HVAC-PT hago library

W Nozzles (Typically referred to as the Universal Nozzle the Hago W produces neither a truly hollow nor a truly solid spray pattern. As such it can be used to replace either. Probably the most misunderstood nozzle in the Industry.)

EcoValve

HAGO NOZZLES TECH TIPS

Oil Nozzle Clogging (Part 1)
Every service technician has experienced their share of service issues related to clogged oil burner nozzles. This is most often found in the smaller flow sizes from 1.00 GPH and down. Although the vast majority of nozzles run successfully for a full season and longer without problems, it is always this particular failure that remains in the minds of techs, service managers and company owners as well. The additional call because of this is an additional expense. When looking at a clogged nozzle we have all found strange and many times unidentifiable materials. Sometimes it is black carbon sludge, other times merely brown slime. We have also been taught that this condition is the result of unstable oils, poorly refined oils, microbial germs and even the water that has rested at the bottom of decades old basement oil tanks. The general recommendation of improved fuel quality through fuel additives is a good start and the additives work when used as prescribed. One frequent problem is the tiny black particles called carbon deposits. These can be easily seen when when the nozzle is taken apart and the contents spilled on a white piece of paper. How did these particles arrive in the nozzle mechanism to begin with? Since the low flow nozzles are manufactured with very fine mesh or sintered bronze filters, the question is a good one and I will share some answers with you. 1. Filtration devices are rated from a point where they can successfully remove 90% or more of the rated particle size of the filter used. In the case of oil nozzles, the filter typically removes contaminates which range in size from 30-40 microns or larger. This equates to about .0012" to .0016" in diameter. Consider that a human hair is about .004" and you can visualize how small the particles really are. However, even given this fine filtration, 10% of particles can find their way through the filtering system and get into the interior of the nozzle. As a result, any installation that that uses highly contaminated oil at the outset is in for trouble, leading to burner call backs. You may recall attending a nozzle class where you were informed that the metering and orifice of a nozzle of a nozzle of .65 GPH as an example would be approximately .007". If the particles are less than a quarter of this size why do they not just pass through the nozzle without plugging it? The reason is called "Log Jamming". Visualize this as pouring small metal "BB's" into a funnel. If you pour small quantities, they will pass through. If you pour the BB's all at once they will jam at the hole in the funnel. This same principle applies to oil running through a nozzle. It is not one particle of contamination that causes nozzle clogging but rather many at once. This is why manufacturers stress the use of high quality in-line filters with ratings down to a 10 micron particle size. The more particles removed by the in line filter, the less the risk of clogging.

Oil Nozzle Clogging (Part 2)
I'm sure that many of you have opened a nozzle or two in your travels and have seen black carbon deposits that often disrupt the spray pattern even given a quality 10 micron filter in place with a vacuum gauge. Perhaps you have seen larger particles of carbon that you would think impossible to pass through any filter. How do these particles of carbons get by the line filter and the nozzle filter? In order to answer this question we need to have a better understanding of what can happen after the burner cycle ends. In many installations, particularly those with small combustion chambers and the lack of a post purge burner cycle there is great deal of heat that is reflected back onto the nozzle. This is particularly true when a hard chamber is used. Hard chambers retain heat longer than their soft felt like counterparts. Sometimes, enough heat is reflected causing a few drops of oil trapped within the nozzle to actually boil. When this occurs, that tiny amount of oil can undergo a secondary cracking, resulting in the creation of carbon particles inside of the nozzle. These particles then have the ability to enter and interfere with the fuel metering slots or the nozzle orifice. Over the past several years, nozzle manufacturers, chemical companies and filter makers have searched for a better method to eliminate problems created based upon fuel contamination. Anyone who has attended recent National Oil Heat Service Managers round tables on oil quality may be familiar with advances taking place. Solutions so far are advanced oil conditioners that work more effectively than ever before. One filter manufacturer has suggested a "tank sump method" where the filter cartridge is removed at the tank filter to allow this larger area to be used as a pre-collector. This would help reduce the larger volume of contaminates before the fuel enters the 10 micron spin on filter located directly after the canister. The fuel oil reps gave many good reasons why oil treatment is so important given the lack of oil stability and differing tank conditions. The nozzle manufacturers also make suggestions that make good sense. Nozzles today are moving to smaller sizes as pump pressures become greater. This means that nozzles may become even more vulnerable to contamination. Along with additives and tank filtration comes the need for better nozzle filtration. The design must be capable of providing the added protection needed to avoid unwanted repeat service calls that can be a problem with low flow rate nozzles. One nozzle company offers an additional filter that can be installed at the oil pump; another recently introduced a tamper proof duel filtered nozzle. This dual filtration product comes in standard flow rates (0.30GPH-1.00GPH)with common spray angles and patterns. It features a secondary 30-40 micron sintered bronze filter constructed internally that is supported by a standard external filter. I recommend that all company owners, service managers and suppliers get more details on products whose goal is to reduce contamination and clogging and as a result reduce those costly call back service calls.

The Importance of Atomization to Combustion
Would you believe that even though fuel oil is classified as a flammable liquid, it does not burn in a liquid state? This is why. If you were to drop a lighted match in a container of fuel oil it would go out almost immediately. In order for fuel oil to burn, it must be transformed from a liquid to a vaporized state. To create this vapor, pressure is applied to the fuel, forcing the liquid through the tangential slots, swirl chamber and orifice of an atomizing nozzle. Air is then applied from the burner air handling components, causing the oil to atomize into very small droplets in preparation for combustion. For your information, a nozzle of .60 gallons per hour can generate as many as 50 million droplets of oil in that hour. It is these small droplets that once ignited, provide the maximum combustion efficiency that is required in heating appliances. It is also important to understand how the next stage, combustion takes place. The two main ingredients in fuel oil are carbon and hydrogen. The surrounding air contains oxygen and nitrogen. When the air and oil are brought together in the proper proportion, they will burn once a source of ignition is established. It is critically important to remember that only the correct air/nozzle selection will generate clean, efficient combustion and heat.

Oil, Water, Vacuum Effect Nozzle Performance

Over the years I and other nozzle manufacturer representatives have received calls that their oil burner nozzles have failed or are not performing properly. When these calls are received by our technical support personnel, the call is taken seriously. After all, as I have said in the past the goal of all the nozzle manufacturers is to put a quality product in the hands of the technicians. When we get these calls, we often ask the caller if they have saved the nozzle, in order for us to examine the product in question. Most often the caller will say that they just “chuck the nozzle” install a new one and the problem goes away. Fortunately some technicians actually have saved the problem nozzle for our examination which actually helps us to identify the real problem. Nearly all issues pertaining to nozzle failure are caused by some type of contamination like water, rust, or just plain old tank sludge. However, there is something else that can cause the nozzle to experience a reduction in expected performance that is often overlooked or never even considered. This problem is created by excessively high oil pump vacuum. I’m sure that many of you know that vacuum is required in order to pull oil from a specific length and size of pipe or tubing. There are times when vacuum is not measured by some technician’s as specified by the pump manufacturers and often there exists vacuum that is greater than the oil pump is designed to function at. Pump vacuum can actually reach a point high enough to affect the nozzles performance and this can happen even though the burner is running. Although not efficiently. What we don’t see with high vacuum is the oil pump starts to develop foam within the cavity of the cover. Again this may occur when the vacuum rating of the pump is exceeded. For example if you have a single stage pump, single pipe that is rated for vacuum of 6 inches, the foam will occur in the pump as you start to reach this measurement. So how does this affect the nozzle? Remember that nozzles are pressure tested at (100 PSI). When the vacuum reaches the limit of the pump, the pressure at the nozzle will decrease causing such problems as a smoky fire due to improper atomization from the pressure drop at the nozzle. In order to avoid poor nozzle performance due to high vacuum, follow the pump manufacturer’s specifications as stated in their technical guides. In general the best rule of thumb, as told by one of my friends representing a pump manufacturer, is that if the vacuum is in the single digits a single stage pump will work fine, but if it is in the double digits select a two stage unit. I would bet that many pumps are returned as defective due to high vacuum conditions and nozzles are “chucked”, because high vacuum that has affected the performance. By the way as an FYI, make sure the correct pump strainer (round hole) gasket is used when servicing the pump, as this will also help to reduce nozzle plugging because it provides a positive seal at the strainer unlike the square hole that will allow contamination to pass by the strainer.