One Line Vac or Two?

Over the last couple weeks, I have received a couple Line Vac inquiries that have featured some tips and common questions about Line Vacs that I thought I would share with you, our regular readers.  Line Vacs are EXAIR’s air operated conveyors that connect to tubing to create a powerful conveying device that is powered only by compressed air.  The Line Vac range in size from 3/8″ to 5″ ID tube.  These air operated conveyors can move materials of every shape and make up.  Standard Line Vacs will convey plastics, foam, grain, metal chips, and anything that you might move with a motorized industrial vacuum.  Additionally, Heavy Duty Line Vacs can uses more compressed air to convey materials further or heavier materials than the Standard Line Vac.  Line Vacs work wonderfully to replace bucket and ladder operations or to convey material across a warehouse floor.  They do not replace Super Sack loaders or dumpers, where you need to move 1000’s of pounds of material in a matter of minutes.

LineVacApp

“Can we use two Line Vacs, if material needs to be move further than one Line Vac’s power?” is one of the things that we are always asked.  The short answer is yes, but you will not double the performance of the Line Vac.  Because the restrictions of the conveying hose size, the material being conveyed will move faster with two Line Vacs than it would with one Line Vac, but it will not be double the performance of single Line Vac.

The situation with the greatest reward for two Line Vacs is to convey material much further.  The second Line Vac can be installed more than halfway though the run to maintain the particle velocity through the entire length of the run or at a sweep where the particles will slow down because of the turn.  Also, the second Line Vac will face a restriction in the size of the line, which means it will improve the performance, but adding three and four Line Vacs back to back will net diminishing returns for the amount of compressed air used.  It is better to spread out multiple Line Vacs evenly along the run.

The second thing I want to talk about is that just like a water pump, Line Vac can only vacuum so much.  Absolute vacuum can only produce 14.7 PSI differential from atmospheric pressure, so a Line Vac will always be able to blow much farther and faster than it can vacuum.  This means that you only want to have about 1 or 5 feet of feed hose before a Line Vac and the majority of the distance you are trying to convey after the Line Vac.  We don’t mention this in the videos, but you will notice that we will always use a short amount of tubing on the inlet side of the Line Vac and a much longer run on the outlet side.  See this video of a short inlet hose to the Line Vac.  This ratio will make the most efficient use of the Line Vacs.

Dave Woerner

Application Engineer

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