With the increased demand to meet higher safety standards, engineering consultant Wood Group has collaborated with Emerson Automation Solutions to implement advanced technologies and techniques. These are meant to verify and validate integral safety loop components for the chemical, refining and oil and gas industries. The new process combines Emerson’s digital valve controller technologies with Wood Group’s field knowledge and expertise to address industry concerns over verification and validation of emergency shutdown valves to meet the stringent International Electrotechnical Commission (IEC) requirements for Safety Instrumented Systems.
Using an Emerson microprocessor-based digital valve controller, Wood Group engineers improved upon traditional measurement processes by conducting remote analyses through partial stroke testing (PST) techniques, which can be applied either during initial installation or during operation. Through this method, diagnostic data is collected without fully stroking the valve and without upsetting the critical process line.
According to Wood Group instrumentation and control engineer Bridget Spencer, the valve signature can be used to refine the PST parameters, such as minimum pressure and upper operating pressure. If the valve is stuck or malfunctioning, an alert is given, and the operator can either adjust the speed or minimize pressure until the correct configuration is assured. If the condition persists, proper maintenance can be implemented.
Emergency shutdown valves, more commonly known as the “final control element” in a Safety Instrumented Function (SIF) loop, are critical components in refining, chemical, and oil and gas operations, but recent accidents worldwide – and the fact that approximately half of all safety implementation issues result from faulty or ineffective shutdown valves – have directed the spotlight toward the verification and validation of these instruments’ integrity during the operation phase of the safety life cycle. Specifically, there has been increased demand for new devices that not only meet IEC standards but also provide a method for testing safety valve operation without disturbing the process while providing diagnostics information about the final control element.
Typical valve failure, especially in older systems, often results from the valve sticking or remaining static for long periods of time. When the valve fails during operation, the result is often dangerous conditions that could lead to an explosion, fire, or leak of lethal chemicals and gases into the environment. To protect against failure, these valves must be manually inspected during normal plant operation, sometimes causing slowdowns or shutdowns accompanied by extensive engineering, operation and maintenance costs. Under these conditions, SIS verification and validation are typically accomplished through the capture and assessment of diagnostic data or through full stroking of the final control elements. Unfortunately, traditional methods of testing these safety valves do not provide any internal valve diagnostics and are often unsafe for personnel; whereas microprocessor-based Digital Valve Controllers not only provide the necessary diagnostics, but can also dramatically increase the reliability of the safety system, while reducing the risk of false trips, unscheduled maintenance and manual laborious test procedures.
These new methods implemented by Emerson and Wood Group not only provide diagnostic analysis but can dramatically enhance the reliability of the safety system while reducing risk of false trips, unscheduled maintenance and manual and laborious test procedures. Moreover, these methods promote more effective verification and validation of the final control element, ensuring safe and continued operation of the system’s safety valves. This results in reduced systematic failures in the SIS, decreased engineering and maintenance costs, increased process up-time, reduced risk, and consistent design practices.