Instrumentation engineering root cause analysis of multistage flash drums erratic level instrument readings.
Article Type: | Root Cause Analysis (RCA) |
Category: | Instrumentation |
Equipment Type: | Sensors |
Author: | S. Raghava Chari |
Note: This root cause analysis (RCA) is from real-time scenarios that happened in industries during the tenure of two or three decades ago. These articles will help you to improve your troubleshooting skills and knowledge.
High Pressure (HP) side extended seal diaphragm differential pressure transmitters (DPT) never developed pinholes, unlike the previously discussed urea plant seal DPTs, shop calibrated, and static pressure tests passed before field installation.
Yet the 5-stages flash drums erratic level readings stopped the 750 T/d NH3 commissioning.
Because of drift-free calibration, all differential pressure level transmitters (DPLT) erratic outputs and the excellent brand name the author’ attributed root cause was:
HP, LP or both representative signals did not reach the differential pressure level transmitters (DPLT). Therefore, he studied the high-pressure (HP) and low-pressure (LP) taps carefully from the vessel drawing and noted the following
He considered these observations and concluded:
½ hour thought flashed solution was: insert a supplementary nozzle via the LP tap penetrating ½‑extension skirt (above figure) to feed the skirt tranquil pressure to the DPLT LP port.
The diagnosed root cause impressed management ordered, “Go ahead; modify all stages LP taps”, to avoid a second shutdown if this step succeeds.
A crew took the below-listed steps:
The DPTs read correctly, as expected, and commissioning progressed rapidly.
Author: S. Raghava Chari
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