【Haichuan’s Insights from Other Sources】What do you think of machine pump oil mist recovery systems?

Does your device already have such a feature?

Oil mist lubrication technology is a new method of lubrication that utilizes the energy of compressed air to turn liquid lubricant into small particles ranging from 1um to 3um in size. These particles are suspended in the compressed air to form a mixture known as oil mist. Under the force of their own pressure, this oil mist is delivered through transmission pipelines to various locations where it is needed, thereby providing lubrication. I. Classification of oil mist lubrication: Oil mist lubrication methods are divided into pure oil mist lubrication and cleaning-type oil mist lubrication. (1) Pure oil mist lubrication, also known as “dry-box” oil mist lubrication, involves no oil level in the bearing housing; only the atomized oil provides lubrication. It is suitable for rolling bearings. The advantage of this atomized lubrication method is that it cleans and freshens the lubricating bearings with clean, fresh lubricating oil ； Eliminate the possibility of contaminated impurities and worn particles returning to the bearing ； There is no need to check or maintain a constant oil level ； The pump does not have any open areas that could allow the lubricant to become contaminated, so there is no need for manual oil replacement ； No need to discharge or replace lubricant, reducing the workload on workers ； It eliminates the heat generated by the bearings and slinger rings in stirring the lubricating oil, resulting in lower operating temperatures for the bearings ； Lubricating oil does not require cooling, and the cooling water for the bearing housing can be eliminated. (2) Lubrication using misted oil for cleaning purposes is known as \"wet-box\" oil mist lubrication. The oil level must be maintained at a certain level; the misted oil should fill and flow through the space above this oil level. The traditional oil chamber equipped with a splash lubrication device is still used to supply lubricant to lubricate the bearing surfaces. In both pure oil mist lubrication and cleaning-type oil mist lubrication technologies, a certain pressure is maintained inside the bearing housing, which prevents external contaminants from entering and ensures that a layer of oil film covers the exposed bearing surfaces. Cleaning-type atomized lubrication is suitable for sliding bearings, gearboxes, and other devices that require the oil level in the oil sump to be maintained. II. Characteristics of oil mist lubrication Oil mist lubrication belongs to the gas-liquid two-phase fluid cooling and lubrication technology. As a relatively advanced form of minimal lubrication, it has been successfully applied to various friction pairs such as rolling bearings, sliding bearings, gears, worm gears, and sprockets. In metallurgical machinery, oil mist lubrication is also used in applications such as the backup roll bearings of strip rolling mills, the working roll and backup roll bearings of four-roll cold rolling mills, and the rolling guides of high-speed wire rolling mills.

Oil mist lubrication appeared in Europe as early as the 1930s, and it wasn’t until the 1950s that it reached the United States. The oil mist lubrication system is a cost-effective, environmentally friendly, and safe centralized lubrication system that consists of a lubricator, nozzles, oil mist delivery pipes, and lubrication accessories. This lubrication system can continuously and efficiently automate the atomization of lubricant into fine particles, and precisely deliver fresh, clean misty lubricant to multiple lubrication points, covering the components to be lubricated evenly in order to lubricate and cool them. Oil mist nozzles can be selected based on the operating speed of the component to be lubricated, and each lubricator can be equipped with multiple nozzles. 1. Advantages of oil mist lubrication: It offers high lubrication efficiency; fresh oil mist can be dispersed via compressed air to the areas that require lubrication, thereby providing these areas with a good and even level of lubrication, which significantly extends the lifespan of the moving parts. Compressed air has a low specific heat and high flow velocity, making it easy to carry away the heat generated by friction; as a result, the temperature of the frictioning surfaces decreases, and the power consumption of the equipment is reduced. It significantly reduces the oil consumption of lubricants, ensures that the friction pairs always have fresh, adequate amounts of lubricant, and also has a spraying function that facilitates clean operation of the friction pairs. The thinner oil circulation lubrication system features a simple and lightweight structure, occupies less space, has low power consumption, is easy to maintain and manage, offers a high degree of automated control, and is cost-effective. Due to the pressure exerted by the oil mist, it can provide an effective seal, preventing external impurities and moisture from entering the friction pair. It has a wide range of applications; currently, oil mist lubrication is already being used in calendering equipment and metallurgical machinery. Such as: aluminum foil rolling mills, strip rolling mills, rotary kilns, ball mills, machinery for the petroleum and paper industries, fiber processing equipment, chain conveyors, vibrators, blowers, mineral processing machines, crushers, high-speed spindles, and various other types of machinery. The economic benefits are significant. The entire system has virtually no moving parts, resulting in high operational reliability and facilitating long-term safe operation. Centralized automatic lubrication is used, **reducing the workload on operators. In summary, the oil mist lubrication system has many advantages, and these advantages become even more evident when it is used in applications with light loads, multiple points of lubrication, and high dust levels. Especially at high speeds, the advantages of oil mist lubrication are more evident.

To deliver lubricant to the friction points, it is first necessary to atomize the lubricant into very fine particles using a lubricant atomization device. The surface tension of the lubricant particles after atomization is greater than the attractive force between those particles. As a result, the finely atomized lubricating oil is in a state close to gaseous. The atomized lubricant can, in this state, be delivered from the atomization device through a distributor to various friction points. However, since oil mist cannot form the oil film required for lubrication upon reaching the lubrication point, it is necessary to install appropriate condensation nozzles at those points depending on the operating conditions, so that the oil mist turns into droplet-shaped oil particles after passing through the nozzles. Oil mist lubrication systems are unable to convert the atomized lubricating oil back into liquid droplets entirely. In early versions of such systems, only 60–75% of the oil droplets reached the points where lubrication was needed; the remaining lubricating oil ended up in the atmosphere in mist form. With subsequent improvements, the efficiency of using lubricating oil increased to 90%, but still a small amount of it ended up in the atmosphere as mist, causing environmental pollution. Furthermore, oil mist can only be transported at a low speed, as it can remain stable only under laminar flow conditions. In a turbulent state, the particles of lubricating oil gather together due to mutual collisions, forming larger lubricating oil droplets, thereby returning to a liquid state once again. In this liquid state, the lubricant flows back into the container. Since the pressure of the oil mist is very low, in order to overcome the resistance encountered during its flow, pipes with a relatively large cross-sectional area must be used. It is also well known that the lubricant medium is delivered to the lubrication points within a turbulent air flow. However, when this method is used, problems arise in distributing the droplet-shaped lubricant brought in by the air flow to each lubrication point. At the branching point, gravity comes into play, causing the larger lubricant droplets to settle at the very bottom of the distributor. In this way, the distribution of lubricating oil becomes position-dependent. Someone once conducted such an experiment by putting into use a distributor with moving parts. But these tests did not yield any practical results. Later, another suggestion was put forward, which was to create special air vortices in the distributor. However, since the viscosity of the lubricant varies over a fairly wide range, this recommendation ultimately proved to be ineffective. Considering that lubricants cannot be subject to fluid dynamic calculations due to their varying viscosities, and that the ratio of air volume to lubricant volume also varies according to requirements, the installation location plays a quite important role. As a result, when lubrication is achieved using an oil-gas mixture brought in by turbulent air flow, it is usually necessary to allocate a specific amount of lubricant to each friction point based on the volume of the air flow.

Oil mist lubrication and oil sump lubrication: (1) It offers high lubrication efficiency; the oil mist can spread via compressed air to all friction pairs that require lubrication, thereby forming a clean and high-quality lubricating film on the surface of these friction pairs, which enables efficient lubrication and prevents rusting. (2) Compressed air has a low specific heat and high flow velocity, making it easy to carry away the heat generated by friction; as a result, the operating temperature of the bearings decreases by 10–15 degrees under pure oil mist conditions. (3) Reduce lubricant usage by 40%, thereby lowering costs. (4) Bearing failures related to lubrication are reduced by 90 %. (5) Bearing life can be extended by 6 times. (6) Due to the certain pressure of the oil mist, failures related to damaged shaft seals are reduced by 45% to 65%. (7) The oil mist lubrication system for pump sets features low weight, small footprint, low power consumption, low maintenance costs, and ease of centralized management. (8) The entire system has virtually no moving parts, resulting in high operational reliability and facilitating safe, long-term operation. In summary, the oil mist lubrication system has many advantages; it can significantly reduce the workload on workers and effectively improve their working conditions.

An oil mist lubrication system generally includes an oil mist generator, an oil mist main supply pipe, a downward pipe at the equipment to be lubricated, an oil mist distributor, oil mist nozzles, an oil mist supply pipe, an oil mist discharge collection assembly, an oil mist discharge pipe, an oil residue collection tank, ferrule connectors, etc. In special cases, there are also a purge-type oil mist discharge assembly and a purge-type level monitoring assembly.

A few years ago, HAICHUAN discussed the recovery of residual mist from oil mist lubrication in mechanical pumps: https://bbs.hcbbs.com/thread-1498407-1-1.html (Source: HAICHUAN Chemicals Forum)

Is oil mist a new technology or an old one?

This is a good example. Whether it’s new or old technologies, oil mist recovery is indeed a complex task; its widespread use can significantly reduce VOC emissions in the air.