Appeal No. 2001-1041 Page 3
Application No. 09/219,475
housing, each rigid element having an outer surface for
sliding engagement with the inner curved surface of the
inner housing, and the sealing assembly including a
resilient member for sealed engagement with the tubular
member;
a rotatable piston axially movable within the outer
housing in response to pressurized fluid in the fluid
closing port for causing both axial and radial movement of
the annular sealing assembly;
a lower rotary seal between the piston and a lower
portion of the stationary outer housing for sealing
pressurized fluid within the stationary outer housing from a
lower end of the bore in the outer housing;
a flow restriction member between the rotatable inner
housing and an upper portion of the stationary outer housing
for reducing fluid pressure downstream of the flow
restriction member to less than 40% of the pressure upstream
from the flow restriction member; and
an upper rotary seal between the rotatable inner
housing and the upper portion of the stationary outer
housing and downstream from the flow restriction member for
sealing the reduced pressure fluid within the outer housing
from an upper end of the bore in the outer housing.
16. A method of controlling actuation of a rotatable
blowout preventer for use in a hydrocarbon recovery
operation including a tubular member passing through the
blowout preventer, the rotatable blowout preventer including
a stationary outer housing defining a bore therein for
receiving the tubular member, an inner housing rotatable
within the outer housing, an annular sealing assembly
supported within the inner housing for sealed engagement
with the tubular member, a piston movable within the outer
housing for causing radial movement of the annular sealing
assembly, and a fluid closing port and a fluid output port
in the outer housing for passing pressurized fluid to the
piston, the method comprising:
providing a lower rotary seal between the piston and a
lower portion of the outer housing for sealing pressurized
fluid within the stationary outer housing from a lower end
of the bore in the outer housing;
providing a flow restriction between the rotatable
inner housing and an upper portion of the stationary outer
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