QUESTION:
Not very much is written about it, but does an oil catch muffler really do any good?
Brent Mathews
Harlingen, Texas
ANSWER:
You’re right. The oil catch muffler gets left out of most stories on vacuum trucks and vacuum systems. But before we discard it and think we’re saving money, let’s take a closer look at the function of the oil catch muffler.
Just ahead of the oil catch muffler in the vacuum system is the pump. The pump components — the vanes, shaft and bearings — are lubricated by a specific type of oil as recommended by each pump manufacturer. The shaft and vanes rotate typically at 1,100 to 1,400 rpm and it is the oil from the lubricator that makes sure the works don’t overheat and burn up. As the shaft and vanes spin, there is an excess of oil that builds up and needs to be removed.
ENVIRONMENTALLY SPEAKING
Generally, these vacuum pumps generate 4 to 10 ounces of excess oil an hour, depending on your pump. If it gets expelled into the open air, you have an environmental problem you don’t want to face. More importantly, you’ve got a spill that you absolutely don’t want to pay to clean up.
At the end of the line in our vacuum system sits the oil catch muffler. For this moment, we’ll focus on the oil catch part. As the pump is running, obviously it needs to exhaust air that comes from the tank as the vacuum is created. Along with the air, the excess oil is “vacuumed” out and runs down the line to the oil catch muffler.
Inside the oil catch muffler is a baffle system that blocks the oil and causes it to drop down while the air is blown out into the atmosphere, preserving the environment. The oil catch muffler has a valve for draining and recovering the oil at a later time. Then it can be dealt with in the appropriate manner, depending on where you live and the regulations of your area. At the end of each work shift, the oil catch muffler should be drained just as a matter of routine.
So we’ve saved the Earth and we haven’t even gotten to the muffler side of this device.
So let’s back up again to our vacuum pump and focus for a moment on the bearings that hold the fast-spinning shaft. Anything turning at 1,200 rpm, even with oil lubrication, is going to make some noise. And, depending on the quality of the bearing and the wear and tear on the bearings, the noise will be louder from some pumps than others.
The oil catch muffler doesn’t totally muffle the sound, but it does quiet the sound to a tolerable level. If you are ever curious, and you really don’t have to try this, separate the hose that leads from your pump to your oil catch muffler. Turn on the system. Now you hear the difference.
So to answer the question, the vacuum pump and system will operate without the oil catch muffler, but let’s face it, you need it. It’s a must. Not only does it save the environment, but it does wonders for your hearing. And now you can say the oil catch muffler got a fair hearing in print media, too.
PARTING ADVICE
Just a couple of helpful side notes on oil catch mufflers. They have been manufactured using two different designs. One is horizontal, for a low-profile look, and the other is vertical. Choose the design that best fits your truck. The horizontal lays flat and can be tucked away in the proper place, while the vertical appears more like a stack.
One of the things we’ve learned from experience is that the farther the oil catch muffler is located from the vacuum pump, the quieter the overall system. So take that into consideration when designing your next truck. Move the oil catch muffler to the rear, or at least as far away from the pump as possible. The driver/operator will appreciate it, and you won’t be having to say, “Can you hear me now?”
