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What Causes Hydraulic Fluid to Darken?

May 13, 2015 What Causes Hydraulic Fluid to Darken?

If you operate a hydraulic guillotine shearing machine, it is important to sample the hydraulic fluid regularly to ensure fluid properties and contamination levels are within an acceptable limit. When pulling a sample to send to the lab for a complete analysis, you may find the color of the hydraulic fluid has become much darker. What causes this and what should you do?

The Role Oxidation Plays

‚ÄčOxidation, or when oxygen attacks a hydraulic cutter’s hydraulic fluid, causes oil to become thicker and darker, which introduces excess heat into the system. During the oxidation process, polymerization results in sticky molecular structures, often referred to as “sludge”. These substances are dark in color and can leave deposits on all parts of the hydraulic cutter. Over a period of time, the hydraulic fluid degrades, while also darkening in color.

Overheating and Thermal Degradation

‚ÄčThermal degradation is triggered by excessive levels of heat and occurs when sufficient oxygen is not present. As a result, varnish formation begins in the fluids. In addition to darker hydraulic fluids, you are likely to notice that the hydraulic valves within the machine have taken on a golden hue. This indicates that varnish has been precipitating out of the fluid.

Proving Thermal Degradation is the Culprit

Thermal degradation can be proven by asking the lab to provide the FTIR curve and examining the wave number region where the levels of oxidation are measured. If there is a peak in the nitration region, you can ascertain that thermal degradation is the cause of the darker hydraulic fluid.

If thermal degradation is the cause of the problem, you will need to perform a root cause analysis to identify the actual heat source within the system. If you determine the heat source is related to a flaw in the system’s design, you can opt to use a separation technology to remove any thermal by-products from the hydraulic fluid. Unfortunately, this is only a temporary fix and a new system or system redesign will be needed to correct the problem.

If entrained air caused by an influx of entrained bubbles that form while flowing from the reservoir into higher pressure zones, such as the valves or pumps, appears to be the root cause of thermal degradation, there are products available to remove any bubbles within the hydraulic fluid. This will eliminate the problem.

If you decide you are in need of a new system, contacting a high quality hydraulic shearing machine manufacturer with a reputation for precision and excellence, such as Preci-Shear, is an absolute must. Preci-Shear’s shearing machine designs are based on cutting edge technology and their strength is a force to be reckoned. With machines that outperform the competition every time, there is no other place to buy your next hydraulic guillotine shearing machine. 


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