How to avoid over-greasing to prevent equipment failure

 

Over-greasing insights

• Over-greasing bearings carries many risks, including equipment failure and lost production hours.
• Applying the correct amount of grease and selecting suitable grease for different applications can unlock the competitive advantage of proper lubrication, keeping operations running smoothly and minimizing costly interruptions.

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Bearings prevent metal-to-metal contact, which reduces friction and allows for smooth movement. The transfer of motion and force makes bearings widely used in various applications that experience restricted movement. Because bearings play a critical role in certain machine applications, it’s important to consider lubrication and, in particular, how much lubricant is applied and when.

A common misconception is that adding more grease is always better for bearings. However, too much grease can result in severe problems, such as overheating, damaged seals and bearing failure. Imagine the frustration of a machine going down during peak production hours, only to discover that over-greasing was the culprit, resulting in costly repairs, unexpected downtime and the pressure to get operations up and running again.

Proper lubrication practices are essential to extending equipment lifespan, reducing maintenance expenses and improving operational efficiency. A shift from reactive to more strategic maintenance planning can position lubrication as critical in ensuring consistent performance and reliability. Both can have a positive impact on productivity and profitability.

The critical disadvantages of over-greasing

Bearings rely on adequate lubrication to reduce friction, prevent corrosion, dissipate heat and protect against contaminants. However, many professionals mistakenly apply more grease until it is purged. While this may seem like a safety measure, it isn’t. It’s easy to see why some might think, “A little more grease can’t hurt, right?”

However, well-intentioned practices can backfire, causing the problems they were meant to prevent. Below are three of the critical consequences of over-greasing:

1.     Churning and energy loss

When too much grease is applied within a bearing cavity, the rotating bearing elements must work harder to move through the additional grease (see Figure 1). The excess grease being churned by the bearings is comparable to wading through water; the deeper you go, the harder it becomes to move forward and the more resistance. The added friction increases the energy consumption of machinery and drives operating costs higher. Moreover, the grease breaks down faster due to the excess grease generating additional heat, accelerating the oxidation process. The grease can no longer provide sufficient lubrication to the rotating element parts in a bearing to protect against wear; it loses lubricity and diminishes its overall efficiency. Bearings that need grease to remain cool suffer and will experience frequent maintenance and replacement due to over-greasing. The risks of over-greasing can be severe, including shortened bearing lifespan, increased downtime and costly production delays.

2.     Seal damage and contamination

Another critical risk of over-greasing is damage to bearing seals (see Figure 2). Grease guns can exert pressure up to 15,000 pounds per square inch (psi), while most bearing seals will not require that much pressure, no more than 500 psi. When using a grease gun, there is the risk of applying too much pressure. When the lever is pressed quickly, it sends a surge of grease and bearing seals may rupture or become dislodged. When this occurs, an entry point for contaminants like dust or moisture is created. In harsh environments, dust, dirt and other contaminants will be present; ruptured seals can allow these contaminants to enter, cause wear and lead to bearing failure. Maintaining the integrity of bearing seals is critical because it ensures the proper function of bearings over their operational lifespan.

3.     Increased heat and oil bleed

As excess grease churns and generates additional heat, more friction is created within the bearing. The grease also tends to break down over time. Excessive heat can cause the oil to separate from its thickener, referred to as “oil bleed.” When oil bleeds excessively, the lubricating properties of the grease are compromised, reducing its ability to provide an adequate barrier between moving parts (see Figure 3). Equipment and applications such as electric motors or high-speed bearings require precise lubrication to combat friction and heat. This type of failure can impact them and cause slowed production times, increased maintenance costs and reduced overall efficiency of the machinery.

Nine steps to avoid over-greasing

Understanding the risks of over-greasing is the first step. The next is learning how to prevent it. Taking the time to assess current practices and identify areas for improvement will create the right strategies and tools maintenance teams can implement and strike a balance between too much and too little grease. Here’s how to keep things in check:

1.     Calculate the proper grease volume

Applying the proper grease is crucial for maintaining bearing efficiency and prolonging lifespan. Instead of relying on estimates or visual cues, maintenance teams can simply calculate the grease volume for specific bearing types using the industry standard SKF formula: G = 0.114 × D × B. In this formula, G represents the grease volume in ounces, D is the bearing outside diameter in inches and B is the bearing’s width in inches. This method helps avoid over-application and ensures bearings receive the optimal amount of lubrication for their intended use.

2.     Use feedback tools for precision

Maintenance teams can experience significant relief when they consistently apply just the right amount of grease. For example, ultrasonic sensors improve manual relubrication when connected to a grease gun, helping maintenance teams use the correct amount for the bearings. These sensors can monitor grease application in real-time for various bearing applications: electric motors, pumps and conveyors. The sensors will provide audio and visual display notifications during the relubrication process. With advanced maintenance technology like ultrasonic sensors, the benefits extend beyond applying the right amount of grease needed. Teams that invest in these tools will reduce equipment wear, increase overall productivity, reduce costly repairs and establish a reputation for reliability within their operations.

3.     Train technicians and calibrate equipment

The effectiveness of maintenance practices largely depends on the technicians performing them and the tools they use (see Figure 4). Proper training helps technicians identify issues before they escalate and equip them to apply the correct solutions. Maintenance teams should: update records of equipment, create checklists to ensure that staff are familiar with the procedures and available tools and understand the available lubricants. For example:

• Are they confirming that the relief passage is clear of any hardened grease that might block flow?
• Are they confirming that the grease relief valve is functioning properly or that the drain plug is removed?
• Do they stop greasing if they detect abnormal back pressure?
• Are the grease guns equipped with necessary tools like pressure gauges or relief-type vent plugs?

Regularly calibrating grease guns is also crucial to ensuring each application delivers the exact amount of grease needed, reducing the risk of over-pressurization and component damage. To calibrate the grease gun, follow these steps:

• First, obtain a small scale and set it to ounces.
• Second, with the grease gun, pump 10 slow, steady strokes of grease onto the scale.
• Next, divide the number from the scale by 10, which will be the grease per stroke. Do this for each grease gun.
• Finally, label the grease per stroke on the grease gun and recalibrate each year using the same grease.

4.     Establish a regular lubrication schedule

To prevent over-greasing, maintenance teams must establish lubrication schedules. To create a structured plan, know the right frequency for relubrication and the specific needs of each bearing type. Leverage tools to systematically set accurate relubrication intervals and track critical performance data to enhance further and maintain the effectiveness of these schedules. Missing a lubrication interval or improperly lubricating bearings can significantly impact operations. Using tools that ensure consistent procedures across the team can maximize maintenance efficiency and improve equipment uptime.

5.     Choosing the right grease for bearings

Choosing the proper grease for bearings is as important as ensuring the correct amount is applied. The operating environment, load, speed and compatibility with bearing materials are taken into consideration by maintenance technicians. Here are the critical factors in choosing the proper grease:

6.     Consider the operating environment

Take the following steps before applying grease to bearings:

• Identify the operating temperature range: The manufacturer’s manual is a great reference for the temperature and environmental conditions the bearing will encounter. Grease should be able to withstand these temperatures without losing its lubricating capabilities.
• Consult product information sheets: Always refer to the product specifications, especially the dropping point, which indicates the maximum temperature at which the grease retains its structure.
• Match the grease to the application: Greases with synthetic base oils and high dropping points are ideal for high-temperature environments, such as foundries or pellet mills. In colder environments, grease with a low pour point is best to maintain fluidity.

7.     Load and speed considerations

The bearing’s load and speed must also be accounted for by maintenance.

• High-load applications: Bearings used in mining or construction equipment can be under heavy loads and will need greases with additives that provide enhanced protection against metal-to-metal contact. Extreme pressure greases are a viable choice, as they form a strong barrier against wear.
• High-speed applications: Bearings that operate at high speeds, such as those found in electric motors, benefit from greases with lower viscosity to reduce drag and heat generation.

8.     Grease durability and reapplication needs

Durability is critical for applications where frequent relubrication is challenging. Greases with high oxidation resistance can maintain performance over longer periods, making them ideal for systems that are hard to access, such as wind turbines and conveyor systems. They can also help extend the time between relubrication intervals, reducing maintenance frequency and costs.

9.     Grease compatibility

Mixing incompatible greases can lead to hardening, softening and reduced grease effectiveness. Differences in thickener types, additives or base oils can cause these incompatibility issues. Before switching to a different grease, always verify compatibility with the existing grease. This can help avoid potentially costly mistakes.

Reviewing practices to avoid over-greasing

Adequate lubrication is about finding the right balance (see Figure 5). Maintenance teams should review their current practices, evaluate the grease types and confirm whether technicians can access the right tools and training. Even minor adjustments can significantly position the business for success. It’s an investment in the future reliability of every machine on the floor.

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