Vacuums 101 — Why Some Suck and Others Don’t
The operator’s workhorse.
Ask 100 car wash people how a vacuum works and what the difference is between a good one and a bad one, and nine times out of 10 you’ll either get a blank stare or a shrug of the shoulders followed by “Gee, what a dumb question, it sucks up dirt.” Well yeah, duh, of course vacuums “suck” (lift and move) dirt, but how? And why is this important to you?
First, it’s important to you because your customers know. They know the difference between a vacuum that “sucks” and one that doesn’t. Second, you are in the production business. The longer it takes to clean a car seat or carpet, the longer a customer or employee is bending over to clean, the more your turnover is reduced — your customer’s frustration goes up, and revenue goes down. So look at it this way: a properly designed, sized, and engineered vacuum system performs and provides you the highest customer satisfaction ratings, increases turnover, and puts more money on the bottom line. So now that I have your attention, what is a vacuum, why do some outperform others, and why are some barely capable of “sucking” smoke?
IN NATURE
Going back to your high-school science class, you’ll remember the discussion about atmospheric pressure. As a reminder, at sea level the earth’s atmospheric pressure is 14.7 pounds per square inch or, to put it another way, about one 1 ton per square foot. This pressure is a result of air molecules (which, believe it or not, have weight) pressing against your skin (and everything else). You don’t collapse or get crushed from this pressure because you breathe in air molecules that balance the outward pressure. As you increase your height above sea level, atmospheric pressure is reduced. The higher you go the more the interior of your body needs to compensate. The most obvious noticeable compensation is the “popping of your ears.” It’s the body’s way of regulating the change in exterior pressure. Another way to think about your everyday familiarity with air pressure is barometric pressure measured in inches of mercury. As barometric pressure goes up or down it signals the density and weight of air and the foretelling of weather changes.
VACUUMS
So now let’s think about vacuums and how they work. A vacuum works by fooling Mother Nature. By decreasing the pressure inside a vessel and opening an outlet to the atmosphere (vacuum hose), air rushes in to balance the interior with the exterior. As it rushes it gathers everything not nailed down in its path. The material that gets pulled into its predetermined space rushes along until it is trapped or filtered, falls out of the pathway, and is trapped in separators or some sort of containment devise. Think of your vacuum as the opposite of your blower. Instead of creating positive pressure and volume to push items, think of it as a place where negative pressure is created, gravity and the earth’s atmospheric pressure fills the void with air molecules and whatever else they gather along the way.
Pretty simple so far: just decrease the pressure and let Mother Nature do her thing. No problem. Except Mother Nature needs a helper in the form of a mechanical device known as a pressure differential chamber. Creating negative pressure requires a complex set of impellers (blades) in concert with a correctly designed chamber of inlet and exhaust ports and a properly specified motor rotating at just the right speed — and you’re part way there. Add all this with site-specifics relating to piping distances, number of vehicles served, voltage, altitude, average humidity, hose diameter and length, and total number of vacuum hoses on the system and you can now design a system where all vacuum openings perform with equal pressure differential, regardless of how many are in service.
A general rule of thumb is each vacuum opening requires a minimum of three horsepower to create the pressure differential necessary to create airflow and suction. In other words, if you were planning on 20 vacuum drops and there was a possibility of all being used simultaneously you would at a minimum require a 60 horsepower turbine. The caveat to this rule of thumb is in the diameter and width of the turbine impellers and those other site-specific items already mentioned.
GOOD OR BAD
You now have the basics of understanding how a vacuum is created. But what about a good vacuum versus one that can’t suck smoke? For existing sites there are two easy ways to determine a vacuum’s efficiency. One is to take a vacuum gauge, plug it into the vacuum inlet, and read the pressure. An acceptable range is between 80” and 100” of water. The second is to ask the people who are using the vacuum. Is it fast and efficient or not worth the time spent? You’ll either get thumbs up or maybe some other digital acknowledgement to your inquiry. In any case, you’ll know quickly how good or bad the system is.
The customer’s experience.
So how does one choose a vacuum system or a vacuum supplier? Here are a number of questions you can
ask when interviewing your potential vacuum provider:
- Please provide a list of users who have your system in a similar business as mine.
- Please provide trade references, business history, systems sold, definition of your support team, and warranty.
- Will you provide an engineered system designed for my site?
- Will you provide stamped engineering drawings suitable for permitting?
- Do you and can you provide consultative ideas regarding my car wash?
- What is your philosophy regarding design suggestions or concepts?
- Do you have other industry strategic partners that you recommend or work with?
We hope by now you realize that choosing a vacuum system is not and should not be treated as an afterthought. At most washes the vacuum system, much like the physical site, tells a great deal about how serious you are about providing best-in-class service. In general, there are three critical elements in every tunnel operation: the conveyor, the controller, and the vacuums. Lose the use of any one of them and it’s a bad day at the office. For many, the second largest presence and occupier of space on the site is the vacuum area. Doesn’t it make smart business sense to use the same due diligence you used in choosing all the other aspects of your business when choosing a vacuum system?
John F. Tucker is CEO; E. F. (Tom) Tucker is president; and Fred M. Grauer is executive vice president, new business development of Centennial, CO-based Vacuum Technologies Corporation. You can visit the company on the web at www.vacutechllc.com.
