Understanding Peak Hold

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Portable balancer & Vibration analyzer Balanset-1A

$2,353.83

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Vibration sensor

$107.26

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Optical Sensor (Laser Tachometer)

$147.78

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Balanset-4

$8,107.90

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Magnetic Stand Insize-60-kgf

$54.82

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Reflective tape

$11.92

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Dynamic balancer “Balanset-1A” OEM

$2,067.80

Definition: What is Peak Hold?

Peak hold is a measurement and display mode in vibration analyzers where the instrument continuously monitors the vibration signal and retains the maximum value (or maximum frequency component amplitudes) encountered during the measurement period. As new measurements are taken, the display is updated only if a new maximum is detected, otherwise the previous peak value is “held” and displayed. This creates a cumulative maximum envelope that captures the highest vibration levels experienced, even if they were brief transients.

Peak hold is particularly valuable for detecting intermittent problems, transient events during startup/shutdown, and maximum vibration levels during variable operating conditions. It ensures that brief but potentially damaging vibration events are not missed in periodic monitoring.

How Peak Hold Works

Basic Operation

1. Initial Measurement: First vibration value recorded and displayed
2. Continuous Comparison: Each new measurement compared to stored peak
3. Update if Higher: If new value > stored peak, replace stored peak with new value
4. Hold if Lower: If new value ≤ stored peak, keep displaying stored peak
5. Cumulative Maximum: Result is highest value encountered since measurement began

Application to Spectra

• Can apply peak hold to entire frequency spectrum
• Each frequency bin holds its own maximum
• Creates envelope of maximum amplitudes across all frequencies
• Useful for capturing transient frequency components

Applications

1. Transient Event Capture

Detecting brief, high-amplitude events:

• Startup/Shutdown: Vibration peaks passing through critical speeds
• Load Changes: Transient vibration during load application
• Process Upsets: Vibration spikes from process disturbances
• Intermittent Problems: Faults that come and go (loose parts, intermittent rubs)

2. Variable Condition Monitoring

• Variable Speed Equipment: Capture maximum across speed range
• Cyclic Loading: Maximum vibration during load cycles
• Varying Process Conditions: Peak levels during operational variations
• Long-Term Maximum: Highest vibration over weeks or months

3. Machinery Acceptance Testing

• Run equipment through full operating range
• Peak hold captures maximum vibration at any condition
• Verify maximum doesn’t exceed specifications
• Documents worst-case vibration for acceptance

4. Intermittent Fault Detection

• Faults that appear only occasionally
• Loose components that rattle intermittently
• Temperature-dependent problems
• Load-dependent issues

Peak Hold vs. Other Measurement Modes

Peak Hold vs. RMS

• Peak Hold: Maximum value, catches transients, can be much higher than average
• RMS: Average energy content, ignores brief peaks, represents typical levels
• Relationship: Peak hold ≥ RMS always; ratio indicates impacting

Peak Hold vs. True Peak

• Peak Hold: Holds maximum over extended period (minutes, hours, days)
• True Peak: Instantaneous maximum within single waveform capture (seconds)
• Peak Hold: Can be much higher (includes all transients over full period)

Peak Hold vs. Average Spectrum

• Peak Hold Spectrum: Maximum amplitude at each frequency across multiple spectra
• Average Spectrum: Mean amplitude at each frequency
• Use Case: Peak hold for transients; average for reducing noise

Advantages

Captures Transients

• Doesn’t miss brief events
• Records maximum even if it occurred hours ago
• Essential for intermittent problems

Worst-Case Documentation

• Shows maximum vibration experienced
• Conservative for safety and design purposes
• Verifies equipment stayed within limits

Simple Implementation

• Straightforward algorithm
• Minimal processing required
• Available in most vibration instruments

Limitations and Considerations

No Time Information

• Peak hold doesn’t record when maximum occurred
• Can’t correlate peak to operating condition
• Unknown if peak was recent or long ago
• May need timestamp recording for correlation

Outlier Sensitivity

• Single anomalous spike permanently affects peak hold until reset
• Measurement error or external disturbance can corrupt data
• May not represent typical operation

Hides Average Behavior

• Doesn’t show typical or average vibration
• Equipment might run at low vibration 99% of time but peak hold shows occasional high
• Should be used with average measurements for complete picture

Best Practices

When to Use Peak Hold

• Monitoring equipment through startup/shutdown cycles
• Variable speed or variable load equipment
• Known or suspected intermittent problems
• Acceptance testing across operating range
• Long-term monitoring (weeks/months) to catch occasional peaks

When to Use Other Modes

• RMS/Average: Routine monitoring, trending typical levels
• Instantaneous: Real-time observation of current vibration
• Min/Max: Both extremes over period

Combined Approach

• Record both peak hold and RMS
• Peak hold shows worst-case
• RMS shows typical operation
• Ratio indicates degree of transient activity

Reset Strategy

• Reset peak hold at start of each measurement session
• Or maintain long-term peak hold (monthly, quarterly reset)
• Document when last reset for interpretation

Peak hold is a simple but powerful measurement mode that ensures transient vibration events are captured and retained for analysis. By holding maximum values even from brief occurrences, peak hold enables detection of intermittent problems and worst-case conditions that might be missed by average measurements, complementing standard vibration monitoring techniques in comprehensive condition monitoring programs.

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