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newSchoolWorks.com › VoTechWorks › Manufacturing & Marine › Industrial Maintenance › Bearings: Selection, Installation, Lubrication, and Failure Analysis › Lesson 10
MFG-INDU16-03 · Lesson 10 · 13 clock hours · demo

Vibration and Temperature Monitoring for Bearing Condition

Objective. Students will take a baseline vibration reading and a bearing surface temperature reading on a running training machine, compare both to acceptable limits, and determine whether a bearing should be replaced or monitored.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed engineer or certified journey-level tradesperson or by a certification or approval body. It is a study draft and may contain errors. Do not use it as instructions for work on a job site or on live equipment. Always follow your instructor, your supervising professional, and current official references and regulations.

VoTechWorks program approval and accreditation are still in progress. Credentials are issued only by the certifying bodies named in each program, after their own exams.

Why Monitor Bearings While They Run?

Bearings fail gradually. Long before a bearing seizes or sheds a roller, it gives detectable warning signs: rising vibration and rising temperature. Catching those signs early lets you plan a controlled shutdown instead of reacting to an unplanned breakdown. Two simple, non-contact or lightly invasive tools — the vibration analyzer and the infrared thermometer — give you that early warning without stopping the machine.

Safety First

Before approaching any running equipment, review the hazards:

Vibration Fundamentals

A healthy bearing rolls smoothly; a defective bearing generates repeating mechanical impulses. A vibration analyzer senses that motion and converts it to a number. For overall condition monitoring the most common unit is velocity, expressed in inches per second RMS (in./s RMS). Velocity is preferred because it is equally sensitive across the wide range of frequencies that bearing and imbalance problems occupy.

A vibration pen is the simplest tool: you press its tip against a flat spot on the bearing housing and it displays one overall velocity number. A full handheld analyzer can separate that number into frequency components, but for trending and go/no-go decisions, overall velocity is sufficient and is what you will record today.

Transducer Placement

Measure at three positions on each bearing housing:

| Position | Abbreviation | Sensor Direction |

|---|---|---|

| Horizontal | H | Side to side across the shaft |

| Vertical | V | Up and down |

| Axial | A | Parallel to the shaft centerline |

Hold or press the sensor firmly and flat against a clean metal surface as close to the bearing as the housing allows. Loose contact or placement on a painted plastic cover will give false low readings.

ISO 10816 Zone Boundaries

ISO 10816 (Mechanical vibration — Evaluation of machine vibration by measurements on non-rotating parts) groups machine vibration into four severity zones. The exact boundary values depend on machine class (power, mounting, shaft height). Your instructor will provide the specific zone card for the training machine; the zones always follow this pattern:

Always compare your reading to the zone card that matches your machine class. Applying the wrong class boundaries leads to either ignoring a real problem or shutting down a healthy machine.

Temperature Monitoring with an Infrared Thermometer

An infrared (IR) thermometer measures surface temperature without contact by sensing emitted thermal radiation. Point it at the bearing housing, pull the trigger, and read the number. Because you never touch the surface, you can survey multiple housings quickly and safely.

What Temperature Is Abnormal?

Two criteria, either of which flags a housing as abnormal:

1. More than 25 °F above the established baseline for that bearing on that machine.

2. Above 200 °F (approximately 93 °C) — a general caution threshold often cited in maintenance practice for standard anti-friction bearings and many common greases.

A single elevated reading may reflect a measurement error (dirt on the housing, steam nearby, wrong emissivity setting). Re-measure. If the reading is still elevated, flag it.

Reading the Results and Making a Decision

After collecting vibration and temperature data, you classify the bearing using both signals together:

Neither tool alone tells the whole story. A bearing can run warm with low vibration if it is over-lubricated, or can vibrate in Zone C with normal temperature early in a defect. Use both data points together.

Trending: Why One Reading Is Not Enough

A single reading tells you where the machine is today. A trending log — readings recorded at regular intervals over weeks or months — tells you how fast the machine is deteriorating. A slowly rising vibration slope gives you time to order parts and plan downtime. A sudden jump demands immediate investigation. Record every reading with the date, time, machine ID, point location, and your name. Incomplete records are useless for trending.

Connecting to the Condition Report

Your temperature findings from this lesson add to the condition report started in an earlier lesson. A complete condition report combines visual inspection findings, lubrication records, vibration data, and temperature data. That document travels with the machine and supports the maintenance supervisor's repair-or-run decision.

Key terms9

Overall velocity (in./s RMS)A single number representing the total vibration energy of a machine, measured in inches per second root-mean-square; the standard unit for general bearing condition monitoring.
ISO 10816An international standard that defines four severity zones (A through D) for evaluating machine vibration measured on non-rotating parts such as bearing housings.
Vibration penA handheld, contact-type instrument that displays overall vibration velocity when its tip is pressed firmly against a bearing housing or other machine surface.
Transducer placementThe specific location and orientation (horizontal, vertical, or axial) at which a vibration sensor is applied to a bearing housing to obtain a repeatable and meaningful reading.
Infrared (IR) thermometerA non-contact instrument that measures surface temperature by detecting emitted thermal radiation; used to survey bearing housings without touching hot or rotating equipment.
Baseline temperatureThe normal operating temperature of a specific bearing housing recorded when the machine is known to be in good condition; used as the reference point for detecting abnormal heat rise.
Trending logA written or digital record of vibration and temperature readings taken at regular intervals, used to detect changes in machine condition over time before failure occurs.
ISO Zone CThe ISO 10816 severity zone indicating vibration levels unsatisfactory for continuous long-term operation; bearings in this zone should be scheduled for repair.
Axial measurementA vibration reading taken with the sensor oriented parallel to the shaft centerline; elevated axial vibration often indicates misalignment or thrust-bearing problems.

Worked examples4

1. A vibration pen on the horizontal position of a bearing housing reads 0.18 in./s RMS. The ISO zone card for this machine class shows Zone A: 0–0.10 in./s, Zone B: 0.10–0.28 in./s, Zone C: 0.28–0.71 in./s, Zone D: above 0.71 in./s. Classify this reading.
  1. Identify the measured value: 0.18 in./s RMS.
  2. Locate the value on the zone card: 0.10–0.28 in./s is Zone B.
  3. 0.18 falls between 0.10 and 0.28, so it is in Zone B.
  4. Zone B means acceptable for long-term operation; no corrective action required.
Answer: Zone B — acceptable; continue normal monitoring interval.
2. The baseline temperature for a motor drive-end bearing housing is recorded as 145 °F. During today's survey, the IR thermometer reads 174 °F. Is this reading normal or abnormal?
  1. Calculate the rise above baseline: 174 °F − 145 °F = 29 °F.
  2. Compare to the 25 °F threshold: 29 °F > 25 °F.
  3. Also compare the absolute reading to 200 °F: 174 °F is below 200 °F, so the absolute limit is not exceeded.
  4. Either threshold being exceeded triggers the flag. The 25 °F rise threshold IS exceeded.
  5. Flag this housing as abnormal and re-measure to confirm.
Answer: Abnormal — the reading is 29 °F above baseline, exceeding the 25 °F threshold. Flag and re-measure to confirm.
3. A student records the following three readings on one bearing housing: Horizontal 0.31 in./s, Vertical 0.25 in./s, Axial 0.62 in./s. Zone card: A = 0–0.10, B = 0.10–0.28, C = 0.28–0.71, D > 0.71 in./s. Classify each reading and recommend an overall action.
  1. Horizontal 0.31 in./s: falls in Zone C (0.28–0.71).
  2. Vertical 0.25 in./s: falls in Zone B (0.10–0.28).
  3. Axial 0.62 in./s: falls in Zone C (0.28–0.71).
  4. The worst zone of any of the three positions governs the overall classification.
  5. Two of three positions are in Zone C; overall classification is Zone C.
  6. Zone C action: schedule repair at the next planned maintenance window; elevated axial vibration alongside elevated horizontal suggests possible misalignment — note this in the condition report.
Answer: Overall Zone C — schedule repair. High axial reading suggests possible misalignment should be investigated.
4. During a vibration survey a student presses the vibration pen against a plastic junction box cover near a bearing housing instead of the metal housing itself and records 0.04 in./s (Zone A). Why is this reading unreliable, and what should the student do?
  1. A plastic cover does not transmit vibration efficiently; it damps the signal, producing an artificially low reading.
  2. The standard requires firm contact on a clean flat metal surface as close to the bearing as possible.
  3. The student should identify the nearest accessible metal surface on the actual bearing housing.
  4. Re-take the measurement at that correct location and record the new value.
Answer: The reading is unreliable because plastic damps vibration. The student must re-take the measurement with the sensor tip firmly on a clean metal surface of the bearing housing.
In class: Instructor demonstration of a single-axis vibration pen (or handheld vibration analyzer) on a running motor-pump assembly: students observe correct transducer placement on the bearing housing at horizontal, vertical, and axial positions; instructor explains overall velocity reading in in./s RMS and ISO 10816 zone boundaries. · Student vibration data collection: each student takes three vibration readings (H, V, A) on the bearing housing of a running training machine using a vibration pen or analyzer, records values on a trending log form, and compares to the ISO 10816 zones (or equipment OEM limit provided); students categorize the machine as acceptable, monitor, or schedule repair. · Infrared thermometer temperature survey: students survey all accessible bearing housings on the training rig, record temperatures, compare to a baseline temperature chart provided by the instructor, and flag any housing more than 25 °F above baseline or above 200 °F as abnormal; findings are added to the condition report from Lesson 9.
Materials: Running motor-pump training assembly with accessible bearing housings; handheld vibration pen or basic vibration analyzer; infrared thermometer; ISO 10816 zone reference card (or OEM limit sheet); vibration trending log forms; condition report forms; hearing protection (for running equipment area).
Check: Instructor reviews trending log: vibration readings recorded at all three positions with correct units, correct ISO zone classification for each reading, and temperature data recorded for all accessible housings with abnormal ones correctly flagged — all fields complete and classifications correct to pass.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

NCCER Industrial Maintenance — Preventive and Predictive Maintenance
1. Why is velocity (in./s RMS) the preferred unit for overall bearing condition monitoring?
NCCER Industrial Maintenance — Preventive and Predictive Maintenance
2. A bearing housing vibration reading of 0.55 in./s RMS falls in ISO Zone C on the provided zone card. What is the correct maintenance action?
NCCER Industrial Maintenance — Preventive and Predictive Maintenance
3. When taking a vibration reading with a vibration pen, where should the sensor tip be placed?
MSSC CPT — Maintenance Awareness
4. A bearing housing has a recorded baseline temperature of 160 °F. Today's IR thermometer reading is 183 °F. How should this result be classified?
MSSC CPT — Safety
5. Which personal protective equipment (PPE) is required as a minimum when collecting vibration readings on a running motor-pump assembly in the training lab?
NCCER Industrial Maintenance — Preventive and Predictive Maintenance
6. Why is a trending log more valuable for predictive maintenance than a single vibration reading?
NCCER Industrial Maintenance — Bearings and Mechanical Drive Systems
7. A student notices that the axial vibration reading on a bearing housing is significantly higher than both the horizontal and vertical readings on the same bearing. What machine problem does elevated axial vibration most commonly suggest?
MSSC CPT — Safety
8. Before taking vibration or temperature readings on a running machine, a student discovers that a bearing housing guard has been left off. What is the correct action?
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