Understanding Periodic Monitoring
Definition: What is Periodic Monitoring?
Periodic monitoring (also called route-based monitoring, scheduled monitoring, or interval monitoring) is a condition monitoring approach where trained technicians manually collect vibration and other condition data from equipment at regular intervals (weekly, monthly, quarterly) following predefined measurement routes. Using portable data collectors or analyzers, technicians visit each machine on schedule, take measurements at specified points, and upload data to central databases for trending, analysis, and alarm assessment.
Periodic monitoring is the most cost-effective condition monitoring method for covering large numbers of machines, balancing the benefits of early fault detection with reasonable implementation costs. It is the foundation of most industrial predictive maintenance programs, typically covering 80-95% of monitored equipment with online systems reserved for the most critical 5-20%.
Implementation Elements
Measurement Routes
- Predefined sequence of machines and measurement points
- Optimized for efficient technician travel
- Grouped by area, system, or accessibility
- Typically 100-500 points per route
- Route completion time: 2-8 hours
Measurement Frequency
- Critical Equipment: Weekly to monthly
- Important Equipment: Monthly to quarterly
- General Equipment: Quarterly to semi-annually
- Increased Frequency: When trends show deterioration
Data Collection Tools
- Handheld data collectors with route navigation
- Portable vibration analyzers
- Temperature guns or contact thermometers
- Ultrasonic detectors
- All synchronized to common database
Advantages
Cost-Effectiveness
- No permanent sensor installation costs
- Single set of portable instruments monitors many machines
- Scalable to hundreds or thousands of machines
- Lower per-machine cost than online monitoring
Flexibility
- Easy to add or remove equipment from program
- Change frequencies as needed
- Adjust measurement parameters
- No capital investment to modify coverage
Diagnostic Capability
- Technician can perform detailed analysis on-site
- Multiple measurement points and directions
- Additional testing if problems detected
- Human judgment applied immediately
Limitations
Detection Delay
- Average detection delay = half the measurement interval
- Monthly route: average 2-week delay from fault onset to detection
- Can miss rapid deterioration between measurements
- Not suitable for very rapid failure modes
Transient Events Missed
- Problems during startups, shutdowns may not be captured
- Intermittent faults between measurements
- Process upset vibration
- Requires equipment running during survey
No Continuous Protection
- Cannot provide automatic shutdown
- Equipment unmonitored between route visits
- Relies on other protection (temperature switches, etc.)
Best Practices
Route Design
- Logical grouping of equipment
- Efficient travel path
- Consistent measurement conditions (time of day, loading)
- Adequate time allocation
- Safety considerations
Measurement Consistency
- Same measurement locations every time
- Documented measurement points (photos, drawings)
- Consistent sensor placement and orientation
- Similar operating conditions
- Standardized procedures
Data Quality
- Verify instruments calibrated
- Check sensor mounting and cables
- Ensure equipment at stable operating condition
- Take multiple measurements if values questionable
- Document unusual conditions
Interval Selection
Factors to Consider
- Criticality: More critical = more frequent
- Failure Mode Speed: Slow deterioration = longer intervals
- Historical Data: Known deterioration rates guide intervals
- Cost of Failure: High consequence = more frequent
- Redundancy: Backup available = less frequent acceptable
Typical Intervals by Equipment Type
- Critical Rotating (no backup): Weekly to monthly
- Important Rotating: Monthly
- General Rotating: Quarterly
- Non-Critical: Semi-annually or annually
- Adjusted: Increase frequency when problems detected
Workflow
Data Collection
- Load route into data collector
- Navigate to first machine
- Take measurements per procedure
- Instrument auto-tags data with equipment ID
- Proceed to next point
- Complete route
Data Analysis
- Upload data to central database
- Software auto-trends and checks alarms
- Exception report highlights problems
- Analyst reviews exceptions
- Detailed analysis of concerning trends
Action
- Generate work orders for equipment needing attention
- Schedule maintenance based on severity
- Feedback loop verifies repairs effective
Optimization
Frequency Adjustment
- Start conservatively (monthly)
- Extend intervals for stable equipment (to quarterly)
- Increase for trending problems (to weekly or daily)
- Continuously optimize based on experience
Coverage Optimization
- Remove very stable, non-critical equipment
- Add equipment showing failures
- Adjust measurement point locations
- Balance coverage vs. resources
Periodic monitoring is the practical, cost-effective foundation of most industrial condition monitoring programs. By providing regular equipment condition assessments at intervals matched to deterioration rates and criticality, periodic monitoring enables early fault detection and planned maintenance for large equipment populations, delivering the core benefits of predictive maintenance at manageable implementation costs.
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