Compressor IP Case Discharge Temperature Gradually Increases

Root Cause Analysis (RCA): Steam Turbine Driven centrifugal compressors K-601’s IP case discharge temperatures gradually increases & lead to plant shutdown.

Note: This root cause analysis (RCA) is from real-time scenarios that happened in industries during the tenure of one or two decades ago. These articles will help you to improve your troubleshooting skills and knowledge.

Compressor IP Case Discharge Temperature Problem

Steam Turbine Driven Synthesis gas (SG) centrifugal compressors K-601’s IP case discharge temperatures gradually increased to unacceptable 220^o C from initial 160^o C and throughput gradually decreased to 90% in 6‑months.

Consequent 2-days six-monthly plant shutdowns were perennial problems

Root Cause Analysis

The author noted the crew changed the IP case suction all impellors’ labys instead of just the found eroded discharge end last 2-labys only, due to some past developed the wrong notion. The author instructed changing eroded labys only and saved 80% spares costs.

The LP case outlet moisture separator (MS) Level Controller (LC) regularly dumping confirmed it removes moisture from the syngas as expected.

His relentless rigorous thinking revealed that too small water droplets and some water vapor could escape from the LPC MS and enter the IPC along with the SG.

The water vapor could condense into liquid water at the last two labys where the gas pressure is high and hence the water vapors’ partial pressure too. The condensed water could erode the last two labys.

Solution

He recollected a journal advertised Super Moisture Separator (SMS). The ad said that the SMS traps, coagulates, and discharges even trace moisture, water vapor, mist, and micron-sized water particles from gases.

The plant accepting his suggestion ordered the SMS. The crew readied the foundation to place the SMS and the necessary piping to connect the SMS to the compressor piping.

On its arrival after six months of order completed the connections during an opportune short SD and took the SMS in service.

Realized Benefits

Realized Benefits are:

1. IP case last two labys erosion, the six monthly plant shtdowns due its symptoms vanished
2. IPB overhaul intervals increased to 4-5 years as those of other high-speed centrifugal compressors,
3. Yearly ammonia production shoot up by 10%

Author: S. Raghava Chari

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