Ussivarustus Määrimine — Complete Oil Selection, Interval, and Contamination Guide

Check the oil technical data sheet or safety data sheet (SDS) for these indicators: (1) product is described as ‘EP gear oil,’ ‘extreme pressure gear lubricant,’ or ‘heavy-duty gear oil’ — these almost always contain EP additives; (2) the SDS lists sulfur compounds, organosulfur additives, or polysulfide compounds in the additive package; (3) the product is specifically recommended for helical, bevel, spur, or hypoid gears but does not mention worm gears or bronze compatibility. If any of these apply, do not use the oil in a bronze-wheeled worm drive. Acceptable oils will be labeled ‘worm gear oil,’ ‘suitable for bronze,’ ‘suitable for yellow metals,’ or ‘non-EP industrial gear oil.’

Mixing non-EP oils from the same viscosity grade is generally acceptable in an emergency but not recommended as a normal practice. The additive packages of different oil brands may have compatibility issues — some antioxidants or anti-corrosion additives are incompatible with additives from different manufacturers, potentially forming deposits or reducing additive effectiveness when mixed. For a short-term top-up (adding <10% of total volume), the same viscosity grade from a different brand is acceptable. For a full oil change, always use a single product. Mixing mineral and PAO oils is not harmful chemically, but the drain interval should be set to the shorter of the two individual oils’ intervals.

Yes, almost certainly. At low ambient temperatures, mineral oil viscosity increases dramatically — ISO VG 460 mineral oil at 5°C may be 6–8× more viscous than at 40°C. The high-viscosity cold oil churning through the worm gear mesh creates viscous drag noise — typically a low-frequency rumble that decreases as the oil warms. If this is the only symptom and it resolves completely within 20 minutes, the gears themselves are not damaged. Switch to synthetic PAO ISO VG 220 — PAO’s high viscosity index means it remains more fluid at cold temperatures while maintaining adequate viscosity at operating temperature. If the noise does not completely resolve after warmup, investigate for abrasive wear or bearing damage alongside the lubricant issue.

Yes, significantly. In a horizontal worm shaft configuration, the oil level fills the lower part of the housing and the worm thread dips into the oil as it rotates, carrying oil to the mesh by splash lubrication. In a vertical shaft configuration, gravity drains oil away from the mesh zone, and splash lubrication is less effective or completely absent depending on orientation. For vertical worm shaft configurations, the oil level must be carefully set to ensure the worm thread passes through oil at the lowest point of its rotation — this requires a higher fill level than horizontal orientation. For upward-driving vertical worm configurations, forced lubrication (an oil pump circuit) may be required. Confirm the housing fill level specification with Korea Ever-Power at ordering for any non-standard mounting orientation.

The standard oil level for a horizontal worm shaft configuration is the centre of the worm wheel pitch circle — the oil surface should be approximately level with the horizontal centre plane of the worm wheel when the drive is stationary. Overfilling beyond the centre of the worm wheel increases churning losses, raises housing temperature, and accelerates oil degradation — it does not improve lubrication and may worsen it by increasing viscous drag. Underfilling below the worm wheel centre means the mesh receives inadequate lubrication, particularly during starting and at low speeds. Check the oil level only when the drive has been stationary for at least 15 minutes — the oil level when running will be different from the settled level due to churning and film distribution.

Grease is used in some small, low-power worm gear applications — typically Module M2 and below, at low sliding velocities, and in sealed-for-life designs where oil changes are impractical. The grease must be formulated for worm gears: non-EP, non-sulfurised, bronze-compatible lithium or polyurea base grease. Grease lubrication is inherently less effective than oil immersion at removing heat from the mesh. For continuous-duty drives above approximately 0.5 kW, and for all drives where the housing temperature exceeds 50°C, oil immersion is strongly preferred over grease. Do not substitute standard multi-purpose grease (which typically contains EP additives and may contain molybdenum disulfide) for oil in a worm drive — the chemistry is incompatible with bronze.

Yes. The calendar interval (12 months) applies regardless of operating hours. Lubricant degradation occurs both through operating stress (heat, shear, oxidation from operation) and through calendar aging (oxidation from atmospheric exposure, additive settling, micro-contamination through seals during temperature cycling). A drive that only runs 400 hours per year still undergoes 8,760 hours of atmospheric exposure in 12 months. Annual oil changes remove the products of this calendar aging regardless of operating hours and allow inspection of the drained oil for any contamination that occurred during storage or infrequent operation.

Act immediately. Procedure: (1) Stop the drive at the earliest safe opportunity; (2) Drain the EP-contaminated oil completely; (3) Fill with clean non-EP oil of the correct grade for the flush — use a lower viscosity grade (e.g., VG 100 PAO); (4) Run at 20% load for 30 minutes to circulate the flush oil and dissolve remaining EP-contaminated oil from housing surfaces; (5) Drain the flush oil; (6) Inspect the drained flush oil — if heavily green-discoloured, the EP attack was significant and the wheel flank damage warrants visual inspection; (7) Fill with correct production oil and restart at reduced load for 2 hours before returning to full load.