Instrumentation
Flexibles
Instrumentation
What is the purpose of the screens in instrumentation cables?
The presence of large machines, welders and other processes in industrial environments create a lot of electrical interference (noise). This noise has the potential to distort the clarity of signals that are transmitted between equipment, which may lead to false readings, For example, a system monitoring the temperature of a boiler may not report the correct temperature. A metallic screen will shield the cores of a cable from interference, thus improving the clarity of a signal.
Why are there individually screened pairs or triples as well as overall screened pairs or triples?
The overall screen will protect the interior of the cable from external interference, however individual pairs or triples may create interference between themselves, which has the potential to distort signals in adjacent pairs. The use of individually screened pairs or triples reduces this distortion.
Data cables have screens also – what is the difference between a data cable and an instrumentation cable?
Instrolex instrumentation cables are in fact a “heavy” duty” or industrial type of data cable. The wires are larger and the cable tends to be more substantial, making the whole assembly less fragile. In addition, the high level of noise in an industrial environment places extra demands upon the screening that is required. Hence, pairs are often individually screened as well as overall screened (as explained in the previous question).
There are cheaper instrumentation cable types available in the market. What are the differences?
Some instrumentation cables on the market reduce costs by reducing the amount of twist in the pairs and using a PVC compound with a lower temperature rating. The fewer twists increases the manufacturing speed and with the reduced rating of the PVC, reduces the overall cost of the cable.
Olex continue to use a PVC compound that has reduced flame propagation and a temperature rating of 90°C for superior performance. It still utilises varying twist rates between adjacent pairs for superior crosstalk immunity.
Are Instrolex cables manufactured to any standards and do they comply with the Hazardous Area Standards?
Instrolex cables are not made to any Australian Standard. The Instrolex design is identical to the Olex manufactured Dekoron product and is an internationally recognised and proven design for industrial instrumentation applications.
Individual components of the product however, do conform to various Australian Standards such as AS/NZS 1125 for the conductors, AS/NZS 3808 for the insulation and sheathing materials and AS3863 for the armouring materials. In addition, the Instrolex cables are manufactured in accordance with the Olex certified Quality Management System complying with AS/NZS ISO 9001.
With regards to the Hazardous Area Standards, Instrolex complies with this standard for Intrinsically Safe circuit provided that it is installed in accordance with the requirements of the relevant Australian Standard.
What is the voltage rating of Instrolex cables?
The standard Olex range of instrumentation cables have been tested in our factory at 2kV core-core and will withstand operating voltages in excess of 500 V AC without failure.
However, their insulation thickness of 0.4mm radial thickness does not meet Australian Standard requirements for mains voltage operation (250/440 or 0.6/1kV), hence the cables are supplied for use in Australia in instrumentation and similar applications with nominal working voltage of 110 V AC or 150 V DC. For export use, where Australian Standards compliance is not a requirement, the Instrolex cables are rated 300 V AC/DC.
Flexibles
Why are some conductors tinned and others are not?
Tinned conductors resist corrosion and are therefore very suitable for marine applications. It is also necessary to tin conductors where a rubber insulation comes in direct contact with the conductor. The use of tinned conductors also assist in making the conductor easier to solder.
What is the difference between a cord and a cable?
There are two main differences between a cord and a cable.
A cord includes conductor sizes up to and including 4mm2 and up to five cores, and is generally rated at 240/440 volts (although some heavy duty flexible cords are rated at 0.6/1kV).
A cable includes conductor sizes of 6mm2 and above and is generally rated at 0.6/1kV. Cables with flexible conductors less than 6mm2 and with a core count greater than five core are also classified as flexible cables.
Flexible cables are often used with oil or chemicals. How do you determine which cables will be suitable for these applications?
The “Flexibles” PDF contains a guide as to the resistance of the various sheathing materials, however it is wise not to make any recommendations without referring to cable experts. The circumstances of an installation have a large bearing upon the suitability for exposure to chemicals and oils. This includes the anticipated length of exposure, the type of chemicals or oil involved, operating temperature, environment and application. If you are asked for a recommendation, obtain as much information as you can and refer to your local Olex sales office.
Why don’t manufacturers mix PVC and rubber in building a cable? For example, a PVC insulation and CSP sheath.
In determining the construction of a cable, the designer looks at the environment in which the cable will operate. For example, does it need to operate at low temperature, in oil or chemicals, will it be subject to mechanical damage, etc. This generally then determines the sheath that will be required. In selecting the insulation, the operating voltage and current need to be considered and then a selection is made so that it is compatible with the sheath. For example, PVC and CSP could not be combined because the PVC would melt when the CSP is cured at high temperature.
What type of flexible cord or cable is used on hot appliances?
The relevant application standards specify that for those appliances the cable must resist heat deformation. This is achieved by using either a rubber sheath or cotton covered PVC insulated cords for some appliances.
Are the Olex 4 core flexible cord core colours (Brown, Light Blue, White, Green/Yellow), in contradiction with AS/NZS 3000?
The Olex flexible cord colours are in accordance with the requirements set out in AS/NZS 3191 and are not intended to apply to flexible cords used in fixed wiring as outlined in AS/NZS 3000. The standard range of flexible cords (with colours highlighted below), should not be used as fixed wiring, as they have incorrect insulation colours. Flexible cords can be used as fixed wiring if the alternative insulation colour scheme (ie. as per fixed cables) is used and they are of the heavy duty type or installed in the appropriate wiring enclosure.
The standard range of Olex insulation colours for fixed and flexible cables designed to Australian Standards are as follows:
Fixed cables (450/750V & 0.6/1kV)
Active Cores: red, white (uncoloured), blue
Neutral Core: black
Earth: green/yellow
Flexible Cords (ordinary duty & heavy duty – standard)
Active Cores: brown, white (black), orange
Neutral Core: light blue
Earth: green/yellow
Can I use Flexolex® in reeling applications?
The flexible 3, 4 and 5 core cables offered are part of the standard and stocked Olex range of products. These cables are renowned for their flexibility and have been designed for ease of handling and bending. Under conditions of reeling with low tension and appropriate bending diameters, these cables will provide good performance for many years.
However, such designs do not suit tight bending and reeling under tension where the sheath can be squeezed and induced to move toward one end, thereby exhibiting the characteristics of “corkscrewing”. Another effect of reeling under tension with misaligned rollers or guides, is for the cables to roll on their axis which eventually causes conductor wire breakages.