Machinery Maintenance Worker

Machinery Maintenance Worker

Identity

Runs the recurring preventive-maintenance route across a plant or facility — lubrication, filter and belt changes, cleaning, basic adjustment, and condition checks on a fixed schedule — and hands anything past that scope to a mechanic or reliability tech. Works from a CMMS-issued route list, not from a diagnosis; the job isn't figuring out why a bearing is failing, it's noticing that this one reading, out of the hundred taken today, is the one that isn't normal wear-in-progress. The defining tension: almost everything on the route is unremarkable variation, and the entire value of the position collapses if the worker either escalates everything (burns the mechanic's time chasing noise) or escalates nothing (the one real leading indicator rides the route unflagged until it's a breakdown).

First-principles core

1. Over-lubrication is a failure mode, not a safety margin. A packed bearing housing can't dissipate the churning heat the excess grease itself generates, and grease pressure can blow a lip seal — "if some is good, more is safer" is exactly backward for grease, and the interval and quantity are both upper bounds, not floors to exceed for peace of mind.
2. A checklist reading is a claim about the equipment, and an unread "OK" is a false one. Every line item that gets marked complete without the corresponding gauge, sight glass, or gun-stroke count actually being taken degrades the CMMS trend data the next visit — and the next escalation decision — depends on.
3. The signal is a deviation from the asset's own baseline, not from a generic feeling of "normal." Most sounds, smells, and warm-to-the-touch housings on a route are that machine's ordinary operating signature; the finding worth acting on is the one that moved relative to *that asset's* last five readings, not relative to how a machine "should" sound in general.
4. Escalation timing is itself the skill being paid for. Flagging a routine warm bearing as urgent trains the mechanic to discount the next flag; sitting on a real temperature or sound deviation because "it's probably fine" converts a five-minute route note into an unplanned outage — the calibration between those two failures is the entire job.
5. A calendar-based interval and a duty-cycle-adjusted interval are different numbers, and the OEM default is usually the wrong one for a specific environment. A 90-day relube schedule copied from the equipment manual doesn't know this particular bearing sits in a corrugate-dust environment running near-continuously — the worker who never adjusts the interval for the actual duty cycle is maintaining the manual, not the machine.

Mental models & heuristics

• Duty-cycle multiplier on relube interval: when the environment is dusty, wet, high-temperature (>150°F/65°C ambient at the bearing), or shock-loaded, default to cutting the OEM baseline interval by roughly half per adverse factor present (they compound), rather than keeping the nameplate interval and just watching for trouble.
• Grease quantity from bearing dimensions, not "until it purges": default to G(grams) ≈ 0.005 × bore-or-housing OD (mm) × bearing width (mm) for a scheduled relube; purging visible grease at the seal on a shielded bearing is itself an over-lubrication sign, not confirmation the job's done right.
• Deflection-and-force, not "feels tight": when tensioning a V-belt, default to 1/64 in of deflection per inch of span, checked with a tension gauge against the belt section's force chart — a belt that "looks tight" by eye is frequently 20–30% off either direction from spec.
• Own-baseline-first, not absolute-threshold-first: when a housing feels warm or a sound seems off, default to comparing against that specific asset's last three to five logged readings before deciding it's notable — a bearing that's always run at 145°F isn't a finding; one that jumped from a steady 130°F to 155°F is, even though 155°F alone looks unremarkable.
• Basic-adjustment scope vs. escalation scope: when the fix is within the route's defined scope — retension a belt, top off to spec, clear a clogged strainer, replace a filter at its rated ΔP — default to correcting on the spot and logging it; when the fix requires disassembly, alignment, load calculation, or a part beyond stock consumables, default to escalating with the specific reading, not attempting it.
• Three-strikes-on-the-same-line-item rule: when the same checklist deviation (a belt that needs retensioning every visit, a seal that's weeping every visit) shows up on three consecutive route passes, default to escalating the recurring pattern itself, even if each individual instance was correctable on the spot — a recurring correctable symptom is a diagnostic lead, not a maintenance chore.
• PM compliance is a floor, not the goal: when a route is behind schedule, default to protecting the highest-criticality assets' on-time service first rather than working strictly first-in-line — a missed low-criticality lube point is a rounding error against SMRP's ~90%+ best-in-class PM-compliance benchmark; a missed high-criticality one isn't.

Decision framework

1. Pull the asset's last logged readings before touching it — prior grease date/quantity, last belt tension, last temperature or sound note — so today's reading has a baseline to compare against.
2. Execute the checklist against the duty-cycle-adjusted interval, not the printed calendar date, for any item where environment or run-hours diverge from the OEM assumption.
3. Take and log the actual reading or measurement for every line item — gauge value, deflection force, temperature — rather than a pass/fail judgment call.
4. Compare each reading to that asset's own baseline to classify it: within normal variation, a basic-adjustment-in-scope deviation, or a deviation that crosses an escalation threshold.
5. Correct on the spot what's in scope, log what was found and what was done, and note the before/after reading.
6. Escalate what's out of scope or past threshold with the specific data, not a general impression — what was measured, what the baseline was, and since when.
7. Verify at the next route pass that prior escalations were actually closed, and fold any recurring finding back into the interval or the escalation criteria for that asset.

Tools & methods

• Manual and metered/pneumatic grease guns, with a shot-count or stroke-volume reference per point rather than "until it feels full."
• Belt tension gauge (deflection-force type) and manufacturer belt-section force charts; straightedge for pulley alignment check within basic-adjustment scope.
• IR spot thermometer for bearing-housing and motor-frame temperature checks (not a full thermal-imaging survey — that's the mechanic's instrument).
• Oil sight glasses, dipsticks, and filter differential-pressure gauges; filter cross-reference sheets for correct part substitution.
• Handheld ultrasonic detector or simple stethoscope/tip-stick for a basic sound check — used to confirm a grease point is actually dry before adding grease, not to diagnose a bearing defect stage.
• CMMS mobile app or route sheet for logging every reading, not just deviations — the trend is the deliverable, filled examples in references/playbook.md.
• Basic lockout devices for isolation within the worker's own authorization scope; full LOTO planning for anything beyond that is the mechanic's or supervisor's call.

Communication style

To the mechanic or reliability tech: leads with the specific reading and its baseline ("housing's at 175°F, been running 128–135°F the last five visits"), not an impression ("it felt hot"). To the supervisor: leads with schedule status — what's on-time, what's deferred and why, what's escalated and still open — not individual readings. Logs every checklist line with the actual value taken, even when it's unremarkable, so the next worker's baseline comparison is real. States plainly when something was corrected on the spot versus flagged for someone else, rather than letting an escalation quietly sit as if it were closed.

Common failure modes

• Topping off every visit "to be safe" — re-greasing a point that isn't due because it can't hurt, which is exactly the over-lubrication failure mode in first-principles item 1.
• Rubber-stamping the checklist — marking items complete from memory or habit without taking the reading, which erases the baseline the next visit and every future escalation decision needs.
• Escalation as a reflex — flagging every warm bearing or new sound as urgent without checking it against the asset's own history first, which trains the mechanic to discount the worker's flags.
• Role creep into diagnosis — attempting to chase a recurring symptom to its mechanical cause (misalignment, imbalance) instead of escalating it, spending route time on work outside the position's training and scope.
• Chasing calendar compliance over criticality — hitting the on-time percentage by servicing easy, low-criticality points first when behind schedule, letting a high-criticality point slip instead.

Worked example

Situation. A distribution-center conveyor line runs a corrugate-dust environment, motor and gearbox operating near-continuously at 20 hours/day, 7 days/week. The drive motor's non-drive-end (NDE) pillow-block bearing — OD 110 mm, width 27 mm — carries the OEM manual's default 90-day relube interval. The worker's weekly route has logged this bearing's housing temperature for the last five visits: 128°F, 130°F, 132°F, 129°F, 135°F (baseline average ≈131°F). Prior route history also shows this same worker topping off the point with a partial shot of grease at several visits that weren't due, "since it doesn't hurt."

Naive read. A new worker sees the 90-day interval isn't due yet, tops off with a couple of pumps of grease anyway "to be safe," notes the housing feels "a little warm, like always," and moves to the next point.

Expert read — interval correction and anomaly check, done separately and reconciled. First, the interval: this bearing's environment carries one adverse duty-cycle factor per Noria/STLE guidance — heavy contamination — which cuts the OEM baseline by roughly half: 2,000 operating hours (the OEM's stated normal-duty relube point) × 0.5 = 1,000-hour effective interval. At 20 hr/day × 7 days = 140 run-hours/week, the calendar-based 90-day (≈12.9-week) schedule lets the bearing accumulate 140 × 12.86 ≈ 1,800 run-hours between services — 80% past the 1,000-hour contamination-adjusted interval it should be running. The corrected interval is 1,000 ÷ 140 ≈ 7.1 weeks, not 12.9. Grease quantity for the scheduled relube: G ≈ 0.005 × 110 mm × 27 mm ≈ 14.85 g, roughly 15 grams (about one tablespoon) — a bounded, calculated shot, not the partial top-offs this worker had been adding between scheduled services.

Second, the reading taken today: 175°F against a five-visit own-baseline of ≈131°F is a 44°F (24°C) rise — well past the roughly 15°C (27°F) own-baseline escalation threshold, even though 175°F alone isn't yet an absolute damage-level reading a less careful worker might wave off as "warm but not crazy hot." Because the interval had been running 80% over-length *and* the point had been getting unscheduled partial top-offs, both under-lubrication (interval too long) and over-lubrication (unscheduled topping-off causing churn) are live candidate causes — the worker doesn't need to resolve which one it is, only that a real deviation exists and both contributing practices need to stop.

What gets corrected on the spot vs. escalated. Correcting the interval (schedule the point every 7 weeks going forward, log the 15 g quantity) and stopping the ad hoc top-offs are within route-worker scope and get done today. The 44°F baseline deviation is not — a temperature rise on a bearing that may already have accumulated wear or contamination damage during the under-serviced period is a mechanic-scope call (inspect for damage, decide run-to-next-window vs. now), not a "grease it and see."

Deliverable — route note and CMMS escalation:

> Point: Conveyor drive motor, NDE pillow-block bearing (110×27 mm), Line 4.

> Schedule finding: OEM 90-day (≈1,800 run-hr) interval is 80% past the contamination-adjusted 1,000-hr interval for this environment. Corrected to every 7 weeks; relube quantity set at 15 g per service, replacing prior ad hoc top-offs.

> Condition finding: Housing temp 175°F vs. five-visit baseline of 128–135°F (avg 131°F) — a 44°F rise over this bearing's own baseline. No unusual sound noted on stethoscope check. Not re-greased pending mechanic inspection — schedule correction alone doesn't rule out existing damage from the prior under-serviced interval or churn from repeated unscheduled top-offs.

> Escalated to: Reliability mechanic, same shift. Requesting vibration/thermal check before next relube to confirm no bearing damage before returning this point to the corrected 7-week schedule.

Going deeper

• references/playbook.md — filled duty-cycle relube interval and grease-quantity worksheets, belt deflection/tension tables, escalation-scope decision table, PM-compliance tracking example.
• references/red-flags.md — smell tests with numeric thresholds: what each usually means, the first question to ask, the data to pull.
• references/vocabulary.md — terms generalists misuse, with practitioner usage and the common misuse for each.

Sources

• Noria Corporation, *Machinery Lubrication* magazine and training materials — duty-cycle/environmental relube-interval adjustment factors, grease-quantity-by-bearing-dimension methodology.
• SKF, *Bearing Maintenance Handbook* — grease quantity formula (G ≈ 0.005 × D × B) and bearing relubrication guidance.
• Heinz Bloch and Allan Budris, *Practical Lubrication for Industrial Facilities* — over-lubrication as a distinct, named failure mode (seal blow-by, churning heat) rather than a harmless excess.
• Gates Corporation belt installation and tensioning guides — 1/64-inch-per-inch-of-span deflection rule and belt-section force charts.
• Society for Maintenance & Reliability Professionals (SMRP) Body of Knowledge — PM-compliance benchmarking (best-in-class routinely cited at ~90%+ schedule compliance) and planned-vs-reactive maintenance metrics.
• STLE (Society of Tribologists and Lubrication Engineers) — bearing lubrication interval guidance by duty class and contamination severity.
• UE Systems ultrasonic-assisted lubrication practitioner literature — using airborne-ultrasound feedback to relube to a measured point rather than a visual "until it purges" endpoint, directly addressing the over-lubrication failure mode.
• OSHA 29 CFR 1910.147, *The Control of Hazardous Energy (Lockout/Tagout)* — baseline isolation requirement for any basic-adjustment task within this role's authorization scope.
• No direct machinery-maintenance-worker practitioner has reviewed this file yet — flag corrections or gaps via PR.

View SKILL.md source on GitHub · maturity: draft

Jurisdiction: US (baseline)