Last Updated on December 5, 2022 by Electricalvolt
An instrumentation cable plays an important role in various process industries and manufacturing sectors. The instrumentation cable transmits low-energy signals and the electronic circuity control, regulate and monitor these electrical signals.
This article provides useful information, including the material used in instrumentation cables.
Types of materials for instrumentation cables
There are various materials of instrumentation cables depending on the insulation material and shielding. An instrumentation cable is the best signal transmission cable that offers protection against interruptions and interference. A cable of instrumentation is made up of several non-conductors, conductors that transmit low-energy electrical signals.
LSZH (Low Smoke Zero Halogen)
The presence of the materials such as Halogens such as fluorine (F), chlorine (Cl), bromine (Br), Iodine (I), and Astatine (At) in chemical compounds make the cable more durable. But the amount of these materials should be very limited.
For example, Polyurethane, Polyvinyl chloride comprises halogens (LSZH) in cable insulation emitting zero smoke and having fewer halogens while burning.
Zero halogen insulation for cable is the most important requirement to ensure safety against fire. Moreover, it provides human safety. Therefore, during designing, manufacturing, and testing, the cable manufacturer ensures this factor.
It is important to take into account the installation of this type of cable in locations where fire safety is paramount to prevent the emission of toxic and corrosive substances and to reduce the emission of smoke in the event of a fire.
Its specific qualities of non-fire propagation prevent disasters and improve the safety of the facilities.
Characteristics of zero halogen cables
The essential characteristics of cables with zero halogens are;
- Don’t emit toxic substances.
- They don’t emit corrosive substances.
- Prevent pollution in the environment.
Polyurethane (PU) as an insulating material is suitable for those applications where the cables are normally not subjected to great mechanical load. The most important polyurethane cable characteristics are good tensile strength, bend radius, flexibility at low temperatures, and good resilience.
Compared to rubber, PU cables have better resistance to chemical reactions. The best chemical characteristics are
- Very good resistance against mineral oils.
- Good resistance against non-alcoholic benzene.
- Very good resistance in storage in water.
- Good resistance against many solvents.
- The danger of decomposition via microbes exists with polyester-based polyurethane after prolonged exposure to heat or moisture.
PE and XLPE insulation
Polyethylene (PE) is a thermoplastic polymer material. It is widely used in cable insulation. Polyethylene insulated instrumentation cable is superior heat and moisture-resistant. This type of insulating material has strong three-dimensional molecular bonding structures. The yarn can withstand any form of outdoor adversity, including exposure to UV rays and oils. For maximum electrical conductivity, the cable construction uses stranded copper conductors similar to PVC cables.
Crosslinking is a chemical reaction by which polymers join in chains forming a kind of three-dimensional network. After this reaction the chemical properties of the initial polymer change.
The cable insulation in cross-linked polyethylene cable is manufactured from XLPE. XLPE insulation can withstand temperatures above 90°C. Whereas, polyethylene (PE), in its thermoplastic state (before joining its chains), its operating temperature is limited to 70° Deg Centigrade.
A cable bending scratch must exceed 15 times its outer diameter.
Polyvinyl Chloride (PVC)
The acronym PVC stands for polyvinyl chloride. PVC insulated cables are widely used because of their idyllic properties. Polyvinyl chloride is a thermoplastic material manufactured by the process of polymerization. This process produces an insulating material that is resistant to flames, fires, water, and heat, and also robust to abrasions and moisture.
PVC is also known to be lightweight, and resistant to corrosion, weather, and chemicals. As a result, PVC insulated cable is the ideal option for the chemical and fertilizer industries.
For optimal performance, these interconnect cables must be reliable, have high tensile strength, impeccable flexibility, be rugged, and provide protection against electromagnetic interference.
PVC cables are available for indoor and outdoor use.
Steel Wire Armor
Steel wire armored cable is made of a strong steel wire conductor assembled with a layer of insulation. The armored mechanical construction layer can be added to any cable structure to increase the mechanical strength of the cable. Armor improves its anti-erosion ability which is suitable for bad environment and the armor also protect the conductor from mechanical impact.
Steel wire, steel tape, and aluminum tape are commonly used armor materials. The steel tape and steel wire armor layer have higher permeability and excellent magnetic shielding effect, preventing interference at low frequencies.
Steel wire armored cables provide increased mechanical strength and anti-erosion properties.
It is one of the materials for cable construction. Instrumentation cables make use of copper, as it is more durable and has good current conductivity. The aluminum conductor is also used as a conductor for cables.
The main purpose of cable braid has two main reasons. One is either to shield the cable from electromagnetic interference or to give it better mechanical strength.
Braiding looks like interlaced threads that allow the braiding to bend and stretch without twisting. It provides an electrostatic shield that protects signal integrity. It is made from an excellent electrical conductor such as copper, tinned copper, or aluminum.
Metal braid has the enormous advantage of maintaining the flexibility of the cables. Braiding protects the cable from hot surfaces and abrasion. It prevents rodent attacks.
Metal tape can be used as an alternative to braided wire. Silver-plated copper is the most common material. It provides excellent protection against high frequencies. On the other hand, the metal braid covers 70 to 90% of the cable.
Mica-coated cables use mica tape as an insulation material. Its conductor is wrapped with the tape and then the fiberglass strands are stranded over the mica tape, which is then coated with PTFE or space resin. This type of cable can withstand a temperature of up to 500°C.
Being a high temperature-resistant insulating material, mica tape gives electrical cable incredible heat resistance and good dielectric strength.