Page 38: of Offshore Engineer Magazine (Aug/Sep 2013)

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Drilling &Completion

Figure 3: Piston accumulators offer high reliability and can

Figure 2: Bladder accumulators balance pressure on either outlast bladder accumulators. Source: Technetics Group.

side of the bladder. Source: Technetics Group.

that can quickly be discharged to to reduce spikes and pulsations for acts as a barrier between the fuid and power the shear rams without the need longer system life. The addition of an gas. Pressure is balanced on both sides for pumps or power. Since a blowout accumulator in the system may result of the bladder, Figure 2. preventer operates on the ocean foor, a in increased system weight. This type of accumulator offers a great deal of expense is incurred when number of advantages. Besides being

Suitable for use in any of these maintenance is required. Servicing the lightest and least expensive option, applications are bladder, piston, or a BOP requires the use of ROVs or bladder accumulators can be designed bellows accumulators. In addition to removal of the system to the surface. to ft into a smaller envelope than pis- these types, there are several others

While the BOP is offine, the well is ton or bellows accumulators. They also not discussed. All function essentially also offine, which costs a great deal provide high reliability with regular the same, except for how they separate in lost production and maintenance maintenance. compressed gas and hydraulic fuid. expense. Unfortunately they lose their pre-

In addition, providing a steady pres- charge over time, due to the permeabil-

Bladder accumulators sure to hydraulic components such as Bladder accumulators typically ity of the elastomer. As a result, they actuators and valves can considerably consist of a pre-charged pressure ves- need to be repressurized periodically improve performance and accuracy. sel, elastomeric bladder, fuid port, to ensure safe operation. In addition,

An accumulator can be installed near and gas-charge service port. As system bladder materials are not compatible pumps and other devices, which pro- pressure increases, the fuid com- with corrosive environments such as duce pressure transients, as a damper presses the gas and the bladder, which hydrogen sulfdes, sour gas, and others.

Figure 4: Bellows accumulators use edge-welded bellows to separate the gas charge from the system fuid. Source: Technetics Group.

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