I came across this excellent case study on the use of wireless temperature and acoustic monitoring to help avoid unplanned downtime of a fluidized bed reactor due to leaks in the superheated steam coil piping running through the bed.
The story is told by Ashland Inc.’s John Rezabek in this 3:23 YouTube video, Rapid Deployment of Wireless Pervasive Sensing. You may have seen John’s articles in Control magazine or on the ControlGlobal.com website.
John describes the challenge of the superheated steam coils start to plug. As the plugging worsens, leaks can occur in the coils. When these leaks occur, control of the fluidized bed reactor is lost and the unit must be shutdown.
These unplanned shutdowns can mean millions of dollars in lost production. What was needed was a way to measure this plugging action to get early warning so that the outage could be planned with the necessary materials and expertise to minimize this outage time. The goal was to make it to a planned outage, avoid an unplanned outage and to have the flexibility to schedule it when fully ready.
Flow measurement through the coils was not possible since there were no penetrations or flanges in the piping to insert the flow transmitters.
Working with the Emerson team, a solution was suggested where the coils could be monitored wirelessly with temperature and acoustic transmitter. Rosemount 708 wireless acoustic transmitters were used on the piping going into the fluidized since the temperature of these coils was just below the maximum thermal rating of these transmitters.The steam going out of the fluidized bed was too hot, so they used Rosemount 248 wireless temperature transmitters.
John recounted how from the time the order was placed until 80% of the devices were installed, configured and fully functioning was just a couple of weeks.
The temperature transmitters were most helpful in providing early warning for low and no flow conditions in the piping. John noted that by being able to plan and organize the outages to clean the piping and perform welding and other repairs, it has likely saved them in the millions of dollars.
Update: I wanted to embed the YouTube video with John on the “primary layer” of automation, fieldbussed for closed loop digital control that Jonas Berge references below in his comment: