Lubrication of equipment 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 water ingress, and lubricating oil is also very taboo against moisture. This article mainly analyzes the harm of moisture in steel plants to equipment lubrication and how to minimize the harm of moisture.
Moisture is a major problem faced by the centralized lubrication system in steel plants, and it is an important aspect of lubrication maintenance. Moisture should be controlled within 0.5% as much as possible. Water entering the centralized lubrication system mainly comes from two sources: rolling cooling water and condensate, especially the condensate caused by shutdown. Water exists in three forms: dissolved water (water dissolved in oil), emulsified water, and free water (water separated from oil). Among them, emulsified water is particularly harmful because the lubrication of oil is 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 surfaces of steel and equipment, causing lubrication problems, and ultimately leading to equipment damage.
The lubrication station quickly discharges and removes impurities through a fluid disc separator
The specific hazards of moisture are as follows:
Causing poor oil circulation within the centralized system
Causing blockage of the filtration system, resulting in filtration system problems
● Causing the formation of sludge in lubricating oil
Accelerate the oxidation rate of lubricating oil, causing it to deteriorate before the oil change period
Dilute the viscosity of lubricating oil, weaken the strength of the oil film, and cause metal wear
Easy to breed bacteria, causing oil to spoil
● Reduce anti foaming property and air release property, resulting in increased foam, poor lubrication, and increased oil temperature
Causing metal rusting and corrosion
Reduce the performance of lubricating oil, affect the effect of additives, and weaken the effect of anti-wear agents (ZDDP)
The ultimate consequence of these actions is metal wear and component failure. If it occurs on the main bearing, it will affect the entire production process. Although the harm of moisture is significant, it is difficult to avoid for steel plants. Therefore, a more practical choice is to use lubricating oil with good performance, which can meet the working requirements of steel plants. The demulsibility of lubricating oil is crucial for the humid and heavy moisture conditions in steel plants.
Emulsification of lubricating oil:
The lubricating oil is mixed with water, and after being stirred, its transparency decreases, its color turns white, and it looks a bit like milk, commonly known as lubricating oil emulsification.
Anti emulsifying properties:
Anti emulsification ability, also known as demulsification ability, refers to the ability of lubricating oil to remove water. When lubricating oil and water are mixed, they form a milk like emulsion, which disrupts the lubricity of the emulsified oil. Therefore, lubricating oil should have good oil-water separation ability, separating water and oil into layers, with water generally in the lower layer. This facilitates the drainage and filtration of water, thus avoiding emulsification.
Lubricating oil is composed of base oil and additives, which have a significant impact on the anti emulsification properties of lubricating oil.
To deal with the moisture problem in steel plants, it is required that lubricating oil can quickly remove oil moisture. Other properties include rust resistance, which can prevent metal parts from rusting, as well as good antioxidant and anti-corrosion properties.
The common indicators for the anti emulsification and oil-water separation ability of lubricating oil include ASTM, and there is also a famous MORGOIL certification. Lubricating oil certified by MORGOIL has strong anti emulsification ability. This certification originated in the 1990s, when Morgan initiated a standard on the oil-water separation ability of lubricating oil at room temperature, providing a reference certification for the steel industry to choose high-quality lubricating oil.
Certification from other well-known steel equipment manufacturers (OEMs), such as Morgan, Danieli, and other well-known steel metallurgical equipment manufacturers, as well as industry-leading bearing companies such as SKF and FAG, should be noted when selecting lubricants.
In addition to using high-quality lubricating oil, other measures are also important for waterproofing, as follows:
1. Sealing:
If the seal fails, a large amount of water and other impurities will enter the lubrication system. Choose appropriate seals (applicable temperature, size, shaft speed, pressure, shaft tolerance, compatibility between seals and oil). Seal failure can cause water to enter the oil and cause an increase in liquid level. Daily maintenance should pay attention to observing the seals for aging and cracking.
2. Proper heating:
If there is a lot of moisture on site, it can be heated appropriately. However, please note that the oil temperature should not be too high (easily controlled within 62 ℃). High oil temperature can help water vapor escape, but too high oil temperature can cause oil deterioration.
3. Use spare fuel tank:
If conditions permit, using a backup oil tank (dual tank system) can help extend the service life of lubricating oil. If one of the oil tanks reaches its saturation limit, switch to the backup oil tank, and then separate and discharge the water in the inlet oil tank through an oil-water separator. This does not affect the production process, but also protects the equipment and promptly handles the water in the lubricating oil.
4. Use of water removal equipment:
Lubricating oil dehydration equipment can help us remove water from lubricating oil. Common water removal equipment includes centrifugal and vacuum types. The advantage of centrifugal oil-water separators is their fast speed, but they cannot remove dissolved water. Vacuum water removal equipment has a slower speed, but it can remove all dissolved water and is also less likely to cause loss of additives in lubricating oil.
5. Regular drainage of equipment:
In general, water is heavier than oil. Regularly drain the equipment to remove free water from the bottom of the oil tank. The frequency of drainage depends on the situation.
6. Regular oil testing:
It is possible to detect the status of 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 detect whether there are any abnormal situations inside the equipment.
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