Gear lubricants

CKC is enclosed gear oil with extreme pressure (EP) additives for medium to heavy duty industrial gearboxes. CKD offers higher thermal and oxidation stability for heavily loaded, hot-running gearboxes. The common DIN 51517 part 3 equivalent is CLP.

Bronze worm wheels often need a dedicated oil, in many cases PAG synthetic or a mineral oil with additives that do not attack copper alloys. Some sulphur-based EP additives attack bronze at high temperature. Check the gearbox plate before changing.

No. PAG is not miscible with mineral oil or PAO; mixing forms gel, blocks oil ways and damages seals. Converting requires draining, flushing and often new seals if the seal material is incompatible.

Use gear pitch line speed, load and operating temperature from the gearbox plate or manual; slow, heavily loaded gearboxes need a higher VG such as 220, 320 or 460. Too low causes tooth pitting, too high makes the box run hot and wastes energy.

For mineral oil, the interval is typically about 5,000 to 10,000 hours, with the first change earlier after running in to flush out wear debris. PAO or PAG synthetics can last two to three times longer. Oil temperatures above roughly 80 °C shorten the interval considerably, so oil analysis is a more accurate basis for the decision.

Check with the machine stopped and the oil settled, using the sight glass, dipstick or level plug for the mounting position. Too high a level causes churning, heat and foaming, while too low starves the gears and bearings. Vertically or inclined mounted gearboxes have different levels from horizontal ones, so read them for the correct position in the documentation.

Open gears such as kiln girth gears and mill drives use very tacky lubricants: bitumen type compounds, semi-fluid greases or very high viscosity synthetic oils. They are usually sprayed periodically by an automatic system to keep a film on the tooth flanks. Ordinary enclosed gear oil would be flung off and give no protection.

Take an oil sample and look at it: bright metal particles mean gears or bearings are wearing, cloudy oil means water contamination, and dark oil with a burnt smell means overheating. Check the magnetic drain plug for heavy debris. If the oil looks fine, the cause is usually bearings, coupling alignment or overload.