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The Radoil CD 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 CD 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 CD accumulators perform the
same at the surface as they do at 12,000’ depth.
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