% of an uncompressed thickness of the gasket. 12. A method for preventing over-compression of a manway cover gasket in a manway cover system for a railway tank car, comprising: providing a nozzle having a top edge defining an opening in the tank car;providing a manway cover received on the nozzle with a plurality of slots in a peripheral edge of the cover for receiving bolts to tighten the manway cover on the nozzle, each of the plurality of slots defined by two ears defining opposite sides of the respective slot, and a respective projection extending downwardly from the edge of the cover having a horizontal bottom surface;providing a plurality of bolt lugs on a vertical side surface of the nozzle, each of said plurality of bolt lugs having a top surface;providing a plurality of bolts attached to respective bolt lugs in a pivoting relationship;providing a gasket received between the top edge of the nozzle and the cover;machining the top surface of each of said plurality of bolt lugs to maintain a constant distance between the machined top surface of each of said plurality of bolt lugs and the top edge of the nozzle; andtightening the manway cover on the nozzle to compress the gasket and contact the horizontal bottom surface of the downwardly extending projection with the machined top surface of the bolt lug, and wherein contact between the horizontal bottom surface of the projection on the manway cover and the top surface of the at least one bolt lug prevents over-compression of the gasket from tightening the bolts. 13. The method of claim 12, comprising machining the horizontal bottom surface of each projection extending downwardly from the edge of the cover to maintain a constant distance between the machined top surface of each of said plurality of bolt lugs. 14. The method according to claim 12, wherein the bolts are tightened to an assembly torque in a range of 80 ft·lb to 120 ft·lb when the top surface of each of said plurality of bolt lugs contacts a horizontal bottom surface of a respective projection on the manway cover. 15. The method according to claim 12, comprising tightening the bolts to compress the gasket between 25% and 60% when the projection extending downward from the cover abuts the top surface of a bolt lug, and wherein further tightening applied to the bolts does not result in further compression of the gasket. 16. The method according to claim 12, wherein a bolt exhibits plastic deformation prior to the nozzle or the cover when increasing load is applied during tightening the manway cover. 17. The method according to claim 12, wherein providing a plurality of bolt lugs comprises welding the plurality of bolt lugs on a vertical side surface of the nozzle. 18. The method according to claim 12, wherein providing a manway cover comprises casting the cover including the projection extending downward from the peripheral edge of the cover as a single piece. 19. The method according to claim 12, wherein an axial pressure developed on the nozzle proximate the bolt lug is no more than 10% greater than a pressure developed at any other point on the top edge of the nozzle.