Oil Mist Eliminators: Visi-Mist, Midi-Mist and Maxi-Mist
Oil mist eliminators for vacuum pump exhausts
Every oil-sealed vacuum pump puts a fine mist of pump fluid out of its exhaust, visible as grey smoke at start-up and still there once it clears. Mass-Vac’s oil mist eliminators fit on the pump exhaust and pass it through pleated, low-resistance microfiberglass coalescing filters that take the mist out before it reaches the room and settles on the surfaces around the pump. There are three designs, sized to the pump: the Visi-Mist for smaller pumps, the stainless steel Midi-Mist in two sizes, and the high-capacity Maxi-Mist for pumps up to 300 CFM.
Choosing a size
| Model | Part number | Pump size | Connections | Filter elements |
|---|---|---|---|---|
| Visi-Mist | 360500 | up to 16 CFM, inlet ports to 1.5″ | NW25 or hose, up to 1″ | 1 |
| Midi-Mist 4 | 360300 | up to 20 CFM, inlet ports to 1.5″ | NW25 pump side, 1″ hose exhaust | 1 |
| Midi-Mist 8 | 360200 | up to 40 CFM, inlet ports to 2″ | NW40 pump side, 1.5″ hose exhaust | 3 |
| Maxi-Mist 10 | 360000 | up to 300 CFM, inlet ports to 4″ | NW50 pump side, 1.5″ NPT exhaust | 5 |
Mass-Vac’s advice is to pick the eliminator whose inlet port matches the pump’s exhaust port, and never to fit one with a port smaller than half the diameter of the pump’s inlet port.
Visi-Mist
The Visi-Mist has a polypropylene housing and a clear styrene acrylonitrile sump, so you can check the filter without taking it apart. It’s 140 mm in diameter and 231 mm tall, weighs 1.1 kg, and mounts above or beside the pump, with an exhaust adapter for your pump’s make and model.
| Part | Number |
|---|---|
| Visi-Mist with filter element | 360500 |
| NW25 inlet flange / 3/4″ hose termination | 301025 / 301075 |
| NW25 stand-off adapter (mounts above the pump) | 301100 |
| Pump exhaust adapter to NW25 (give pump make and model) | 301110 |
| NW25 elbow | 301425 |
Midi-Mist
The Midi-Mist gives the same filtration as the Visi-Mist at a higher capacity, for larger pumps and more demanding installations. It’s built in stainless steel, which resists corrosion, with a drain plug for recovering pump fluid and a band clamp closure that makes it quick to take apart and clean. The Midi-Mist 4 is 102 mm in diameter, 199 mm tall and weighs 1.4 kg; the Midi-Mist 8 is 203 mm in diameter, 252 mm tall and weighs 4.5 kg. NW25 and NW40 pump adapters, clamps, centering rings and elbows are available, including adapters for Welch 1402 and 1397 pumps.
Maxi-Mist
The Maxi-Mist is Mass-Vac’s highest-capacity oil mist eliminator, for industrial pumps up to 300 CFM. A parallel bank of five pleated microfiberglass coalescing filters, rated at 0.1 micron, drains the trapped oil into a large reservoir, which can be piped back to the pump to recirculate the oil or emptied through the drain port. It’s stainless steel, 254 mm in diameter and 343 mm tall, and weighs 6.8 kg.
Changing the filters
Coalescing filters don’t absorb oil, so they only need changing when the pump exhaust carries particulate. With clean pump oil, a filter change once a year may be enough. All three designs use the same replacement element, 360915.
What we need for a quote
The vacuum pump make and model, its exhaust port size, and whether you’d like the eliminator above or beside the pump.
