Can Worm Gear Oil Be Replaced By Regular Extreme Pressure Gear Oil?
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Can Worm Gear Oil Be Replaced by Regular Extreme Pressure Gear Oil?
ANSI/AGMA 9005-E02 standard clearly recommends that worm gears should use special worm gear lubricants -Compounded oils (CPs), but not extreme pressure gear oil.
Why is this? If we add normal extreme pressure gear oils into the worm gear box, what will happen?
Classification of gear oil
AGMA 9005 standard classifies enclosed gear oils into
| Gear Oil Type | Main Components in Formula |
| R&O (Rust and oxidation inhibited gear oils) | Base Oil + Anti-oxidants & Rust Inhibitors ( low load--carrying capability) |
| EP (Antiscuff/antiwear oils) | Base Oil + Extreme Pressure Additives ( high load--carrying capability) |
| CP (Compounded gear oils) | Base oil + additives + 3~10% fatty oil or synthetic fatty acid (commonly used in worm gears) |
The Compounded Oil is a special industrial gear oil specially used in the worm gear transmission system.
Why are normal extreme pressure gear oils not suitable for worm gear systems?
The main reasons why EP gear oils cannot replace compounded oils (CPs)are:
1. Lubrication failure
Worm gear systems operate under pure sliding friction, with the helical surface of the worm constantly rubbing against the worm gear teeth. In contrast, conventional gears exhibit primarily rolling friction.
Extreme pressure (EP) gear oils (containing sulfur-phosphorus additives) rely on chemical films (formed by sulfur/phosphorus and iron) at high temperatures to provide wear protection. However, in worm gears, the constant sliding causes these chemical films to break off.
During the constant sliding contact and scratch, the EP additives are quickly consumed, causing a loss of wear protection.
2. Corrosion risk of copper worms
We all know that worm gears are mostly made of bronze/brass, and the active sulfur in extreme pressure oils will cause corrosion:
"After the sulfur-phosphorus EP oil is activated at high temperature, the sulfur may cause the copper worms to corrode, which may significantly shorten the lifetime of the bronze worms."
Never Use Normal Extreme Pressure Gear Oil In Worm Gearboxes
Worm gearboxes must use special lubricating oils (such as L-CKE/P type); otherwise, they will cause corrosion, severe wear, and trigger catastrophic failure.
Fail Case of A port Tractor.
The maintenance engineer assumed that Normal Extreme Pressure gear oils could be used in high-load worm systems of the port tractor. After one year, the sulfur additives, activated under sliding friction, chemically corroded the copper worm wheel, causing rapid pitting and corrosion formation, while the absence of the compounded oil's fatty acid layer exacerbated direct metal-to-metal wear. Within just 3,600 operational hours, severe corrosion pits and spalling dominated the gear teeth, severe vibration/noise occurred, and ultimately, damaged the entire gearbox.
What are the core features of worm gear oil?
Generally, worm gear oil needs to have the following characteristics.
Base oil: high viscosity (above ISO VG 220~) to ensure oil film strength;
Additives: no active sulfur/chlorine: copper corrosion rating ≤1b (ASTM D130);
Compounded formula: contains 3–10% fatty acids or synthetic esters to reduce sliding friction between worm and worm wheel;
Performance verification: passed FZG anti-scratch test (≥10 level) and hydrolysis stability test
Chorus offers T4312 Worm Gear Oil Additive Package, which is specially designed for L-CKE/P Worm Gear Oils and provides excellent wear protection and copper worm protection. Contact us for the latest price and technical information.
