Emerson Exchange 365

Albert Yeats opened his presentation on the reliability and operation of ESD (Emergency Shut Down) valves by explaining why traditional shut-off valves are no longer suitable for today’s challenging applications. Users need large diameter SIL-rated valves with the capability to close in just 4 seconds to cope with high pressures and temperatures.

As the Lead Instrument Engineer for KBR, one of the world's leading engineering, procurement and construction companies, Yeats is currently working on the ACG project in Azerbaijan. KBR has been involved with the development of the ACG project in the Caspian Sea since 1995. During this time, Yeats has seen the requirements for ESD valves change as production from the field has risen to 1 million barrels of oil per day.

Emergency Shutdown Valves traditionally consist of a pneumatic valve with limit switches and solenoid. Actuators for these valves were designed to meet their torque requirements, which generally require a high opening and closing torque.

“Although these valves work well when they are new, dirty flows and corrosion mean that their performance degrades, especially when they are not operated very often,” said Yeats, likening their performance to domestic radiator valves, which are often problematic when they are used after a period of inactivity.

Yeats continued to explain that over time, ESD valve failures have been analysed and unreliable components identified and eliminated to increase reliability and meet the requirements for SIL ratings. As the need for larger more powerful valves has grown, pneumatic valves have been developed and accessories such as boosters, pilot valves and quick exhaust valves have been added to improve performance, especially if fast action is required.

KBR selects various components for its valves based on their performance and KBR’s experience of their operational reliability. Valves installed in harsh environments need to be protected from falling objects and damage by adding mechanical shields − and some need to be resistant to high temperatures, for example if they are installed near a flare.

As the reliability of the ESD valve components has improved, the focus for ESD reliability has been directed at the valve itself.

The solenoids, pilot, boosters, regulator, and actuators are all mechanical devices and don’t self-check. Adding an intelligent positioner improves reliability and operation as well as meeting requirements for SIL-rating and proof testing. Yeats stated that the Emerson DVC 6200 SIS positioners provide diagnostics that can be used to verify the operation of the mechanical components. This includes a solenoid test, partial stroke test, valve characteristic tracking and air leak detection. The diagnostic data is available using Emerson’s Fisher ValveLink software, which provides information about the dynamic performance of the valve actuator assembly. This enables operators to detect problems and schedule maintenance before they affect the process.