Abstract: A blow out preventer is described including a housing with a first annular wedge member fixed to an interior sidewall of the housing. A second annular wedge assembly is provided which includes a plurality of wedge segments disposed within an interior of the housing. The contact face of each of the wedge segments in the second annular wedge assembly is in sliding face to face contact with the contact face of the first annular wedge member. The second annular wedge assembly is movable between an open position spaced from central drill pipe receiving bore and a closed position in sealing engagement with a drill pipe disposed within the central drill pipe receiving bore. An annular piston seal is disposed within the interior at the second end of the housing. The piston has a first contact face and a second contact face. The first contact face engages the second annular wedge assembly.

Abstract: A method of connecting a heat exchanger to a forced air furnace is described. Firstly, connect a valve to the hot exhaust gas outlet of a furnace. The valve has a generally "L" shaped valve body. The valve body includes a primary passage. A diversion passage intersects the primary passage. A diversion return port intersects the primary passage downstream of the diversion passage. A butterfly valve member is pivotally mounted at the intersection of the primary passage and the diversion passage. The valve member has a first wing and a second wing. The valve has an open position and a closed position. The valve member is normally in the open position. Secondly, connect a fresh air outlet of a heat exchanger to a fresh air inlet on the furnace.