The 'Basic Process Control System' (BPCS) - the 'Siemens Simatic PCS7 System' - enables the implementation of the control and safety application.

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With 'Safety Lifecycle Services', Siemens offers the necessary expert knowledge for such safety verifications. The safety specialists have completed a training program organized and implemented in close cooperation with TÜV and have certified qualifications. These training programs are available not only to Siemens employees, but also to employees of operators and solution partners (system integrators). These training programs provide the necessary specialist knowledge as well as advanced tools and methods. One of these tools is a Microsoft Excel-based SIL verification tool.

Safety verification according to IEC 61511 of a complex 'Safety Instrumented Function' (SIF) in the process industry.

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All standard formulas - including the specification of IEC 61511 for German-speaking countries, the VDI/VDE guideline 2180 "Safeguarding of process engineering systems using process control technology" (PCT) - are stored in this tool, as are the device-specific values such as PFD or failure rates of Siemens safety-related systems, such as controllers, peripheral devices or process instruments. Any additional project or customer-specific products required can be easily entered into the tool. The block diagrams of the SIL circuits - called Safety Instrumented Function (SIF) in the standards - are created and integrated using 'Microsoft Visio'. The tool calculates the SIL for each SIF taking into account the applicable standards and allows the selection of different architectures for each of the subsystems of the SIF, for example 1oo1, 1oo2, 2oo2, 2oo3 et cetera. It is also possible to calculate complex configurations containing different architectures.

The tool generates test reports that are accepted by authorities such as TÜV Süd or TÜV Rheinland. The logic diagrams of the SIS architecture can be included in the test reports. Siemens takes over the basic maintenance of the tool and also uses it itself for engineering tasks or safety consulting services. System integrators who have qualified as part of the Siemens Solution Partner Program or as a Siemens Functional Safety Professional (SFSP) are provided with the tool free of charge. These Solution Partners can then use the calculation tool for customer projects and supplement it with the required device data.

Comprehensive functional expansion

One of these Solution Partners is Kiel Engineering, a company of Kiel Industrial Services. Kiel Engineering has been a certified Siemens Solution Partner since 2001 and a Siemens Safety Specialist for the process industry since 2008. The Oberhausen-based company specializes in plant and power plant planning, electrical and instrumentation and control planning, automation and process control technology. For EI&C engineering, the employees use a Microsoft Office add-on developed in-house, which stores all device data and measuring points in an Access database and guides them step by step through the calculation of the verifications. The application uses the Excel tool from Siemens and extends the range of functions to include the generation of Ex i certificates. When the user creates new SIL circuits, all details are logged to ensure complete traceability.

System-specific typicals, i.e. device type-typical architectures of the SIL circuits, can be created manually or added by importing existing lists or databases. The user has access to the individual PCT points via the system structure mapped in the database. Each SIL circuit is connected to all available data via a sensor measuring point. The calculation of the SIL certificates and the document structure of the generated report file are based on the Excel tool created by Siemens. Thanks to the Typicals functionality and the connection to the Access database, Kiel Engineering was able to significantly expand the tool in terms of functionality and user-friendliness.

Lean cost structure

The calculation and management of Ex-i and SIL certificates in a tool that only requires Microsoft Office components and an Adobe Acrobat Reader is convenient for users and reduces costs; after all, Office packages are standard equipment for engineering workstations. The system is based on the so-called top-down-buttom-up approach, i.e. the principle of 'operational proof'. This means that the statistical evaluations of the fault data, including the accompanying documentation of a large number of installed SIL circuits from databases, can be used directly by plant operators.

Franz Handermann is Safety Partner Manager at Siemens in Karlsruhe.

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The list of devices stored in the system now includes over 1500 sensors and actuators as well as over 500 typicals. With the help of these specifications and the reuse of device data once entered, input errors are avoided when calculating verifications, and the calculation is largely automated. This significantly reduces the workload for users when creating and documenting standard-compliant verifications for operational and plant safety.