Selection of Lubricating Oil and Equipment Lubrication Management in Steel Plants
author: Leila
2024-08-12
Equipment lubrication in steel plants is a huge challenge: high temperature, humidity, easy contact with water, and high humidity in the air. Equipment is easily damaged after entering water. In addition, lubricating oil is also very sensitive to water. This article mainly analyzes the harm of water in steel plants to equipment lubrication and how to minimize the harm of water.
Moisture is a major problem faced by the centralized lubrication system of steel plants and an important aspect of lubrication maintenance. Moisture should be controlled within 0.5% as much as possible.
There are two main sources of moisture entering the centralized lubrication system: rolling cooling water and condensed water, especially condensed water caused by shutdown. Moisture exists in three
forms: dissolved water (water dissolved in oil), emulsified water, and free water (water separated from oil). Among them, emulsified water is the most harmful because the lubricity of oil will be destroyed after emulsification, and emulsified water is difficult to remove. The harm of moisture to equipment is mainly reflected in two aspects-causing rust on the metal surface of steel and equipment, causing lubrication problems and ultimately causing equipment damage.
The specific hazards of water are as follows:
Causes poor oil circulation in the centralized system
Causes clogging of the filter system, causing problems with the filter system
Causes lubricating oil to produce sludge
Accelerates the oxidation rate of lubricating oil, causing lubricating oil to deteriorate before the oil change period
Dilutes the viscosity of lubricating oil, weakens the strength of oil film, and causes metal wear
Easy to breed bacteria, causing oil deterioration
Reduced anti-foaming and air release, resulting in increased foam, poor lubrication, and increased oil temperature
Causes metal rust and corrosion
Reduced lubricating oil performance, affects the effect of additives, and weakens the effect of anti-wear agents (ZDDP)
Causes clogging of the filter system, causing problems with the filter system
Causes lubricating oil to produce sludge
Accelerates the oxidation rate of lubricating oil, causing lubricating oil to deteriorate before the oil change period
Dilutes the viscosity of lubricating oil, weakens the strength of oil film, and causes metal wear
Easy to breed bacteria, causing oil deterioration
Reduced anti-foaming and air release, resulting in increased foam, poor lubrication, and increased oil temperature
Causes metal rust and corrosion
Reduced lubricating oil performance, affects the effect of additives, and weakens the effect of anti-wear agents (ZDDP)
The ultimate consequence of these effects is metal wear and component failure. If it occurs on the main bearing, it will affect the entire production process. Although the harm of water is great, it is difficult to avoid for steel mills. Therefore, a more realistic choice is to use lubricating oil with good performance that can meet the working conditions of steel mills. For the humid and water-heavy working conditions of steel mills, the demulsibility of lubricating oil is very important.
Emulsification of lubricating oil:
When water is mixed into lubricating oil, its transparency decreases after being stirred, and its color turns white, which looks a bit like milk. This is commonly known as emulsification of lubricating oil.
Anti-emulsification:
Anti-emulsification is also called demulsification ability, which refers to the ability of lubricating oil to separate water. When lubricating oil and water are mixed, a milk-like emulsion will be formed. The lubricity of the emulsified oil is destroyed. Therefore, lubricating oil should have good oil-water separation ability, separate water and oil into layers, and water is generally in the lower layer, so that it is easy to drain and filter out water, thereby avoiding emulsification.
Lubricating oil is composed of base oil and additives. Additives have an important influence on the anti-emulsification of lubricating oil.
To deal with the moisture problem in steel mills, lubricating oil is required to quickly separate oil and water. Other properties include rust resistance, which can prevent metal parts from rusting, and good antioxidant and anti-corrosion properties.
The common indicators of lubricant's demulsification and oil-water separation ability are ASTM, and there is also a famous MORGOIL certification. Lubricants that have passed the MORGOIL certification have strong demulsification. This certification originated in the 1990s. Morgan initiated a standard on the oil-water separation ability of lubricants at room temperature, which provided a reference certification for the steel industry to select high-quality lubricants.
Other well-known steel equipment manufacturers (OEM) certifications, such as Morgan, Danieli and other well-known steel and metallurgical equipment manufacturers, as well as industry-leading bearing companies SKF, FAG, etc., should pay attention to these relevant information when purchasing lubricants.
In addition to choosing high-quality lubricants, other measures are also important for waterproofing, as follows:
1. Seal:
If the seal fails, a large amount of water and other impurities will enter the lubrication system. Choose a suitable seal (applicable temperature, size, shaft speed, pressure, shaft tolerance, seal and oil compatibility). Seal failure will cause water to enter the oil and cause the liquid level to rise. Daily maintenance should pay attention to observe whether the seal is aging or cracking.
2. Appropriate heating:
If there is a lot of moisture on site, it can be heated appropriately. However, be careful not to overheat the oil temperature (it is best to control it within 62°C). High oil temperature can help water vapor escape, but too high oil temperature will cause oil deterioration.
3. Use spare oil tank:
If conditions permit, using a spare oil tank (dual oil tank system) can help extend the service life of the lubricant. If the water content of one of the oil tanks reaches the saturation limit, switch to the spare oil tank, and then separate and drain the water in the water inlet tank through the oil-water separator. This does not affect the production process, but also protects the equipment and handles the water in the lubricant in time.
4. Use water removal equipment:
Lubricant oil water removal equipment can help us remove water from the lubricant. Common water removal equipment includes centrifugal and vacuum types. The advantage of centrifugal oil-water separators is that they are faster, but they cannot remove dissolved water. Vacuum water removal equipment is slower, but it can remove all dissolved water, and it is not easy to cause the loss of additives in the lubricant.
5. Drain the equipment regularly:
Generally, water is heavier than oil. Drain the equipment regularly to drain the free water separated from the bottom of the oil tank. The frequency of drainage depends on the situation.
6. Perform oil testing regularly:
It can detect the state of the lubricating oil, including the consumption and oxidation of additives and base oil, understand the oil quality, check whether the water content and anti-emulsification performance in the oil are still normal, and also find out whether there are any abnormalities inside the equipment.
Uses and classifications of industrial lubricants
Meaning of engine oil index
