Heating Oil Tank Noises

mromberger

I've been noticing noises when my furnace runs that seems to be coming from the oil tank or the over head pipes. The sound is similar to knocking, almost like shoes in a dryer. I can hear it audibly in my living room through the floor, but it is faint when I'm in my basement next to the tank. I hear trickling when I put my ear to the tank. The sound is not coming from the furnace. I wondered if maybe there was air in the line, as I was very low on heating oil but then got a refill that brought me to 3/4 of a tank, but didn't think bleeding the furnace was necessary since it never stopped running at any point and didn't require being reset. Any ideas on why this sound is happening/how to fix it? 

leonz

If you have a 2 pipe system attached to your oil burner one pipe feeds the oil to the burner and the pump in the oil burner is returning the overflow oil back to the tank. As long as the suction line is below the oil level your burner should only need to be bled if and when the filter is changed.

EBEBRATT-Ed

sometimes with 2 pipe you get: "harmonic hum" which is noise transmitted from the pump.. Putting a loop in the return line. a flex oil line or hanging the line fro the joists instead of rigidly secured to it will help

EdTheHeaterMan

Fuel pumps on oil burners have what is known as a positive displacement pumping action. On fuel oil burner pumps that is accomplished with a set of gears that cause a void to increase in size at the inlet of the pump, then as the gears mesh together the void will decrease in size causing hydraulic pressure to force the fuel to the outlet of the pump. This pressure operates a pressure regulator that opens the nozzle port so high pressure oil can exit the pump to the nozzle line. Any oil that the nozzle can not dispense is bypassed past the pressure regulator and returned to the tank by way of the return line on a two pipe setup.

The gears in the pump may cause a harmonic vibration during operation. If you have an older burner that operates at a 1725 RPM, the vibration happens at a frequency that is able to be heard by the human ear more commonly. The 3450 RPM pumps can have the same problem but it is less common.

On some occasions the design of the fuel line from the pump to the tank can carry those vibrations and when the fuel lines are attached to the building with rigid straps, that vibration can be amplified thru the structure. In many cases the fuel tank can also become an amplifier of that vibration. This was a common problem in older burners that it was necessary to install an "Anti-Hum" device in the fuel line to the pump in order to suppress the vibrations.
As it turns out, this product may be hard to find. I have found that a coil of 3/8" copper made by wrapping the copper around a 6" diameter pipe, or can, or bottle two times will interrupt the vibration’s harmonics so the tank no longer acts like an amplifier. So you can try to purchase one or make one to stop the HUMMMMM

And to finish this comment I can’t help it. I must say that when you hear that hummmmm, it is because the tank forgot the words. If you place the sheet music with the words on the floor near the tank, you may find that the tank stops humming

mromberger

I wish I knew how to better describe the noise. It isn't what I would consider to be a humming sound. It's not a steady noise, it fluctuates and occasionally is somewhat louder than the rest of the time the furnace is cycling. I have touched the pipes and the tank and noticed no vibrations...unless they are so miniscule I can't detect them, and just audibly loud. It sort of sounds like water in a kettle, gurgling/bubbling. I'm just wondering if it's problematic/dangerous. I'm calling to have it serviced soon.