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Valve Techbook 2017

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6 | September 2017 | VALVE TECHBOOK: TECHNOLOGY Safety, reliability and robustness are key factors in valve re-engineering and redesign for deeper wells, larger wellbores or HP/HT environments. Improving Valves for Reliability, Robustness By Scott Weeden Contributing Editor W ith oil and gas drilling and production having to deal with HP/HT environ- ments, more corrosive fluids and greater water depths offshore, the industry is challenged to design valves to operate safely and reliably. Many valves were designed years ago when envi- ronmental demands were not as stringent. What worked at 2,000 psi or 3,000 psi isn't always as effi- cient or safe at 10,000 psi or 20,000 psi. Manufac- turers know the valve requirements and are asking questions such as how can that piece of equipment be more robust and reliable, is that feature needed, is there a need for that much pressure and how do we make sure this failure doesn't happen again? John Sangster, technical director and co-founder of Interventek Subsea Engineering, believes that the future of valve technology lies in the creation of simpler, more fit-for-purpose designs that are re-engineered from the ground up to reduce cost and suit the logistical requirements of projects. Adapting existing solutions is simply not viable when address- ing the increasing safety challenges faced by deeper, longer, larger bores or HP/HT wells. "Over the last 20 years or so, in-riser valves have developed into extremely complex designs as bore size, pressure and temperature requirements have increased. Complexity, along with the use of exotic materials, has increased costs but reliability has been reduced and forced some operators to consider if the use of subsea landing-string systems can continue," he explained. "Interventek's new valve technology not only provides superior shear and seal capability in a single unit, but vastly increases reliability and provides HP/HT capability at a significantly reduced cost leading to major savings for the oper- ator," he continued. "Open-water intervention valve manufacturers have also taken the 'one-design-fits-all' approach, but this creates a huge burden on the system pro- vider as they are invariably left with an unnecessar- ily high shearing capacity and operating volume. This approach has a major impact on the system's weight, control volume requirement and ultimately vessel size and type," he added. "In times of low oil price where low cost, fit-for- purpose solutions are increasingly desirable this is an out-of-date, unrealistic approach. The limited valve choice on the market has a direct implication on operational cost. Technology such as ours is hugely exciting because it is enabling and disrup- tive. We are changing the way the industry has been conditioned to operate," Sangster emphasized. BOP valve redesign eliminates shock Subplate-mounted (SPM) valves have been around for more than 30 years on subsea BOP stacks. The pressure and shearing requirements have gone from about 1,500 psi to 5,000 psi. The fundamen- tal design had not changed much in that time, said Frank Springett, director of engineering for research and development and the NOVOS product line for NOV. The SPM valve uses a water (98%) and glycol (2%) mix as the hydraulic fluid in an open-loop system. With an open-loop system, the fluid is pumped subsea and then exhausted into the ocean since the fluid is mostly water.

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