Fieldbus in Hazardous Areas
Methods of ignition protection
Fieldbus in hazardous areas requires an infrastructure with suitable ignition protection. The table below shows the major protection methods. Each method can be chosen for the segment as a whole, or for parts of the segment, i.e. the trunk or the spurs.
| Protection | Ignition Protection | Applied in | Attributes |
| Mechanical |
Increased safety (Ex e) |
Zones | Protects against unintentional opening circuit. The same as for any electrical installation, such as lighting fixtures, motors, etc. Enables long cable runs and high device counts |
| Explosion proof Non-incendive wiring |
Divisions | ||
| Electrical | Intrinsic safety (Ex i) | Zones and Divisions | Hot work permitted. For shorter cable runs. For any hazardous area |
*) Although this is not necessary with FieldConnex® components, on occasion a flameproof enclosure is applied for fieldbus junction boxes.
Where standard operation procedures require a hot work permit to be included with the work order, users often prefer mechanical methods of ignition protection.
This Design Guideline lines out aspects with regards to planning the fieldbus infrastructure and with particular focus on hazardous areas, both: Divisions and Zones. Download the free document and make engineering and planning fieldbus segments for your process automation system a simple and straight forward task …
Live maintenance on instruments
In order to enable work on instruments without a hot work permit, the spur and instrument connection must be installed intrinsically safe (Ex i) or with non-incendive field wiring. However, to fulfill demands for high device count and long cable runs, more power is required than is technically feasible with intrinsic safety.
The high-power trunk concept fulfills these demands. The trunk carries power to 31 V and 500 mA requiring a means of mechanical ignition protection similar to those of electrical lighting or motors. The device coupler is the intrinsic safety barrier installed in the fieldbus junction box near the instrument. Up to four device couplers per segment provide power and protection to the maximum number of 31 instruments as per the fieldbus standard.
Benefits:
- Installation and maintenance crews benefit from working on field instrumentation without requiring a hot work permit during normal operation.
- Engineers can utilize the maximum cable length permitted for fieldbus and a high device count per segment in any hazardous area.
This topology shows the most common installation methods for fieldbus. Mix and match of ignition protection methods on one segment is permitted.
Download and install the free software tool that provides planning support for power supplies and device couplers designed for hazardous areas. It helps you check and verify that the fieldbus installation will work according to your specification …
Three steps to right product
Use the FieldConnex® product selector to see illustrations of all installation methods with and without ignition protection as well as appropriate products.
From decisions to planning, installation, and commissioning up to operation and maintenance: Discover how to make the most out of your fieldbus infrastructure …
Pepperl+Fuchs GB Ltd.
77 Ripponden Road
Oldham OL1 4EL, Lancs.
United Kingdom
sales@gb.pepperl-fuchs.com
+44 161 6336431
Pepperl+Fuchs is a leading developer and manufacturer of electronic sensors and components for the global automation market. Continuous innovation, enduring quality, and steady growth have been the foundation of our success for more than 70 years. Pepperl+Fuchs employs 6,300 people worldwide and has manufacturing facilities in Germany, USA, Singapore, Hungary, Indonesia and Vietnam, most of them ISO 9001 certified.