Chapter 4 - Materials
Material resistances
The plastic coatings on conduits are fairly soft and yielding but they are still able to resist attack from many substances in solid, liquid or gaseous forms. The resistance charts in the Kopex Technical Data Sheets (TDS) will give a "guide" to the conduits performance when in contact with these substances. These are compiled from Laboratory tests and sometimes could be different from the actual conditions on site. Before referencing the Technical Datasheets it is important to have the details of the chemical, etc. which may cause a problem, for example oil is not just oil, there are mineral, vegetable, hydraulic, lubricating, etc. etc, etc. so it is important to know exactly which one is being used. Smoke
When things go wrong, the plastics in a conduit system can start to burn. The smoke produced can vary from a slight wisp to billowing black clouds.
Standard PVC is messy when it burns and more users are turning to alternative Low acid PVC materials, which provide lower or no smoke and reduced or no dangerous gases. These include special material mixes, treated nylons and materials like PEEK all of which can provide varying improvements over and above normal PVC. These can be particularly important when used in confined spaces or public places where safety is highly important.
Radiation A few materials found in nature are radioactive and send out radiation signals like a miniature radio transmitter. In addition man made radioactive isotopes exist varying between "pace-maker" batteries and nuclear power stations.
Radiation such as X-rays and gamma rays, flow through the air passing through most materials including bodies and conduits. Depending on the dosage, human tissue could die and conduit materials, particularly the plastic coverings will be degraded giving only a fraction of their original performance. The amount or dose of radiation absorbed is measured in Rads., the Kopex Technical Data Sheets details conduits with resistance to radiation.
Hazardous areas A Zone 1 area is a place where the working conditions could easily result in an explosion such as an explosives factory, gas/chemical plants, dust filled flour mill. Because of the obvious dangers in a Zone 1 area, minimum standards of work have been set to keep the number of accidents as low as possible. Electrical systems are notorious for sparking off an explosion and so any conduit systems must be able to resist explosions or prevent the spread of flame outside the area.
All Zone 1 equipment must be tested and approved by a recognised testing authority (BASEEFA, SIRA etc.). The Flameproof Gland (HAM's and HAA's) has approval against the ATEX directive (for use in Europe) but it must be used with one of the conduits from the Kopex Liquid Tight Conduit range or Kopex Stainless Steel equivalent. The epoxy putty inside the gland stops the spread of flame through the conduit system during an explosion and so prevents further fires.
Below Zone 1 and with safer working conditions are Zone 2 areas. These are places where explosions are unlikely to occur but equipment must still be certified accordingly for use in such areas. In these cases, flexible conduits with KF-F connectors may be used.
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