Gearboxes are an essential machinery component, and they need to be correctly lubricated in order to function efficiently and for their expected lifespan. However, choosing the right lubricant for a particular gearbox can seem daunting. 

National Sales Manager for Lubrication Engineers (LE) South Africa, Llewellyn Owen, says that the first thing to look at is what lubrication specifications an original equipment manufacturer has recommended, and the second is to assess the gearbox’s current situation – whether it is new or in use, the environment it is operating in, and if the correct sight glasses, breathers and filtration are in place. “It’s very important to be able to understand what your specific needs are on your plant in order to know what lubricant will work best,” says Owens. 

However, once these have been determined, if a gear oil is failing, it may not always be clear why this is happening. Lubrication specialists can use a gear oil test for a root cause analysis to determine the reason an existing gear oil is failing. 

A gear oil test visibly demonstrates what happens in a simulated gearbox environment and can show how a particular oil traps air when it runs for a long time, for instance. 

If a new specified gear oil is in use, then a new test can be done to determine how that oil works in comparison to the old oil in the simulated gear oil test environment. This can show whether the new oil has overcome the problem of the old oil or will potentially cause the same issues. 

Common issues in gearbox lubrication

During gear operation, oil is distributed across the gear faces. However, several problems can arise. These include:

• Decreased viscosity: As gears heat up, the oil viscosity can drop, reducing its ability to stick to the gear faces and provide adequate lubrication. This leads to increased friction and potential gear damage.

• Trapped air: When the oil is not sticking to the gear faces, air can be introduced to the gearbox and sump as the lubricant foams, which can cause gear failure over time.    

• Increased fling: As gears move at higher speeds or for longer durations, the amount of lubricant that flings off the gear face increases, which can compromise the lubrication of key components and cause other issues in the gearbox compartment.     

• Surface fatigue: Without proper lubrication, gears suffer from increased wear and tear, leading to   surface fatigue. 

• Running hotter and drier: When a lubricant stops working effectively, over time gears begin to run much hotter and drier, which shortens their lifespan.   

LE’s propriety products for gearboxes, contain an additive called Duolec®, which is a liquid additive that provides anti-wear and extreme pressure capabilities to gearbox lubricants. Both its Duolec® Industrial Gear Oil (semi-synthetic) and Duolec® Syn Gear Lubricant (a synthetic based oil) are extremely effective solutions for gears. 

Owen says that the Duolec® range has been successfully used in multiple sectors, including marine applications and large and small industrial gears. 

“This is because of the way that it is able to cling to the metal of the gears and the amount of air that it can push out,” he says. Over time, these two factors have a significant effect on gearboxes as they help to protect the gear components and enable them to work efficiently.  

“Not only does it save you in the long run, but it will definitely also extend your asset life,” says Owen.