Post on 19-Jan-2017
Instrumentation - CablesGSS Srinivas
Introduction to Cables
General SpecificationBS 5308
Conductor Insulation and Jacket
ShieldArmoring Selectio
n of cable
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TIntroduction to Instrumentation CablesUsed within industrial manufacturing plants for control, communication, data and voice transmission signals. These cables are used typically in industrial projects. They are used to connect electrical instrument circuits and provide communication services in and around process plants with detail signal transfer.
PurposeInstrumentation cables are multiple conductor cables that convey low energy electrical signals used for monitoring or controlling electrical power systems and their associated processes. Applicable Standards BS 5308 or EN 50288-7 Basic Design; IEC 60332-1 Flame Retardant; IEC 60332-3 Fire retardant (cat. C or A according to requirements); IEC 60754-1 Halogen free properties (only for LSZH cables) IEC 61034-2 Low smoke emission (only for LSZH cables)
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Instrumentation Cables -Typical Configuration
BS 5308
Part list:1. Conductor 2. Insulation to conductor3. Individual Screening4. Overall Screening5. Bedding6. Armoring7. Sheath8. Drain wire9. Non hygroscopic
Type 1Polyethylene insulated Un ArmoredPVC SheathedIndividually and collectively Screened
Part 1
Type 2Polyethylene insulatedArmored- Steel wireIndividually and collectively Screened
Type 1PVC insulatedUn ArmoredPVC SheathedIndividually and Collectively Screened
Type 2PVC insulatedArmored – Steel wirePVC SheathedIndividually and collectively Screened
Part 2Screening:Collectively screened by a laminated, bonded aluminum/ polyester tape.
Drain WiresThe metallic side of the screen are in contact with one or more tinned annealed copper drain wirePairTwo insulated conductors uniformly twisted together to form a pair with max. lay length of 100mm
7 6
5
4 3
2
1
8
6
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Conductors For instrumentation cables conductors are generally plain annealed electrolytic copper wire for signal transmission or special alloy, for thermocouple /compensating cables. Conductors can generally be according to EN 60288: class 1 (U) Solid, class 2 (R ) stranded and class 5 (F) flexibleType of conductors are chosen according to electrical characteristics, required flexibility, type of connection systems or specific installation conditions, for example: Class1 solid conductor is preferable for
permanent installation, crimping termination,
In presence of vibration or movement or reduced bending radius is preferable class 5 flexible conductor,
In presence of corrosive atmosphere, high temperature or to facilitate the soldering is preferable tinned conductor.
Conductor
Size
BS EN 60228
Stranding
Bare or Tinned
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Conductors – Class 1, Class 2 and Class 5&6 Plain Or Metal coated annealed Wire Coatings:Applied on the conductors to prevent some insulations from attacking or adhering to copper. Also helps in soldering and prevents deterioration of copper at high temperaturesAnnealing:A process in which the conductor is heated to over 700 deg F and allowed to cool. This will allow conductors to bent without breaking, remove stiffness and improve flexibility.
Wire Bars:Approx. 200 pound billet of cu, roughly 54” long X 3-7/8” wide X 3-5/8” high used as the feedstock for making the rod
RodsA 5/16” or 3/8” dia. rod drawn from wire bars to make solid conductors & individual strands
StrandingTwisting together small wires to form a single conductor. Provide flexibility, ease of handling and vibration resistance
Bunch Strand (ASTM B-174)A conductor formed by simple twisting in one direction of many small wires. Used in flexible cords, flexible control cables and flexible lead wires
Concentric Strand ( ASTM B 8)A conductor is formed as a layer with 7,19,37,61 or 91 wires. Normally adjacent layers are reversed direction. Control cables favor 7 and 19 wires.
Rope Lay – Bunch Stranded members and Concentric stranded members (ASTM B-172&3)7 or 19 strands form a conductor. Used in portable power cables and welding cables
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Insulation and JacketInsulation applied over conductors for electrical isolation between conductors or from groundJacket applied over conductor insulation or cable core for mechanical, chemical or electrical protection
0102
0304
0506
0708
Size
Electrical
Physical
Chemical Resistance
Environmental Conditions
Service life
Reliability
Flexibility
Wall Thickness
Capacitance, Attenuation, velocity of propagation, Dielectric Strength, working voltage and Dielectric constant
Elongation, Tensile Strength, Temperature rating , Flexibility, Flammability, Resistance, Specific gravity
Chemicals can destroy cable materials.
Extreme temperatures brittle at low and soft at high. Vaccum leaches oils out of cables. Radiation cause damage to cables
Ideal cable system should be engineered to last the life of the product in any environmentligula
Ability of a cable to bend
09 Radiation resistance
10 Smoke Generation and Flame Resistance
Ability of a cable to burn, construction dependent and industry standard apply
Is based on the both durability and signal integrity
Radiation index is the absorbed dose in Gray (Gy) of the material after exposure having 50% elongation of brake of its unaged value at least.
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Insulation Working conditions need to be taken into consideration to choose the right insulation material.Material can be divided into thermoplastic and thermoset (cross linked). Thermoplastic material are more sensitive to high temperatures, as material melts at the increase of temperature, while thermoset, due to stable polymeric chain bonds are more resistant to temperature and deformation. Most popular insulations are PE and PVC for general installation conditions and LSZH thermoplastic materials (low smoke zero halogen). Other class includes, XLPE, silicone rubber, other rubbers such as EPR, HEPR, EVA. Special techno polymer can be used in case of specific installation condition, such as fluoro- polymer or techno-polymer materials.For fire resistant cables two types of insulation are used: silicone or mica tape plus XLPE (or other thermoset compounds).
Insulation
Type
BS 6234/50363/7655
Wall Thickness
Temperature
Voltage
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ScreeningElectrostatic noise can be
reduced by screening around the cable, around each pair or
bothMagnetic noise can be reduced by increasing distance between
cable and offending power cable and screening the cable
Screening
Communication Cable
Prevent Noise InterfaceSurge Protection
Lighting Protection
Control Cable
Provide Circuit IsolationPrevent Noise Interface
Surge ProtectionContain Intelligence
High Voltage Cable
Prevent CoronaSurge Protection
Fault Path Provision
Shield
Electro Static Screen (Grounded at one end)
Metal Tape
A flat Metal Tape applied with
overlap around pairs cable core or inner jacket.Tape,
Al or Cu 75μm thick
Metal Tape with Drain
Wire
Copper Drain Wire
Metal Laminate and Drain
Wire
A flat polyester supported foil tape,
applied with overlap, around
pairs, triples, etc., cable core, or inner jacket. A drain wire
is normally used with this type of shield for ease of
terminating.
Conducting Plastic and Drain Wire
Drain Wire & Semi
conducting PVC or PE
Sheath
Metal Braid
A double serving of uninsulated wires
interlocking in a two over-two under
pattern. The second serving is applied in the reverse direction
of the first
Magnetic Screen (Grounded at both ends)
Copper Tapes
Copper Tape overlap intrinsic
screening factor 0.95
Copper and Steel
Tapes
Cu and Mild Steel tape Intrinsic
screening factor 0.9
Steel Tape Armored
Cable
Lead or Moisture
Sheath with two layers
of Steel Armour tape, IS
factor 0.4 to 0.5
Aluminum and Steel
Tape Screen
Moisture barrier, Al wire/strip, two layers
of steel tape, IS
factor 0.06
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Screening ■ Cross-talk from adjacent pairs or triples;■ Interference induced by external source Aluminum /polyester tape with a tinned copper drain wire, the most popular construction. Aluminum /polyester or copper/polyester tapes normally have a total thickness from 25 to 100 μm, according to standards and are wrapped with an overlap > 125% to assure a full coverage even in case of bending.Bare copper braid for electromagnetic interference or when the cable is subject to movements.Tinned copper braid for electromagnetic interference in presence of corrosive atmosphere or high temperature. Copper braid normally has a coverage from 80% to 95%. This type of screen presents a lower electrical resistance, a very good protection also to electromagnetic noises and a higher mechanical resistance compared to aluminum /polyester tape.
Screening
Type
Overlap
Coverage
Isolation
In continuous contact with metallic side there is a drain wire, normally tinned copper, 0.5 sq mm, stranded or solid. Screens can be applied to each pair/triples (individual screen) and/or on the bundle of the cable (overall screen).
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Basic Design BS 5308 or EN 50288 - 7
ArmoringMetallic armor are used when cables have to be installed direct buried, or if mechanical protection is required. ■ Required tensile load■ Expected pressure on cable during service■ Protection against rodent■ Protection against accidental damage■ Minimum required bending radius.
SWA: Single layer of galvanized steel wires, with diameters according to relevant standards, coverage min. 90%. This armor assures a very good mechanical protection and tensile strength. An additional counter spiral tape increases solidity, if required.
GSWB: Galvanized steel wire braid, diameter of wire: 0.20 – 0.25 – 0.30 – 0.40 mm, with coverage of > 80%. It assures a good mechanical resistance, allowing a lower bending radius compared to other armor. It is preferable when there is movement or vibration. For special application is possible to use stainless steel, tinned copper or special alloy wires.
Armoring
Direction
BS EN 1027
Coverage
Application
GSTA: Galvanized steel tape armor, composed by two tapes with overlapped edge; thickness of each tape: 0.20 – 0.30 – 0.40 mm, according to cable diameter. It grants a coverage > 100%. Very good crush resistance, but fair tensile strength. Brass tape of minimum thickness 0.075 mm can be used for special applications.
GSFA: Galvanized steel flat armor. It is composed by flat wire of thickness 0.6 mm or 0.8 mm, it is similar to SWA, but with higher mechanical protection.
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Sheath Many compounds can be used as internal/external protection of cables. Working condition need to be considered for the right choice. PVC, PE and LSZH are the most popular materials, but we have to consider that different grades are available to meet specific working conditions. Anyway the following conditions have to be evaluated: Type of installation (indoor/outdoor, direct
buried…) Possible presence of humidity, oil,
chemicals… Behavior in case of a fire (fire propagation,
fire resistance, emission of gases and smoke…)
Range of temperature UV resistance in case of sun exposure
Screening
Type
Wall Thickness
Temperature
Color
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Basic Design BS 5308 or EN 50288 - 7
ProtectionProtectionIn addition to mechanical protections, special protections can be considered for specific installationsMoisture barrierIf moisture barrier is specified it shall be applied over the total cabling of elements and is possible to choose two alternatives:Water swellable tapesLaminated sheath, consisting of a longitudinal overlapped metallic foil, bonded to an extruded sheath.Lead SheathIt is applied between two other sheaths and is the best protection against aggressive chemicals. This is an expensive solution, increases weight and bending radius. It presents poor vibration resistance and normally an armor is required to protect it from crushing.
Cable
Protection
Moisture Barrier
High Pack
It is an alternative to Lead Sheath and is composed by a longitudinal overlapped aluminum copolimer coated tape bonded to HDPE jacket and additional special alloy of polyamide/polypropylene sheath.■ Excellent protection against corrosion and humidity.■ Excellent impact resistance that in some cases prevents the use of the armor. This protection has a lower weight compared to lead sheath, cables have a smaller diameter, with a reduction of costs. Hi-Pack is the right choice to protect the environment.
Thank youSome tables below
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MaterialsInsulatio
nSheath Temp.
LowTemp. High
Abrasion resistance
Oil resistance
Solvent Resistance
Water Resista
nce
Nuclear radiation resistance
Flame retardan
cyFlexibili
ty
PVC -40 +105 3 3 2 3 2 3 3
Polyethylene -40 +80 3 2 3 4 2 1 2
Polypropylene -40 +105 4 4 4 4 2 1 2
Nylon -70 +120 4 4 4 2 2 1 2
Polyurethane -40 +80 4 4 2 3 3 3 3
XLPE -60 +90 2 3 3 3 2 1 2
Fluoropolymer FEP -80 +205 2 4 4 4 1 4 2
FP PTFE -80 +260 2 4 4 4 1 4 2
FP PFA -80 +260 2 4 4 4 1 4 2
FP MFA -80 +240 2 4 4 4 1 4 2
FP ETFE -80 +155 2 4 4 4 1 4 2
4. Very Good ; 3. Good ; 2. Fair ; 1. Poor Can be used
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MaterialsInsulatio
nSheath Temp.
LowTemp. High
Abrasion resistance
Oil resistance
Solvent Resistance
Water Resista
nce
Nuclear radiation resistance
Flame retardan
cyFlexibili
ty
FP ECTFE -60 +160 3 4 4 4 3 4 1
Hytrel -40 +80 3 4 4 3 1 1 2
Peek -60 +250 2 4 4 4 4 4 1
Kapton -75 +200 4 4 4 4 4 4 1
Technopolymer LSZH
-30 +90 2 3 2 4 4 3 2
G10 -40 +90 2 2 1 3 3 3 3
Silicone Rubber -60 +200 2 2 1 3 3 3 4
Thermoplastic Rubber
-55 +125 4 3 2 3 1 3 4
Neoprene -40 +90 4 3 2 3 2 3 4
EPR -50 +90 3 2 1 3 3 1 3
LSZH -30 +90 2 3 2 3 3 3 2
4. Very Good ; 3. Good ; 2. Fair ; 1. Poor Can be used
Insulation and Jacket Materials Properties
PropertiesP= PoorF= Fair
G= GoodE= Excellent
O = OutstandingThe ratings are based on average performance of general purpose
compounds. Any given property can usually be improved by the use of
selective compounding.
Thermoplastic Thermoset
PVC
Low Density Polyethylene
Cellular
Polyethylen
e
High-
Density Polyethylene
Polypropylene
Cellular Polypropylene
Polyurethan
eNylon
CPE (Chlorinated Polyethylen
e)
Premium
grade PVC
FEP Tefzel(ETFE)
PTFE Teflo
nSole / Kynar
Halar
Neopren
e
Chlorosulfonated Polyethylene
Ethylene Propylene Rubb
er (EP, EPR, EPDM)
XLPE
CPE (Chlorinated Polyethylen
e)
Silicon
Rubber
Oxidation resistance E E E E E E E E E E O E O O O G E E E E EHeat resistance G-E G G E E E G E E G-E O E O O O G E E G E OOil resistance F G-E G G-E F F E E E F O O E E-O E G G P G G-E F-GLow-temperature flexibility P-G E E E P P G G E P-G O E O O O F-G F G-E O F OWeather, Sun resistance G-E E E E E E G E E G O E O E-O O G E E G E OOzone resistance E E E E E E E E E E E E O E E E E G G-E O Abrasion resistance F-G G F E F-G F-G O E E-O F-G E E O E E G G F-G G-E P Electrical Properties F-G E E E E E P P E G E E E G-E E G E E F-G G Flame resistance E P P P P P P P E E O G E E E-O G P P G F-G Nuclear radiation resistance F G-E G G-E F F F G F-G O P-G E P E E F-G E G E G EWater resistance F-G E E E E E P-G P-F O F E E E E E E G-E G-E G-E G-E Acid resistance G-E G-E G-E E E E F P-E E G E E E G-E E E G-E G-E E F-G Alkali resistance G-E G-E G-E E E E F E E G E E E E E E G-E G-E E F-G Gasoline, Kerosene, etc resistance P G-E G G-E P-F P P-G G E P E E E E E G F P F F P-FBenzol, toluol etc resistance P-F P P P P-F P P-G G G-E P-F E E E G-E E P-F F F F F PDegreaser solvents resistance P-F G G G P P P-G G E P-F E E E G E P P-F P F P P-GAlcohol resistance G-E E E E E E P-G P E G E E E E E F G P E G-E GUnderground Burial P-G G F E E F G P E-O P E E E E E G-E E E E E G
Percentage Oxygen (Typical) 23-42 21 18-30 21 21 17 21 24-29 28-36 38-42 30-32 93 43-45 55 32 34 21 30-40 28-36 21Dielectric Constant ( Typical) 3.6 - 6 2.3 1.5 2.3 2.2-2.3 2.2-2.3 4-7 3.2-5 12 4.5-6.5 2.6 2.1 7-9 2.6 9-10 8-10 3-3.2 3.4 -5 12 3-4Thermal Characteristics - Deg C (Min) -30 -50 -40 -50 -10 -55 -40 -20 -100 -190 -40 -30 -30 -30 -40 -60Thermal Characteristics - Deg C (max) 70 100 70 100 100 80 100 105 150 260 135 80 90 90 100 180
Halogen Content in Typical Insulation and Jacket/Sheath Materials
Material Application Voltage Weight %PE insulation or Jacket <0.02XLP insulation 600 V <0.02XLP insulation 5-35KV <0.02EPR insulation 5-35KV <0.02
Polyurethane jacket <0.02EVA jacket <0.02XLP insulation 600 V 7–13
FR-EPR insulation 9–14CSPE (insulation grade) 13–16
FR-XLP insulation 11–17CSPE jacket 16–26
Neoprene jacket 16–18CPE jacket 14–28
CSPE jacket 18–33PVC jacket 22–29