Instrumentation engineering root cause analysis of unreliable ammonia flow transmitter reading and problems.
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.
6 Nos. of orifice and DPT flow meters measuring around 3-bars; near 00 C liquid ammonia read erratically. Reliable and accurate flow metering would improve NPK fertilizer production and quality
The Author solution: The process licensor disregarded the author guessed root cause (RC): the stagnating liquid ammonia at 3-bars pressure of 1000 C boiling point boils in the orifice to differential pressure transmitter (DPT) leads; hence, the erratic flow readings. After failed attempts of leads shortening, he suggested buying seal-type DPTs.
The seal instruments’ problems plagued the author rejected it; proposed installing Target Flow Transmitters (TFT, below figure), which requires no process leads would perform reliably.
The meter body carried target forms an annular orifice. Flow caused differential pressure across the target exerts a force F on it. The force beam conveys F to the meter body bolted pneumatic transmitting head which outputs 0.2 to 1 bar pneumatic signals proportional to Q2 (Q –> flow rate).
Electronic heads output 4-20 mA current signals. He accepted it and the plant ordered the TFTs.
Below listed are the Author Root cause solution benefits:
Author: S. Raghava Chari
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