Exhaust Filters
Exhaust filters are often used on oil sealed rotary vane vacuum pumps. The main reason to use an exhaust filter is to eliminate or minimize oil mist that can often be a byproduct of the vacuum pumps operation. Oil mist is often generated by vacuum pumps for a variety of reasons. The most prevalent and common cause is operating the vacuum pump at "high" pressures. Generally speaking operating pressures above 1 Torr or 1000 micron can cause oil mist to be apparent. Oil mist creation is not unusual and "No the pump isn't on fire." The most common cause is operating the pump by pumping against an "open" or leaky system. The pump then has very high gas flows going through it, and in the process will atomize oil molecules (aerosol) and they will then attempt to exit the pump and, baring no filter media to prevent this, they will.
If you received an exhaust dome on one of our vacuum pumps, this is not really a substitute for a true exhaust filter. An exhaust dome keeps dirt and particulates from getting into your pumps' exhaust port and then into the oil. It is a very rudimentary filter, and sometimes just a mesh screen.
An exhaust filter or "oil mist eliminator" is a more advanced filter usually containing a replaceable element that will stop oil mist on a molecular basis or at least make a good effort at it. Exhaust (oil mist) discharge can be cut significantly by adding one of these filter items to your vacuum pump. Not only does it keep the oil mist out of your workspace; it also will keep the pump oil in the pump where it belongs.
Types
There are two basic types and numerous variations in these two categories. The first is a standard exhaust filter; generally coalescing, that will trap most of the oil mist, keep the oil in the pump and exhaust into the workplace. Coalescing means that the oil drains back into the pump after it condenses on the insides of the filter element itself. The second type of exhaust filter does the same as the first, but also includes an exhaust port from the exhaust filter.
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