Distributed Intrinsically Safe Fieldbus Applications

Transcription

1 Application Note FB Distributed Intrinsically Safe Fieldbus Applications Emerson Process Management DeltaV DCS System Pepperl+Fuchs June 2003

2 Application Note FB c Pepperl+Fuchs Inc. All rights reserved. Printed in USA Pepperl+Fuchs, FieldConnex and FieldBarrier are registered trademarks of Pepperl+Fuchs Inc. All other marks are property of their respective owners. The information set forth in this manual is designed to assist the Purchaser in the installation, operation and maintenance of the FieldConnex range of products. Such information should not be construed as a warranty or representation, express or implied, regarding the products or its use in, or suitability for, a particular application, any such warranties or representations being specifically disclaimed. The terms, conditions and limitations of any product warranties may be obtained from Pepperl+Fuchs. Pepperl+Fuchs reserves the right to modify or improve the designs, specifications, features and/or functions of such products at any time without notice.

3 Application Note FB Distributed Intrinsically Safe Fieldbus Applications Introduction The Pepperl+Fuchs FieldBarrier is the latest enhancement to intrinsically safe fieldbus applications. Approved for use with Emerson Process Management DeltaV systems, the FieldBarrier labeled with the logo allows distributed fieldbus architectures to be exploited to their full capacity. This loop-powered instrument is mounted remotely and provides energy-limited, intrinsically safe circuits for transmitters mounted in hazardous locations. Description FieldBarrier combines the features of a short-circuit protected fieldbus junction box and an intrinsic safety barrier. The FieldBarrier makes any spur on a fieldbus trunk intrinsically safe. By connecting a maximum of 4 FieldBarriers on a standard network trunk, up to 16 intrinsically safe I/O points can be created. The FieldBarrier mounts within a Class I, Division 2 or Zone 1 hazardous area and provides intrinsically safe circuits for Class I, Division 1 or Zone 0 hazardous locations. This reduces the wiring costs and hassles of conventional isolatorjunction box combinations and saves valuable cabinet space. The ability to mount the FieldBarrier outside the control room allows the distributed nature of fieldbus architecture to be fully supported. The FieldBarrier is a 4-channel unit that provides power for the connected field instruments and serves as an isolated link to the non-i.s. trunk. Each channel supplies up to 40mA to the field instruments with spur lengths up to 120 meters - nearly 400 feet. Other features of the FieldBarrier include overload protection, galvanic isolation, selectable fieldbus terminator and extreme environmental operation in temperatures up to 158F (70C). For distributed intrinsically safe fieldbus applications, Pepperl+Fuchs recommends the following FieldConnex branded FieldBarrier products: F2D0-FB-Ex4.C F2D0-FB-Ex4.CG F2D0-FB-Ex4.CGB F2D0-FB-Ex4.CGS RD0-FB-Ex4 (3/4 NPT conduit version) (Plastic cable gland version) (Nickel/Brass cable gland version) (Stainless steel cable gland version) (DIN rail mounted version) For more information on this product, refer to the Pepperl+Fuchs documentation and/or visit the DeltaV website and follow the links to Pepperl+Fuchs.

4 Application Note FB Technical Specifications FieldBarrier Specifications Input voltage Rated operating current, no load Rated operating current, 20mA/spur Rated operating current, 40mA/spur Rated operating current, short/spur Fieldbus spur rating (intrinsically safe) Safety Parameters (U o,i o,p o ) Operating temperature range Relative humidity Storage temperature range Dimensions of junction box version Mounting 16 32Vdc 25 22mA* mA* mA* mA* Table 1 FieldBarrier specifications 40mA; 30mA (Emerson spec is 30mA), 1 instrument per channel 15.75V, 248mA, 975mW -40C to 70C (C, CGB, CGS, RDO versions) -30C to 70C (CG version) <95%, non-condensing -40C to 85C 258mm x 114mm x 84mm (10.2in x 4.5in x 3.3in) Panel mounting with 2 screws (DIN rail mounting RD0 version) Fieldbus Line Specifications Transmission Type Cable Type Communication speed Network addressing 2-wire Type A fieldbus cable, twisted pair, shielded (recommended) 31.25kbits/sec Not required Table 2 Fieldbus line specifications * - The current is directly related to the 16-32Vdc operating range.

5 Application Note FB Design The Pepperl+Fuchs FieldBarrier is housed within a rugged industrial enclosure for direct field mounting or it can be supplied in a DIN rail version for easy cabinet mounting. The following illustrations show the basic design of the FieldBarrier. Intrinsically safe fieldbus spur connections Selectable terminator LED indicators Non-intrinsically safe fieldbus connections Fig. 1 - FieldBarrier mounted within Type 4/IP66 junction box (F2D0-FB-Ex4*) Cable tiedowns Ground lug Intrinsically safe field wiring Non-intrinsically safe field wiring Encapsulated electronics Fig. 2 - DIN rail mounted version of FieldBarrier (RD0- FB-Ex4)

6 Application Note FB Wiring and Termination All versions of the FieldBarrier come equipped with integral cable tie-downs to help insure segregation of intrinsically safe and nonintrinsically safe wiring. It is recommended that each cable be secured with a tie wrap to prevent intermingling of wiring and maintain separation. The product also comes with a clear plastic partition that mounts directly over the green colored Trunk In / Trunk Out terminal blocks (Terminals 3+, 4-, 5s / 6s, 7-, 8+ respectively) and over the LED s to additionally help maintain intrinsic safety separation requirements of the internal wiring. As is the case with any hazardous location system, it is important to refer to Pepperl+Fuchs control drawings for proper installation guidelines and requirements. The intrinsically safe spur connections are located on the left side of the FieldBarrier and are identified by blue terminal blocks. These terminals are labeled SPUR1, SPUR2, SPUR3 and SPUR 4 (Terminals 10 through 21 respectively). Located adjacent to the intrinsically safe terminals is the selectable trunk terminator. Although the terminator switch is located on the spur side of the FieldBarrier, the switch enables or disables a 100ohm, 1uF terminator on the trunk. It is not required to use the internal FieldBarrier terminator as the sole termination means for the segment. Stand-alone terminators can be implemented externally if the application or customer prefers or requires them. External terminators can be mounted within junction boxes or control cabinets as required with no adverse effect on the operation of the FieldBarrier. Shielding According to the FOUNDATION fieldbus specification, grounding of the twisted-pair shield should only be done at one point. Keeping this requirement in mind, Emerson recommends removing any shielding jumpers (1B and 2B) from the FieldBarrier, isolating (tie-back) the trunk shield from the FieldBarrier electronics and earth grounding Remove any jumpers P+F FieldBarrier with clear plastic wiring partition the spur shields. Emerson also recommends isolating (tie-back) the spurs at the individual field instruments. Since the trunk and spur connections are isolated from one another through the FieldBarrier, the trunk shield should be normally grounded at a single point in the main control panel. If you require more information regarding shielding and grounding, contact P+F technical support.

7 Application Note FB Power The FieldBarrier contains an integral power source that provides conditioned, intrinsically safe energy to each of its 4 independent channels. The minimum trunk voltage necessary for proper operation is 16V. This minimum voltage guarantees that 30mA is available for the connected field instruments. Emerson recommends the maximum loading of each channel to 30mA in order to maintain optimum performance, to connect maximum length spurs and to allow an IS test meter with 10mA of current consumption to be connected. The Pepperl+Fuchs SegmentChecker program is available as a free download from our web site It is meant to help perform the necessary FieldBarrier power supply calculations during the design phase of your FOUNDATION fieldbus project. It also provides information regarding the proper sizing of the fieldbus power supply. FieldBarrier requires an external fieldbus power supply or fieldbus power conditioner to operate. Presently, the only Emerson recommended power supply for use with the FieldBarrier is the Relcom FPS-I. Additional power supplies will be added as soon as they are certified and available. In order to present a general understanding of the FieldBarrier characteristics, the following parameters where entered into the P+F SegmentChecker: Controller: DeltaV Series 2 Redundant H1 Cards (Current Requirement = 24mA) Power Supply: Relcom FPS-I (Power Specification = Field Instruments: 12 Intrinsically Transmitters 17mA & 20mA) Ambient Field Conditions: 40C By setting the parameters to simulate this configuration, three FieldBarriers are located at the end of the trunk with 3 meters of cable between one another to simulate the worst-case architecture. The SegmentChecker program calculates the maximum trunk and spur cable lengths and determines whether enough power is available from the supply. The following results are calculated: Maximum current requirement of the FieldBarriers = 281mA Maximum trunk cable length = 430m (1400ft) Maximum spur cable length = 90m (295ft) Available trunk voltage at last FieldBarrier = 19.21V Short circuit check (operational during channel short) = yes As illustrated in this example, this software tool is extremely useful in determining the basic operating parameters of a fieldbus network involving FieldBarrier.

8 Application Note FB Installation The FieldBarrier is intended to be used in applications requiring intrinsic safety. Intrinsic safety, as a protection method, has long been considered the safest method of protecting circuits installed within hazardous (classified) locations and FieldBarrier fully supports its features. In Zone 1 mounting applications, increased safety wiring methods must be followed for the trunk connections. In either Division or Zone designated areas, the intrinsically safe and non-intrinsically safe wiring must be separated according to local requirements. Figure 1 below illustrates the basic architecture involving P+F FieldBarriers and a distributed intrinsically safe fieldbus application. Redundant Series 2 H1 cards Optional P+F F*-JB-* junction boxes Non-hazardous location H1 H1 Carrier shield bar F2D0-FB-Ex4.IEC-* FieldBarrier Shielded pair with drain wire GND Fieldbus Power Supply F2D0-FB-Ex4.IEC-* FieldBarrier Hazardous Location Class I, Div. 2 or Zone 1 Optional P+F Cables and Cordsets Hazardous Location Class I, Div. 1 or Zone 0/1 Devices Distributed Intrinsically Safe Fieldbus Application Example If you have any questions regarding this brief overview, any feature of the FieldBarrier or other P+F FieldConnex products, please contact our technical support groups located throughout the world or visit our web site dedicated to our complete line of fieldbus products and services at