Hydraulic support special lubricating oil quality screening methods
Appearance check
Color: The color of normal lubricant for hydraulic support should be uniform. If the color is too dark or has obvious discoloration phenomenon, it may indicate that the lubricant has been oxidized or contaminated. For example, the new high-quality hydraulic oil is usually light yellow or light brown, if it becomes dark brown or even black, you need to be vigilant about its quality.
Transparency: clarity is one of the most important characteristics of a quality lubricant. If the lubricant appears cloudy, precipitation or suspended matter, it may contain impurities, water or additives decomposition products, its quality may have defects.
Odor: Generally speaking, quality lubricants should have a slight petroleum odor. If you smell pungent odor, such as sour, burnt, etc., it may be the lubricant oxidation or thermal decomposition, its performance has been seriously affected.
Physical and chemical performance index test
Viscosity determination: use viscometer to determine the kinematic viscosity of lubricant at different temperatures according to relevant standards. For example, the kinematic viscosity at 40℃ and 100℃ should meet the specifications of the hydraulic support lubricant. If the viscosity deviates too much from the standard range, it will lead to poor lubrication or increased energy consumption and other problems. For example, if the viscosity at 40℃ is lower than the lower limit of the standard, it may not be able to provide sufficient oil film protection during low temperature startup; while higher than the upper limit will increase the system resistance and increase the oil temperature.
Acid Value Measurement: The acid value reflects the amount of acid in the lubricant. High acid value indicates that the lubricant has been oxidized or contaminated, and the acid will corrode the metal parts of the hydraulic support. Generally, the acid value is determined by acid-base titration method, and the acid value of qualified lubricant for hydraulic support should be controlled at a low level, such as no more than 0.2mgKOH/g.
Flash point determination: Flash point is the lowest temperature at which the lubricant is heated under the specified conditions to the point where the mixture formed by its vapor and air contacts the flame when flash fire occurs. Lubricating oil with low flash point is easy to volatilize under high temperature environment, which will not only cause oil loss, but also may lead to fire hazards. The flash point of lubricating oil for hydraulic support is usually high, generally above 200℃.
Pour Point Measurement: Pour point is the lowest temperature at which the lubricant can flow under specified conditions. For hydraulic supports used in cold areas, the pour point of the lubricant must be low enough to ensure that the equipment can be started normally in a low-temperature environment. For example, in cold northern mining areas, the pour point of lubricants for hydraulic supports should be 5 - 10℃ below the lowest local winter temperature.
Additive Composition Analysis
Antiwear testing: Spectral analysis and other methods are used to determine whether the lubricant contains the right amount of antiwear additives, such as zinc dialkyl dithiophosphate (ZDDP). Antiwear additives can form a protective film on the metal surface and improve the anti-wear performance of the lubricant. If the content of antiwear agent is insufficient, it will increase the wear of the moving parts of the hydraulic support.
Antioxidant testing: Analyze the type and content of antioxidants in the lubricant. Common antioxidants include phenols, amines and so on. Sufficient antioxidants can effectively extend the service life of the lubricant and prevent it from oxidizing and deteriorating prematurely. For example, the content of antioxidants in lubricants can be accurately determined using High Performance Liquid Chromatography (HPLC) and compared with standard formulations.
Rust inhibitor testing: Checking the presence of rust inhibitor components such as calcium sulfonate and other rust inhibitors. Rust inhibitors are able to form an antirust film on the metal surface, preventing water and oxygen from attacking the metal. Determine whether the content of antirust agent meets the requirements through chemical analysis method to guarantee the antirust performance of hydraulic support.
Translated with DeepL.com (free version)
