Introduction

Grease is one of the components that works out of sight, inside the bearings and housings. As a result, its problems often go unnoticed until the equipment fails. It is also rarely tested during servicing. The grease problem does not occur from its chemical formulation alone; various other factors like handling, application methods, storage, and operating conditions also play a key role in these issues. Let’s dive into these issues and ways to troubleshoot them.

Why Does Grease Harden?

Hardening is also known as caking. It happens when the grease dries up or forms a stiff, crusty layer that can no longer lubricate properly. Below are some of the causes of hardening:

• Excessive oil separation or evaporation, especially at high temperatures.
• Mixing the grease with incompatible thickeners.
• Over-greasing sealed housings.

Grease compatibility deserves special attention. Mixing two incompatible greases can create a runny mess that leaks out a hard, rock-like material. Although thickeners are the biggest cause of incompatibility, base oils and additives can also play a key role.

How to Fix It: To fix this issue, use a grease made with synthetic base oils, which resist evaporation better than mineral oils. Also purge the old grease as fully as possible before changing the product, and monitor temperatures after the changeover.

Why Grease Bleeds?

Bleeding occurs when oil separates from the thickener and leaks out, leaving behind a dry, less effective grease. Various factors can trigger this, including heat, vibration, gravity, poor formulation, or long storage. If the separation is minimal, around a quarter or an inch, the oil can be stirred back in. However, if the grease looks heavily separated or runny, discard it. Stirring is only a temporary fix for grease already in service.

How to Fix It: To fix this issue, choose a grease with a more stable thickener. For example, one can use lithium complex grease or calcium sulfonate grease instead of basic lithium grease to improve mechanical stability. It is also important to control storage temperatures and rotate stock.

Why Grease Washes Out?

Water washout is a common problem for equipment exposed to washdowns, rain, or process water, and for shielded bearings in wet areas. When water strips grease from the bearing, it leaves the metal surface unprotected, resulting in wear and corrosion. Different grease types have different water-resistance capacities. For example, calcium sulfonate, calcium complex and aluminium complex greases offer excellent water resistance. Lithium complex greases can perform well but may struggle in extremely wet conditions. Water can turn grease milky, a clear sign of contamination.

How to Fix It: To fix this issue, first remove or reduce the source of water. Then select a grease designed for wet conditions, ideally water-resistant and hydrolytically stable. Choosing good seals and guards also helps in reducing water ingress.

Why Does Grease Get Contaminated?

Contamination is one of the biggest challenges in grease-based applications. It can occur due to various factors like dust, dirt, water, process chemicals, and wear debris from the bearing itself. Common causes include improper storage, careless handling, and faulty seals. Below stated are some signs of contamination:

• Discolouration, including grease turning black or dark.
• A foul or burnt smell.
• Change in texture or consistency.
• Visible foreign particles
• A milky appearance due to water.

Dark grease often signals oxidation, overheating or bearing debris. In some of the rare cases, stray electrical current passing through a bearing can also cause arcing damage.

How to Fix It: The first and foremost step is to remove the source of contamination. Next, check storage conditions, inspect seals, and look for equipment faults. You should also clean the lubrication system and replace contaminated grease with fresh, clean grease. Use a dedicated, clearly labelled grease gun and close the container properly to reduce the risk.

Over Greasing and Overheating

Overgreasing is a major problem because it raises internal pressure, can damage bearing seals, and increases operating temperatures. It also speeds up oxidation, bleeding and hardening, which is often a common starting point for other problems. To prevent this issue, add small amounts of grease at a time and monitor the temperature. If it falls, increase the greasing frequency; if it rises, purge the excess grease and reduce the fill amount.

How to Prevent Grease Problems

Below are some of the ways to prevent grease problems:

• Select the right grease for the speed, load, temperature and environment.
• Always check grease compatibility before mixing.
• Store grease in clean, cool, dry conditions, and use the older stock first.
• Refer to the manufacturer's guide and supplier recommendations for quantity and interval.
• Inspect the grease regularly for any signs of damage.

Take Away

This is a brief explanation of different types of issues that can arise when using grease, how to fix them, and how to prevent grease problems. We hope this information will be effective for you. Please let us know through your valuable feedback and suggestions in the drop box.