Vibration Data Collection: Routes, Measurement Points, and Trend Analysis

Why Vibration Routes Matter

A vibration measurement route is a planned, repeatable path a technician walks through a facility to collect vibration data from rotating machinery. Routes are the backbone of a route-based predictive maintenance (PdM) program. By visiting the same machines, at the same measurement points, in the same order, every collection cycle, you build a historical trend database. That trend database—not any single reading—is what tells you a machine is deteriorating. Random, one-off measurements have limited value. Consistent routes turn raw data into actionable intelligence.

In industrial and marine environments, machines that benefit most from vibration monitoring include motors, pumps, gearboxes, compressors, fans, and propulsion components. All share a common characteristic: rotating parts that generate repeating forces. When those parts wear, corrode, or go out of balance, the forces change—and vibration changes with them.

Setting Up a Route and Defining Measurement Points

Before you touch a sensor, you build the route in your software and on paper. Start with an asset list—every machine to be monitored, its identification number, speed range, and bearing locations. For each bearing location you define at least three measurement points:

• Horizontal (H): Sensor placed on the side of the bearing housing, perpendicular to the shaft, in the horizontal plane. Sensitive to unbalance and misalignment forces that push the rotor sideways.
• Vertical (V): Sensor placed on top of the bearing housing, perpendicular to the shaft, in the vertical plane. Also sensitive to unbalance; often picks up looseness.
• Axial (A): Sensor placed on the end of the bearing housing, parallel to the shaft axis. Most sensitive to misalignment, thrust issues, and certain resonance conditions.

For a typical motor-pump set you will have measurement points on the motor drive-end (DE) bearing, motor non-drive-end (NDE) bearing, pump bearing nearest the coupling, and pump bearing opposite the coupling—twelve individual measurement positions for a single motor-pump pair when all three axes are collected.

Mark each position with a paint pen or center punch so future readings land in exactly the same spot. Placement consistency is critical; moving a sensor even a short distance can change the reading and corrupt your trend.

Sensor Coupling and Safe Data Collection

Safety first: Before entering the measurement area, don on safety glasses and hearing protection. Rotating machinery creates entanglement hazards—keep hair, clothing, cables, and tools clear of shafts, couplings, and fan guards at all times. Never reach across a rotating shaft. Never remove guards to access a measurement point; if a guard blocks your point, notify supervision and follow your facility's machine guarding policy.

The magnetic mount transducer must seat firmly, flat, and squarely on a clean metal surface. A tilted or dirty mount introduces noise and reduces high-frequency sensitivity. Before each reading, wipe the surface with a rag, press the magnet firmly until you feel it snap flat, and keep the cable from vibrating freely against the housing. The data collector will prompt you to accept or reject the reading based on its own signal checks—follow those prompts and do not override a rejection without re-seating the sensor.

Record ambient conditions (temperature, nearby equipment running or stopped, any unusual noises) on your route sheet for every collection cycle. Conditions affect readings and are important context for the analyst.

Reading Vibration Data: Overall Values and Spectra

Your data collector captures two key outputs at each point:

1. Overall vibration value: A single number—typically velocity in inches per second (in/s) RMS or acceleration in g's—that summarizes total vibration energy at that point. Quick to collect; used for trending and alarm comparison.

2. Frequency spectrum (FFT): A plot of vibration amplitude versus frequency. Shows which frequencies carry the energy, helping analysts diagnose the root cause (unbalance appears at 1× running speed; misalignment often at 2×; bearing defects at characteristic defect frequencies).

Both are stored in the data collector and uploaded to the software at the end of the route.

Trend Analysis and ISO Alert Thresholds

Once data is downloaded, open the trend plot for each measurement point. The trend plot shows overall vibration on the Y-axis and date/collection cycle on the X-axis. You are looking for:

• Steady, low readings: Machine is healthy.
• Gradual upward slope: Early deterioration; schedule inspection.
• Step change or spike: Sudden event (fastener loosened, impeller cavitating, bearing race cracked); investigate promptly.

ISO 10816 and its successor ISO 20816 provide severity zones for different machine classes based on overall velocity. Your lab's severity chart will show you the Alert (yellow) and Danger (red) threshold values for the machines on the training rig. When a reading crosses the Alert threshold, you must flag that point and write a corrective action recommendation—for example: "Motor pump 2, drive-end bearing, horizontal: overall velocity has crossed the Alert threshold over three consecutive cycles with an upward trend. Recommend scheduling bearing inspection and lubrication check within 30 days."

A corrective action recommendation always includes which point, what was observed, and what should be done and when.

Completing Your Route Sheet

A fully completed route sheet for each machine shows: asset ID, measurement point label, date and time, overall reading, data-collector acceptance status, ambient conditions, and any flags. Missing points fail the route—every point must be collected or the trend database has a gap. Your instructor will review both the paper route sheet and the software trend report before signing off.