What Is a Mist Collector?
A mist collector is a device that sucks oil mist generated during cutting operations of machine tools, separates the oil from the air, and collects it.
Oil mist is the result of oil that has turned into smoke and diffused into the air. Most oil mist is classified as hazardous substance, and must be removed without fail because it is harmful to the human body and can cause malfunctions if it adheres to other machinery.
Currently, mist collectors can remove oil mist by using filters, by electrically electrifying the mist, or by centrifugal force.
Applications of Mist Collectors
Mist collectors are used to collect mist oil generated when using NC lathes, drilling machines, and machining centers.
Oil mist is especially generated during cutting operations, especially high-pressure lubrication, grinding, and high-speed cutting operations where the cutting oil is subjected to high shear. Mist collectors are used in conjunction with such machine tools.
Mist Collector Principle
There are three main types of mist collectors: filter-type, electrostatic precipitator-type, and centrifugal separator-type. The following is an explanation of the principle of each type:
1. Filter-Type
Filter-type mist collectors remove oil mist by filtration using a filter. This is the most common type of mist collector, and filters are usually layered.
The advantages of the filter-type are that it is simple in structure, inexpensive to install, easy to manage on site, and safe. The disadvantages include the need for periodic maintenance such as filter replacement, the increased power consumption of the electric motor due to the ventilation resistance of the filter, and the fact that the replaced filter must be disposed of as industrial waste.
2. Electrostatic Precipitator
Electrostatic precipitator is a type of oil collector in which oil mist is given an electric charge by corona discharge using high voltage, and oil is then adsorbed and collected by the electrostatic force of the voltage-using negative electrode plate. Corona discharge is a phenomenon in which a part of a gas that normally does not conduct electricity is ionized when a high voltage is applied, and electrons and positive and negative ions are generated and move in an electric field, causing an electric current to flow in the gas.
The advantages of electrostatic precipitator are that it can collect even very fine oil mist particles of 1 μm or less. It does not use filters, and so does not need filter replacements or disposal. Additionally, electrodes can be reused by cleaning. On the other hand, demerits include high installation costs, the need for careful handling of high voltages, and the time and cost required for maintenance and cleaning of electrodes.
3. Centrifugal Separation-Type
The centrifugal separation-type is a mist collector that uses centrifugal force to break down the air containing collected oil mist into air and oil mist. The advantage of the centrifugal separation-type is that it is easier to maintain and install than other types of systems. However, it is not suitable for collecting oil mist particles finer than 1μm.
Other Information on mist collectors
1. Installation of Mist Collector
Care must be taken when installing mist collectors, depending on the machine in which they are installed. If oil mist is not collected properly, it can cause health hazards to workers and even lead to malfunctions of air conditioning equipment. Mist collectors can be installed in three different ways. It is important to choose the one that best suits the machine tool and factory environment.
Direct Intake Method
On machine tools with partitioned machining areas, such as machining centers and NC lathes, air is drawn directly from the sealed area. Oil mist can be collected most efficiently.
Localized Air Intake Method
For machine tools such as general-purpose lathes and grinders, where the machining area is an open space, oil mist is collected by the local intake method. A hood or hose is placed close to the part of the machine tool where oil mist is generated, and the oil mist is sucked in.
Wide-Area Intake Method
The wide-area intake method sucks in air from the entire factory. This method is used in combination with the direct intake method and the local intake method.
2. Difference Between Mist Collector and Dust Collector
A dust collector is similar to a mist collector. A dust collector is a device used to collect dust and other individuals generated by the cutting process. While mist collectors are used in cutting processes that use cutting fluid, dust collectors are used in dry processes that do not use cutting fluid.
Dust generally refers to all fine particulate solids suspended in air. Conversely, fine particulate matter (PM2.5) is particularly small, and there is concern that PM2.5 can penetrate deep into the lungs and affect the respiratory and circulatory systems.