What are mist collectors?
Mist collectors are machines designed to clean the air by removing toxic oil & coolant mist, on metalworking machines as well as milling and grinding processes.
Oil mist is harmful to the health of machine operators as well as other people in an industrial shop. The metal cutting tools of machines are lubricated to keep metals cool while in action, reduce friction and protect their functionality. Oil mist is created when the oils used in lubricating metal come in contact with machining processes and are expelled as mist into the air. In situations with high temperatures, the oil could burn and turn into oil smoke that is also dispersed into the air.
Oil mist is toxic to the human system. People that are exposed to oil mist could suffer from irritation of the eye or skin, burning sensation in the mouth and throat, fever, rapid heart rate, shortness of breath, vomiting, headaches, etc. Exposure to oil mist could also result in cancer, and other skin and respiratory diseases. Employers could be at risk of litigation from employees who have fallen ill from exposure to oil mist as a result of poor indoor air quality in production facilities.
The exposure of industry workers to oil mist is also regulated by bodies like the Occupational Safety and Health Administration (OSHA) along with the National Institute for Occupational Safety and Health (NIOSH) and Association Advancing Occupational and Environment Health (AAORH). These bodies have exposure limits set to reduce the level of oil mist that workers are exposed to. For instance, OSHA limits exposure to 5mg/m3 for all employees that work 8hr/day and 40 hrs/week, and any employer that does not comply with these restrictions could risk a lawsuit or fines. Health and safety committees work to achieve a recommended limit of 0.3-0.5 mg/m3 to provide a safe working environment. To ensure that your industry stays within the stated guidelines, an industrial hygienist should be consulted to determine the air quality in your environment.
Staying within the permissible exposure limit is a necessity for employers, however, they cannot be achieved if effective mist collectors are not installed. There are two general types of mist collectors:
Source capture (Machine Mount) Mist Collectors
Usually mounted on top of the machines, they are peripheral and filter air directly from the source. With this type of mist collector, oil or coolant is drained back into the machine, while the filtered air is released back into the working atmosphere.
It works by a multi-stage process:
- Pre filtration
- Primary filtration
- Exhaust of clean air
Pre-filter – oil mist is collected into the pre-filter by a fan or blower immediately after leaving the machine. At this stage, coolant or oil mist is collected into larger droplets. are collected and drained back to the machine to be reused.
Drainage – Once mist is collected into larger droplets in the pre-filtration stage, they are drained back into the machine to be re-used.
Primary Filtration – At this stage, the finer particles are collected, and the air is purified by going through the final filter. The efficiency of the main filters varies by type.
· ASHRAE Filter (MERV): capable of filtering particles down to 0.5 microns
· HEPA Filter: capable of filtering particles down to 0.3 microns
· ULPA Filter: capable of filtering particles down to 0.12 microns
Exhaust of clean air – This is the final stage where the filtered, clean air is exhausted back into the atmosphere.
Ambient Mist Collectors
Are suspended from ceilings or installed on floor stands of the industrial facility and filter any particulates in the air created by production processes.
They work in a similar multi-stage process as source capture mist collectors. Ambient mist collectors often utilize progressive filtration stages to increase filter life.
Washable pre-filtration stages – Pre-filtration is used to collect larger particles of oil mist as well as other contaminants from the atmosphere. The collected oils are subsequently drained out of unit through a drain hose. Since they constantly collect and retain particles of varying degrees, these filters are washable and ought to be cleaned regularly to ensure proper functionality of the unit.
Primary Filtration stages – At this stage, the remaining particulates are removed from the pre-filtered air using filtration with a higher efficiency rating
Filtered air – Filtered is exhausted back into the industrial shop
Specifics To Look Out For When Purchasing A Mist Collector
There are serval good mist collectors in the market, however, choosing an effective one would require that you consider the specifications indicated by their manufacturers to see if they are suitable for your industrial air quality needs. The following are specifics that industries should look out for when purchasing a mist collector:
· Installation indicates how the mist connectors are to be mounted and connected for optimum performance
· Power specifications voltage requirements to power the mist collector
· The efficiency or MERV rating of filters shows the percentage of oil mist or particulates of a specific size in microns that can be collected by the mist collector.
· Delivered Airflow indicates the amount of airflow that a mist collector can deliver factoring airflow loss due with filters installed. Usually measured in cubic feet per minute.
· Minimum particle size is measured in micrometres. Signified with the unit µm, they show the minimum diameter of aerosol that a mist collector is capable of filtering.
· Size specifications indicate the dimensions of the mist collector unit. They are usually measured in feet (ft) and inches (in), and they go a long way to help an industry decide based on the machines and environment that they want it would apply to.
· The sound levels of mist collectors are also indicated to show the amount of sound that it would produce in operation. They are measured by sound decibels (dBA). However, good mist collectors should not rate high on their sound levels, as they should be able to run quietly.
· Maintenance intervals this determines how frequently the filter or collector must be cleaned or replaced.
· The weight of the mist collector is also given in pounds (lbs).