What causes lubrication to fail?

Reliability-Centered Maintenance (RCM) is becoming more popular in manufacturing and process plants in determining failure modes of equipment and processes. When we understand the failure modes, a complete and strategic maintenance program can be developed. This program outlines the maintenance processes needed to keep the equipment or plant functioning the way it was designed.

Many other uses are coming to light for the use of the RCM process methodology. I have used this failure modes process for many of my training programs on motors, mechanical seals and even V-belts. For this article, we will look at lubricants and a program to address it. The failure modes can then be individually addressed and a complete strategy developed for eliminating them.

History of lubrication
If we look back at the history of lubrication, we find efforts more than 2,000 years ago to use many different products as lubricants. As mankind developed equipment to gain mechanical edge, methods to take the advantage of moving heavy materials and rotating equipment, the needs of lubricants became important. Many different lubricants, made from waxes, vegetable oils and fish oils, were used to help with this mechanical revolution. All of these lubricant types had major failure modes such as rapid temperature degradation and oxidation.

In these early lubrication years, it was very easy to find failure modes. Most lubricants would only last a few days or weeks. This was with mechanical components that did not rotate very fast and did not develop the loads we work with today. The engineers of the age were challenged regularly with ways to eliminate the failures of the lubricants. The mixing of many different products and adding soaps were just a few of the methods attempted at eliminating friction issues.

Then in the 1800s, the discovery of petroleum oil immediately started a revolution in equipment lubrication. As we learned how to refine this petroleum product, it quickly became apparent that equipment could be eveloped that could operate faster and under greater loads and still maintain a film barrier to eliminate friction and metal to metal contact.

Lubrication became easy and everyone assumed, even up to today, that lubricants have longer life than they actually do. As long as the lubricant was in there and felt good, it was doing its job. I can remember growing up on the farm and my dad telling me to change the oil in the tractor or the truck because it had been a while or it was pretty black. I would grab the funnel from the nail in the garage and pull out the shop rag that was stuffed into it and take a quick look in the funnel. I would then remove the small bugs and dust that had been captured over the last few months in the old oil film. I would usually get all the ones I could easily see.

I can still remember asking about some of the other dirt in the funnel and he said, “Don’t worry about it. That’s what the filter is for.” You know that shop rag and funnel was the same one I used from about 8 years old until I moved out when I was 18. I returned to the farm many times and helped him numerous times many years after. The rag changed at some time, but the same funnel was used until he moved from the farm. Was that funnel and rag a failure mode?

Most of industry has also operated major plants and processes with the same thought process that my dad had in the 1970s. If it looks OK, then it’s probably OK for the machine. The difference is our understanding of lubrication excellence and what it takes to make our equipment last forever.

Lubrication failure modes
Let’s look at common failures modes in lubrication.

Temperature: Temperature of the lubricant determines the lubricant life. So, how do we control temperature in our process?

Temperature Failure Modes

• Overloading
• Over-greasing
• Location (no air movement)
• High viscosity
• Wrong viscosity
• Poor lube circulation
• Improper cooling
• No lube cooling
• Multi-speed/load components (high-speed input, low-speed outlet)
• Thermal conditions
• Sunlight
• Ambient atmosphere
• Process heat

Are there ways to eliminate temperature failure modes which shorten lubricant life? There are many ways to reduce or eliminate the cause of temperature life reduction of the lubricant. Look at the failure modes above and determine how to eliminate each of them; most can be eliminated. A better understanding of the life of the lubricant based on temperature must be attained. Maybe a better lube!

Moisture: Moisture is another major contributor to lubrication failures. Let’s look at some of these.

Moisture Failure Modes

• Ambient conditions/humidity/rain
• Washdown practices
• Hot operation, then shutdown
• Improper seals on equipment
• Additive depletion
• Lubrication storage methods
• Lube equipment storage methods
• Improper vent/breather device
• Lack of or depleted desiccant
• No vent/breather device
• Start/stop operations
• Leaking cooling system
• Dipsticks

All the issues related to moisture can be controlled or eliminated with training and readily available products and systems. Moisture is one of the main failures of lubricating oils because it greatly increases the oxidation rate of the lubricant.

Foreign material: Foreign materials in oils such as particles very seldom affect the lubrication oils but greatly decrease the life of the equipment components. Below are some of the sources of the failure modes.

Foreign Material/Particles

• Ambient conditions
• Contaminated new oil
• Oil lube practices
• Component wear particles
• Greasing practices
• Improper filtration of lubes
• No filtration practices
• Combustion
• Improper external vent filtration
• No vent breather filter
• Particles in new grease
• Poor lube storage methods
• Poor lube equipment storage

Foreign materials in the particle form are probably the easiest to eliminate and remove, but it takes training and equipment – from the lubricants coming into the plant all the way through the lubricants in the equipment during operation. They need to be removed in the lubes and eliminated from entry into the equipment.

Viscosity: Viscosity is another area that affects equipment life. Improper or changing viscosity can reduce the life of components by 30 percent. In hydraulic systems, viscosity cannot only shorten the component life but reduce the operational functions of the process.

Viscosity Failures

• Temperature
• Lube procedures
• Mixing, storage/receiving
• Oxidation
• Contamination
• Moisture/chemicals
• No/lack of additives

I have heard a number of times, “This is exactly what the manufacturer told me to use for the oil or grease.”  The manufacturer was probably correct for the ideal conditions for the system. But not many plants’ operations have ideal conditions.  Not many plants have procedures and processes in place to eliminate or control the conditions in the box above.

Contamination: Care must be taken in lubrication storage or use to make sure that contaminants can never get into the lubricants.

Contamination

• Environmental condition
• Leaking coils
• Lube practices
• Lube storage area
• Lube vendor
• Lube equipment procedures

The purpose of RCM is to identify failure modes and then develop strategies to eliminate them. Determine the strategy to eliminate each failure mode. Is the failure solved with a program, process, procedure or redesign?

Take these 50 failure modes and use your ability to go back to your operations and start the process of making positive changes. Lubrication excellence training will start your elimination process.