מגבלות רעידות — Steam Turbines & Generators >40 MW

ISO 20816-2 applies to steam turbines and generators with power output greater than 40 MW, operating at speeds between 1500 and 3600 RPM (for 50/60 Hz power generation). This includes:

• Large power station turbine-generator sets
• Industrial steam turbines driving generators
• Combined-cycle plant steam turbines
• Nuclear power plant turbine-generators

Bearing housing vibration is measured with sensors mounted on the bearing pedestal, expressed in mm/s RMS. It reflects the vibration transmitted through the bearing to the support structure.

Shaft relative vibration is measured with proximity probes inside the bearing, expressed in μm peak-to-peak. It measures the actual shaft orbit relative to the bearing clearance.

Both measurements are essential — bearing housing vibration alone may miss internal rotor issues on stiff foundations.

Steam turbines use fluid-film (journal) bearings where the bearing housing may show low vibration even when the shaft has significant movement. Shaft relative measurement captures:

• Rotor unbalance and thermal bowing
• Oil whirl and oil whip instabilities
• Rotor cracks and rubs
• Misalignment between coupled rotors

Monitoring shaft vibration is critical for early detection of developing faults.

For Zone C on a steam turbine or generator:

• Immediately notify plant management and operations
• Investigate root cause — check balance condition, alignment, bearing condition, foundation, thermal state
• Increase monitoring frequency to continuous if not already
• Plan corrective action for the next available outage
• Monitor trend — if approaching Zone D, consider load reduction or planned shutdown

ISO 20816-2 consolidates the former ISO 10816-2 (bearing housing vibration) and ISO 7919-2 (shaft vibration) for steam turbines into a single unified standard. The zone boundaries are essentially the same, but the new standard provides updated guidance on combined evaluation using both measurement types.