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Instrumentation Cables Questions & Answers

What standards / guidelines are available for cable tray systems?

1. The National Electrical Code publishes the standards for all types of electrical applications. Articles 318, 250, and 800 cover various aspects of cable tray systems.

2. NEMA, (National Electrical Manufacturers Association), is an association comprised of the major cable tray manufacturers in the industry. This committee has published three documents to date: NEMA VE1, FG1 and VE2.

NEMA VE1 covers general cable tray definitions, manufacturing standards, performance standards, test standards, and application information.

NEMA FG1 addresses the standards for fiberglass cable tray systems.

NEMA VE2 is a cable tray installation guideline which covers receiving and unloading material, storage of material, and general installation practices.

What is the difference between the Power & Control Cables?

Power Cables – No. of Cores 2,3, 3 1/2 & 4 Core

Control Cables – Upto 63 Cores or above Standards Applicable for both – IS-694 & IS-1554 .

What is the difference between Unsheathed & Sheathed Single Core Cable as per IS-694?

Unsheathed – Only Core Insulation will be done and there will be no Sheathing.

Sheathed – Sheathing will be done on Core Insulation.

What is the difference between Control & Instrumentation Cable?

Control Cables – They are generally Core Constructed.

Instrumentation Cables – They are generally Pair Constructed with Shielding.

What is the difference between Thermocouple & Instrumentation Cable?

Conductor Material is different for both.

What is the difference between Armoured & Unarmoured Cable?

a. Armour.

b. Inner Sheath will be provided for Armoured Cable before Armouring.

What is a Co-Axial Cable?

This type of cable is used for Very High Frequency (V.H.F.) Applications.

What is the Voltage Grade?

Low Voltage Grade — upto and including 1.1 KV

High Voltage Grade — above 1.1 KV

Number of Strands for Cables ?

a. Solid Conductor – One

b. Multistrand – either 3 or 7

c. Flexible – No of Strands above 7 – Dia of Strands upto 0.3 mm .

Dia of Strands for 1.5 Sq.mm can be:

a. Incase of 7 Strands – 7/0.52

b. Incase of 0.3 mm dia each – 21 Strands

c. Incase of 0.2 mm dia each – 48 Strands.

What is the Core / Pair Identification incase of LDPE Insulated Cable?

By Colour or By Number printed Al-Mylar Tape / Polyster Tape.

What is the Purpose of Screening?

To reduce the interference by nearby sources.

What are the different types of Screenings?

a. Al-Mylar / Cu-Mylar Tape

b. ATC or ABC Braiding.

What will be the Normal Insulation Thickness for Telephone Cables?

a. Core Insulation – 0.2, 0.3 mm

b. Sheath – 0.5 to 1.2 mm.

What is the difference between RTD / Instrumentation Cable?

RTD Cables will be Triad Constructed.

Instrumentation Cables are Pair constructed.

What are the normal sizes of Control Cables?

1.5 & 2.5 Sq.mm

What will be the normal Conductor sizes for instrumentation / RTD Cables?

0.5, 0.75, 1.0, 1.5 & 2.5 Sq.mm

Thermocouple Cable Conductor normal sizes ?

a. Single pair – 16 AWG (1.295 mm dia)

b. Multi pair – 20 AWG (0.813 mm dia)

What is the Temperature Tolerance (+/- deg. C) allowable for Thermocouple cables?

a. IS 8784 +/- 3 Deg. C

b. ANSI MC 96.1 +/- 2.2 Deg. C

Colour code as per IS 1554 for Core constructed Cables ?

a. Upto 5 Cores by different colours i.e for 2 Cores Red & Black, for 3 Cores Red, Yellow & Blue, for 4 cores Red, Yellow, Blue & Black, for 5 Cores Red, Yellow, Blue, Black & Grey.

b. Above 5 Cores : One Core Yellow and One Core Blue remaining Grey in each layer (or) any single colour with numbers printed.

For above 5 Cores Grey with number printing is our normal practice.

What are the 3 types of Braided (Metal Braiding) Cables manufactured?

a. Annealed Tinned Copper Braided Cables

b. Annealed Bare Copper Braided Cables

c. Nickle Plated Copper Braided cables

d. G.I. Braided Cables.

What is the Temperature with standability of PTFE & Fibre Glass?

PTFE – 250 Deg.C, FG Cables 400 Deg.C

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1 comment

Technical Gyan October 12, 2018 at 8:16 pm

Thanks for sharing your valuable knowledge with us. It is really appreciable .

But There is one issue with this article format , it is not being downloaded plz solve this issue so that we can also download this article in pdf format.


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