Appeal No. 2001-1041 Page 6
Application No. 09/219,475
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] sealing pressure in a well 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] input port
and a fluid output port in the outer housing for passing
pressurized fluid [to the piston] through the rotatable
blowout preventer, 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
housing] for reducing fluid pressure downstream of the flow
restriction member to less than 40% of the pressure upstream
from the flow restriction; and
providing an upper rotary seal [between the rotatable
inner housing and an upper portion of the stationary outer
housing and] downstream from the flow restriction for
sealing the reduced pressure fluid within the stationary
outer housing from an upper end of the bore in the outer
housing.
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