Avoid Spurious Shutdown in SIS Loop by Unleashing Advanced Diagnostics via THUM & AMS

Burcu Karakulak

Burcu Karakulak

Norbert Nagy

Norbert Nagy

Emerson’s Burcu Karakulak and Norbert Nagy shared a story on how diagnostics from IEC 62591 WirelessHART devices helped avoid compressor spurious shutdowns. Their abstract:

…compressors in their facilities… compressors have 3 stages where dP flow is measured at each stage using impulse pipelines. Each dP is part of a safety loop & will shutdown the compressor & subsequently the plant in case of a safety issue. Estimated costs of a shutdown are on the order of hundreds of thousands of dollars each day. This presentation discusses how spurious shutdowns can be avoided using diagnostics via WirelessHART.

After an introduction of the petrochemical facility, Burcu describes the causes of plugged impulse lines in the compressors. A plugged line causes an incorrect reading back at the control system. While the value of the transmitter appears normal, advanced diagnostics recognize a reduction in the normal variability in the signal. Using unique statistical process monitoring techiques, this abnormal condition can be reported back to operators to avoid a compressor shutdown condition.

Burcu described the solution chosen was to add a wireless THUM device to existing Rosemount 3051S HART devices to add WirelessHART communications. This allowed the diagnostics from the device to be brought back to the asset management software.

The wireless gateway was connected via MODBUS to the control system controlling the compressors as well as AMS Device Manager to monitor the DP flow measurement transmitters from a single location.

Burcu explained the statistical process monitoring technology. The Rosemount 3051S samples the signal at 22 times/second to see the process at a much higher resolution than is available back at the control system which receives signals from the transmitter at a much slower rate.

Two months after the wireless devices were commissioned, a spurious shutdown was avoided through the early detection of an impulse line in the process of plugging. Estimated annual cost savings from shutdown avoidance and reduced maintenance costs in the hundreds of thousands of dollars.

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