The Complete Steam Turbine Overhauling Checklist for Plant Engineers

Why a Structured Checklist Matters

Unplanned turbine shutdowns cost Indian power and sugar plants lakhs of rupees per hour. A structured overhauling checklist ensures nothing is missed during planned maintenance windows — reducing the risk of early failure after recommissioning and avoiding costly repeat shutdowns.

1. Pre-Shutdown Planning (4–6 Weeks Before)

Begin with a detailed scope of work covering all rotating equipment in the train. Inspect all stocked spare parts and generate a shortfall report. Order critical items — bearings, seals, labyrinth packings, carbon rings — with adequate lead time. Arrange for specialized tools: alignment laser, vibration analyser, dial indicators, and feeler gauges.

• Confirm OEM clearance data for all turbine stages
• Arrange lube oil flushing equipment (mobile centrifuge filter unit)
• Book ex-OEM engineers if required for major overhaul
• Prepare condition monitoring baseline readings (vibration, temperature, pressure)

2. Shutdown & Isolation

Follow the OEM-specified shutdown procedure. Allow adequate cool-down time before breaking any flanges. Lock out / tag out all energy sources including steam, lube oil, condensate, and control air. Drain the lube oil system completely before disassembly.

3. Disassembly & Inspection

Record all clearances, gaps, and fits before removing components — these are essential for comparison with OEM specification and for detecting wear trends. Photograph every stage. Measure rotor run-out at journal, thrust collar, and coupling faces.

• Bearing clearances (radial and axial)
• Labyrinth seal diametral clearances
• Coupling alignment offset and angularity
• Carbon ring face condition and spring tension
• Nozzle and diaphragm condition and throat dimensions
• ESV seat and disc condition

4. Workshop Repairs & Replacements

Send the rotor for journal grinding and dynamic balancing if run-out or vibration readings were outside tolerance. Replace carbon and graphite gland rings, labyrinth packings, and babbitt bearings as per condition report. All rotor balancing should be performed to ISO 1940 or API 670 standards.

5. Reassembly & Alignment

Reassemble in reverse order with new gaskets and fastener torque per OEM specifications. Perform final rotor alignment using laser alignment equipment — turbine to gearbox and gearbox to generator. Record all clearances post-assembly and confirm they are within OEM tolerance.

6. Lube Oil Flushing

Before commissioning, flush the lube oil system with a mobile centrifuge filter system targeting ISO 4406:99 cleanliness class 16/14/11 or better. Take oil samples before and after flushing and retain reports. Never commission a turbine without completing an oil flush — bearing failures from contaminated oil account for a significant portion of post-overhaul failures.

7. Commissioning & First Run

Follow the OEM pre-commissioning procedure step by step. Monitor vibration, bearing temperatures, and lube oil pressure continuously during the first run-up. Confirm ESV and governor operation. Fine-tune alignment if vibration levels are elevated. Document all commissioning readings for the plant maintenance record.