Wireless Integration for Better Performance of Process Instrumentation Figure 1: Multiplexor for Highway Addressable Remote Transducers Control System Asset Management or maintain.
• Use Modbus transmission control protocol (TCP) to monitor process data via the wireless link.
•
Use instrument standard integration files for configuration and fault drill-down.
Controller/PLC
Often people’s experience with wireless networks (WiFi) at home is frustrating, especially when there are other networks nearby taking all the channels or the advertised signal range does not reflect your experience. How do we overcome such concerns with an industrial wireless network?
Multiplexor Marshalling Figure 2: Wireless Adapter
Asset Vision Professional
Existing DCS
Marshalling Cabinet
Adds condition monitoring
and asset mangement
Existing DCS
4-20mA loop
Add Wireless Gateway Add FieldKey Wireless Adapters
Modbus TCP
link provides other process values from multivariable instruments
Figure 3: Wireless Mesh Network Asset Vision Professional
Instrument set up via DTM Condition monitoring Link to CMMS (MAXIMO)
Ethernet Gateway
Marshalling cabinet
Standards Provide Integration, Security and Reliability An industrial wireless network, at the instrument level, must address the concerns of host integration, security and reliability along with the ability to integrate devices from multiple vendors into the same network using the full feature set.
A standard such as WirelessHART (IEC62591) provides the solution by building in multiple levels of security (see Figure 4), data authentication and redundant pathways back to the host which vendors can use to develop wireless solutions. These functions are built in to the standard so that compliant devices can exchange data in a reliable and secure way through a WirelessHART network. Building a wireless solution upon HART is also cost-effective as the engineering tools remain unchanged; you need only update the HART DD (device description)/DTM (device type manager) for the new devices.
Host Integration
Host integration is achieved by using standard integration methods such as DDs and DTMs to provide full drill-down into the field instrument via the wireless network. Cyclic access for additional process information provided by the wireless network is often achieved via a Modbus link, or other high-speed buses, such as PROFINET and FF HSE, in the near future.
Security
WirelessHART has several strategies to satisfy the end-user requirements for security which include:
•
Secure instrument/device authentication by local join procedure. Security credentials (join key, network ID, etc.) are passed to new devices wishing to join the network via a short-range physical connection. The join key can be changed after commissioning to provide additional security.
• ABB FieldKey Wireless Adapter
The addition of a wireless network provides the key to unlock the stranded information with the following benefits:
• •
No need to rewire the marshalling cabinet and update the relevant drawings.
Wireless can be added point by point without a plant shutdown. • Energy harvesting means there are no batteries to fit
118
The wireless message is encrypted at the source (wireless adapter for example) with the key to unlock it held at the final receiving device (the gateway).
• Message authentication is carried out to check that the message received by the wireless network has not been altered en route.
• Channel hopping and the short message length used by WirelessHART will make it difficult to read a wireless message.
Reliability
Wireless message reliability is improved with the use of a mesh network (see Figure 3) which provides redundant pathways and
EXPLORATION & PRODUCTION – VOLUME 9 ISSUE 2
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