As prices of their products remain depressed, oil and gas companies and operators are increasingly looking for the new ways to make existing processes more efficient by eliminating waste and reducing fixed costs. Greater efficiency often calls for more plant instrumentation, but instrument wiring systems and cable infrastructures (cables, junction boxes, conduits, termination racks, cabinets, marshalling panels, enclosures, cable trays, tray support systems, etc.) can significantly add to capital expenditures.
The traditional approach to reducing network costs is using radio-frequency wireless. An alternative approach uses light fidelity (Li-Fi) instead of radio transmission. Li-Fi instrument communication network is a high-speed, bidirectional, multiple-access, fully networked, secured, optical wireless communication technology. It's a form of visible light communication and a subset of optical wireless communication technologies, using visible light instead of radio waves to transmit data streams. Like radio-frequency wireless, implementing Li-Fi solves challenges related to instrument wiring system/cable infrastructure, and may reduce the capital expenditure of instrumentation systems.
The same technology can also support the world’s transformation from isolated systems to networks of Internet-enabled “things” capable of generating data that can be analyzed to extract information. Li-Fi goes beyond basic machine-to-machine (M2M) communication, and offers advanced connectivity among field devices, systems and services. Along with avoiding challenges related to physical wiring, optical wireless enhances the ability to achieve the Industrial Internet of Things (IIoT).
Li-Fi bits and pieces
The Li-Fi instrument communication network consists of optical wireless field instruments, optical access point (OAP) transceiver modules and fiber-optic Ethernet converter modules installed in the field and/or transceiver modules, with multiple control network switches installed in communication cabinets or DCSs in the control room or substation (Figure 1).
Optical wireless instruments (OWI) are located inside or outside of the process module in a plant's process area to measure/ control its process variables. Optical access point (OAP) transceiver modules are deployed in the ceiling of closed areas and either in the outside handrail platform or in the structure platform/ grating/support for the open areas. OAPs are connected to fiber-optic Ethernet media converters via redundant Ethernet cable (copper, twisted pair, Cat5, RJ45, 8P8C) to convert fiberoptic media into Ethernet and vice versa.
Fiber-to-Ethernet media converter modules are located in the field and/or closed areas to facilitate media conversion between fiber-optics and Ethernet. Redundant fiber-optic cables are routed in separate, divergent routes to connect field-installed OAPs and control network switches in industrial control system (ICS) communication cabinets. Cabinets and DCSs in the control room or substation are connected by redundant Ethernet cables to an ICS cabinet and DCS and PLCs in the local control room (LCR), local electrical room (LER) or substation.
Li-Fi-enabled OWIs provide robustness, real-time response, reduced installation time and reduced power consumption.
The impacts of using OWIs should be viewed from engineering/design and construction/fabrication point of view (Table 1). These are major impact areas, not only for clients, but also for EPCs, other contractors and vendors.
The author surmises that applying OWIs in process plants can have many positive impacts on project engineering, such as reduced installation costs, quicker installation time, faster commissioning, , removal of requirements for power supplies and protection barriers with power-replaceable battery packs, increased system/vendor compatibility, device and system compatibility, removal of redundant equipment, ease of self- or remote-diagnosis and faster or real-time responses.
In addition, extension of plant systems and moving or adding I/O points during construction would be easier without the need for unit or application downtime Implementation of OWI may reduce project engineering/ design costs through
- Reduced materials weight (instrument wiring system or cable infrastructure);
- Reduced system design-time requirements;
- Less piping and electrical work for cable routing;
- No 3D modeling for cable tray routing, trays and supports, location and design of junction boxes, and local panels, conduits, sleeves, etc.;
- Less time and effort for installing cable infrastructure such as instruments and multi-core, home-run cables, main and intermediate junction boxes, conduits, main and branch cable trays, termination racks, cable tray supports, panels and enclosures, multiple cable transits (MCT) and system or marshalling cabinets; and
- Less consideration based on area classification and protection.