Corrugator Bearing Temperature Monitoring

A corrugator bearing rarely fails without a temperature story, but one hot number is not the story. The useful record is the same point on the same housing, at the same speed, compared with that housing’s own baseline. Operator side and drive side do not share a limit. A preheater journal next to a steam chest does not share a limit with a bridge roll. Plants that write “bearings OK” after a walk-by with an infrared gun pointed at shiny steel will miss the climb, then stop the line when the roll seizes. This page is how to take the reading so the next shift can trust it. The bearing maker’s grease limit still governs the stop. Nothing here replaces that figure. If the maker has not given a limit, build the baseline first. Do not invent one temperature and paint it as the stop standard for the whole line.

Measure the bearings that actually take the load. On the single facer that means both ends of the corrugating rolls and the pressure roll. On the glue unit it means the applicator and metering roll journals. Add preheater and preconditioner journals, and the mill-roll stand bearings that carry a full reel. A complete line has more bearings than a shift can trend. Pick the set whose failure stops the order, mark the housings, and leave the rest to the lubrication route in corrugator-lubrication-schedule-guide. Do not add a new favourite point every week. A trend needs the same point. A point that was moved and not noted cannot be compared with last week.

Take the reading after the line has been at the intended speed for about 30–45 minutes, not in the first ten minutes after a cold start. A cold housing warms as a normal duty cycle. Calling that warmup a failure trains people to ignore the gun. If the order changes speed by more than about 30 m/min, wait again before you compare the number with yesterday’s baseline. Write the speed next to the degrees. A temperature without a speed cannot be trended, because load and heat both move when the single facer speeds up. A row with the speed cell empty is unfinished at review.

Prefer a contact probe for the trend, and use an infrared gun only on a prepared target. Shiny steel has low emissivity, so an infrared gun aimed at bare metal often reads low and hides a hot bearing. Put a dull paint spot or a piece of the maker’s recommended tape on the housing and shoot that, from the distance the gun’s manual states. Do not shoot through a steam plume or a washdown mist. Both scatter the reading. If the only access is through steam, the mount is wrong; find a dry face of the same housing. Record which instrument was used. Mixing a contact probe on Monday with an infrared gun on Thursday creates a jump the bearing did not have. Keep the allowed gap for the two instruments separate. Do not mix them into one curve.

Build a baseline for each housing before you set an alarm. Run three normal shifts at the usual speed and average those readings for that point. A later reading about 10–15°C above that housing’s own baseline, at the same speed, is a warning to inspect, not an automatic proof that the bearing is dead. Absolute stop limits depend on the grease and the OEM. Many plants start a planned inspection when a housing is around 70–80°C and treat a climb through about 90°C as stop-and-look, but those bands move if the grease is different or the housing sits against a hot roll. Confirm the stop number with the machine maker before you paint it on the guard. Do not copy the number from the bearing on the other end of the roll. Do not set a formal alarm until the baseline has three full shifts.

Watch the slope, not only the snapshot. A rise of about 2–3°C per week at constant speed and the same grease interval is more serious than one afternoon that sits 4°C high and returns. A jump of more than about 10°C in a single shift, with speed unchanged, is an immediate check: grease condition, seal, alignment, and noise. It is not a note for the Friday meeting. If the temperature falls back only because the crew slowed the line, write the new speed. A cooler number at 120 m/min does not cancel a hot number at 200 m/min. The baseline you compare against has to be the baseline for the speed you are actually running. A cooler number after a slowdown does not close the earlier hot warning.

Grease changes the temperature on purpose and by mistake. A fresh shot can lift the housing about 5–10°C while the extra grease is worked out. That lift should settle within about an hour at running speed. If it is still climbing after that hour, stop adding grease and inspect. More grease in a hot bearing is a common way to make the failure faster. Starvation also heats, so the log has to show the last grease date from the lubrication schedule, not a guess. A bearing that was greased yesterday and is hotter today is a different job from a bearing that has not been greased in a month. corrugator-lubrication-schedule-guide is the route. This page only says when the temperature means the route was not enough. If the grease date is missing, do not write the heat up as a defect in the bearing itself.

Separate process heat from bearing heat. A journal next to a hot plate or a steam-heated roll runs warmer because the housing soaks heat, even when the rolling elements are healthy. Compare that housing with a bearing on the same machine that is not beside the heat source, at the same speed. If only the hot-side housing is high and it matches previous weeks, you may be reading the process, not a failing race. After a conversion to a boiler-free line, the air and the rolls near the single facer are often cooler than they were on steam. The old baselines are then the wrong comparison. Rebuild them on /products/boiler-free-line conditions before you alarm. Keeping the steam-line numbers will either cry wolf or hide a real climb against a baseline that was already hot from the chest. The first week after conversion only builds the baseline. Do not keep the alarm values from before the conversion.

Read the pattern before you condemn the bearing. One side hot and the other normal points to load, alignment, or a seal on that side, not to “the roll is old.” Both sides hotter after a lasting speed increase can be a new normal; set a new baseline after three shifts, and do not grease them into submission. A housing that is hot after a washdown often has water in the grease. A housing that is hot and noisy, or hot and rough when you listen at the same speed, belongs with corrugator-noise-vibration-diagnosis. Temperature without a noise note misses a spall that has not heated yet. Noise without a temperature note misses a grease problem that has not started to rattle. Write both, or say which one you did not do. A card that only says “abnormal,” with no temperature and no noise note, is not a reason to change the bearing.

Do not keep the order running only because the board still looks acceptable. A corrugating-roll bearing that lets go takes the roll, the stack, and the shift. Slowing down can be a bridge to the next planned stop if the temperature has stabilised below the OEM stop limit and someone is watching the trend every hour. It is not a repair. If the housing is climbing through the stop band, or the rise is more than about 10°C since the last reading at the same speed, clear the web and look. A seized bearing repaired on the weekend is cheaper than a scored roll repaired after a full-speed failure. The decision belongs on the card with the degrees and the speed, not in a radio call that nobody logs. Write the time you stopped to look, and the speed you returned to, on the same row.

The log is the monitoring system. Each row needs the bearing identity, operator or drive side, speed in m/min, instrument, the marked point, temperature in °C, the date of the last grease, and the name of the person who measured. A pass/fail tick without the number cannot be trended. Keep infrared and contact readings in separate columns if you must use both. Review the sheet weekly against the baselines. A housing that has climbed about 2–3°C each week for three weeks is a planned job, even if it has not reached 80°C. A blank week is not a healthy week. It is a week you cannot defend when the roll fails. A bearing with blank weeks in a row is remeasured before the next shift starts the line. Do not assume it is still healthy.

Train the measurement, not only the gun. A new fitter should take one supervised round and should be shown two false readings: shiny metal that reads cold, and a steam plume that reads nonsense. They should also see a housing just after a correct grease shot so they do not write a failure for a 5–10°C work-out. The marked point has to be visible without removing a guard that the procedure says stays on. If the only way to read the bearing is to defeat an interlock, the route is wrong. Fix the access, then trend. Guessing through a slot from two metres away is not the contact method and should not be entered in the contact column. A person who has not finished a supervised round does not sign the trend sheet alone.

Xuegong New Materials Group does not set the OEM temperature limit for your bearings. We can help a plant see when process heat changed, including after a move to boiler-free running, so the baselines are rebuilt instead of copied. Grease intervals stay with corrugator-lubrication-schedule-guide. Noise and roughness stay with corrugator-noise-vibration-diagnosis. Adhesive choice does not cool a journal. Use /products/boiler-free-line only as the reminder that a different heating method needs a new temperature baseline. The first deliverable is a week of comparable readings, each with a speed, not a single red number on an unmarked housing. A red number with no speed is not a reason to stop either. A baseline row missing speed or the measurement point goes back for a retest before the week is reviewed. A blank row is not counted as that point already normal or already checked.