What an inspection is for
An inspection is a quick, repeatable look at a running or stopped gearbox that catches changes early. It is different from a full service, where oil is changed and parts are replaced. The aim is to notice things that are different from last time, and to decide whether each finding can wait, needs a planned job, or needs attention now. This list is general. Adapt it to your equipment and manual, and follow site procedures; most items below can be done from a safe distance without removing guards.
Before you start
- Know what normal looks like for this unit: usual noise, usual casing temperature, usual oil level. Previous notes make today’s observations meaningful.
- Stay clear of rotating parts. Do not reach past guards while the machine is running.
- If the check requires opening a plug or removing a guard, isolate the machine first using your site’s lockout tagout procedure.
Walk-around checklist
1. Leaks and oil stains
Look at the casing joints, the shaft seals at both ends, plugs, the breather, and any pipe fittings. Fresh, wet oil means an active leak; dried dust-caked oil may be older. Record where it is. Remember that a seal leak is often a symptom, and understanding why shaft seals leak, including pressure from a blocked breather or shaft wear, helps you decide on the proper repair.
2. Oil level and condition
Check the sight glass or dipstick as the manual describes. Note the color: clear amber to light brown is generally unremarkable, while dark, burned, milky or visibly gritty oil should be reported. A falling level between checks means oil is leaving somewhere.
3. Noise
Listen from a consistent spot. Things to notice are a new whine, rumble, knocking, grinding or a rhythmic click. A change is the main cue. Using a mechanic’s stethoscope or similar listening tool, where permitted and safe, can help locate a noise to the gearbox, the motor or the coupling. Be careful, as these tools bring you close to rotating parts.
4. Heat
Compare surface temperature with the usual value, using a contact thermometer or infrared thermometer, or a mounted gauge where one is fitted. Touching the casing is not a reliable test and can burn. Note hot spots near the bearings and compare with the motor. Also check that cooling fins and fan covers are not buried in dust or product.
5. Vibration
Feel is not precise, but a new buzz or shake in the casing, base or guards is worth noting. In plants with vibration analysis equipment, periodic readings at the input and output bearings give far more detail and allow trending. Even without instruments, a written comment such as “more vibration than last week” is useful.
6. Mounting and base
Check for loose, missing or corroded bolts, cracked grout or a shifted base, signs of fretting such as reddish-brown dust at mounting surfaces, and torque arms or bushings on shaft-mounted units. Look at the coupling guard and, if visible, the condition of the coupling. Shaft alignment issues often show up first as seal leaks, heat or noise.
7. Breather and vent
Is it present, clean, undamaged and not painted over? A blocked breather can push oil out of seals.
8. Guards and surroundings
Make sure guards are fitted and secure, the area is clear of clutter, and no oil is pooling on the floor, which is a slip hazard.
9. Drive connections
Look at belts, chains or couplings connected to the gearbox. Loose or worn drive components can overload the unit; guidance on belt drives and chain drives explains typical wear signs.
Recording what you see
Use a simple form with the unit’s tag number, date, and a tick or short note for each item above. Add temperature readings with a note on load. Where a plant uses a CMMS, findings can become work orders directly, and the clarity of the work order quality matters for the technician who follows up. Photos of leaks and oil samples are helpful for comparison.
When to escalate
Decide in advance what findings go to which person. A reasonable general scheme:
Note and watch
- A very slight seep that has not changed
- Small changes in temperature within the normal range of the load
Plan a job soon
- A steady leak that needs frequent topping up
- A breather that is damaged or saturated
- Oil that looks darker than usual but is not milky or gritty
- Loose guards or minor mounting issues
Escalate promptly to a qualified person
- New grinding, knocking or loud noise
- Rapidly rising temperature or a casing that is much hotter than usual
- Metal particles in the oil
- Cracks in the housing
- Milky oil indicating water
- Vibration that is increasing
- Loose or broken mounting bolts
Stop and isolate
- Any condition that you judge unsafe, such as an active hazard to people, burning smell or smoke, or a gearbox that is visibly failing
If you are unsure, ask. Waiting on a gearbox with a failing bearing can turn a small repair into a large one, and the decision on whether to repair or replace is easier when the unit has not been run to destruction.
Setting frequency
Frequency depends on how critical the unit is and what the manufacturer recommends. Critical, heavily loaded or harsh-environment units are usually looked at more often than lightly loaded ones, which is the same logic as asset criticality ranking. Start with a realistic interval, and adjust as the records show what the unit actually does.
Keep the inspection lightweight
An inspection that takes too long will be skipped. Keep it focused on the items that give the earliest warning, and use the full service routine for deeper work such as oil changes and component replacement.