On a paper machine, the dryer section takes the wet sheet from the presses and dries it over a long line of steam-heated cylinders. The steam inside each cylinder heats its journals, and that heat flows straight into the bearings at the tending and drive sides. Add the humid air of the dryer hood and continuous high-speed running, and dryer bearings live in one of the toughest environments in any mill.
Most dryer section bearings are lubricated by a central circulating oil system, where the oil carries heat away as well as lubricating. Use the heat-stable paper machine oil grade the machine or bearing maker specifies, keep the oil clean and dry, and watch the flow to every bearing, the return temperatures and the oil's condition. Grease-lubricated felt and guide roll bearings need a heat- and water-resistant grease applied in the right quantity at the right interval.
A central tank supplies oil through pumps, a cooler and filters to a distribution header. Flow meters or dividers send a set flow to each bearing, and the oil drains back through return lines to the tank. The oil does three jobs:
The temperature rise between supply and return for each bearing is a useful health signal. A bearing whose return gets hotter than its neighbours, or whose flow drops, needs attention.
Dryer bearings need a heavy, heat-stable oil, often in the higher viscosity grades, chosen to give enough film thickness at the bearing's real operating temperature. Beyond viscosity, a good paper machine oil needs:
Use the paper machine oil the machine or bearing maker specifies. General hydraulic oil is not a substitute. If you send us the specification, our team will advise on the grade.
| Check | Why | How often |
|---|---|---|
| Flow to each bearing | No flow means no cooling and no lubrication | Every shift (flow indicators) |
| Return oil temperature per bearing | Early sign of trouble at one bearing | Every shift, trended |
| Tank level and temperature | Leaks, cooler problems | Daily |
| Filter differential pressure | Blocking filters, rising contamination | Daily |
| Water content | Steam and condensate ingress | Monthly lab test, plus visual checks |
| Particle count (ISO 4406) | Wear and contamination | Monthly or quarterly |
| Oil condition (viscosity, acid number) | Ageing and oxidation | Quarterly |
Our ISO 4406 guide explains how to read a particle count.
Water enters circulating oil from leaking steam joints, condensate, humid air and wash-downs. It speeds up oxidation, causes rust and weakens the oil film. Remove it continuously: allow it to settle in the tank and drain it off, and use a centrifuge or vacuum dehydrator on larger systems. Fix the source, too; a leaking rotary joint can put large amounts of water into the oil.
A rotary steam joint that leaks next to a dryer bearing can wash it with condensate and push water into the oil system. Repair leaking joints quickly; they cost far more in bearings than in steam.
Felt rolls, guide rolls and some hood-area rolls are greased rather than oil-lubricated. In hot, humid conditions they need a grease that resists heat and water. Calcium sulfonate complex grease handles water, heat and load together and runs continuously to 180 °C. Use the right quantity per bearing (our regreasing guide gives a simple formula) and shorten intervals for hot positions. Compare thickeners in our high-temperature grease guide.
Dryer and calender drive gearboxes run hot and continuously. A synthetic PAO gear oil of the maker's grade runs cooler and lasts longer than mineral oil in these positions. See our guide to industrial gear oil grades.
For lubricants across the whole mill, from pulpers to converting lines, see our page on paper mill lubricants.
Why are dryer section bearings oil-lubricated instead of greased?Because the heat from the steam-heated journals must be carried away continuously. A circulating oil system lubricates and cools at the same time.
Which oil viscosity is used for dryer bearings?A heavy, heat-stable paper machine oil of the grade the machine or bearing maker specifies, chosen for the bearing's real operating temperature.
How do I detect water in circulating oil?Look for a cloudy oil or free water at the tank bottom, and test the water content in a lab regularly. Rising water usually points to steam joint leaks or condensate.
Can hydraulic oil be used in a paper machine circulating system?No. Use the paper machine oil the maker specifies; it is formulated for the heat, water and filtration demands of the system.
Running a paper, board or tissue machine? Send us the machine sections and your circulating oil specification, and our team will advise on oils and greases for the wet end and the dry end.