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News from Profibus / Profinet – Part 6 PROFIBUS — Simple and Safe in Explosion Hazard Zones

| Editor: Dr. Jörg Kempf

The high-power trunk with FISCO spurs is a de facto standard for PROFIBUS in explosion hazardous areas. Based on this concept, PROFIBUS PA can be installed without difficulty or the need for major cost analysis in the chemical, pharmaceutical, food pro-cessing, biogas, offshore oil production or mining industries.

(Bild: Profibus Nutzerorganisation)

The man with the beard picked up the youngster’s smartphone, looked at it from all sides and played a bit with the touch screen. “Black magic,” he grumbled. “Can you actually make phone calls with it”? Before the young engineer had a chance to respond, the man continued: “It’s good that this thing was not lying around on the table. The drink would probably have ruined it.” “There would have been some damage to it,” said the engineer, “and it is not certified for explosion hazardous areas. But we do have devices that are completely suitable for field deployment and are a huge help when we carry out maintenance during operation." The man with the beard continued to grumble and play with the smartphone’s touch screen. “Watch out for your cellphone. This guy could never walk past any piece of equipment without playing with it,” said the older man. “But let’s talk a bit about your fieldbus systems and explosion hazardous areas.”...

The high-power trunk with FISCO spurs is a de facto standard for PROFIBUS in explosion hazardous areas. Based on this concept, PROFIBUS PA can be installed without difficulty or the need for major cost analysis in the chemical, pharmaceutical, food pro-cessing, biogas, offshore oil production or mining industries.

The FISCO Model

The FISCO Model (Fieldbus Intrinsically Safe Concept; IEC 60079-11) serves as the basis for validation of explosion protection with-
out application-specific engineer-​ing calculations. It was developed by PTB (German Federal Stand-​ards Laboratory) and confirms that a communication network is intrinsically safe if the compo-​nents deployed (i.e. field devices, cables, segment couplers and bus terminators) comply with predefined voltage, current, power, inductivity and capacitance specifications. Components in accordance with FISCO fulfil these requirements. With only FISCO certified components on a segment the validation of intrinsic safety is provided by the bill of materials. It doesn't get easier than that. FISCO, however, has limitations with respect to cable length (up to 1,000 meters) and the number of field devices that can be connected. This is where the high-power trunk comes in.

The High-Power trunk

Ex i “intrinsic safety” with or without FISCO allows modifications of electrical systems without requiring a hot work permit. It is really only needed in process automation when intervention is required on a device during ongoing operation for maintenance purposes or when it is necessary to swap a device. At the trunk cable, this is rarely necessary, thus higher power is enabled with Ex e “increased safety” ignition protection is normally sufficient. The High-Power Trunk concept combines elements from the Ex e and Ex i protection types. The trunk with Ex e ignition protection carries high power permitting cable lengths up to 1,900 meters and a higher number of devices. The devices are attached to fieldbus barriers and the installation is FISCO compliant. With the high-power trunk, PROFIBUS PA is suitable for simple device installation in explosion hazardous areas wherever the need arises.

Following the youngster’s remarks on explosion protection, the old man and the man with the beard exchanged looks of approval. They were obviously impressed with the explanations and the new technology. Com-​pared to the old days, the FISCO concept and the high-power trunk apparently take a lot of complexity out of fieldbus design, installation and operation in explosion hazard zones. How-​ever, they wanted to take a closer first-hand look …

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To be continued: Part 7

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Further parts of our Profibus series:

Part 1: PROFIBUS – a Proven Technology

Part 2: PROFIBUS — Diagnostics the Easy Way

Part 3: Profibus — Device Management the Easy Way

Part 4: PROFIBUS — for Stable Process Control

Part 5: PROFIBUS — Certification Ensures Compatibility

Part 6: PROFIBUS — Simple and Safe in Explosion Hazard Zones

Part 7: PROFIBUS — Lowering Lifecycle Costs

Part 8: PROFIBUS Simplifies Device Management

Part 9: How PROFIBUS Makes Network Planning a Breeze

Part 10: Condition Monitoring with PROFIBUS PA

Part 11: PROFINET for Process Automation

Part 12: PROFIBUS — Cost–Efficient Throughout the Lifecycle

Watch the video to find out more about the young engineer, the older man, the man with the beard and PROFIBUS PA.

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