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How the Oil Flash Point Test Works & What it Tells You
Effective preventative and even predictive maintenance involves identifying small problems before they become larger, more expensive issues that cause costly downtime. Oil flash point testing provides valuable insights into oil quality and contaminant levels, informing future maintenance and repair decisions.
The guide below explores what an oil’s flash point means, how to test it, and ways to apply any valuable information you receive moving forward.
What Is an Oil Flash Point Test?
Oil flash point tests determine the lowest temperature at which oil vapors momentarily ignite when exposed to an ignition source.
Laboratory technicians use oil flash point tests to measure the flash point of motor oils and assess fire and explosion hazards. In addition to informing the handling and storage of automotive oils, oil flash point tests are often included on an oil analysis report when screening for contamination.
It’s important to distinguish an oil’s flash point from its fire point and autoignition temperature. The fire point is typically 50 to 75 degrees Fahrenheit higher than the flash point. An oil reaches its fire point when the vapors hovering above the surface sustain a flame for a minimum of five seconds.
In contrast, the oil’s autoignition temperature describes the point at which the vapor combusts without any ignition source. Most mineral oils have an autoignition temperature ranging from 650 to 700 degrees Fahrenheit.
How Does an Oil Flash Point Test Work?
There are two primary methods for conducting an oil flash point test, both of which typically yield different readings for samples from the same oil. The difference in readings between the Cleveland Open Cup and the Pensky-Marten Closed Cup methods stems from the procedures used to test the oil’s flash point. Technicians can also use a smaller sample for what’s known as a Small Scale Closed Cup test.
It’s important to understand that oil flash points typically fall within a range because the exact method of measurement depends on multiple variables, including the oil’s composition.
For instance, mineral oils normally flash around 440 degrees Fahrenheit, while synthetics have a higher flash point. Oil contaminated with gas will flash below 350 degrees Fahrenheit, while diesel-contaminated oil flashes between 380 and 410 degrees Fahrenheit.
During the oil flash point test, a pilot flame heats the oil sample at a controlled rate, and at set intervals, the machine introduces an ignition source. This process continues until the oil flashes, which occurs when the vapors floating just above the oil’s surface ignite for a brief moment. Explore more intricacies of the three types of oil flash point tests below.
Cleveland Open Cup
The Cleveland Open Cup oil flash point test procedure begins with a 100 mL sample of oil heated at a controlled rate. The testing device measures the oil’s temperature as it increases, recording the point at which the ignition source, when passed over the oil’s surface, causes the oil vapors to ignite.
This method is one of the most commonly used Open Cup oil flash point tests, typically for oils with a known flash point between 175 and 752 degrees Fahrenheit.
Pensky-Marten Closed Cup
In contrast to the Cleveland Open Cup method, the Pensky-Marten Closed Cup oil flash testing protocol requires a 75 mL sample of oil held within a closed container. Again, the oil is heated, and a flame is introduced into the sealed cup at set intervals. The oil’s flash point is detected electronically.
Oils with a flash point between 104 and 698 degrees Fahrenheit are often tested using this method. The closed environment enables a more accurate reading than is achieved using the Cleveland Open Cup method.
Small Scale Closed Cup
The Small Scale Closed Cup method is preferable for smaller samples and faster results. The test requires heating 4 mL or less of the sampled oil to a predetermined temperature, typically at or near the estimated flash point.
A test flame is introduced; if the oil flashes, the flash point is equal to or lower than the set temperature, but if the oil doesn’t flash, the test is repeated at one to two-degree increments until a flash occurs.
What Can You Learn From an Oil Flash Point Test?
Oil flash point tests were originally designed to determine whether a fluid was flammable (flash point below 100 degrees Fahrenheit) or combustible (flash point above 100 degrees Fahrenheit).
Modern-day tests allow you to:
- Identify signs of oil contamination or degradation
- Gather insights into oil quality and behavior
- Determine, in combination with other tests, the base oil type and refining quality
For example, if the results of the oil flash test show a lower flash point than what’s expected, the oil is likely contaminated by fuel or solvent or there may be thermal cracking or microdieseling occurring. In contrast, a higher reading can result from polymerization, antifreeze buildup, water contamination, or the evaporation of the oil’s lighter fractions.
When Should You Use a Flash Point Test?
Equipment maintenance crews often rely on oil flash point testing as part of routine oil analysis and preventative maintenance measures. If the machine in question begins to overheat or exhibit higher operating temperatures or the oil’s viscosity unexpectedly drops, an oil flash point test can help identify contamination or fuel dilution.
Oil flash point tests can also help evaluate oil integrity, especially if you plan to continue using a particular oil.
Know Your Oil: Flash Point Testing As a Preventive Tool
As a top-tier oil, fuel, and lubricant distributor, Cadence understands the importance of identifying oil issues before they become significant equipment problems. An oil flash point test plays a significant role in preventative maintenance, especially in determining contamination levels.
Contact us at 336-629-2061 to discover how our oil analysis services can help keep your operations running smoothly and efficiently.
Sources:
Flash Point - an overview | ScienceDirect Topics
IEC 60079-10-1:2020 | International Electrotechnical Commission