Open Gear Lubrication Management in a Pit Mine

Lubricating open pit mining equipment effectively introduces a number of unique challenges that are not present in the industrial environment.

However, like the industrial environment, an effective lubrication management program will improve productivity and the quality of planned maintenance, and reduce unscheduled downtime and the amount of lubricants consumed annually.

Because a dollar value is difficult to assign to these benefits, most lubrication management programs calculate a return on investment (ROI) using the savings on lubricant consumption alone. Several factors must be considered when seeking to optimize the lubrication systems for mining equipment. They include:

1. Understanding the demands of each lubricated component within each particular lubrication system.

2. Thorough knowledge of the operation of the lubrication systems.

3. How best to manipulate the lubrication systems to meet the needs of each application in the forever-changing climate that the equipment is subject to.

4. Fully understanding the products used within each lubrication system.

As is the case with any healthy lubrication program, regardless of the environment, an effective open gear and grease lubrication management program for open pit equipment must be based on putting the right lubricant, in the right amount, in the right place, at the right time. This, combined with quick, effective lubrication system maintenance practices, ensures the benefits are maintained.

The three key elements of an effective lubrication management program include benchmarking, system efficiency and
communication.

Benchmarking

To truly recognize all of the benefits of a program, one must establish a starting point for the program. Following are some examples of benchmarking:

1. Calculate the product consumption, of both multipurpose grease and open gear lubricants under the current lubrication system settings.

2. Photograph any and all visible wear or damage to the lubricated component surfaces like gear teeth.

3. Document the current lubricated component lifecycle including the target component life expectancies.

4. Calculate an average of previous common component adjustments (such as saddle block adjustments) and begin tracking these adjustments for future comparison.

System Efficiency

For any program to be successful, all of the components within the program must operate at maximum efficiency.

1. Repair or replace all faulty components within the lubrication systems.

2. Pressure-test the lubrication systems to ensure there are no leaks and ensure all injectors or measuring valves are operating properly. When pressure testing, it is not uncommon to see slight drops in pressure over time. This is primarily due to line expansion. Stabilize the system pressure above the system manufacturer’s minimum recommended operating pressure.

Communication

Like a part of any successful program, communicating the change with members involved in the process is important.

1. Evaluate current lubrication systems preventive maintenance schedule (PM). Ensure the PM is executed properly. Revise as required.

2. Ensure people are continuously informed of the task at hand. This includes operations, all equipment operators and all pit maintenance personnel. Throughout the tuning process, it is not uncommon to experience slight setbacks in determining the optimum settings. Having the operators of the test unit diligently report any lubrication problems they experience is vital to the accomplishment.

3. Environmental details are key. Dust, snow, rain and temperature can affect the lubricant performance. Setting up the lubrication systems to meet the demands of the ever-changing elements can be executed only with knowledge of climatic conditions.

4. Consider assigning one or two people to implement and see the program through to completion. Ownership produces results.

Open Gear Lubrication Issues

Over the years, the composition of open gear lubricants has changed to meet new environmental regulations. By now, most lubricant manufacturers have developed open gear lubricants, commonly known as semifluid grease-based products, to replace the solvent diluted asphaltic compounds (cut-back) that were used for many years. The reason for the change is that the EPA identified the preferred solvents for elimination. This forced a major shift in thinking about the use of diluent (cut-back) products.

The different composition of these products has created new challenges with respect to applying the product. In many cases, application alone can turn a good product into a great product.

When using grease-based open gear lubricants, there are three elements to consider in achieving an optimum lubricant film:

1. The adhesive properties of the product - The ability of the product to stick to the component.

2. The cohesive properties of the product - The ability of the product to stick to itself.

3. And finding the balance between these two properties (Figures 1 and 2).

There are a number of other contributing or possible factors that have damaged the shroud of this pinion. The ribbon of purged multipurpose grease (MPG) from the shipper shaft bushings at the far left depicts the MPG migrating onto the open gear lubricant (OGL) application. This causes contamination, resulting in possible damage.

Figure 1 is an excellent example of contamination issues, as well as an upset adhesive-cohesive balance. Applying this particular lithium complex based OGL product incorrectly (in this case, overapplying) will result in boundary lubrication identified through the excessively transparent lubricant film visible over the complete application.

The same OGL product applied properly in the same application of a different unit produces a thick, black, tenacious lubricant film supporting the application properly through incremental climatic conditions, as shown in Figure 2.
This picture was taken during a sleet and rainstorm.

In most cases, the end result of a proper semi fluid OGL application will look much like an old asphaltic solvent cutback application, but appearances will vary between manufacturers.

While each lubricant manufacturer may have a unique product formula, all of the semifluid products now start with a viscous base oil versus the asphaltic material that used to be the starting point.

Because the new semifluid open gear lubricants generally don’t include a solvent, the lubricant won’t thicken like the old solvent cutback type products. Balancing the adhesive and cohesive properties through lubrication system manipulation is key to acquiring a thick, durable, tenacious lubricant film. This is typically achieved by providing smaller quantities of product more often.

There is no set standard for lubrication system set-up because formulations of semifluid open gear lubricants vary significantly between manufacturers. Each different lubricant will require tailoring of the lubrication systems to maximize product performance, especially with open gear applications.

Since tailoring is required, it makes sense to use one unit as a test (pilot) unit. Here, the lube system settings can be optimized and these idealized settings can quickly be implemented throughout the remainder of the fleet, provided the fleet is of similar model.

Multipurpose Grease Lubrication Issues

Like open gear lubricants, product manufacturers have continued to improve the design of new products to meet the lubrication needs of today’s bigger, faster equipment. For the most part, changes in formulations haven’t affected the application of these products as much as open gear lubricant changes.

The biggest concern when using open gear lubricants and multipurpose grease products is lubricant incompatibility. Compatibility is necessary to assure that the lubricated component life is achieved. Typically, the crowd area of an electric cable shovel will have these open gear and multipurpose greases in close proximity.

Problems can occur if the purged multipurpose grease from the saddle block bushings migrates onto the open gear application of the crowd pinions. This is a common problem when the saddle block bushings are over lubricated. Even if the two products in this case are compatible, the multipurpose grease migration will dilute the effectiveness of the open gear lubricant.

This dilution will upset the adhesive-cohesive balance achieved through tuning the open gear application, creating a washing effect and significantly reducing the performance capabilities of the open gear lubricant.

Taking Control of Your Lubrication Program

Understanding the composition of today’s products requires a change in habits. For those who have been trained in the approach, “if a little is good then more is better,” throughout their careers, they should ask themselves just how much money should be invested in this theory before re-educating employees to seek the benefits of an effective lubrication management program using today’s products.

Let’s face it; there are not many who are truly interested in dealing with the responsibilities of effective lubrication, especially when it comes to open gear and grease lubricants. Typically, it’s a dirty, messy, slimy job. The mindset is “as long as there is lube there, it’s working fine.” This is precisely the philosophy that needs to change.

Because there are so many variables in determining the actual savings one can expect from an effective lubrication management program, a cost-benefit analysis is often difficult to perform. In most cases, the reduction in lubricant consumption by itself will more than pay for the costs of getting expert assistance.

The benefits that can typically be realized by re-educating staff on the value of proper lubricant management are limitless are as follows::

1. Significant reduction in consumed lubricant

2. Improved environment (less loss provided)

3. Cleaner, safer working conditions

4. Increased productivity and machine availability, due to the reduction of unwanted lubrication system failures

5. Meeting or exceeding component life expectations

6. Significantly reduced housekeeping costs

7. Training and education required to achieve and maintain the change