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A new piston accumulator design now addresses the issues of offshore accumulator service and reduces disassembly times of piston accumulators from weeks to minutes.
Kocsis Technologies, Inc. (KTI) has developed a new piston accumulator design to address the issues of offshore accumulator service. THIS NEW PATENT PENDING DESIGN IS CALLED LOCKBOX™.

Since the Deepwater Horizon disaster in the Gulf of Mexico, the oil and gas industry has seen an increased need for scheduled maintenance of critical equipment. Such equipment includes the blowout preventer (BOP) and its main components such as the piston accumulators. Commonly referred to on offshore platforms as “bottles”, these hydraulic energy storage vessels are the muscle of the blowout preventer. In the event that the shear rams are actuated, the accumulators are called upon to provide the necessary energy to drive the rams together in order to shear and crimp the pipe containing the product and avoiding a spill of oil.

The common maintenance interval between overhauls is five years. During this essential maintenance period the piston accumulators are disassembled, inspected, repaired and recertified. This process is something that is not easy and certainly does not happen fast. In an industry that time really does mean money, downtime can approach and surpass the seven figure mark quite rapidly. In an effort to minimize the impact of this downtime, rig personnel will attempt to disassemble these accumulators offshore. This most often results in frustration and disappointment as the units are not easily serviced without complex tooling. In some instances, the offshore service may damage the accumulators beyond repair resulting in the need for the accumulators needing to be completely replaced.

KTI has been supplying piston accumulators for the offshore industry since the early 2000’s and has seen its fair share of units come back from the field for recertification. Some of the units have been repairable and some are not. The traditional design features a threaded retaining ring which holds the head into place at the end of the housing. This configuration is commonly supplied by various piston accumulator manufacturers and has been the industry standard. The problem is the large thread, sometimes exceeding 18 inches in diameter, is quite susceptible to corrosion even when made out of common subsea grades of stainless steel. When this corrosion “eats away” at the parent material of the ring and housing it often fuses the two parts together thus making offshore service nearly impossible.