גבולות רעידות — טורבינות הידרו & יחידות משאבה

ISO 20816-5 applies to hydraulic machines including:

• Vertical Kaplan turbines
• Vertical Francis turbines
• Vertical pump-turbines (reversible)
• Horizontal Pelton turbines
• Vertical pumps

These machines operate in hydroelectric power plants with typical speeds from 60 to 1000 RPM.

Hydraulic machines operate at much lower speeds (60–500 RPM vs 1500–3600 RPM for steam turbines) and experience unique hydraulic excitation forces:

• Draft tube surge and pressure pulsations
• Cavitation-induced vibration
• Wicket gate and runner vane pass frequencies
• Von Kármán vortex shedding

Vertical machines also have additional considerations for thrust bearing vibration and axial hydraulic forces.

Shaft displacement is measured using proximity probes mounted near the guide bearings, measuring peak-to-peak displacement in micrometers (μm p-p). This is critical for vertical machines where shaft orbit monitoring reveals:

• Unbalance and misalignment
• Hydraulic instabilities
• Guide bearing wear
• Seal rub conditions

Horizontal Pelton turbines have lower vibration limits than vertical machines because:

• Horizontal bearing arrangements are more sensitive to dynamic forces
• Impulse loading from the Pelton bucket jet impact produces distinct vibration
• Gravity loads on horizontal bearings create different dynamic behavior

The Zone A/B boundary is 2.3 mm/s vs 2.8 mm/s for vertical machines.

For Zone C on a hydro turbine:

• Investigate root causes: runner cavitation, draft tube surge, guide bearing wear, shaft misalignment, hydraulic resonance
• Increase monitoring frequency to continuous if not already
• Consider load restrictions to reduce hydraulic excitation
• Plan corrective action during the next scheduled outage
• Monitor trend carefully — if approaching Zone D, consider shutdown