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Imatech Newsletter Open Gears

Processes involved with open gear lubrication.

Imatech Cutting Edge Technologies Newsletter

We look at open gears and how best to lubricate them.  Commonly used for power transmission, open/semi enclosed gear drives (AKA: heavy-duty gear drives or girth gears) have been around since the beginning of the Industrial Revolution.

Application of open gear lubrication includes;

  • Spray/atomisation systems
  • Gravity-feed or Drip-feed systems
  • Oil bath (splash and idler immersion) system
  • Hand, brush or pour on

Generally, an open gear lubricant should be fluid enough to flow through equipment if applied by a drip-feed system, spray system or force-feed lubricator. Similarly in brush applications, the open gear lubricant should be sufficiently fluid enough for an even coat to be brushed onto the teeth. In any case, it’s important for the open gear lubricant to be viscous and tacky to resist the gear teeth from squeezing out. When a splash pan or a splash and idler immersion system is present, the lubricant drips inwards so it is important for it not to be so heavy that it channels as the gear teeth dip into it.

Ideally open gear lubricants should have the following properties:

  1. Tackiness (adhesive/cohesive properties) – excellent adhesion to the gears and resistance to extrusion under extreme pressure
  2. Resistant to water washout and spray-off
  3. Provide an elastic retractable film which cushions and lubricates load bearing surfaces
  4. Protection of the gears against rust and corrosion
  5. Resistance to fling-off
  6. No build up in the roots of the gear teeth
  7. Alleviate housekeeping and maintenance issues
  8. Spray ability and/or ease of dispensability




When considering the properties and application methods best suited to open gear lubrication there are a variety of products to choose from. They work on various principals of lubrication with the most effective being elastohydrodynamic (EHD) lubrication. Some products use boundary lubrication with the help of solid lubricants such as molybdenum, disulphide and graphite as part of their makeup to separate metal to metal contact.

Types of open gear lubricants:

  1. Asphaltic type (also referred to as residual compounds)
  2. Semi-fluid greases (also known as paste type)
  3. Semi-fluid grease cutbacks
  4. Gel/polymer-thickened types
  5. High viscosity synthetics

Chesterton 715 Spraflex is a tacky, asphaltic based material which adheres to surfaces to form a cushioning film. It resists extrusion and replaces its own lubricant every revolution by forming a film which naturally flows to fill voids.

If staining or soiling of equipment or process material is a concern, Chesterton 715 Spraflex® Gold (715G) is the alternative solution.  715G has a full synthetic polymer base that presents clear on surfaces and is 100% active. It offers a self-replenishing action which cushions and reduces noise while continuously lubricating areas of tooth contact on gears with a flexible film. It can also be applied to wet metal surfaces unlike most other lubricants.

Both old and new technologies of the 715 Spraflex range meet the properties and performance criteria required to successfully lubricate open gears.

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