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Nozzle Knowledge

Many of you I’m sure have had situations during a service call where you found that a nozzle failed and you replaced it. Why the nozzle failed was most likely that it was plugged with sludge, as that black stuff is commonly called.

Let’s be sure we first understand the function and the different brands of nozzles, such as Monarch, Delavan, Steinen, Danfos and Hago. Except for the Danfos, these nozzles are manufactured in the U.S. and distributed throughout the world.

These nozzles all have the same function, which is to atomize the oil, at a specific pressure, angle, pattern and droplet size. Each of these specifics is extremely important to the performance of a piece of equipment, whether it is a boiler, furnace, water heater, power washer or portable space heater.

Critical to the nozzle are the tangential metering slots, as they limit the amount of oil that can pass through the nozzle. These same slots are about the size of a human hair and for that reason they must be protected from contaminants that can be released from an aged oil tank. These same slots also force the oil into what is referred to as the swirl chamber, forming a spiral action. The oil leaves the orifice in a spinning motion; at approximately 1/64 of an inch from the face of the nozzle the oil stops its spinning motion and droplets form. Also, be aware that some manufacturers cut the metering slots in an opposite direction, which only reverses the oil’s rotation in the swirl chamber. The only thing that can make the droplets continue to rotate after leaving the liquid sheet is the oil burner’s air pattern, established by a specific air cone. Keep in mind that all nozzles, regardless of the brand, have no moving parts. The oil moves through the nozzles.

Have you ever wondered why there are so many nozzles in a box? The answer is simple. Every boiler, furnace or water heater is lab tested by the appliance manufacturer (not the nozzle manufacturer) to find the correct pattern, angle, and pressure that will produce the maximum efficiency for the appliance. Keep in mind that you will experience smaller nozzle ratings and much higher pump pressure ratings as we move ahead with new equipment ratings. There are boilers manufactured in Europe that have pumps operating at 190 PSI with .30 GPH nozzles. And, as I have written in the past, the Babington burner will really be an eye opener when it comes to low firing rates.

I’m also sure our own doctor at the Brookhaven National Laboratory has tested equipment with lower flow rates and higher pressures. The real problem with lower flow rates is keeping the oil flowing through the nozzle for the entire heating season without contamination issues.

Oil filtration is the key to a nozzle’s longevity. One method that can extend the nozzle’s performance is adding more than one oil filter from the tank to the burner. I would suggest more attention be given to the location of the oil filter and type. I’m a big proponent of placing two filters at the tank. The first being a standard fiber-type filter and the second being a spin-on filter with a 10-micron media with a vacuum gauge. The vacuum gauge will help identify the condition of the fuel system.

I would also recommend an oil safety valve be included at the tank. In fact, some cities and towns in several states make it mandatory. Check your local code.

In closing, think about how inexpensive the nozzle is and the roll that it plays in the performance of every oil-fired appliance.

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