Both Air Amplifiers (especially the FX40 fixed unit and 40002 adjustable unit) and Ring vacs (of various sizes and materials) are used for gas venting applications. In fact, we have manufactured Teflon Ring Vacs for moving gasses in scrubbers to eliminate the maintenance required with vacuum pumps.
Sometimes the Air Amplifiers are first considered for venting because they use the Coanda effect which moves a large volume of gas. They are excellent in moving atmospheric air for example, in venting an enclosure or chamber in emergencies.
However, if the gas in question is dirty in any way, and/or the material needs to be moved a greater distance, then the Ring vac is a better choice.
First, an Air Amplifier is limited to about ten feet (3) meters of conveying. It is more sensitive to back pressure than a Ring vac so the distance is limited. Also, the longer the distance, the less the “amplification”. The Ring vac is much less sensitive to back pressure and can move any vented gas much farther with less back pressure effect. It is used extensively in venting the crank cases of gas transmission compressors for example, eliminating the maintenance and regular checks needed on electrically operated vacuum pumps. Air Amplifiers also need at least 80 PSIG (5.5 bar) pressure to work well in venting while Ring vac may do the job with even small pressures of well under 20 PSIG (1.4 bar) minimizing energy use.
Second, if the gas being vented contained any particulate that may condense out or in any way deposit inside the conveying unit, this can be problematic with Air Amplifiers. The Coanda profile which makes them operate needs to be relatively clean. If a deposit builds up over time, the Air Amplifier may no longer vent well and perhaps even stop working. The Ring vac however, operates differently and the holes in the “generator” of the Ring vac is well insulated against the movement of the gas and any buildup would take much longer to occur, if at all.
Third, Ring vac units are generally less costly than Air Amplifiers and special versions are easier to make to adapt to special applications. If the particular application requires it, special materials can be used, special flanges can be provided or other attachment variations, and other things can be added to suit the customer requirements.
The above explanations seem to favor the Ring vac but it all depends on the specific application. Always speak to a Nex Flow representative for advice on the most appropriate choice.