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The Radoil SC Accumulator provides a ready
supply of pressurized hydraulic fluid to operate subsea equipment.
A conventional accumulator is charged with
nitrogen gas at the surface (i.e. to 3000 p.s.i.), and provides a charge of
hydraulic fluid to do useful work at that pressure (i.e. 3000 p.s.i.). When the
accumulator goes to a depth of approximately 6000 feet, the ambient pressure of
seawater is approximately 3000 p.s.i. The accumulator which provides the
hydraulic fluid at 3000 p.s.i. to the 3000 p.s.i. ambient conditions is blocked
from doing any useful work. It is functionally “dead”. To do the useful work at
6000 feet, the accumulator would need to be charged to 6000 p.s.i. at the
surface to provide a pressure with a 3000 p.s.i. differential above the seawater
ambient. This high pressure conventional accumulator is more dangerous at the
surface, and won’t work at 9000 feet depth.
The Radoil Type SC Deepwater Accumulator
provides a relatively constant working pressure (i.e. 3000 p.s.i.) to the BOP
Control System, irrespective of seawater depth. Ambient (seawater) pressure is
loaded onto the lower piston across from a vacuum. The resulting force is
transmitted up the piston rod to the upper piston and added to the pressure from
the nitrogen charge. This means the greater the depth, the greater the actual
output oil pressure. Units of various working pressures and capacities will be
designed to order. The type SC accumulators perform the same at the surface as
they do at 12,000’ depth.
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