Several reader questions come up frequently and bear repeating. A few of these questions might seem elementary to the experienced pumping professional, but they can be of critical importance to new company owners or technicians picking up their first issue of PRO. So using a rapid-fire approach, we’ll review some of the most common questions we hear from contractors who operate vacuum trucks. We appreciate all your positive response to our column. Keep those questions coming!
QUESTION:
What is the difference between a vacuum pump and a blower?
ANSWER:
A vacuum pump evacuates the air out of a tank. That is to say, the air is forced out of the tank, putting the tank in an unstable state, and wanting the air to come back so it can return to normal pressure. When a valve is opened, the air rushes in. If the valve is hooked to a hose, whatever is at the end of that hose will be pulled into the tank. When the vacuum pump is turned off, the vacuum will remain inside the tank until the valve is reopened.
A blower is essentially a high-speed fan. The fan turns at a high RPM and creates a temporary vacuum inside the vacuum tank. When the blower is stopped, the vacuum dissipates. The operation is relatable to a vacuum cleaner, where air is brought into the machine and then vented out or exhausted to the atmosphere.
QUESTION:
What precisely are the vanes inside a vacuum pump?
ANSWER:
Vanes are made of a composite material. Each manufacturer uses its own formula to manufacture them. They are rectangular slats that slide into the rotor of the vacuum pump. As the rotor turns, the vanes rotate, pulling air from the tank and preventing air from returning, creating vacuum. As time goes on, vanes wear down and need to be replaced. When your pump is taking longer than usual to create vacuum, it can be a sign that the vanes are wearing out.
QUESTION:
What is the purpose of a primary shutoff valve? Is it really needed or just an extra expense on a vacuum tank?
ANSWER:
The primary shutoff valve blocks and collects waste as it progresses to the pump. It is a simple stainless steel device with a ball surrounded by a cage. As waste materials begin to fill the vacuum tank, the ball rises and eventually seals the line and prevents the waste from moving on to the secondary and the pump. It is a safety device for your pump. Your system can run without a primary shutoff valve, but why risk your pump? Pumps are one of the costliest things on the truck. Why take a chance that debris and waste will get into the pump and cause damage?
QUESTION:
Water-cooled pumps are more expensive than air-cooled pumps. Does that mean they are better, longer lasting pumps?
ANSWER:
Water-cooled pumps serve a purpose somewhat different than an air-cooled pump. An air-cooled pump is exactly what it says it is. It is cooled by the atmosphere as it works. Air-cooled pumps operate best at sea level or slightly above. Once you move into mountain country, the water-cooled pump is going to be your best bet.
The thin air of the mountains means you will have a longer work cycle to create the vacuum necessary for any job. The longer work cycle means the pump is going to generate heat. Cooling it with the water from the truck’s radiator will prevent overheating and help ensure a longer pump life. An air-cooled pump at high elevations will overheat a lot quicker. Make sure you have the right pump for your elevation.
QUESTION:
How often should I drain the secondary?
ANSWER:
Drain your secondary moisture trap at the end of every workday. Don’t wait until the next morning. If you do, you will forget this critical maintenance once in a while. Imagine the waste trapped by the secondary and then starting the pump the following morning. The waste quickly jumps through the line and moves to your vacuum pump. We’ve heard this story too many times, with technicians simply forgetting to drain the secondary moisture trap after a long day’s work. The secondary is the last filtering part in place before the waste gets to the pump. So shout it from the hilltops: “Drain your secondary after each day’s operation!”
QUIZ YOURSELF
Jerry and I want to throw a bonus question back at you: Do you know the brand and model number of your vacuum pump? Could you find parts for the pump quickly if you had to? This is important information to know when you suffer a breakdown and want to get back on the road as soon as possible. Keep on pumping!
