Page 36: of Offshore Engineer Magazine (Aug/Sep 2013)

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Protecting

Drilling &Completion subsea hydraulic systems

Determining accumulator they can be used to store potential accumulators, each with its advantages energy, accommodate fuid expan- and disadvantages, to consider when best suited for an application sion or provide damping for pressure designing hydraulic systems for subsea depends on the environment in transients. Accumulators are typically applications, including thermal and which it will operate, reliability, positioned on the high-pressure side of volume compensation, energy storage, a system, whereas similar devices on and water-hammer damping. Among and maintenance cost.

the low-pressure side are referred to the key criteria in the selection process

By Aaron Glafenhein and Tim Leister as reservoirs. For this discussion, the are cost, service life, maintenance, per- ccumulators are energy stor- term accumulator refers to both device formance, and reliability. Reliability is age devices that have a variety types. particularly important, since the wrong of applications. Most notably, There are many different types of choice can cost millions of dollars in

A additional maintenance and operating costs.

Thermal-compensa- tion accumulators are required to accommo- date fuid expansion and contraction due to temperature changes in the environment or operating conditions.

These accumulators also can be used to store extra fuid in case of leaks in the system.

Energy-storage accumulators can be used as a backup in the event a pump fails, or to temporarily provide a higher fow rate than the pump can supply, much like a capacitor in an electrical system.

These accumulators store potential energy using compressed gas or a spring to supply hydraulic pressure to a system on demand. One such instance is actua- tion of the shear rams on blowout preventers (BOP) to seal off wells, even during a loss of power, Figure 1. A bank

Figure 1: Accumulators can store potential of accumulators stores a energy for actuation of BOP shear rams to large volume of hydrau- seal wells. Source: Technetics Group.

lic fuid at high pressure

OE | August 2013 oedigital.com 38 038_OE0813_DC2_Accumulators.indd 38 7/22/13 12:33 AM