ÖLFLEX® & UNITRONIC® Cables

• Why are cables with black outer jackets better suited to outdoor use than cables of different jacket colors?

  In outdoor use, cables are subjected to higher levels of UV radiation than when used indoors. They are also exposed to ozone effects and other atmospheric influences. In principle, all plastics are susceptible to oxidation. However, different types of plastic possess varying degrees of UV stability. Light and oxygen cause premature ageing of plastics as a result of photooxidation. The UV rays contained in sunlight penetrate the molecular chains of the cable jacket. This causes the chains to split and results in the formation of highly reactive radicals, which continue to attack the molecular structure of the plastic. The ultimate consequence of this process is that plastics age and brittle faster in outdoor use. PVC cables in particular are subject to increased wear as the added volatile plasticisers or softeners in the thermoplastic polymer vaporize more quickly. There are a number of ways of protecting plastics against the effects of UV radiation. The material can be shaded from the light or special UV absorbers can be added to filter out the UV rays. The simplest way of making a cable UV-resistant is to add carbon black to the polymer used for the outer jacket, thus coloring it black. This ensures full shading of the jacket material, which results in complete light absorption. The harmful UV rays are absorbed by the carbon particles in the outer jacket and transformed into far less damaging thermal energy. This also prevents the formation of free radicals as well as the occurrence of photo-oxidation. As mentioned above, the different materials possess very different degrees of UV resistance. Some jacket materials display a good level of resistance to ultraviolet rays without the need for black coloration. Most of these substances are not thermoplastic polymers, which often require the addition of plasticisers, but belong to the group of cross-linked elastomers or TPE types. Non-black-colored PUR cables, for example, may fade or whiten in outdoor use, but usually maintain their flexibility and mechanical stability. Silicone cables without black-colored jackets, like the ÖLFLEX® HEAT 180, also possess a good level of UV resistance. However, such cables are only suitable for temperate climates. If used in locations with persistently high levels of UV radiation (coastal areas, deserts, oceans, high mountains, Polar Regions and areas with very high UV radiation such as South Australia or New Zealand), these cables should also be encased in a black, carbonized outer jacket.

• What is the difference between ÖLFLEX® or UNITRONIC® cables certified as "UL AWM recognized" and those that are "UL-listed"?

  If the manufacturer of an electrical device, appliance or machine wishes to obtain an officially approved "UL listing" to release the relevant item as a series product or acquire a "field labeling" for a stand-alone machine or system, the US body tasked with the certification (the National Recognized Testing Laboratory or NRTL) must be provided with all construction-relevant documentation. The entire certification process will be significantly faster, simpler and cheaper if all cables and wires used in the product are already "UL-listed" or at least "UL-recognized". Any cables without UL certification must first be subjected to protracted testing in the UL laboratory. All machine exporters are therefore advised to employ UL-certified cables and wires as a matter of course. UL AWM recognized cables with AWM style numbers, e.g. ÖLFLEX® 150 QUATTRO: Appliance wiring material or better known as "AWM" comprises cables and wires intended solely for use in factory-wired electrical equipment, devices, appliances, control cabinets and industrial machinery as part of a "listed assembly". AWM is not intended for on-site or field wiring purposes. Cables and wires with UL AWM Style labeling must be used for the applications stipulated by the relevant style designation. The use of AWM-recognized cables and wires is restricted to the applications detailed in the corresponding style specification (www.ul.com). AWM styles are not part of the North American NEC (National Electrical Code). Following the introduction of the 2007 edition of the NFPA 79 standard, the use of UL AWM recognized cables in industrial machinery and systems can be very problematic in terms of the machine certification, as the installation of AWM cables in this environment is only permitted under strict observance of specific conditions. "UL-listed" cables, e.g. ÖLFLEX® CONTROL TM: The intended use of cables and wires in this category is for fixed wiring in residential buildings as well as for commercial and industrial use. UL-listed cables and wires not only have to meet individual UL product standards, but must also comply with the relevant paragraphs of the National Electrical Code (NEC). The NEC contains detailed specifications relating to the correct usage of listed cables and wires. Such products can be used both for factory wiring of electrical equipment, devices, appliances and machines as well as for on-site or field wiring of industrial machinery and systems according to NFPA 79.

• What is the difference between so-called extension and compensating cables?

  Extension and compensating cables are connected to thermocouples, which always contain two different metal wires that are insulated from one another. The greater the price or quality of the metal wires in the thermocouple, the more accurately higher temperatures can be measured. By welding the two wires together to form a measuring point, the prevailing temperature of a medium can be determined on the basis of the "Seebeck effect". If the temperature between the measuring point on the thermocouple and the comparison point (cold junction) varies while the applied temperature remains constant (e.g. 0°C), this represents a very low thermoelectric potential in the microvolt range; a specific temperature value can be assigned to this voltage, depending on its size. The most common metal combinations used in thermocouples are Fe/CuNi (iron/cupro-nickel), NiCr/Ni (nichrome/nickel) and PtRh/Pt (platinum-rhodium/platinum). Extension cables always include identical conductor alloys like the metal alloy wires used in the thermocouple. Fe/CuNi (iron/cupro-nickel) is a typical example of a extension cable as the metals and alloys employed (also known as constantan) are widely available and relatively affordable. The conductor materials of compensating cables are not identical to the metal wires in the thermocouple, but instead use completely different metal combinations. PtRh/Pt is one typical combination used in compensating cables. Unlike with thermocouples, it is obviously not possible to use kilometers of real platinum and purest rhodium as a core conductor material. The resulting cable drum would probably cost several million Euro! For this reason, the industry employs compensating metals, which offer virtually the same thermoelectric properties as the original thermocouple material, but at a fraction of the cost. A compensating cable for a platinum-rhodium/platinum thermocouple actually contains copper/cupro-nickel conductor alloys. In the case of cables for NiCr/Ni thermocouples, the customer can choose between expensive extension cable versions or cheaper compensating cable versions, whereby the measuring tolerance and accuracy can vary accordingly. The decision if a extension or compensating cable should be used must always be made by the customer on the basis of his intended application. As a cable manufacturer, we can only offer limited advice in this regard.

• Where can I obtain information on the chemical resistance of ÖLFLEX® and UNITRONIC® cables?

  The resistance of our cable products to specific organic and inorganic chemicals is already detailed in table T1 of our technical catalogue appendix. If the required substance is not contained in this table, it is possible to contact our laboratory in Stuttgart to enquire whether any data or information concerning resistance to this chemical medium exists in the relevant technical literature. Statements regarding the resistance of our cables to specific branded products, such like for instance “Exxon Mobile XY or Castrol XY transmission fluid”, are not generally possible since these constitute unknown mixtures of different oils and additives. In the case of commercially attractive projects, the laboratory may agree to test our cable products with the specific chemical substances (usually oils) used in the customer's application. The customer would have to supply one liter of the relevant substance along with the corresponding safety data sheets. However, we reserve the right to refuse any chemicals that present even the slightest safety risk to our lab personnel. For this reason, the general test scope and schedule should be agreed with the laboratory in advance. The resistance tests are generally performed in accordance with the relevant VDE, EN, IEC or UL test methods.

• What is the difference between the flammability tests IEC 60332-1, IEC 60332-3 and IEC 60331 specified on our catalog pages and data sheets?

  The above flame resistance and fire propagation tests are often confused with one another on the basis of their very similar designations. However, the test methods employed are quite different.
  
  IEC 60332-1-2: Test for vertical flame propagation for a single insulated wire or cable
  This flame resistance test is passed by most cables constructed of flame-retardant materials, e.g. PVC and chloroprene rubber, or materials with special flame-retardant additives such as PUR. In the test, a single core or cable with a length of approx. 60 cm is mounted vertically using two clamps, after which a pre-defined flame is applied to the bottom end for a period of 60 seconds (or 120 seconds in the case of cable diameters > 25 mm). The test is deemed passed if, after the flame has been removed, the burning cable extinguishes itself and the fire damage is at least 50 mm from the upper mounting clamp. It is irrelevant how long the cable burns before extinguishing itself.
  
  IEC 60332-3: Test for vertical flame spread of vertically-mounted bunched wires or cables
  This fire propagation test is also known as the "bundle fire test" and is generally only passed by specially developed cables and wires with highly flame-retardant insulation and sheath material. This includes cables such as the ÖLFLEX® CLASSIC 110 H and ÖLFLEX® PETRO C HFFR. In most cases, the flame resistance of the plastics used is greatly enhanced by the addition of aluminium or magnesium hydroxide. Multiple cables are bundled or layered in lengths of approx. 3.5 m and vertically affixed to a ladder-like metal structure, after which a flame is applied to the lower end of the cables using a propane burner. The cable volume and time of flame application is defined by the test method, since IEC 60332-3 comprises four different bundle fire tests:

  
  • IEC 60332-3-22 Category A:    7 litres of combustible material per metre / flame application: 40 minutes
  • IEC 60332-3-23 Category B: 3.5 litres of combustible material per metre / flame application: 40 minutes
  • IEC 60332-3-24 Category C: 1.5 litres of combustible material per metre / flame application: 20 minutes / cable diameter > 12.0 mm
  • IEC 60332-3-25 Category D: 0.5 litres of combustible material per metre / flame application: 20 minutes / cable diameter< 12.0 mm

  
  The test most frequently performed with our highly flame-retardant ÖLFLEX® cables is IEC 60332-3-24 Category C. IEC 60332-2-22 Category A is often used for maritime applications on oil rigs and ships, for example. The test is deemed passed if, after the burner has been switched off, the burning cables extinguish themselves and the fire damage does not cover more than 2.5 m measured from the bottom cable end. It is impossible to say which of the four test categories poses the most difficult challenge, since there are a range of different factors to consider.
  
  IEC 60331: Functional integrity and fire resistance of electric cables
  Unlike IEC 60332-1-2 and IEC 60332-3, this test does not assess the flame propagation but instead checks the electrical functioning of the cable in the event of a fire. In the test, a flame is applied across the entire horizontal length of a single, 120 cm cable for a period of 90 minutes. The test is deemed passed, if the cable continues to conduct electricity without shorting throughout the 90 minute flame application and for a subsequent 15 minute cooling period. This test is generally only passed by cables and wires with special, flame-retardant glass or mica wrapping enclosing the individual cores as well as the entire cable bundle.