Ask any plant maintenance engineer what one of their biggest equipment issues is, and varnish problems will surely be at the top of the list. Varnish issues are an ongoing headache for many engineers, operators, and mechanics because they are so hard to spot. Once varnish issues start to appear, you can bet that equipment performance will be affected, and severe maintenance and equipment downtime may be needed. If left unchecked, varnish issues can significantly damage a system, especially in turbines, compressors, and hydraulic systems.
What is varnish?
You may not be familiar with varnish issues if you’re not an engineer, mechanic, or operator. You might even think that varnish is something you use in woodworking! But for those in the lubricant world, varnish is a big deal. So let’s explore what we mean by varnish and how it can affect your equipment.
In the lubricant world, varnish refers to the degradation of lubricants and oils. All oil-based products eventually start to degrade, and when that happens, varnish and sludge can begin to appear. Varnish appears as the by-product of the oil products breaking down. It can form deposits or sludge that will eventually gum up a machine or reduce effectiveness.
What does varnish look like?
Experienced mechanics learn to quickly spot the telltale signs of varnish problems on their equipment. It can take a few different forms, but two common types of varnish issues appear. The first is the formation of deposits on the equipment itself. According to an article from Machinery Lubrication, common varnish deposits may look like:
- Black deposits on seals
- Golf rings on valves
- Charcoal deposits on sleeve bearings
- Brown sludge that’s gooey and soft on oil filters
- Soot-like deposits on mechanical moving surfaces
No matter what form the varnish or sludge takes, these deposits will eventually reduce the effectiveness of the machinery’s movements and interfere with the flow of lubricants. In large-scale plant machinery or complex turbine or hydraulic systems, that can be a big problem. It’s difficult to take these large, complex machines apart to clean and remove these deposits.
The second way varnish can begin to affect machinery is by flowing through the machinery as part of the lubricant process. This occurs when the oil starts to degrade enough in one spot, forming varnish that is then filtered throughout the machinery. Unlike varnish deposits, this issue can affect the entirety of the machinery and reduce the overall effectiveness of the lubricants and oils used to keep the machinery in good working order.
What causes varnish?
Varnish issues always start as a by-product of oil degradation. Oil-based lubricants and products will naturally begin to break down over time. But certain conditions can cause this process to happen faster, like:
- Oxidation: Oxidation is the most common form of lubricant degradation because it’s a natural process. Oxidation is the chemical process that occurs when a substance comes into contact with oxygen, which is always happening. It’s why our apples turn brown after we take a bite and leave it, or rust forms on a car. But in the mechanical and lubricant world, oxidation can be a big problem. If this process occurs too quickly, it can affect the chemical makeup of a lubricant or oil-based product and reduce its effectiveness, which is why monitoring for oxidation is essential. Oxidation can happen faster in higher temperatures or when water, metal, or other products contaminate lubricant supplies.
- Thermal degradation: Heat doesn’t only cause oxidation problems in lubricants. Adiabatic compression can cause thermal degradation when oil comes into contact with a very hot surface (over 400 degrees Fahrenheit). This process can occur from steam, intense friction, and gas combustion, eventually leading to oil degradation and varnish formations.
- Electrostatic discharge: Electrostatic energy is generated by movement, and in complex machinery with many moving parts, it’s easily generated. But when too much electrostatic energy is created, it can begin to affect the internal molecular structure of oils and lubricants and eventually lead to degradation and varnish issues.
How do you monitor for varnish?
Now that we know what varnish is and why it occurs, it’s time to talk about how to monitor for varnish issues. As we mentioned, varnish issues are a challenging problem for plant engineers, large-scale machinery and heavy-duty equipment. In these complex pieces of machinery, it’s not easy to determine where varnish issues may be occurring or address them when they start. So to determine if your machinery is experiencing varnish problems, it’s essential to test for it.
Varnish measurement is calculated by taking samples from machinery and measuring for varnish using the Membrane Patch Colorimetry (MPC) test. The MPC test is completed by running a sample from a piece of machinery through a fine membrane filter, which captures contaminants. The membrane filter is designed to capture contaminants that are attracted to metal, are sticky, or larger than a certain number of microns. These captured contaminants color the membrane patch, which is then analyzed by a spectrophotometer. The spectrophotometer analyzes the color on the membrane, and typically the darker the color, the more likely it is that varnish issues are occurring.
The MPC test is the standard for measuring varnish issues, but it’s not the most accurate method. It doesn’t give any insight into the type of varnish issues or even what type of containment is being picked up by the test. Experienced analysts have learned to differentiate different results over time, but it’s still an imperfect process. The goal of the MPC test is to see if varnish is present and to make sure it’s below the acceptable ASTM standard.
Chevron has a new varnish testing method
The limits of the MPC test are a known problem, so Chevron, in conjunction with Polaris Laboratories, has designed a new testing method for varnish issues. Unlike the MPC test, this new testing method is designed to give insight into what is in your oil and the deeper issues causing varnish problems. This new method relies on more than just a color analysis like in MPC testing, but also takes into account the weight of the membrane patch once the sample has passed through it and how the containments on the patch respond to a polar solvent. This extra level of measurement allows the lab to differentiate between containments and determine what is and is not causing varnish problems. To learn more about this newly developed testing method, watch a webinar hosted by Chevron and Polaris.
Sign up for the LubeWatch® Oil Analysis Program
Varnish issues are a very common problem, and the only way to detect if they are occurring in your machinery is by oil analysis. We offer membership in the Chevron Lubewatch® Oil Analysis program for our customers. If you sign up for this program, we will teach you how to take proper samples from your equipment to send to our partners at Polaris Laboratories for analysis. Their technicians will perform a variety of testing to measure your lubricant and oil supplies. Using their findings, they will provide detailed lubricant and mechanical recommendations based on your equipment’s specific needs and how you use it. It’s a highly effective program that can help improve the effectiveness of your lubricant program, reducing equipment downtime and maintenance. If you’re interested in signing up for this program, please get in touch with your Greg’s Petroleum representative today!