Industrial gearboxes continue to play a vital role in keeping the wheels of industry turning, whether directly as part of a production process, or indirectly by enabling a company’s valuable assets to operate smoothly and efficiently.

While the function of the industrial gearbox might appear straightforward, namely to change the speed of the input energy and increase the torque provided to the application required, the importance of ensuring it operates efficiently and tirelessly throughout its lifetime cannot be overstated. Effective operation enables increased production efficiencies and lower operating costs, while gearbox failure can lead to a total shutdown in production, lost output, lost revenues and even lost contracts.

Industrial gearboxes face a wide range of challenges such as particulate contaminant ingress in mining, cement and quarrying applications, or excessive water contamination and water ingress in paper or steel industries. In each case this can cause problems for the lubricant to function properly and in turn adversely affect the efficiency and durability of the industrial gearbox. Access to industrial gearboxes can also be a challenge in many applications; with the requirement for low maintenance and longevity of components and gear oils offering extended life being a main driver in the decision making process.

Today’s industrial gearboxes are not only smaller and lighter, but are delivering greater power densities than ever before. Higher gear teeth loading, higher bearing loads and increased oil temperatures are all impacting the requirements of a modern industrial gear oil (IGO). This is resulting in the need for IGOs to perform to the exacting standards demanded by the gearbox original equipment manufacturer (OEM).

Delivering IGOs that satisfy the performance requirements of the individual application requires the careful formulation of the base oil, additive package and compatibilizer. The use of synthetic base oils in IGOs continues to grow; their selection affected by both performance and total cost considerations. Mineral IGOs are often preferred in applications which have stable ambient temperatures, are easier to access and where initial cost may be a major consideration. From a performance perspective however, the lower thermal and oxidative stability of mineral oils mean they are less effective in applications with intermittent ambient temperatures and where long life and low maintenance are required. Providing improved thermal and oxidative stability, a correctly formulated synthetic IGO can address these limitations, while delivering around three times longer life performance over a mineral IGO.

Synthetic IGOs are typically formulated from either polyalphaolefin (PAO), polyalkylene glycol (PAG) or ester base oil. PAOs continue to account for the vast majority of synthetic IGOs available today, and are regarded by many as the synthetic base oil of choice.

Alongside the synthetic base oil, the performance additive package plays a pivotal role in delivering the required levels of performance and protection to the gearbox. Bearings are one of the fundamental components of an industrial gearbox; their main function being to support spinning shafts and keeping them in place while torque is transmitted between gears. If a gearbox fails, it is the bearing that is the most frequent failure point within the unit. While much attention is therefore paid to protection of the bearings, IGOs must be formulated to perform for all of the potential failure mechanisms including gear scuffing, load damage, micropitting and white etching cracks (WEC).

In addition to bearing and gear protection being delivered through the careful formulation of extreme pressure additives, anti-wear additives and friction modifiers, a range of complementary additive technologies are typically needed to meet the needs of today’s modern industrial gearboxes. High performing IGOs need to rapidly remove water from the gearbox, resulting in the requirement for demulsifiers to agglomerate the water before its removal. Anti-foam additives are needed to prevent high surface foaming, so avoiding the IGO escaping through the breather system. Additionally, corrosion control additives to prevent ferrous metals from corroding, as well as yellow metal passivators to protect copper, brass and bronze components from corroding are required.

Due to the relatively poor solvency of synthetic base oils, the compatibilizer is a key component in the formulation; its primary role to ensure the performance additive package does not separate from the synthetic solution. When formulating IGOs it is critical to recognise that the addition of a compatibilizer is typically done so at the expense of the base oil. It is therefore essential the compatibilizer is properly formulated to ensure the performance benefits of the synthetic base oil are not diminished.

Given today’s gearboxes have to operate in hotter and more severe conditions than ever before, OEMs are stepping-up the performance levels required from their gear unit oils. Many gearbox OEMs often use baseline industry oil standards, such as AGMA 9005-F16, DIN 51517-3 and ISO 12925-1, in addition to their own specific performance requirements. This results in more stringent performance standards for the gear oil, irrespective of the base oil used in the final formulation. Despite this, leading gearbox OEMs across all segments recommend synthetic PAO-based lubricants amongst other technologies to their customer base; acknowledging the added value these higher-performing IGOs are delivering to both their hardware and the individual application.

Our View

The demand for synthetic IGOs continues to grow, enabling modern gearboxes to deliver efficiency gains and lower total cost of ownership. Today’s higher-performing synthetic IGOs are having to deliver superior levels of performance and protection than ever before, not just for the gears and bearings, but for every single part of the gearbox, including adhesives, paints and seals. At the same time, IGOs must not promote the formation of WEC and be formulated to deliver to the exacting requirements that OEMs are demanding for their modern gearboxes.

The delivery of a high-performing synthetic IGO requires the careful formulation of base oil, performance additive package and compatibilizer, each working in complete harmony as a key component of the complete industrial gearbox system. By doing so, today’s modern gearboxes are enabled to perform to their full potential, in applications where longer life, lower maintenance and lower cost of ownership are all highly valued by the customer.

Originally published in LUBE Magazine.