How can you scientifically determine whether hydraulic oil needs to be replaced?

The most scientific and economical method is to "change oil based on quality," meaning the decision to replace the oil should be made based on the actual condition of the oil. Below are key recommendations for determining hydraulic oil replacement intervals, compiled by the editors of Jianlong Hydraulic Technology, for your reference when replacing your hydraulic oil.

1. Oil Testing (Most Scientific and Recommended)

It is recommended to perform regular oil changes, such as every six months or every 1000 operating hours. Take an oil sample from the operating hydraulic press's oil tank and send it to a professional laboratory for testing. Key indicators to consider include:

1.1 Kinematic Viscosity: Has the oil changed by more than ±10% to ±15% of the new oil standard?

1.2 Acid Value: Has the oil increased by more than 0.3 to 0.5 mgKOH/g compared to new oil?

1.3 Moisture Content: Has it exceeded 0.1% (1000 ppm)?

1.4 Cleanliness (ISO Code): Has the solid particulate contamination level exceeded the target value (e.g., ISO 18/16/13)? 1.5 Spectral Elemental Analysis: Detects the content of wear metals (Fe, Cu), contaminants (Si), and additive elements (Zn, P).

Based on the above indicators, the laboratory will provide a clear report and recommendations: such as "Oil is qualified, continue to use" or "Oil deterioration, replace immediately."

2. On-site Visual Inspection (Assisted Judgment)

2.1 Color and Smell: Place a drop of oil on white filter paper. New oil is usually light yellow and transparent. If the oil becomes dark brown, turbid, or black, or has a pungent, sour, or burnt odor, it indicates severe oxidation.

2.2 Feel: Feel the oil with your fingers to feel for noticeable graininess and decreased lubricity.

2.3 Filter Condition: If the return or recirculating filter frequently displays blockage alarms, it indicates rapid oil contamination and is a key sign of oil deterioration.

The hydraulic oil replacement cycle is dynamic and should be determined based on actual usage. Overall, oil testing is the most cost-effective and scientific method. It can avoid unnecessary oil changes and provide early warning of equipment failure. If testing conditions are unavailable, consider the severity of the operating conditions (high temperature, high load, and harsh environment) and on-site observation to appropriately shorten the manufacturer's recommended conservative oil change interval. Frequent oil changes are always much cheaper than replacing pumps and valves, especially in high-temperature and highly polluted environments. When changing oil, be sure to also replace all hydraulic oil filters and clean the oil tank, otherwise the new oil will be quickly contaminated by old oil sludge. For more information/advice on hydraulic oil change intervals or to purchase other high-quality hydraulic presses, please contact us (or scan the WhatsApp QR code below). Jianlong Hydraulic Technology will provide you with personalized, customized professional solutions and is dedicated to serving you.