Work log — Press shop, lube interval and oil selection week
Engineer: R. Suto (plant lubrication)
Project: PL-4 press line, straight-side 400-tonne press and feed system
Log period: Week 01 to Week 02
Document ref: WL-2026-0911-LB08
Week 01, Monday — morning stand-up, and the bearing that talks back
Walk-in at 07:50. The PL-4’s feed roll bearings started a growl on the graveyard shift, and the night log noted a rising temperature on the roll end, 51 C against the 40 C normal. The press line lubricates from a central grease system that has run on the same programme for eleven years, 60 shots every 4 hours to every point, and the maintenance system flags no missed shots, so the equipment has been lubricated on schedule, and the bearing is warm anyway, which makes the week’s question an oil question rather than a schedule question. The night engineer’s guess was that the grease has separated in the reservoir, and the smell test he marked on the log, a rancid, sour note off the nozzle, says he is probably right.
Monday morning I pulled an oil sample from the central system’s release valve, the little barrel that catches what the ports purge, and the sample confirmed the suspicion: a grey, milky phase sitting on top of a clear layer, with a rough test showing the grease’s base oil has bled out of the thickener, and the separated grease from the reservoir is pumping a low-viscosity, half-drained fluid into the bearings. The bearing growl is not a dry bearing, it is a bearing being fed a grease whose structure has collapsed, and the fix is not more shots, it is a better product and a schedule that matches the actual duty.
Evening note: the reservoir separation is eleven years of a storage and top-up policy colliding with a pump that refills from a bulk drum that sat in the sun. Before I change a single interval I want a picture of what every bearing actually sees, not what the programme thinks it delivers.
Week 01, Tuesday to Friday — the audit, and the points that were slowly starving
Tuesday I audited the line, point by point, 46 lubrication points across the press slide, the feed rolls, the cam followers, and the pick-and-place unit. The finding that reframed the week: fourteen of the forty six points were being over-shot by a factor of three on the same interval that was under-feeding the high-cycle points by half. The central system’s fixed programme treated a slide bushing that moves twice a minute exactly the same as a cam follower that spins at 180 rpm, and the result is a line where the glamorous high-speed points run marginal while the slow bearings drown in purge. The feed roll bearing that growled, 180 rpm, was on the under-fed list, and the milky separated grease had been delivering a fluid that bled through the purges faster than a proper grease would stay put.
Wednesday I tested the new candidate grease in the back shop: a lithium complex NLGI 2 grease with a higher base oil viscosity and a much better shear stability, against the incumbent greaseline, and the test rig, a small bearing spinning at 1700 rpm with weights, showed the candidate holding 20 degrees cooler after two hours, with negligible bleed as measured by paper spot, while the incumbent bled a detectable wet ring by the end of the first hour. The decision for the press line is not clever: the incumbent’s base oil viscosity at 40 C is a 150 cSt fluid that the feed rolls of this press cannot keep in place at 180 rpm, and the plant has been topping up separation with more shots instead of asking whether the grease belongs on the line at all.
Thursday I wrote the oil audit into the PM system. The new schedule, which the press line adopts next Monday, is grouped by duty class rather than by clock: high-cycle spin points get 3 shots every 90 minutes, slow reciprocating bushes get 2 shots every 8 hours, and the once-weekly pivot and pin points get a full purge-and-refresh on Friday shutdown. The central programme’s total grease consumption drops by twenty eight percent on paper, and the bearings that matter get three times the fresh grease they were silently missing. Friday I also flagged the storage: the bulk drum comes out of the direct sun, into the lube bay’s shade, and the reservoir gets a monthly stir cycle so separation cannot build quietly again.
Week-end note: the growl cost the week its Monday, paid for with an audit that found a programme built for a machine that no longer runs the way it did eleven years ago. The line was not under-lubricated, it was mis-lubricated, and the difference is the whole difference between a schedule and a lubrication strategy.
Week 02, Monday to Friday — the new schedule on a live line
Week 02 the line ran the duty-class schedule, and Monday was the cable-day excitement: the feed roll bearing that started the job, freshly packed with the lithium complex grease, dropped to 39 C by the end of the first shift and stayed at or under 41 C all week, versus the 51 C that opened the chapter. The growl was gone by Tuesday’s first light, and the vibration collector’s point reading came back at the noise floor by Thursday, so the bearing that talked back has gone quiet on a grease that stays where it is put.
Wednesday I did the consumption check the finance desk wanted: the line’s grease use for the week totalled 11.8 kilograms against the old programme’s projected 16.9, a twenty nine percent reduction that matches the paper audit, and the over-fed slide bushes that used to weep grease down their housings are dry at the seats for the first time in months. The pressure on each zone, logged at the distribution block, shows the high-cycle zone now drawing three times the fresh grease it used to, and the reciprocating zone’s purge cups are no longer overflowing between shifts.
Friday’s shutdown refresh on the once-weekly pivots went without drama: the old grease on those pins was dry and cracked at the edges, confirming they had been under-fed for an interval that treated them like the slide, and the fresh pack took the pins from a 22 N·m free-swing friction to 14 N·m, a measurable loosening that the maintenance staff felt in their hands. The next dump is on the Friday PM schedule, every week, and the audit lives in the PM binder so a future change of programme starts from the duty classes, not from the eleven-year-old recipe.
One correction I took on the chin this week: the reservoir’s monthly stir cycle I proposed turned out to be unnecessary once the drum is shaded and topped fresh, and after two weeks the sample comes out uniform, no separated phase, so I am marking the stir option as optional and the shading as mandatory, a small revision to my own Week 01 idea, recorded honestly in the log.
Closing the two weeks with the numbers: feed roll bearing from 51 C to 39 C, growl gone by Tuesday, fourteen points reclassified from over-fed to correct, three duty classes defined, grease use down from 16.9 to 11.8 kilograms a week, dry cracked grease found and purged on the once-weekly pins, and a base oil viscosity choice, the 150 cSt bleed-out that lost its place at 180 rpm, replaced by a grease that holds its structure through the run. The line is quieter, cooler, and twenty nine percent cheaper, and the failure that started it was a reservoir that separated while the schedule swore it was on time.
Attachment A — lube audit summary
| Duty class | Example point | Old interval | New interval |
|---|---|---|---|
| High-cycle spin | feed roll, cam follower | 60 shots / 4 h | 3 shots / 90 min |
| Slow reciprocation | slide bush | 60 shots / 4 h | 2 shots / 8 h |
| Occasional pivot | toggle pins | 60 shots / 4 h | purge weekly |
Attachment B — oil selection checklist
1. Sample the reservoir for separation before blaming the schedule. 2. Audit every point by actual speed and duty, not by clock. 3. Look for over-fed points drowning and high-cycle points starving. 4. Bench-test candidate grease for bleed and temperature rise. 5. Match base oil viscosity to the point’s speed and load. 6. Check storage and top-up practice, shade the drum and stir the reservoir. 7. Re-read the consumption after two weeks, not a paper projection.
Glossary
Lithium complex grease: a grease whose thickener resists separation and shear loss at working temperature. NLGI grade: the consistency class of a grease, 2 being a standard multi-purpose body. Base oil viscosity: the viscosity of the oil held by the grease thickener. Purge: grease that is pushed out of a bearing as fresh grease displaces the old. Separation: the bleed of base oil out of the thickener, leaving a weak structure.
Week-end reflection
Friday evening. Three lines for the file. First, an on-schedule lube programme can still be failing, because eleven years of clock-based shots told the press exactly nothing about what each bearing needs, and the reservoir separation sat in plain sight until a bearing growled. Second, the fix was a duty-class map and a grease that holds its oil, not more grease, and the twenty nine percent saving is the footprint of a programme that stopped over-feeding the slow points and starving the fast ones. Third, the honest amendment to my own proposal, the stir cycle demoted to optional, is the part of the week I will take into the next plant, because a lube audit that learns from its own first draft is a lube audit that survives contact with the floor.
A note for the line’s CMM and SVM files, because the week produced a clean number worth keeping: the feed roll bearing’s envelope spectrum now shows no raceway line at its ball-pass family, where the Monday of Week 01 carried a clear 3.4 kHz sideband from the marginally lubricated race. The collector confirmed the sideband is twenty dB down by Friday, which is the kind of evidence a plant records in the trending file so a future growl is read against a healthy baseline, not against the silence of a forgotten failure. And for the record, the 22 N·m to 14 N·m free-swing number on the toggle pins belongs in the same file, because a pin that swings free is a pin that is getting the grease it was designed to get.
One arithmetic note for the finance desk that asked how a cheaper-looking programme costs less: a lithium complex grease at a slightly higher drum price paid for itself in the first week because the line burns twenty nine percent fewer kilograms, and every kilogram that no longer gets purged onto the floor is a kilogram that no longer has to be floor-swept, incinerated, or argued about in the waste manifest. The audit’s true saving is not the drum price, it is the cycle: better placement, less consumption, less disposal, and a bearing that opens each Monday at its design temperature instead of at the top of its alarm band.
