NH3 Plant Turbo-compressor Sudden Rise in Temperature

Root Cause Analysis (RCA): NH3 plant turbo-compressor Tilting Pad too high temperatures sudden affected and entire plant indefinite shutdown threat eliminated.

Article Type:	Root Cause Analysis (RCA)
Category:	Mechanical
Equipment Type:	High Speed, Hi KW Major Rotating Machines
Author:	S. Raghava Chari

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.

Problem

A turbo-compressor (K-601 T) Tilting Pads’ too high 108 to 110^o C close to the 115^o C trip pad metal temperature threatened surprise K‑601 T trip and hence total indefinite plant outage.

Author solution

A skilled Japanese technician from the manufacturer working in a neighboring plant suggested scrapping the Babbitt as in fig. However, he declined doing it due to heavy current task deadlines.

Undaunted, the author inspired and guided as under plant crew scraped the pads successfully the very first time.

1. Grip the pad between 3-mm thick aluminum flats in a vice placed on a lathe bed
2. Level the pad placing a machinist spirit level across AB (below figure) and tighten up.
3. Pencil mark axial line CD  ²/₃ L from A – this view does not show D;
4. Place a dial gauge on the lathe bed touch point B and zero it.
5. Scrap the pad along the line BC till point B is 500 µ below point A – checked with the dial gauge – and the surface BC checked axially and along BC with a tri-square.
6. The pad is ready

These pads installed in the machine taking a 2‑hour plant shutdown (SD) attained max metal temp 98^oC even in hottest ambient temperature summer months, eliminated the K‑601 T trip threat forever, and put all in peace!

Author: S. Raghava Chari

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