4 cable and wiring
Post on 22-Nov-2015
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1Fieldbus FoundationTMFacts and Figures
about Cable and Wiring
Raymond NgBelden Singapore Pte Ltd
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2Agenda
Foundation Fieldbus Cable Standard IEC 61158-2 FF-844
Cable Selection Standard instrumentation cable vs- FF cable AWG size, Shielding, Jacketing, Armor types
Cable Installation & Termination Q & A
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3IEC 61158-2 Type A Cable Specification
Impedance: 100 Ohms Attenuation: < 3 dB/km Capacitance Unbalance:
4nF/km max. Conductor DC
Resistance: 24 Ohms/km max.
Maximum Propagation Delay Change: 1.7 s/km
Wire Size: .8mm sq.(18 AWG) nominally
Shield Coverage > 90%
CcS
Ccc
Insulation
Drain wire
Shield
CcS
Conductor
Jacket
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4FF-844 Cable Test Specification
Builds on IEC Requirements to further qualify cables
Addition to IEC requirements Expands on shielding requirements Specifies 10 to 22 pair twists/meter Jacket Resistance Required and optional cable ratings Recommended connector characteristics
Cable registration is in process
Lay Length
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5Instrumentation vs- FF Cable
FF Cable Polyolefin Insulation
Electronic grade insulation
100 Ohm Impedance 66% Velocity of
Propagation Designed with tolerances
necessary to meet FF specifications
Instrumentation Cable PVC or XLPE Insulation
35-65 Ohm Impedance 55 to 60% Velocity of
Propagation Designed to meet general
minimum instrumentation cable requirements
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6Instrumentation vs- FF Cable
FF cable has lower Capacitance FF cable is designed to a specific impedance to
reduce signal reflections and maximize network length
FF cables are tested during production to meet specific requirements: Capacitance Unbalance Impedance Conductor D.C. resistance
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7Cable Selection
First consult with local authority having Jurisdiction to ensure regulatory compliance
Selection Guide Conductor Size Shielding Armor Jackets
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8Cable Selection Conductor Size
Most common design is one pair 18 AWG Larger AWG (16, 14) provide:
Improved pull strength Electrical benefits, such as:
GreaterCurrent
Capacity
More FieldInstruments
LessVoltage
Drop
LongerDistance
ReducedResistance
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9Cable Selection Shielding
Most common design:foil shield only ~ 35 dB of Shield effectiveness Most effective at high frequencies
(>10 MHz) Drain wire for easy termination
Combination shields Foil in addition to braid Shield effectiveness of ~ 80 dB Effective from 60 Hz to GHz
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Cable Selection Armoring
Interlock Steel Aluminum
SWA (Steel Wire Armor)
Protective Metal Tapes: Smooth or Corrugated (Steel, Copper, Aluminum)
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Cable Selection Armoring
Why use Armor? Rodent protection Physical integrity Direct burial Reduces cost of conduit Hazardous Locations
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Cable Selection Jacketing
PVC most common jacketing material CPE good chemical and abrasion resistance LSZH low smoke zero halogen applications HDPE direct burial applications FEP high or low temperature applications (-70
to 200C)
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13
Cable Installation
Follow manufacturers recommendations Bending radii: generally 10 to 12x cable diameter Maximum pulling tension Installation temperature Pulling lubricant selection
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14
Cable Termination
Ground shield at one end only The near or host end Use provided drain wire or pigtail the braid Grounding both ends results in ground loops Required to prevent noise ingress, which could distort the signal
Shields should be trimmed back flush with jacket Isolate shield using heat shrink tubing or tape This keeps the shield from being inadvertently shorted to the (+)
or (-) wires or grounding at the device end
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15
Post Installation Verification
Follow FF Engineering Guide AG-181 Procedure for installing and commissioning fieldbus
segments Use DMM for Resistance & Capacitance
measurements Use Fieldbus Handheld tester to verify installation and
operation
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16
Common Installation Issues
Cable shield shorted to (+) or (-) wires Cable shield grounded at both ends, increasing
noise susceptibility Routing of cables in parallel with AC power lines
Minimum of 6 separation per IEEE 518 Minimize parallel runs Cross power lines perpendicularly, when possible
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Summary
FF-844 created to clarify cable requirements & register products
FF cable requirements are much more stringent than Instrumentation cabling requirements
Select cable that is compatible with application Consult manufacturer for installation &
termination recommendations Follow AG-181 guidelines for testing FF
segments
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www.fieldbus.org
Slide Number 1AgendaIEC 61158-2 Type A Cable SpecificationFF-844 Cable Test SpecificationInstrumentation vs- FF CableInstrumentation vs- FF Cable Cable SelectionCable Selection Conductor SizeCable Selection Shielding Cable Selection ArmoringCable Selection ArmoringCable Selection JacketingCable InstallationCable TerminationPost Installation VerificationCommon Installation IssuesSummarySlide Number 18
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