Productivity Tip: Optimizing Gear Reliability and Life – Part II

This is the second post in a two-part series on gear wear. If you’re an industrial operator of any kind, this post will apply to you, as gears are one of the most ubiquitous components found in the industrial world. They’re found in everything from gearboxes at manufacturing plants to open gears at a mine to gear mills used in a variety of industries.

Our last post on this topic examined the basic types of gear wear. This week’s post will look at gear inspection and lubrication implications.

Gear inspection

You may have noticed in the last post that I have tried to make a careful distinction between wear and failure. Not all wear modes are failures and not all failure modes start as wear. That said, it is important to understand all gear conditions, their causes, remedies and the benefits of taking corrective action.

Understanding how a gear is performing starts with routine gear inspection – and gear inspection is particularly important for any gear reducers that are critical to the process. Critical is often defined as a gear box whose failure will alter the production process.

The key deliverables of any gear inspection are:

  • A record of component condition.
  • A comparative history of wear / failure progression.
  • A recommendation to correct the conditions noted.

Here’s a quick visual that takes a closer look at the key steps to a gear inspection:

When conducting a gear inspection, it’s particularly important to document the benefits of the corrective actions taken so that faster and more informed decisions can be made.

Gear oil basics

There are two basic types of oils used in gear applications – those fortified with rust and oxidation (R&O) inhibitors (circulating oils), and those fortified with extreme pressure additives (EP gear oils).

Circulating oils may be used in gear reducers that run at a steady state and are not shock loaded. This is defined by the American Gear Manufacturers Association as AGMA numbered series oil, where the number indicated equals the viscosity of the R&O oil required. Typical Mobil circulating oil families are Mobil SHC 600 Series, DTE Named series, Teresstic ISO series or Vacuoline 500 series of lubricants. Turbine oils are R&O oils as well, but they are specially designated for use in turbines and as such are often too light for gear applications.

An EP lubricant is one fortified by an agent that prevents wear, and the EP protection is typically provided by some form of sulfur / phosphorus. These oils actually bond to the gear surface and absorb shock loads presented by the application. This is defined by the American Gear Manufacturers Association as AGMA numbered “EP” series, where the number indicated equals the viscosity of the R&O oil required, and EP designates that the lubricant is designed to take shock loads. Typical Mobil gear oils include Mobil SHC Gear oils, Mobilgear 600 series, Mobil Spartan EP Series and Mobilube HD Series.

Circulating oils and gear oils have other characteristics which are worth pointing out:

  • Circulating oils tend to run cleaner, have improved filterability, provide longer oil life and will readily separate from oil.
  • EP oils may lay down more varnish-like deposits, strength depends on the type of and amount EP additive used. And, they will typically not readily separate from water due to the polarity of S/Ph and water.

When selecting the oil, it is important to understand the application and the operating environment, making sure that the needs of the gear unit in the application are met.

As mentioned at the outset, gears are absolutely essential to the success of most industrial operations. If properly maintained through routine inspections and the use of the right oil, operators can reduce potential downtime, maintain or increase productivity, and save significant costs in the long haul.

I hope this two-part series was helpful, and please let me know if you have any questions!

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