Abstract: The harsh external environment can cause more severe pollution to the hydraulic and lubrication systems, and also affect testing. The article discusses the application of effective purification and online detection for heavily polluted hydraulic and lubrication systems through examples. Keywords: lubricating oil; Environmental pollution; Centrifugal purification; Pollution detection; Online detection Solid particle pollutants are the most common and harmful pollutants in hydraulic systems. According to data statistics, hydraulic system failures caused by solid particle pollutants account for 60% to 70% of hydraulic system failures. Solid particle pollutants can accelerate the wear of hydraulic components, block the gaps and ports of components, and cause control components to malfunction, leading to system failures. Therefore, effectively monitoring the pollution status of hydraulic oil and timely purifying the hydraulic oil in the system is of great significance for improving the reliability of hydraulic equipment and the service life of components. The main method for monitoring hydraulic oil contamination is through the use of a light shielded particle counter. The international oil grade control standards NAS1638, ISO4406, and China's military standard GJB420 all specify the classification of oil grades for monitoring using a light shielded particle counter. At present, particle counters can be divided into three categories according to their usage: desktop (laboratory) particle counters, portable particle counters, and online particle counters. Desktop (laboratory) particle counters are used for bottle sampling detection, while portable particle counters can be used for both bottle and online detection. These two practical applications are the most widespread. The commonly used technical methods for removing pollutants from oil are filter filtration, electrostatic filtration, centrifugal separation, etc. The high-precision filter element has high purification accuracy, but its service life is short and requires frequent replacement. It may also cause secondary pollution and cannot effectively filter out moisture and colloidal products in the oil. Electrostatic filtration technology has a small pressure difference, strong ability to absorb pollutants, and low noise. It has a purification effect on various pollutants in the oil, but there are also obvious shortcomings. The main reason is that the purification efficiency of the oil passing through once is low, and the speed of the oil flowing through the electrostatic filter should not be too fast, otherwise the purification effect will be very poor. Centrifuge separation technology has high purification accuracy, is not limited by oil flow rate, has strong pollution capacity, low resistance, and high work efficiency. The current mainstream purification technology is filtration technology.
1. Current Situation of Oil Pollution in a Chromium Industry Company The smelting workshop and pellet workshop under a certain chromium industry company. Introduction of Outotec (German OUTOTEC company) in the smelting workshop × 75MVA large OPKTM preheating sealed electric furnace with an annual output of 300000 tons of high carbon ferrochrome. The pellet workshop has introduced Outotec belt roasting oxidation pellet technology, with an annual production capacity of 700000 tons of SBSTM chromium ore pellets. High carbon ferrochromium is produced by continuous melting of chromite as raw material, silica as slag flux, and carbon reducing agent in an electrically heated submerged arc furnace, resulting in intermittent carbon reduction products. SBSTM chromium ore pellets are products produced by mixing chromium concentrate with a small amount of coke powder and going through processes such as grinding, filtration, pelletizing, and roasting.
The working conditions of both workshops are relatively poor due to manufacturing processes. The smelting workshop has a large amount of dust and a small amount of coal ash in the air. The working conditions of the pelletizing workshop are even worse, with workers cleaning the ground every day and rinsing the floating dust with water after cleaning. However, even so, it cannot avoid dust falling from the equipment and floating in the air.
Although both hydraulic and lubrication stations are strictly sealed, it is still difficult to avoid the impact of environmental pollution during refueling or replacing parts, as well as during system operation.
Taking the high and low pressure static pressure oil station of the ball mill in the pellet workshop as an example, this oil station is a dual system hydraulic and lubrication station, with a hydraulic system pressure of 12Mpa and a lubrication system pressure of 0.63Mpa. Equipped with two sets of pumps, one set of high-pressure gear pump (1 for backup and 1 for use), and one set of ordinary gear pump (1 for backup and 1 for use). The fuel tank has a capacity of 2500L and uses Mobil 630 Gear Oil.
The fuel tank of this oil station is cleaned once a year, which can remove approximately 2-3 kilograms of iron powder and oil mud mixture. The oil station has not changed the oil for 3 years and requires frequent cleaning of the filter element. Four high-pressure gear pumps (imported from Germany with a unit price of approximately 40000 RMB) have been damaged due to oil pollution.
How to solve the pollution problem of the oil station is an urgent problem that the company needs to solve.
In addition, the 501 hydraulic station and 502 hydraulic station in the pellet workshop, as well as the 25 meter high platform hydraulic station in the smelting workshop, all need to maintain a minimum cleanliness level of NAS 5. How to maintain such high oil cleanliness requirements in heavily polluted environments is also a challenge faced by the company.
2. Solution for centrifugal purification
The chromium industry company previously used traditional filtration methods for oil purification, which used the system's built-in filter element. The high and low pressure static pressure oil station of the ball mill has purchased a vacuum oil filter to remove water due to the possibility of water entering the oil. Due to its low purification efficiency and high purification cost, filter element purification cannot effectively solve the problem of oil pollution. The vacuum oil filter has good water removal efficiency, but its volume is large and inconvenient to use.
To solve the purification problem, the chromium industry company has applied a centrifugal oil purifier. This centrifuge has excellent solid impurity removal ability, with a maximum purification accuracy of NAS level 3, a purification speed of 8-10 times that of filtered products, and can simultaneously remove water and air from the oil.
The centrifugal oil purifier underwent purification tests at the hydraulic station of the slag scraper in the smelting workshop, the high and low pressure static pressure station of the ball mill in the ball milling workshop, and the 501 and 502 hydraulic stations.
Summary:
Choosing a centrifugal oil purifier with high purification accuracy and fast purification speed has solved the problem of oil purification for chromium industry companies with severe environmental pollution. The selection of online detection to evaluate system pollution has solved the problem of chromium companies being unable to accurately grasp the status of system oil pollution. The application of the above purification methods and detection methods enables the hydraulic lubrication stations of the chromium industry company to operate in a clean and stable environment for a long time, providing strong guarantees for the smooth production of the chromium industry company, while avoiding various economic losses caused by oil pollution. This case can provide valuable reference experience for enterprises of the same type.
