Control valve supplier Dresser South Africa reports that it has introduced a new digital instru-ment, offering enhanced functionality for safety instrumented systems.
The new SVI II emergency shutdown device (ESD) provides in-service partial stroke testing of emergency shutdown valves.
“The partial stroke test is performed by invoking only a limited movement of internal valve components, providing the required valve operating verification without any impact on a process,” Dresser South Africa sales director Piet Botha explains.
The SVI II ESD is an extension of Dresser’s SVI II AP line of digital control valves and is certified to safety integrity level three by equipment safety auditor Technischer Überwachungs-Verein, in accordance with International Electrotechnical Commission standard 61508, and its associated stringent reliability criteria.
Botha says the SVI II ESD is unique in its single wire pair, enabling the designated safety and partial stroke testing functions. “This dual but separate functionality gives the unit the patented capability to remain live during and after a shutdown, enabling key benefits, such as capturing the shutdown event signature,” he notes.
In normal plant operations, the SVI II ESD energises the pneumatic actuator and partially strokes the valve assembly to validate fail-safe operation.
Further, the SVI II ESD delivers sophisticated valve diagnostics, allowing users to proactively manage their safety valve assets. The valve provides for integration with modern digital safety system architecture, with full functionality available through a database-driven companion software, known as ValVue ESD.
Botha reports that several SVI II ESD units have been sold to local petro-chemicals companies.
Meanwhile, Botha says that Dresser is also supplying more than 200 control valves to petrochemicals company Shell Nigeria. He says that the company is busy upgrading the valve equipment at all its oil and gas operations in that country. The R6-million project is expected to take about a year-and-a-half to complete.
“Shell Nigeria has sophisticated valve equipment applications, owing to the large quantities of oil and gas it handles. Our electronic product is proving to be suitable for the company’s advanced systems,” Botha adds.
Further, the valve replacement project also entails the addition of antisurge valves, which are automatically actuated from a central control point to protect large centrifugal compressors from damage when valves, situated further down the process line, are suddenly closed.
The antisurge valves comprise 400 mm valves that weigh about 3,5 t each, including the casing. Botha explains that controlling these valves involves intricate automation configuration, as they are able to close in half a second.
“The valve is actuated by compressed air but, as soon as the valve nears its closed state, the momentum must be slowed to prevent the 200 kg valve from breaking under its own weight. “This is achieved by making use of a sophisticated mechanism, using pneumatic boosters and electronic technology,” Botha concludes.