Process control and safety systems have always had one word in common: Separation. They were always separate and independent of each other. The safety system would be ready to kick in and take action no matter what the condition of the process control system.
These days safety standards and certification requirements have changed. So have approaches to the design and implementation of safety systems – a fact that affects not only the replacement of aging systems, but also the selection of safety and control systems in new facilities.
Traditionally, the required Safety Integrity Level (SIL) came through complex system architectures that emphasize redundancy and isolation from process control systems.
But that approach creates a different set of issues that affect not only safety but also operating costs, which is a key factor in today’s lean economic climate.
It’s harder for operators to do their job when they need training on multiple interfaces. When process states are changing quickly and operators most need instant access to information, it may be difficult to identify the relevant data in a timely manner, said Luis Duran, product marketing manager for safety systems at ABB.
“I believe in technology, but I also believe in the function of people,” Duran said. “It’s important to consider the human element in the design of safety systems. You can have an instance of operators working to reduce pressure in a vessel when the safety system kicks in. So the pressure may drop, but the operators may not have any idea if it’s a result of their actions or something the safety system did.”
One approach that can ease all the issues operators face is an integrated safety and process control. In such a design, the safety system works independently of the process control system, but has been designed specifically to allow high levels of visibility and understanding to be delivered to operators through the control system interface.
The concept isn’t new; but it is often misunderstood.
“There can be confusion about what this really means,” Duran said. “It doesn’t necessarily mean you’re mixing process control and safety. You’re maintaining the independence of each system. There are still two independent layers of protection. But it’s a functional independence.”
An integrated safety system includes:
A process control system designed to enable integration through such fundamental features as open standards.
A safety system designed and certified according to the functional safety standards and best practices – that feeds data seamlessly to the process control system
Field devices and instrumentation built around open standards for improved flexibility, effective bidirectional movement of data and reduced system life cycle costs
Built-in intelligence to present all data to operators through a single interface in a way that increases their visibility, knowledge and control
Testing, validation and finally certification to all necessary standards
“From the operations standpoint, the operator can monitor what’s happening in the regular process control and, when a situation arises that calls for some kind of action, he can look for a holistic solution,” Duran said. “You can take action before it becomes a safety issue. And if it does become a safety issue, you have more ability to keep track of safety mitigation as it is happening.”
There are other advantages as well. One is cost. An integrated safety system can be less expensive to own and operate. Another is in engineering. A common engineering environment for the process and safety systems simplifies the work engineers do.
It reduces training costs and expenses related to problem solving between disparate systems, and may improve response time when troubleshooting. Of course the safety components of such an engineering environment must also follow the standards and adhere to the design, testing, validation and certification of the safety system.
Duran said the degree of integration is flexible. The end-user can decide how much separation to maintain between safety and process control, Even if a user utilizes fully segregated systems, they can achieve functional benefits.
“As safety systems get replaced, or as new projects are developed, there is an opportunity to decide how you want to address safety in your operation – not just today but for the next 20 years,” Duran said. “With an integrated safety system, the strategy is very simply to provide an operating environment that runs better at less expense for a longer period of time.”
Click here for an integrated safety white paper.