Industrial lubrication management: viscosity, quantity, cleanliness and control

Almost every plant has a lubrication plan. Far fewer have a plan that comes from a calculation. Typically the intervals are inherited from the equipment manual, adjusted by habit, and end up as a weekly round where everything gets a bit of grease. The result is over-greased points sitting next to dry ones, and neither shows up in a report until something stops.

Viscosity first, brand second

Viscosity is the only parameter that decides whether a lubricant film exists at all. Everything else — additives, base type, price — acts on an assumption that only holds if viscosity matches the real operating temperature, not the ambient one.

For industrial oils, ISO 3448 defines the ISO VG grades by kinematic viscosity at 40 °C: an ISO VG 68 has 68 cSt at that temperature, within ±10 %. For engine oils, SAE J300 uses two numbers, one for cold behaviour and one at 100 °C, while API service categories — CK-4 and FA-4 for heavy-duty diesel — define the required performance level.

How much grease, and how often

Excess grease is the most frequent cause of overheating in relubricated bearings. Surplus grease is churned between the rolling elements, generates heat, oxidises the base oil and eventually hardens. As a general reference, a bearing at normal speed runs with 30 % to 50 % of its free volume filled with grease.

For relubrication, quantity is estimated from the bearing outside diameter and width, and the interval depends on speed, temperature, load and shaft orientation. Manufacturers publish calculators for this; what should not happen is the same interval applied to every point in the plant because it is the day the round falls due.

• Above roughly 70 °C operating temperature, the relubrication interval roughly halves for every additional 15 °C.
• A vertical shaft retains grease less well than a horizontal one and needs greater frequency.
• A point with vibration or shock loading requires shorter intervals than the same bearing running steadily.
• Inaccessible points are the ones most often neglected: they are the first candidates for single-point automatic lubricators.

Mixing greases: the silent mistake

Two good greases can produce a mixture worse than either. Thickener incompatibility causes softening — the grease runs out and leaves the point dry — or hardening, where the grease stops flowing towards the contact zone. Neither effect is visible from outside until the temperature climbs.

Cleanliness: the ISO 4406 code

ISO 4406 expresses fluid cleanliness with three numbers corresponding to the count of particles larger than 4, 6 and 14 microns per millilitre. Each number is a range code, not a quantity: dropping one point on the scale means roughly halving the number of particles.

Setting a cleanliness target per system — stricter for servo valves than for a low-pressure circuit — and measuring it periodically makes filtration manageable. The filter is then selected on its beta ratio at the micron size that matters, tested to ISO 16889 in hydraulics or ISO 4548-12 for engine oil filters, rather than on appearance or price.

Storage and transfer

A good share of contamination enters the oil before it ever reaches the machine. New lubricant is not necessarily clean lubricant: it can arrive with a particle count above the target of the system it is going into.

• Store drums under cover and horizontally, or with the bung off vertical, so condensation water is not drawn past the seal as the drum cools.
• Filter during transfer with a filter cart; it is the cheapest place to bring the particle count down.
• Use closed, dedicated transfer containers with a colour code per product. One shared funnel undoes any plan.
• Label every lubrication point on the equipment with its assigned product, using the same colour code.

Building the plan in six steps

1. 01

   Inventory the points

   Every machine, every point, with its current lubricant, quantity and interval. Without this census there is no plan, only habit.

2. 02

   Consolidate products

   Fewer references means lower mixing risk and simpler stock. A whole plant can usually be covered with fewer products than are currently in use.

3. 03

   Calculate quantities and intervals

   From the real speed, temperature and load of each point, not from an inherited weekly round.

4. 04

   Label in the field

   The plan has to be visible on the equipment, not only in a file. The label is what makes a different shift apply the same thing.

5. 05

   Record every application

   Which product, how much, what date and by whom. That history is what makes investigation possible when something fails.

6. 06

   Audit and adjust

   Review operating temperatures and lubricant condition, and correct intervals against the evidence. A plan that never changes is a plan nobody is looking at.

Product backing

Rodacaribe distributes Q8 Oils lubricants for engine, transmission, hydraulic and general industrial use, SKF greases for bearing applications and WIX filtration for heavy-duty applications. When the lubrication plan is defined first and the product chosen afterwards, the conversation stops being about the price of the drum and becomes one about cost per operating hour.