PCS 7 Logic Matrix streamlines process interlocks

New tool reduces engineering effort required to generate interlocks and shutdown logic, helps operators quickly recognize equipment states.

By Jim Montague

Everyone wants customer feedback and input on product development, but Siemens Industry and its users at Dow Chemical, DuPont, Air Products, aeSolutions and Pigler Automation have been taking collaboration to a whole new level lately—saving 15-25% on project programming costs over the life of a control system.

These companies are members of the Siemens Process Automation Advisory Council and Product Requirements Working Group and the Siemens User Community. Their representatives recently contributed use-case requirements and specifications that were crucial in helping Siemens develop innovative and groundbreaking capabilities for the latest edition of its Simatic PCS 7 control system—Version 8.2 with Logic Matrix process interlock tool. This latest system enhancement is designed to help engineers efficiently program and operators effectively visualize and take action on complex process interlocks to improve production and increase safety. The users also participated in several beta testing cycles of the new PCS 7 V8.2 Logic Matrix, and provided more feedback.

Two of the beta testers—Jeff Sibley, R&D Research Scientist at the Dow Chemical Co., and Guy Burnaman, A&PC Manufacturing Technology Manager at DuPont Performance Materials' Sabine River Works (SRW) facility in Orange, Texas—described their work during "Siemens New Process Interlock Tool" at the Siemens Automation Summit 2016. Sibley also co-chairs the Siemens Users Community, and Burnaman is a member of the process automation advisory council and leads the product roadmap working group.

From shutdown to interlocks

"When we did interlocks in the past, we often used a lot of flip-flops in resets for our interlocks, and so we needed more error-free coding method and a way to visualize the matrix, which was accomplished by hand," explained Sibley. "So, the user advisory board and Siemens began collaborating on a solution, and proposed using PCS 7's Safety Matrix tool for non-safety, basic process control systems (BPCS)."

Paul Morgan, Consulting Application Engineer at Siemens Process Automation, confirmed that PCS 7 V8.2 Logic Matrix was developed from the earlier PCS 7 Safety Matrix for failsafe systems, PCS 7 APL control module types, and APL interlock block capabilities. These enable Logic Matrix to provide a dynamic matrix for visualization of the process and associated interlocks. PCS 7 Logic Matrix also leverages the American Petroleum Institute's (API) 14C standard for cause-and-effect diagrams.

"The users really loved the Safety Matrix tool, and so they also wanted to use it for non-safety BPCS," reported Morgan. "Logic Matrix uses a process upset and response method; each matrix in the tool can have 128 causes, each cause having up to six inputs—and 128 effects. For example, the tool’s visual filter with APL programming language navigation shows devices that are able to trigger effects, such as an interlocked motor, while its other column shows its effect, such as the level in a tank below a threshold." 

Morgan added that Logic Matrix outperforms interlock function blocks (FB) because they can't use analog process variables (PVs), can’t formulate complex trip conditions, such as XooN voting, timing delays, latching and overrides. "Likewise, using engineered charts for complex trips means logic can be difficult to trace and understand, HMI indicators and actuators must be added to the logic," said Morgan. "However, when developing programs with Logic Matrix, users have simple to use engineering interface; support for analog and discrete tag/logic types; a rich feature set of cause-and-effect options; automatic generation of controller programs; and automatic generation of HMI graphics. Logic Matrix's key benefits are a significant reduction in the engineering effort required to generate interlocks and shutdown logic, and fast recognition of equipment state for operators."

Engineering efficiency, operator visibility

Thanks to these capabilities, Sibley reported that PCS 7 Logic Matrix is critical for complex interlock management of the small, complex R&D process controls at Dow Chemical. "Logic Matrix gives us more efficient programming of complex interlocks schema, and makes our processes less prone to errors, and require less testing after a change," said Sibley. "It's also saving us considerable time on current visualization, and we have better visualization of causes and effects for our technologists and scientists. I estimate that utilizing Logic Matrix will save 15% to 25% of project programming time over the life of a system."

"We've used Safety Matrix extensively for safety interlocking functions since 2007," added DuPont’s Burnaman. "The benefits we've achieved consist of better visualization for operations, including cause-and-effect understanding, first-out monitoring and sequence of events, as well as better configuration efficiency for engineering, including cause-and-effect strategy, commissioning and checkout, plus considerable time savings on console design. We estimate time savings of 15% to 20% by using Logic Matrix for project programming at an average of 50 hours savings per standard system."

In general, Morgan reported that Logic Matrix makes engineering of interlocks convenient and simple because the parameters for interlock functions are parametrized in an editor, according to the cause-and-effect principle. This gives planners, operators and inspectors a standardized view and common understanding of all interlock functions, which makes traditional programming skills necessary. Also, engineering is efficient, and bulk data interconnection options and import/export mechanisms allow shutdown parameters in PCS 7 to be quickly adapted. As a result, Logic Matrix accelerates engineering and enables reduced testing times in acceptance procedures for automation tasks.

In addition, Morgan added that Logic Matrix integrates seamlessly into the look and feel of PCS 7's controls. Process-relevant events and alarms are transmitted to the operator and integrated in the message system. Options are added to face plates to access Logic Matrix directly. This lets operators jump directly from Logic Matrix to the event at the process tag in the process image. At the same time, all interdependencies with other measuring points are clearly depicted. This means Logic Matrix can be used for efficient and secure interconnection of interlock states in any production plant. Further, it provides for logical depiction of plant states, helping operators to avoid plant downtime.

For more information about Simatic PCS 7 V8.2 and Logic Matrix, visit the website

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