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Wireless HART

PostPosted: Mon Jul 30, 2018 11:24 am
by Prasanth
Wireless HART

The WirelessHART standard is a robust technology yet simple to implement. It provides the same safe, easy, dependable experience that users know and expect from HART-related products by maintaining compatibility with existing HART devices, tools, and systems. This enables users with HART experience to quickly and easily gain the benefit of wireless technology. Wireless technology can also be used to aid in regulatory compliance such as health, safety and environmental compliance monitoring. The easiness comes partly from the automatic network features.

A WirelessHART mesh is a self-organizing self-healing adaptive network. It automatically adjusts to changes in plant infrastructure, e.g., when a new instrument is added to the network. The easiness also comes from the wireless nature. Reduced wiring and materials costs leads to easy installation and commissioning, hence reduced labour cost. Without wires the network can be easily extended to remote areas. And the network can be created one device at a time rather than one big configuration start up. Compatibility with the wired HART standard makes the deployment of wired and wireless devices together possible, and allows WirelessHART systems to be seamlessly integrated to existing host, DCS or asset management applications. Reduced engineering and project cost and time lead to other operation benefits as well.

Accessing additional measurements through WirelessHART mesh is fast and easy, which eliminates manual data collection, extends visibility to remote plant areas such as tank farms, utilities, etc. Having access to additional measurements and diagnostics enables loop troubleshooting, streamlines maintenance procedures, and makes it possible to a much wider range of sites to realize predictive maintenance.

WirelessHART Technology is Reliable

The WirelessHART standard includes several features to provide reliable communications in all industrial environments, which are often unfriendly to wireless communications. Industrial facilities usually have dense infrastructure with metals that interferes with wireless transmission. There are frequent movement of large equipment and changing conditions. Numerous sources of radio-frequency and electromagnetic interference may cause communication challenges. The Wireless HART standard uses both direct sequence and frequency hopping spread spectrum techniques to spread communications among different physical channels.

A WirelessHART mesh is a redundant, self-healing network. Instead of star or tree topology, it is a truly a mesh network with multiple access points. It monitors paths for degradation and repairs itself, finds alternative paths around obstructions, and randomly communicates on different channels. During the lifetime of the mesh network, it constantly adapts itself to changes in the environment.

Adaptation makes use of health reports and diagnostic information which are continually communicated by all devices in the network. A WirelessHART mesh also includes many techniques to coexistent nicely with other wireless networks; they being WirelessHART networks or different networks. It employs clear channel assessments tests on the targeted channel before actual transmission.

WirelessHART Technology is Secure
The WirelessHART standard employs robust security measures to protect the network and secure the data at all times. These measures include the latest security technologies to provide the highest levels of protection available. It uses industry standard 128-bit AES encryption algorithm at multiple tiers. The secret network key is used at the data link layer to authenticate each data transmission. At the network layer, each session has a different key to encrypt and authenticate per-to peer communication. A different join key is used for each device to encrypt and authenticate during device join process. In addition, the network manager periodically changes all the keys during the life time of the network.

The Wireless HART standard also employs several technologies to protect the mesh network itself. It uses channel hopping at the timeslot level; the actual physical transmission channel is selected at the point of transmission. Device transmission power is controllable by the network manager. High power can be used in noisy environments while low power can be used when the physical area the network is installed in is very small – for example when a bioreactor is being used. Low power also makes it more difficult for intruders to sniff communication traffic.

The WirelessHART1 standard focuses on the needs of the industry. It supports all phases of the plant life cycle, from fast engineering, deployment and commissioning, to easy diagnosing and trouble shooting, to cost-effective move from scheduled to predictive maintenance. Officially released in September 2007, it is the first open and interoperable wireless communication standard for process automation.