Ever since the Deepwater Horizon disaster in the Gulf of Mexico, a more-urgent need for scheduled maintenance of critical equipment has occurred in the offshore oil and gas industry. Such equipment includes the blowout preventer (BOP) and its main components, such as the piston accumulators. Commonly referred to on offshore platforms as “bottles,” the accumulators provide the energy to actuate shear rams, which shear and crimp the pipe containing the product to prevent spilling of oil.

Existing challenges

The common maintenance interval between overhauls for this equipment is five years. This maintenance involves disassembling, inspecting, and repairing the piston accumulators for re-certification. This process is extremely time consuming and labor intensive because continuous exposure to saltwater deep in the ocean causes heavy corrosion that complicates disassembly. Rig personnel may attempt to disassemble the accumulators offshore, but working around the heavy corrosion usually requires complex tooling and skilled labor. As a result, offshore service may damage the accumulators beyond repair, resulting in the need for complete replacement.

The traditional design of piston accumulators uses a threaded retaining ring to hold the accumulator end plate in place. The problem is that the large thread — sometimes exceeding 18 in. in diameter — is susceptible to corrosion, even components made of subsea grades of stainless steel. Corrosion often fuses the parent material of the ring and housing together, making offshore service nearly impossible.

Faster, easier alternative

Brandon Richards, general manager at Kocsis Technologies Inc., Alsip, Ill., said, “We developed our patent-pending design to solve this problem — the Lockbox piston accumulator. The Lockbox is a revolutionary design that takes the issue of corroded large threads out of the equation. Disassembly times can now be measured in minutes instead of weeks. Piston accumulators can be disassembled, inspected, have the seals replaced, and be reassembled on-site using common tools — and in a fraction of the time.”

Richards continued, “The Lockbox design was created based on feedback from our customers and the difficulty they were having in servicing piston accumulators offshore. The simplicity of the Lockbox makes servicing the accumulators on the rig more efficient and gets the product back into service quicker.”

A prototype was subjected to hydrotesting at 1.5 times the working pressure, and also tested extensively in a hyperbaric chamber at a third-party lab to prove reliable function at depth. Test results show the unit works as intended and can be assembled, tested and disassembled multiple times without issue.

For more information on the Lockbox accumulator design, call (708) 377-2681 or click here.