(57) This invention relates to centralizers for use in maintaining a tubular member such
a conductor or string in a substantially co-axial arrangement within a bore, for example
a platform guide or an outer tubular member or conductor. In particular, this invention
relates to a centralizer for use in an oil or gas-drilling or production installation.
A centralizer (1) for centralising a tubular member (5) within a bore (7) comprises
a main body (2) connectable around a tubular member to be centralised, the main body
defining a longitudinal axis (4) of the centralizer, and a plurality of longitudinally
extending abutments (18) spaced apart around the main body (2) that extend radially
outwards from the main body to abut the bore. At least one of the abutments has an
adjustment mechanism (3, 34, 36, 42) for making a radially adjustable abutting contact
with the bore. This mechanism comprises a radially movable outer blade (34), a longitudinally
movable wedging member (36) located between the outer blade and the main body (2)
for moving the blade radially into the abutting contact, at least one guiding mount
(3) for guiding the radial movement of the blade, and at least one longitudinally
extending ramp surface (42) that is inclined with respect to the axis (4). The outer
blade (34) is constrained to move in a substantially radial direction by the at least
one guiding mount. The wedging member (36) is constrained between the outer blade
and the main body (2) to move in a substantially longitudinal direction, The wedging
member and the at least one ramp surface are configured to engage with one another
such that as the wedging member moves longitudinally, the wedging member causes the
outer blade to move radially. The arrangement of the wedging member and the outer
blade is such that when the longitudinal axis (4) is substantially vertical, the weight
of the wedging member (36) automatically causes the wedging member to drop, thereby
moving the outer blade (34) in the radially outwards direction.
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