Emerson Exchange 365

• Not Answered

Article: Wired vs. Wireless

Due to advancements in wireless technologies, automation professionals in process plants have a choice to make for all new installations: wired or wireless?

For plants with existing wired and wireless infrastructure, the choice hinges on a straight comparison of the two technologies, and the selection of the solution making the most sense for the particular application. For plants without an existing wireless infrastructure, the cost of installing one must be considered, although these costs have dropped dramatically in recent years.

This article from the Jan-Feb 2015 edition of InTech shows the advantages of each technology, recognizing that almost every plant will end up with a mix of wired and wireless. Wireless is predicted to gain mind and market share because it can be used to quickly, easily and inexpensively monitor and control plants and processes.

 By Moazzam Shamsi, Emerson Director, Global Solutions Architects, MSc, BEng, CEng, MinstMC

 

https://www.isa.org/intech/20150204/

• #wireless #article #[solution architect]

Deanna K Johnson

• 19 Feb 2015 8:37 PM
• Cancel

1 Reply

• Jonas Berge

  

  • 20 Feb 2015 9:28 AM

  I personally agree using both FOUNDATION fieldbus and WirelessHART is the right architecture for new plants. Many plants that were built years ago before wireless instruments existed are now being modernized by adding plant-wide WirelessHART infrastructure. For a new plant being built it makes sense to put it in right from the start.
  
  FOUNDATION fieldbus takes the place not only of 4-20 mA but also of the various types of on-off I/O signals such as dry contact, sink and source for DC, as well as relay and Triac for AC. That is, you can mix transmitters, gas chromatographs, control valves, intelligent on-off valves, and two-wire tank gauging systems on the same bus.
  
  I agree that a bus is typically designed for up to 12 devices but would also like to highlight this is roughly equivalent to 36 conventional I/O as many devices have multiple signals each such as 3 signals on a control or on-off valve, up to 16 signals each for an electric actuator / motor operated valve (MOV), a.s.o.:
  http://www.fieldbus.org/images/stories/technology/aboutthetechology/overview/fieldbus_brochure.pdf
  
  If more fieldbus devices have to be added later wires only have to run up to the junction boxes. Additional signals in fieldbus devices can be enabled at a click of a button.
  
  A fieldbus segment can be, and usually is, far longer than 120 m. The distance from the control system to the junction box can be more than 1000 m. 120 m is the distance from junction box to the device.
  
  Plants now use couplers with short circuit protection as standard thus ensuring a short at one device does not affect the others
  
  Most of the time the fieldbus interface card sits in the DCS backplane such that HSE is not required
  
  Redundant interface cards and power supplies is common, but redundant cable is extremely rare
  
  Using repeaters, fieldbus can reach several kilometers but since a bus segment can reach more than 1000 m without repeater, a repeater is extremely rare
  
  When upgrading 4-20 mA to 4-20 mA/HART make sure the cable is shielded twisted pair grounded in one end, meeting capacitance and separation requirements:
  http://en.hartcomm.org/hcp/tech/using/usinghart_wirelength.html
  
  I personally agree that wireless is an excellent way to add instrumentation in existing plants, and that plant-wide WirelessHART infrastructure is an excellent way to modernize existing plant to improve reliability, maintenance and operation productivity, energy efficiency, and to reduce HS&E incidents and response time. New plants should build in this WirelessHART infrastructure from the very beginning so that it need not be added later. This requires an early involvement of the run & maintain organization in the project. Problem is, the run & maintain organization may not have been established yet when the project is in FEED. Plants need to figure out how to make sure the automation, data collection, and data processing needs of the maintenance and reliability engineers, energy managers, and HS&E officers for a new plant are taken care of at the start of the project. Anyway, even if you have missed this step in FEED in your current project, you can still add WirelessHART in the detail design stage because the infrastructure can be installed plant-wide with minimal wiring.
  
  WirelessHART is the most cost effective way to add instruments when there is no junction box nearby
  
  I personally agree that fieldbus and wireless complement each other and modern plant automation should be designed with both. Learn more about WirelessHART for operational excellence from these articles:
  
  Beyond the Control Room
  http://www.ceasiamag.com/article/beyond-the-control-room/10658
  
  Second Layer of Automation
  http://www.ceasiamag.com/article/second-layer-of-automation/10354
  
  Maintenance with a Hart
  http://www.ceasiamag.com/article/maintenance-with-a-hart/9894
  
  Smart Sensing: Situational Awareness
  http://www.iaasiaonline.com/more.php?id=2222&cat=im
  
  Are you sending people in harm's way?
  http://www.iaasiaonline.com/more.php?id=1956&cat=ii
  
  Wireless for Asset Uptime
  http://www.ceasiamag.com/article/wireless-for-asset-uptime/8689

  • Cancel