(57) A casing hanger system, particularly for mudline hangers in offshore wells. An inner
casing string (24) which includes a running hanger body (20) is suspended by a split
ring hanger (40) from an outer casing (44) which includes a receiving hanger (52).
The receiving hanger (52) and split ring hanger (40) have complementary profiles (58,60)
which lock together when the split ring (40) expands. The split ring (40) is carried
down through the outer casing (44) contracted into an annular recess (28) in the running
hanger body (20), and temporarily restrained to the lower end of the recess (28).
When the running hanger body (20) reaches the receiving hanger (52), the split ring
(40) expands so that the complementary profiles (58,60) engage and suspend the ring
from the receiving hanger (52). The temporary restraint is released, and the running
hanger body (20) descends a further short distance until the upper end (30) of the
annular recess lands on the ring (40) to suspend the inner casing string (24) on the
ring (40). Two annular arms (48,46) on the recess (28) apply positive locking to the
split ring hanger (40) in this position. With dual positive locking, the split ring
hanger regains hoop strength.
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