Unscrambling safety regulations

FIGURE 3: FERTILIZER SAFETY

The safety system for a chemicals and fertilizer plant is integrated with the process control system. (Click to enlarge image)

Similar to Rashtriya and Rompetrol’s safety equipment, Triconex’s Trident system integrates process controls and safety at oil and gas wells for the Al Noor and Al Shomu oil fields in the desert of South Oman. The oil wells are unmanned, and operate continuously. The main function of the Trident PLC at the wellheads is to act as an instrumented protective system for the pipeline to a production station, the wellhead, and the oil reservoir. Trident’s triplicated architecture helps maintain production of the well from a single fault or processing error. If a hardware fault occurs, the module can be replaced on-line, so the well can keep operating and flowing at all times.

Teams Refine Answers
As you might expect, some users in refineries are somewhat reluctant (or prohibited) from talking about safety issues. Two end users—Ed and Bob—described their company’s efforts, but have to remain anonymous.

Ed claims to understand all the safety requirements, as far as control systems, process equipment and Safety-Instrumented Systems (SIS) are concerned.

“Within this sphere, I’m very knowledgeable about the design, maintenance, and operation of safety-instrumented systems,” says Ed. “This doesn’t imply I know it all, but rather that I am competent enough to lead and oversee design efforts.”

Ed reached that point by leading his plant’s safety effort. “I participated in the early phases of developing our internal SIS standard and application practices, and most recently in the design and application of several systems.  While I can’t claim to know it all, experience and knowing who else in and outside the company to call for answers to certain questions does help.”

Refineries are big places with lots of equipment, and no one can be expected to know all their safety regulations. “My knowledge is limited to the design of systems and the intent of our standards. It doesn’t extend to the specific process hazards of any given process. No control engineer could be reasonably expected to understand all the hazards of the processes in his facility, nor should he advertise or assume that he does.”

Like Marcelo’s coffee plant, Ed and Bob’s refinery takes a team approach to safety. “The team determines where safety systems need to be applied and what their design should be,” he explains. "The team is run by a project engineer, who is knowledgeable about safety system design. Other team members include Operations, Engineering, Instrumentation, and Maintenance departments. We use outside consultants to facilitate the design meetings, develop the detailed design, and implement the system in cooperation with the control group. For design, it’s best to involve external consultants, who are experts at SIS design and implementation. We also have corporate support on safety system design and process technologies.

“Once systems are operational, the responsibility for operating them safely falls to the operations organization, while maintenance and support falls to the instrument maintenance and controls group. The controls group provides a lot of support for troubleshooting and ‘design intent interpretation.’ ”

Because refineries are subject to many rules, Ed’s team has to meet ISA S-84, API-521, API-556 and NFPA-85 specs. They also use Triconex’s Trident to meet SIS requirements. However, the refinery goes beyond the rules. “While ISA S-84 is a performance-based standard, and this is a good thing, it’s not enough,” he says. “Our internal standards and design practices are more prescriptive.”

Our other refinery engineer, Bob, takes a similar approach. “We have a fire and safety manager, a PSM coordinator for OSHA 1910 Process Safety Management, and a corporate charter related to safety,” he says. “The fire and safety manager has all the responsibilities and authority of being a manager of a department that has corporate scrutiny.  The PSM coordinator is primarily responsible for paper.”

Bob explains that safety requirements are necessarily widespread in a refinery. “There’s process safety related to relief valves, vessel pressure ratings, design and SIS,” he notes. “Also, there’s personnel safety, such as clothing, training, ergonomic designs, and injury reduction. Then there’s infrastructure safety, including electrical safety and physical property protection, such as fences, barriers, lighting, cameras, and guards.”

Because of its complexity and scope, safety is an ongoing task. “We use Triconex PLCs to meet our basic practice specification which is based on S84. We’re currently revising our Basic Practice to meet the revised S84, which follows the IEC specification,” adds Bob. “We follow the safety lifecycle in our design phase, do SIL reviews, develop SRSs, and do everything advised by our safety consulting firm. We require our primary engineering contractor to work with our designated safety consultant to complete designs. We presently have safety systems on all of our processes, with one-third meeting the S84 standard, but with plans to convert all the plants on a scheduled basis. We have active projects to convert six plants this year.”