Split non-welded casing cap for high temperature service

Abstract

A casing cap to seal the annulus formed between an upper end of an outer casing and an inner casing. An annular casing cap housing is formed in split portions which when joined at their splits form the casing cap housing to cover and seal the annulus. The joined casing cap split portions form a side wall which surrounds the outer casing. The upper end forms an annular top section adapted to rest on the upper end of the outer casing, cover the annulus and form an upper annular seal to the inner casing. The lower end is adapted to form a mechanical connection, preferably non-welded, to the outer casing and to form an annular seal to the outer casing. Connectors between the casing cap split portions clamp together the sealing surfaces of the casing cap split portions with the sealing element to form pressure-containing, non-welded seals.

1 . A casing cap to seal the casing annulus formed between an upper end of an outer casing and an inner casing extending through and above the outer casing, the casing cap comprising:
 a generally annular casing cap housing formed in two or more split portions which when joined at their splits form the casing cap housing to cover and seal the casing annulus, the joined casing cap split portions forming a side wall having an upper and a lower end, the upper end forming an annular top section adapted to be supported by the outer casing, to cover the casing annulus and to form an upper annular seal to the inner casing, the lower end being adapted to form a mechanical connection to the outer casing and to form a lower annular seal to the outer casing, and each casing cap split portion forming a sealing surface at each split for sealing together to form the annular casing cap housing;   a sealing element for placement between opposing sealing surfaces; and   connectors between the casing cap split portions to clamp together the sealing surfaces of the casing cap split portions with the sealing element to form pressure-containing, non-welded seals at the splits.   
   
   
       2 . The casing cap of  claim 1 , wherein:
 the casing cap housing is formed in two split half portions with one or more sealing surfaces being formed at each left and right split of each casing cap split half portion; and   the sealing element is a gasket seal or a ring seal adapted for sealing when clamped between the sealing surfaces, or a sealing compound adapted for sealing when applied and clamped between the sealing surfaces.   
   
   
       3 . The casing cap of  claim 2 , wherein the sealing element is an epoxy sealing compound and the connectors are external clamp connectors provided at the top section and side walls of the cap housing at the splits. 
   
   
       4 . The casing cap of  claim 2 , wherein the sealing element is a gasket seal and the connectors are screw connectors extending through the side walls and the sealing surfaces. 
   
   
       5 . The casing cap of  claim 4 , wherein the sealing element is a high temperature gasket seal formed from a graphite sealing material. 
   
   
       6 . The casing cap of  claim 2 , wherein one or both of the upper and lower annular seals is an annular compression seal. 
   
   
       7 . The casing cap of  claim 6 , wherein:
 the upper annular compression seal to the inner casing comprises an upper annular seal pocket formed by the top section of the cap housing; a top packing seal in the upper annular seal pocket, and a top packing gland adapted to connect to the top section and to compress the top packing seal in the upper annular seal pocket so as to seal the casing cap housing to the inner casing; and   the lower annular compression seal to the outer casing comprises a lower annular seal pocket formed by the side wall of the cap housing, a bottom packing seal in the lower annular seal pocket, and a bottom packing gland adapted to connect to the lower end of the side wall and to compress the bottom packing seal in the lower annular seal pocket so as to seal the casing cap housing to the outer casing.   
   
   
       8 . The casing cap of  claim 7 , wherein:
 the top packing seal and the bottom packing seal each comprise a plurality of stacked split ring graphite packings;   the top packing gland and the bottom packing gland each comprise a split packing gland connected to a split retaining ring, and which are bolted to the casing cap housing;   the splits of the split ring graphite packings are circumferentially offset one from another in the stack to improve sealing;   the splits of the packing gland are circumferentially offset from the splits of the casing cap housing portions; and   the splits of the packing glands are circumferentially offset from the splits of the retaining rings to more evenly distribute compression on the top and bottom packing seals.   
   
   
       9 . The casing cap of  claim 7 , wherein:
 the side wall surrounds the outer casing and is adapted at the lower end to form the mechanical connection and the annular seal to the outer surface of the outer casing; and   the mechanical connection to the outer casing is non-welded and includes an outwardly extending circumferential extension adapted to be fastened to the outer casing at the upper end of the outer casing, and a recess formed in the side wall of the casing cap split half portions to accommodate the circumferential extension and prevent upward displacement of the casing cap.   
   
   
       10 . The casing cap of  claim 7 , wherein the mechanical connection to the outer casing is non-welded and includes a friction type connection to the outer casing. 
   
   
       11 . The casing cap of  claim 10 , wherein the mechanical connection is a slip lock connection to the outer casing. 
   
   
       12 . The casing cap of  claim 9 , wherein the circumferential extension is formed by a plurality of retention screws adapted to be fastened around and through the upper end of the outer casing such that a head end of each retention screws is outwardly extending from the outer casing, and wherein the recess in the side wall of the casing cap split half portions accommodates the head end of the retention screws. 
   
   
       13 . The casing cap of  claim 9 , wherein the circumferential extension is formed by a split retention ring or ring portions adapted to be fastened to the outer surface of the outer casing, and wherein the recess in the side wall of the casing cap split half portions accommodates the retention ring. 
   
   
       14 . The casing cap of  claim 7 , wherein the casing cap further comprises a vent formed through the top section of the cap housing to provide access to the casing annulus.