Optical cable for industrial spectroscopy 600VIS-IR
Ready-to-lay special optical cable for use in harsh industrial environments and potentially explosive atmospheres (ATEX).
The new product family of optical cables offers professional protection for all harsh industrial environments – even for potentially explosive atmospheres (ATEX).
You can also enjoy the benefits of automated cable production for large-core fiber assembly.
The term ‘optical fiber’ typically conjures up an image of the kinds of cable systems that can be used to transmit data signals at very high speeds. Alongside this specific type of fiber-optic application for data transmission, however, there are also other applications in manufacturing where light is transmitted.
One example is laser technology, where a very high intensity laser beam is guided by the laser device to the workpiece along a fused silica fiber. Another area of application is optical metrology, where light is transmitted from a process to a measuring device to determine quantities such as temperature and substance concentrations. In the chemicals and pharmaceuticals industries, Process Analytical Technology (PAT) is used for real-time process monitoring. In many cases, this can avoid the need to take samples for later lab analysis while increasing measurement cycles.
The optical fibers used for laser technology and optical metrology are fundamentally different to the fibers used in optical communications engineering: typically, fibers with much larger diameters of up to 1 mm are used (large-core fibers). The fiber coating is also different, due to requirements for light output and temperature conditions. The fiber cable manufacturing process also differs in terms of the protective sheath that shields the optical fiber from the environment: while optical communications engineering cables are manufactured on fully automated extrusion plant in a cable factory, large-core fiber cables are produced almost entirely by hand. This process involves manually pulling the optical fibers into a protective tube – usually a metal spiral tube – and then terminating the fiber ends with connectors.
Leoni has now applied the advantages of automated cable production to industrial large-core fiber cables, and has introduced its new optical cable product family, which has been specially optimized for applications in industrial environments and explosion hazard areas. The result is a special optical cable that not only meets but in many respects actually exceeds all of the relevant requirements from manufacturing.
Polyurethane, an exceptionally rugged material with properties such as crush resistance as well as resistance to oils, acids, and UV radiation was chosen for the cable outer cladding. This results in a substantial cost advantage for customers. Since it features an unusual, ruggedized design, this special cable can be laid directly into industrial indoor and outdoor cable ducts without needing to first be pulled into corrugated protective tubes. The cables are also supplied with our Easy Pull system, which mechanically protects the sensitive fiber connectors during the installation process.
Process analysis in particular requires the use of optical waveguide cables in potentially explosive atmospheres (ATEX). Here, LEONI has designed a cable that fully meets the requirements defined in the German Explosion Protection Ordinance. The outer cladding is electrically conductive, while the entire cable – even when not terminated with connectors – is barrier sealed, which therefore prevents zone entrainment.
LEONI is first starting production of the new product family of optical cables with fused silica fibers with a core diameter of 600 µm: this size of fiber is compatible with a wide range of PAT applications. Cable designs are naturally not limited to this specific type of fiber but can be extended to include other kinds of fibers as required by the customer.
Usage information for specialized usage in potentially explosive atmospheres (ATEX)
LEONI Fiber Optics has developed an optical waveguide cable featuring a 600 µm fused silica fiber especially for use in process analysis that can be deployed in harsh industrial environments and potentially explosive atmospheres. This usage information is designed to offer an overview of the relevant provisions from the ATEX Directive 2014/34/EU that were used as the basis for developing the cable.
In Germany, this Directive was transposed into the German Explosion Protection Ordinance (11th ProdSV).
The Directive classifies cables as ‘components’. Since only active parts – ‘devices’ as defined by the Directive – need to be certified, this is not required for cables. Accordingly, CE or ATEX markings are not (and must not be) used on the cable sheath or in accompanying documents.
Technical standards that must be met to comply with the Directive and national laws are described in IEC 60079-0 ff. and IEC 80079-36 ff. Essentially, a distinction is made between cables that carry live current and fiber optical cables, which are a different type of cable. Fiber optical cables are covered by IEC 60079-28, which states that cables of this type are always safe according to the ignition protection type ‘op pr’ for the EPLs (equipment protection levels) Gc and Dc, but may need to pass certain specialized tests to meet requirements for some EPLs. On the other hand, fiber optical cables that do not form part of devices with optical fibers are exempted from the standard if they meet relevant industrial standards.
Our new optical cable design also offers protection from the buildup of electrostatic charge in accordance with IEC 60079-32: this is achieved with a specialized polyurethane compound that makes the cable conductive as defined by the standard. The limit values for conductive materials lie between 104 Ω and 109 Ω at 50% ± 5% rel. humidity, and between 104 Ω and 1011 Ω at 30% ± 5% rel. humidity.
The dangers of zone entrainment have also been accounted for. One example of zone entrainment is a situation where explosive mixtures can escape from the pump to the outside due to the presence of leaks. As a result, the inner explosive zone is entrained (trapped) and moved outside, where the plant operator does not expect to need to handle explosive mixtures. This therefore increases potential hazards. To avoid zone entrainment via the cable, steps have been taken in its design to ensure that the cable is barrier sealed and has passed the corresponding test according to IEC 60079-14, annex E1. This involves the cable being installed under a constant ambient temperature in a sealed housing of 5 l ± 0.2 l (one cable end is located inside, the other end is located outside). The cable passes the test if the time required to reduce an internal overpressure of at least 0.3 kPa (30 mm of water column) to 0.15 kPa (15 mm of water column) is not less than 5 s. The cable is therefore suitable for use in zones 0–2 and 20–22.
While, as mentioned above, the standard is not directly relevant for a fiber optic cable, this changes when the system is considered as a whole. For LEONI as a cable specialist, working with our customers is the first and most important step towards fulfilling the system requirements for successful qualification according to the ATEX Directive.
Our expertise in light transmission for the field of optical metrology has been clearly demonstrated in a number of real-world projects featuring high-end metrology applications, including the Cold Atom Lab on the International Space Station (ISS), NASA’s New Horizons mission to Jupiter and Pluto, and the detection of gravitational waves with LIGO. Your sophisticated measuring environment can also benefit from the insights gained from these projects.
Please contact us for further information. We look forward to your inquiry.