Retrievable plug for offshore platforms having shear type retaining means

Claim 1

A plug for sealing the interior of a hollow cylindrical member to prevent the flow of fluid therethrough, said plug releasably secured within said hollow cylindrical member being removable therefrom by the application of a first force and a larger second force thereto, said plug comprising: cylindrical housing means connected to said hollow cylindrical member, said cylindrical housing means comprising: hollow cylindrical means having a first interior annular chamfered surface, having a first cylindrical interior surface, having a second interior annular chamfered surface, having a second cylindrical interior surface, having an exterior cylindrical surface and having a plurality of apertures in the exterior cylindrical surface extending into the second cylindrical interior surface; central body means releasably secured to said cylindrical housing in sealing engagement with an interior surface of said cylindrical housing means, said central body means comprising: dished circular plug means having a central opening therein; annular wall means secured to the outer periphery of the dished circular plug means, the annular wall means having seal cavity means in the outer surface thereof, having annular seal means installed in the seal cavity means sealingly engaging the second cylindrical interior surface of said cylindrical housing means and having aperture means located in the outer surface thereof extending through a portion of the thickness of the annular wall means; hollow cylindrical body means secured about the periphery of the central opening of the dished circular plug means, the hollow cylindrical body means having aperture means extending through the wall thereof; and a plurality of lifting means secured to the dished circular plug means to allow the removal of said plug from the interior of said hollow cylindrical member, each lifting means of the plurality of lifting means having a portion thereof secured to the dished circular plug means and having aperture means in another portion thereof; pressure equalization means for allowing the pressure of said fluid to equalize across said central body means before the removal thereof from said cylindrical housing means to allow the flow of said fluid through said hollow cylindrical member, said pressure equalization means comprising: plug means releasably secured to the hollow cylindrical body means of said central body means having seal cavity means in the outer surface thereof, having annular seal means installed in the seal cavity means in the outer surface of the plug means sealingly engaging the interior of the hollow cylindrical body means, and having aperture means in the outer surface thereof; and rod means secured to the plug means to release said plug means from said sleeve means when a force is applied to said rod means; first shear pin means having a portion thereof releasably secured within the apertures in the hollow cylindrical body means secured about the periphery of the central opening of the dished circular plug means and having a portion thereof extending into the aperture means in the outer surface of the plug means of the pressure equalization means to releasably secure the plug means to the hollow cylindrical body means, said first shear pin means being sheared by the application of said first force; and second shear pin means having a portion thereof releasably secured within the apertures of said cylindrical housing means and having a portion thereof extending into the apertures located in the outer surface of the annular wall means of said central body means to releasably secure said central body means within the said cylindrical housing means, said second shear pin means requiring said larger second force to shear the same, thereby allowing the removal of said central body means from said hollow cylindrical member.