Thums up for sensors
22 Jan 2010
London Many of the sensors on a process plant can detect and signal when there is an abnormal plant condition, for example an over-temperature situation. Few plants, however, have HART- or fieldbus-based monitoring systems that can decode and present these signals on an engineering database.
Recent information suggests that less than 10% of all the HART-capable transmitters supplied to date are actually installed within a control system that can automatically provide such diagnostic information to the maintenance team.
While a maintenance engineer can access this diagnostic data with a hand-held communicator directly wired into the 4-20mA loop, this activity usually happens only during a plant shutdown or when the HART sensor is due for inspection or maintenance anyway.
To overcome this situation there is now the THUM wireless adaptor, from Emerson Process Management. This screws into the existing transmitter, takes power from the loop and uploads the HART diagnostics via the wireless network. This would, for example, enable the transmission of control valve performance reports, in-service valve testing, alert monitoring and valve position trending.
Since industry experts estimate that 75% of control valves are unnecessarily removed from service for maintenance, the addition of a THUM could enable engineers to reschedule the maintenance onto valves where it is needed.
