| Screened
Cables/Instrumentation |
|
SHIELDED / BRAIDED
WIRES & CABLES
Cables used for process industry have
to be shielded to avoid electrical interface disturbances,
shielding is a metallic cover over the conductor or
the cable itself with the facility to ground the metal,
copper & aluminum are used for this purpose, based
on the type of cable, it's insulation, bending radius
required and mechanical protections required.
' Prestige' offers the complete range of shields designed
specially as required by different type of cables along
with customer requirements and specifications.
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I. BRAIDED:
Multiple copper wires are braided over the conductor / single
pair / 1 triad with a minimum coverage of 70% to 90% max.,
this braid can also used as an overall shield on multicore
/ multipair / multi triad cables where individually shielded
conductors / pairs / triads are layed to form a multi core
/ pair / triad cable.
II. TAPED / SCREENED:
Aluminum bonded polyester tapes are wrapped along with a drain
wire ( flexible tin plated copper wire rope ) in continuous
contact with the aluminum side of the tape which is wrapped
with an overlap of at least 20% creating a virtual screen.
III. DOUBLE SHIELDED:
In certain data networks the cable is double shielded i.e.:
has two shields : the conductor is shield with Aluminum tape
and overall shielding of the cable is done by copper braid
shield. Here both the drain wire and outer copper shield is
connected to ground or common mode to get best shielding results.
|
Shield
chart ( suggested ):
|
Cable |
Shield
type |
Shield
wire/tape |
Coverage |
| PTFE |
Braided |
Silver plated copper wire |
90% |
| Silicon |
Screened |
Aluminum polyester tape |
120% |
| Fibre glass |
Braided |
Tinned copper wire |
70 to 90% |
| PVC/XLPE |
Taped / Double shield |
Aluminum polyester tape + Braided |
120% |
|
'High
Temperature shielded ( varnished ):
Individual conductors are insulated with fibre glass braid
and constructed jacket with fibre glass braid. A high temperature
saturant improves abrasion resistance. A silicon saturant
is also available on special order.
For details see Fiber Glass / Asbestors
Mechanical Shield:
Cables are armoured with an overall braid of Stainless Steel
/ Galvanized Steel wire to add high resistance to abrasion
and mechanical damage and superior tensile strength. It is
especially valuable in application where wire must undergo
longitudinal stress such as those encountered in long vertical
runs. These over braids furnish a minimum coverage of 85%
and can be done on all types of cables.
MULTI
CORE INSTRUMENTATION & CONTROL CABLES:
Prestige' Instrumentation & control cables are made as
per customer requirements based on various parameters, with
the choice of multipair construction, pair identification
& proper shield to avoid electrical interface disturbances.
| Cable |
Conductor
type |
Wire
Plating |
| PTFE |
Stranded / Solid |
Silver / Nickel plated copper wire |
| Synthetic
Rubber |
Bunched / Solid |
Tinned copper wire |
| Fibre glass |
Bunched / Solid |
Bare /Tinned copper wire |
| PVC/XLPE |
Bunched / Solid |
Tinned copper wire |
Standard Characteristics of Instrumentation Cables
|
| Test |
0.5 |
0.75 |
1.0 |
1.5 |
2.5 |
| |
Sq.mm |
Sq.mm |
Sq.mm |
Sq.mm |
Sq.mm |
| Mutual capacitance core to core(max).pF/metre
< |
250 |
250 |
250 |
250 |
250 |
| L / R ratio (max). µH/Ω< |
25 |
25 |
40 |
40 |
40 |
| Conductor resistance @ 20°C.
Ω / kM< |
39.7 |
26.5 |
26.5 |
12.3 |
7.41 |
Insulation resistance Meg Ω
/ kM > |
100 |
100 |
100 |
100 |
100 |
Core to core / screen / armour
-
Resistance for 1 hour @ 20°C. Meg Ω / kM>
|
10 |
10 |
10 |
10 |
10 |
Screen to screen resistance -
1 hour @10°C. Meg Ω / kM> |
1 |
1 |
1 |
1 |
1 |
MULTIPAIR
THERMOCOUPLE EXTENSION / COMPENSATING CABLES
A
Thermocouple measuring point is formed by joining two dissimilar
metals as one circuit, which when exposed to different temperatures
generates a net thermal electromotive force ( E.M.F.) Each
thermocouple cable has two cores of such dissimilar conductors
forming a pair and for multiple measuring points multi pair
cable is used.
'Prestige' offers the complete range of cables suited for
High Volt & Temperature application with various combinations
of different conductors, insulations and shields as as per
customer application & requirement.
INSULATION
CHART
| Material |
Operating
temp |
| PTFE |
260°C |
| Synthetic Rubber |
180°C |
| Fibre Glass Braid |
250°C |
| XLPE |
90°C |
HRPVC |
85°C |
General Purpose PVC |
70°C |
|
