A TOTAL LOOK AT OIL BURNER NOZZLES ISO 9001 CERTIFIED
A Reference Guide for the Burner Service Technician The complete oil heating system begins at the tank and ends at the chimney. At the heart of the system is a tiny, yet important piece of hardware — the nozzle. It performs the vital functions that keep the flame generating warm, comfortable heat. In fact, it plays such a significant role in the entire system that we feel the technician should know all about the nozzle.
NOTE The information in this pamphlet is based on experience and is to be used as a general guide only. WARNING Improper modification to combustion units may create a fire hazard resulting in possible injury. Contact the original equipment manufacturer before modifying the combustion unit. Why Use Nozzles? For a better understanding of how a nozzle fits into the performance of an oil burner, let us first review the steps in the process of efficient combustion.
What the Nozzle Does The atomizing nozzle performs three vital functions for an oil burner: 1. Atomizing As just discussed, it speeds up the vaporization process by breaking up the oil into tiny droplets…something like 55-billion per gallon of oil at a pressure of 100psi (standard in the industry). The exposed surface of a gallon of oil is thereby expanded to approximately 690,000 square inches of burning surface. Individual droplet sizes range from .0002 inch to .010 inch.
How A Nozzle Works Now that we know what a nozzle is supposed to do, let’s see how it does it. But before we do, let’s take a look at the cutaway showing the functional parts of a typical Delavan nozzle (Fig. 1). The flow rate, spray angle and pattern are directly related to the design of the tangential slots, swirl chamber and orifice. FIGURE 1 Cutaway view of a Delavan nozzle. First, a source of energy is needed to break up the oil into small droplets.
Nozzle Selection To match a nozzle to a burner takes field-service experience, trialand-error, or a good foundation of understanding angles, rates and patterns. Nozzle Ratings and Testing To insure consistent quality, every Delavan nozzle is tested for flow rate and spray angle on modern, high instrumented test stands. Spray quality is observed during testing for uniformity, balance and flutter. Delavan Nozzles Nozzle Vial Test oil is mixed to nominal no. 2 oil Type Color specifications.
Type B Solid Cone (For larger burners & where air pattern is heavy in the center or for long fires) Figure 4 Solid Cone Nozzle (Type B) Type B nozzles produce a spray which distributes droplets fairly uniformly throughout the complete pattern. This spray pattern becomes progressively more hollow at high flow rates, particularly above 8.00 GPH. These nozzles may be used in larger burners (those firing above 2.00 or 3.00 GPH) to provide smoother ignition.
Burner Manufacturer’s Recommendations* Manufacturer Aero Burner R.W. Beckett The Carlin Co. Riello Burners Intertherm Wayne Home Equipment Weil-Mclain Model Delavan Nozzle F-AFC HF-US HF-AFC SV-SSV AF/FG (F) AF/AFG (M) AFII (FB) AF II (HLX) 99 FRD (Std.) 80° W, A or B 80° W, A or B 80° W, A or B 70° or 80° B 60°, 70° or 80° A or B (100-150 PSI) 60° or 70° A or B (100-150 PSI) 45°, 60° or 70° A, W or B (140-200 PSI) 45°, 60° or 70° A, W or B (140-200 PSI) .50-.75 GPH 60°A .85-3.
Flow Rate Atomizing nozzles are available in a wide range of flow rates, all but eliminating the need for specially calibrated nozzles. Between 1.00 GPH and 2.00 GPH, for example, seven different flow rates are available. Generally, with hot water and warm air heat, the smallest firing rate that will adequately heat the house on the coldest day is the proper size to use and the most economical. Short on-cycles result in low efficiency.
Determination of Proper Firing Rate for a House Two procedures for determining the optimum nozzle size have been developed. One is the standard heat loss calculation method and the other is the K-factor sizing formula. 1. Standard Heat Loss Calculations Method If the amount of heat loss is known, the amount of replacement heat (heat load) needed is also known. From this information, the proper size of a boiler or furnace can be determined, thus the correct nozzle size.
Spray Angle Spray angles are available from 30° through 90° in most nozzle sizes to meet the requirements of a wide variety of burner air patterns and combustion chambers. Usually it is desirable to fit the spray angle to the air pattern of the burner. In today’s flame retention burner, it is possible to fire more than one spray angle with good results. Generally, round or square combustion chambers should be fired with 70° to 90° nozzles. Long, narrow chambers usually require 30° to 60° spray angles.
Burner Air Patterns Burner air patterns are much like nozzle spray patterns in that they fall into the same general classifications, either hollow or solid. As you would expect, a burner with a hollow air pattern generally requires a hollow cone fuel nozzle. A burner with a solid air pattern will give highest efficiency with a solid cone nozzle, but the flame will probably be longer. Recommended Combustion Chamber Dimensions Nozzle Size or Rating (GPH) 0.50 – 0.65 0.75 – 0.85 1.00 – 1.10 1.25 – 1.35 1.
Effects of Excess Air On Nozzle Performance Excess air in the system can be a trouble spot. Of course the burner must have sufficient air to provide good mixing of air and fuel oil, or you get incomplete combustion and smoke. Unfortunately, as the amount of air is increased, the transfer of heat is reduced. A delicate balance must be achieved between smoke problems (caused by insufficient excess air) and reduced heat transfer (caused by unnecessary excess air).
Effects of Pressure On Nozzle Performance Normally, 100 psi is considered satisfactory for the fixed pressure supplied to the nozzle, and all manufacturers calibrate their nozzles at that pressure. It is interesting to observe the sprays of a nozzle at various pressures. See Figures 11-13. At the low pressure, the cone-shaped film is long and the droplets breaking off from it are large and irregular. Then, as the pressure increases, the spray angle becomes better defined.
Effects of Pressure On Nozzle Flow Rate Nozzle Rating at 100 PSI 120 PSI 0.40 0.50 0.60 0.65 0.75 0.85 0.90 1.00 1.10 1.20 1.25 1.35 1.50 1.65 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 4.00 4.50 5.00 5.50 6.00 6.50 7.00 7.50 8.00 8.50 9.00 9.50 10.00 11.00 12.00 13.00 14.00 15.00 16.00 18.00 20.00 22.00 24.00 26.00 28.00 30.00 32.00 35.00 40.00 45.00 50.00 0.44 0.55 0.66 0.71 0.82 0.93 0.99 1.10 1.20 1.31 1.37 1.48 1.64 1.81 1.92 2.19 2.46 2.74 3.01 3.29 3.56 3.83 4.38 4.93 5.48 6.02 6.57 7.12 7.67 8.22 8.
Figure 12 Spray at 100-psi pressure Figure 13 Spray at 300-psi pressure Effects of Viscosity On Nozzle Performance (Also see page 26) One of the most important factors affecting nozzle performance is viscosity, technically defined as a measure of resistance to flow within a liquid. More commonly, viscosity is thought of in terms of “thickness.” For example, a gallon of gasoline can be poured through the spout of a can much faster than a gallon of tar.
ity s Visco rature e Temp Temperature F 100 80 30 20 Viscosity (SSU) 35 37 52 65 Figure 14 How temperature affects viscosity. Although such situations are not widespread, it is good to know how to diagnose the problem and find a solution for it. While some success has been reported with special nozzles, most service technicians have found that the surest solution is to increase the energy input. This is done by increasing pump pressure from 100 psi to 120-125 psi.
Examples of Proper Nozzle Selection The following recommendations are solidly based on many years of field experience and laboratory testing. But, like most recommendations, they are subject to exceptional cases or conditions. Figure 17 Hollow Air Pattern Burners with Hollow Air Pattern The burner air pattern shown above produces a very definite hollow “air spray,” with no measurable air velocity at the center of the pattern.
Burners with Flame Retention Heads This type of firing is standard on all new equipment and most upgraded conversions. As the name implies (flame retention), the flame front is retained, or locked in close to the burner head. This is accomplished by means of a specially designed disc, with slots or edges over which the air flows, creating a recirculating airflow. Properly designed and located, a flame retention head produces an efficient, compact, bushy fire that is free from smoke or excessive noise.
Fuel Savings Devices For the Consumer Fuel-saving devices and systems available to the consumer are numerous and vary in cost, benefit and function. Since each homeowner’s circumstances differ, the service technician can determine what option will benefit the homeowner the most. Several of these options have been tested by the Brookhaven National Laboratory, Upton, NY. They report that: 1.
Residential Oil Burner Adjustments for Optimum Fuel Utilization For complete instructions refer to these publications: “Guidelines for Residential Oil Burner Adjustments,” U.S. Environmental Protection Agency “The Professional Serviceman’s Guide to Oil Heat Savings,” R.W. Beckett Corp., 38251 Center Ridge Road, P.O. Box D, Elyria, OH 44035 Adjustments Concerning Nozzles Annual replacement of the nozzle is recommended. The nozzle size should match the design load. DO NOT OVER SIZE.
Oil Burner Nozzles Delavan ProTek™ Nozzle System The Delavan ProTek™ Nozzle System combines a Delavan nozzle and the unique Delavan ProTek™ Valve Component, a patented nozzle filter with a built-in control valve. This unique System has been designed to improve nozzle performance at start up and prevent poor shut off and after drip.
Nozzle Filters & strainers Sintered Filter Mesh Strainer Sintered filters (for lower gph nozzles) are made of thousands of tiny bronze pellets fused together into a most effective filtering medium of uniform thickness and density. Delavan mesh strainers are constructed of brass bodies and monel screens. Nozzle filters and strainers cannot be expected to handle the complete filtering job. A line filter between the tank and burner is strongly recommended. Furnished as Standard on these sizes .40 .50 - 2.
Other Helpful Delavan Residential Oil Heat Accessories Adaptrap / Nozzle Adapters Part Number 1 5/8” 1 3/8” Length Length 37231-3 37231-4 37231-1 37231-2 Pipe Size 1/8 1/4 Available in brass only.
Nozzle Care and Service Tips An oil burner nozzle is an intricate piece of hardware, designed to do an accurate job of atomizing and metering fuel oil in the spray pattern best suited to a given burner. You can help assure top performance of this vital component by following the important guidelines in this section. Until installation, keep nozzles in their original containers and preferably in a suitable box or rack.
VERY IMPORTANT Before installing a new nozzle, it is very important to flush the nozzle line and adapter with at least a pint of oil pumped through it to remove sludge and dirt. Or you can blow out the line with compressed air if it’s available. Failure to do this has been the reason for numerous callbacks for plugged nozzles. The nozzle orifice is polished to a glasslike finish. Don’t ruin it with a wire or pin, or by bumping it with a wrench. This can cause streaks in the spray.
Make sure the fuel tank is clean. Water and sludge in the tank can clog lines, filter or nozzles. Be sure the supply line filter (between tank and burner) is adequate for the size of nozzle used. It will remove many of the small particles which may be present in the fuel oil or formed in the tank. Filtration is particularly recommended for burners using small nozzles. The filtering element should be replaced at each summer cleanup and the line flushed out with oil.
General Trouble Shooting Guide DETERMINING BURNER PATTERN To establish the correct spray pattern, try a hollow cone nozzle with an 80° spray angle (a popular angle in the industry). If the pattern is not satisfactory change to a solid cone nozzle. Reducing nozzle angle in 10° increments from 80° is a good way to find proper angle. (Mobile home units usually require 90° spray angles.) NOISY FIRES Pulsation and thumping or rumbling can be most objectionable to a homeowner.
DELAYED IGNITION Check the following items: • Check for proper electrode setting. • Check the insulators for cracks or for a conducting coat of soot or oil. Cracks sometimes occur under the electrode bracket, causing a short circuit. • Check to see that the air shutter isn’t too wide open. Nozzle 45° 60° 70° 80° 90° GPH (.75-4.00) (.75-4.00) (.75-4.00) (.75-4.00) (.75-4.
SMOKY FIRES Since there are a number of possible causes, it follows that there are several things to check: • Check the air handling parts of the burner. Make sure the fan blades, air intake and air vanes in the combustion head are clean. If dogs or cats are kept in or near the furnace room, it’s not uncommon to find hair in the oil burner fan. • Check combustion chamber or the burner tube for damage. In the case of a stainless steel chamber, it might be burned through in one or more places.
OFF-CENTER FIRES • May be caused by off center location of the nozzle in the burner tube. The nozzle tube or bracket may be bent or improperly located • If the heavy flame always appears on the same side in a particular burner, this is due to a peculiarity of the air pattern in that burner and it can’t be corrected by changing nozzles. • A nozzle contaminated by sludge or other foreign matter will usually produce an off center fire.
Questions Asked by Oil Heating Service Technicians I have a job on which it is difficult to clean up the fire. What should I do? 1. Check the fire to see whether it is off center (see discussion of off center fires next column). 2. Check the fan blades and if they are covered with lint and dirt, clean them. 3. If this is a conventional oil burner, check for a burned-off end cone. 4. Check the oil pressure to be sure that it is at least 100 psi. 5. Check for a plugged line filter or pump strainer. 6.
The fire in a burner is always off center and heavy on the right side. I can’t find a nozzle that will straighten up the fire. 1. If the flame is always heavy on one side, the nozzle does not cause it. It would be impossible to make a nozzle spray that is heavy on one side and always have it come up on the same side of the burner. 2. Check the position of the nozzle in the burner head. The chances are it is off to one side or the other. 3.
If the burner sometimes fails to ignite smoothly and starts with a puff, what can be done to improve it? 1. Check the electrode points for proper spacing. The points should be 1/8” to 3/16” apart, 9/16” above the centerline of the nozzle and then spaced correctly forward from the face of the nozzle for each different spray angle. 2. Clean carbon and dirt from the points and from the insulators. 3. The transformer may be weak and not delivering full voltage or current.
Other Delavan Nozzles Available (See Oil Burner Nozzle Catalog #1709E for ordering and technical information.) Oil Burner Nozzles for Industrial Applications VarifloTM Pressure Atomizing Nozzles for good atomization over a wider flow range. AiroTM Pressure Atomizing Nozzles for good atomization over a wider flow range. Siphon Type SNATM Air Atomizing Nozzle for extremely fine spray particle over a wider flow range.
The Delavan Promise: QUALITY Delavan has been designing and manufacturing nozzles for the oil heating industry for over 55 years. Quality assurance was important to us in 1945 and still is. Since those early days, Delavan has grown and expanded into other product lines as well, such as gas turbine engine nozzles and accessories; nozzles, pumps and accessories for agricultural and industrial spraying, and controls for process instrumentation.
