A visible twist on wireless

March 10, 2017
Light fidelity (Li-Fi) presents a fast, safe, secure alternative to radio-frequency networks.

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.

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 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.

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Engineering/design impacts

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. [sidebar id =6]

Deliverable/documentation impacts

Implementation of OWIs in harsh, corrosive environments also creates impacts on engineering/design documents and construction/fabrication deliverables. The engineering/design documentation effort can also considerably reduce by reducing requirements for:

  • Cable schedule, cable schematic diagram, cable philosophy diagram and logic diagram;
  • Junction box loading
  • Loop/segment diagrams;
  • Wiring connection schedule, wiring reports (intermediate and main junction box, marshalling and shield bar reports);
  • Design index (data base for wiring system detail) and specification sheet for cable/junction box;
  • Cable electrical detail and junction box standard installation detail drawing;
  • Enclosure and equipment room layout drawing;
  • Cable tray routing plan and cable tray support detail drawing;
  • MCT layout and drawing; and
  • Documents related to effecting corrosion control.

In short, OWIs can dramatically cut costs in instrument wiring systems throughout the project life cycle, including increased data-gathering flexibility, as well as allowing for easier future expansion. 

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Severe and changing environments

Wireless instruments are also cost-effective solutions for process plants when applied in bulk. They provide inexpensive, easy-to-install measurements in unclassified areas, and can also be implemented in hazardous locations and harsh, corrosive and reactive environments. Along with the savings described above, advantages in hazardous or corrosive/reactive harsh environments include eliminating hazardous area-rated or chemical/corrosion- resistant conduits, wiring and junction boxes, as well as the need for corrosion control measures or breakdown costs due to corrosion induced failures.

Extension of the plant becomes easier during operation without the need for shutdown of the plant. Li-Fi's topology eliminates the impact of late changes due to a philosophy change or process requirement. The optical wireless instruments can be configured and reconfigured without being exposed and/or connected to test terminal leads in hazardous or harsh corrosive/reactive environments.

They also allow easier expansion of I/O for future extension.

Li-Fi vs Wi-Fi

Li-Fi instrument communication Network also offers certain advantages over other wireless, as well as wired, systems:

Instant start-time: The scan time of the OWI and optical access point are very short due to the high speed of optical signals.

No interference: Li-Fi equipment does not  interfere with sensitive electronic equipment, such as radio equipment installed in nuclear power plants.

Works under water: Li-Fi instrument communications can be used underwater in the ocean. Seawater doesn’t absorb light waves as it does radio-frequency waves.

More bandwidth: Li-Fi can solve issues related to a shortage of radio-frequency bandwidth because it has 10,000 times more space available in the electromagnetic spectrum.

Energy-efficient: Update rates can be very high because LED lighting is energy-efficient, and data transmission requires negligible added power. For example, LED light consumes 6-8 watts for 800 lumens or 25-28 watts for 2,600 lumens.

Secure: Since it doesn’t penetrate walls, Li-Fi is more secure from remote jamming, phishing, cyber attacks and electromagnetic interference (EMI).

Works in sensitive locations: Li-Fi is the best suitable solution for power plants, where Wi-Fi and many other radiation types present problems for sensitive areas. This could offer safe, abundant connectivity for all areas of these sensitive locations.

Cost-effective: As previously described, Li- Fi instrument communication network has low CapEx and OpEx costs, and also saves time, weight and space.

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Facilitates IIoT: This technology could enable IIoT through advanced communication among field devices and systems, beyond basic M2M connections.

Works around corners: Direct line of sight isn't necessary for Li-Fi communication. Light reflected off walls, objects, structures, pipes, equipment, etc. can achieve 70 mbps data transfer speed (Figure 2).

Defined range: Communication is confined to the illuminated area (generally inside the module), providing a very controllable environment. This eliminates the threat of data being hacked remotely, so there's no risk to remote privacy.

Long battery life: Power consumption is minimized by using LED lights, with data transmission requiring negligible added power.

Robust and reliable: A network of light locations and infrastructure can be used to deliver robust and reliable connectivity in plants.

High capacity: Dense light locations can provide great wireless capacity (i.e. mbps per square meter).

High speed: Recent studies show that 3 Gbps can be achieved with single micro-LEDs, and it's possible to go up to 100 Gbps with laser LEDs combined with an optical diffuser to achieve broad illumination.

Initial investment costs of optical instruments wireless are lower than Wi- Fi-based wireless instrument systems. Analysis of the different instrument communication protocols and standards, technical factors, costs, space, weight and time basis consideration may show that Li-Fi is the best solution for applications inside a closed module, in hazardous locations such as nuclear power plants, and for in-plant monitoring (Table 2).

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Li-Fi is the best solution in some cases for critical monitoring (due to its fast data/media transfer rate, update rate and/or scan rate) and easy connectivity to neighboring instruments. It's also sometimes the most suitable solution for on-off monitoring or remote monitoring.

However, Li-Fi has not been proven yet as a networking solution for safety system and is expected to be less efficient than Wi-Fi in wellhead areas (due to optical access point arrangement problems).

Author has concluded that a Li-Fi Instrument communication Network should be applicable for both control and monitoring application due to its high-speed media transfer, scan rates, update/ continuous  monitoring rate. Li-Fi and its application are expected to continue to evolve for better control and monitoring.

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