Hydril Company

H Paul Barringer

Keith C Mott

Gary E Kirsch

Lawrence Y Tung

Patrick E McDonald

A threaded pipe connection is disclosed comprising a box having internal threads and a pin having external threads for mating with the internal threads of the box. The mating threads exert radial forces on the box and pin creating compressive hoop stress in the pin and tensile hoop stress in the box. A conical sealing surface on the pin between the threads and the end of the pin engages conical sealing surface on the box and forms a metal-to-metal seal when the connection is made up. Means are provided for reducing the radial forces exerted by the threads adjacent the conical sealing surfaces to reduce excessive metal-to-metal contact bearing stress and better distribute the remaining stress in the engaging sealing surfaces while maintaining the contact stress required to provide an adequate seal.

Threaded pipe connection

The same size and weight of tubular products, but in different grades of material, are made for universal connection but with seal areas that differ appropriately for adequate sealing without overstressing the connection members for the pressures encountered where each tubular length is put in service. The angle of the conically tapered seal on all box members is made the same for all grades of the products. The pin member of medium grade is made with an equal length seal area and adjacent contracting area on its forward end. The pin member of lower grade is made with a shorter length seal area than its adjacent contacting area, thereby also placing the seal area further from the pin member distal end. This stiffens the pin member. The pin member of higher grade is made with a longer length seal area than its adjacent contacting area.

Universal tubular connection having a variable metal-to-metal seal width

A tubular connection includes a shallowly tapered conical sealing surface. The areas on the pin member where make up and sealing respectively occur in the various embodiments comprise multiple angles and surface texturing for the purpose of lubricant retention, facilitate burnishing and reduce the propensity for galling in multiple make up and break out situations. The pin taper in each case is slightly less than the box taper. The area on the pin member is textured ahead of the very smooth seal area to retain some thread compound even after repeated makeups of the connection. The area ahead of the sealing area where stabbing contact is made is textured in the 125-250 R.sub.a range while the smooth seal area is textured about 63 R.sub.a to provide a gas tight seal under high pressure and severe conditions of combined loads and thermal shock. Hence, the invention allows the use of a smoother seal surface for high temperature gas tight integrity than would otherwise be achieved after the connection is subjected to repeated make ups and break outs.

Growing community of inventors

Humble, TX, United States of America

H Paul Barringer