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Myths, Fables & Fact About Vacuum Science
To keep from being vulnerable to claims that go beyond the real world of vacuum physics, let’s explore some of the misconceptions out there.
Myth #1: The more lift a system has, the better the cleaning will be
To illustrate why this is a myth, put a marble on a table and place your vacuum hose over it, sealing the cuff to the table. Now start your machine. Because of the seal, the vacuum gauge will show its highest lift, but the marble hasn’t moved. Now crack the seal of the cuff and let in some air. Even though the gauge show a drop in lift, the marble races down the hose due to air flow. So while lift is easily measure on a gauge, it doesn’t tell you how much air is being displaced in a vacuum system, and it is airflow (usually expressed in cubic feet per minute or CFM) that conveys soil back through the hoses to the recovery tank.
Myth #2 The more CFM a vacuum has, the drier the carpet will be after cleaning.
Airflow, measured in cubic feet per minute (CFM), can’t be evaluated alone any more than lift can. That’s because lift and airflow are inversely dependent. If one goes up, the other goes down.
To illustrate, let’s suppose your truckmount vacuum gauge reads 6” Hg level of lift. At this level, the system is capable of moving about 175CFM of airflow. Now suppose you add more hose or improve the wand seal. The gauge will probably show lift climb to a level of 10”Hg, but airflow will drop to about 150 CFM. One goes up, the other down.
So, you can’t give too much weight to CFM measurements alone when judging a vacuum system. The most effective cleaning is accomplished only when there is proper balance between lift and airflow.
At HydraMaster, we measure air watts to quantify and predict where the “sweet spot” of a vacuum’s performance curve lies. And we calculate the speed at which air is flowing at every point in the system to ensure enough velocity to suspend the recover water and keep it moving throughout the system.
Myth #3: The more air velocity a vacuum has, the better the system.
Velocity is important, but as it increases, so does friction loss which robs vacuum power from cleaning. For instance, when a silencer is added to the vacuum pump, the result is back-pressure. When air is run through pipes and elbows and down long vacuum lines, even more restrictions occur. If the vacuum tank air filter is too small or clogged, airflow is restricted again. These all cause losses in air velocity due to friction along the walls.
At some point, the law of diminishing returns comes in, and it takes massive increases in power to achieve any small amounts of air velocity improvements or benefits.
Vacuum science is complex and interrelated. So when buying a cleaning unit, don’t be confused by how much lift or CFM the vacuum system offers. One thing you can count on is that HydraMaster takes into consideration the practical effects of vacuum theory to design the most effective cleaning systems possible.
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