A petroleum burner is a combustion device that atomises liquid fuel oil into a fine spray, mixes it with combustion air, and ignites it to release heat. Unlike a gas burner, which burns vapour directly, a petroleum burner must first break the liquid into droplets small enough to vaporise in flight — typically 20-100 µm. We use them to fire steam boilers, kilns, asphalt plants, and marine auxiliary plants where the energy density of fuel oil (around 140,000 BTU/gal for No. 2) beats compressed gas storage. A modern pressure-jet burner running 0.85 GPH delivers roughly 119,000 BTU/hr at 80% combustion efficiency.
Petroleum Burner Interactive Calculator
Vary fuel flow, heating value, and burner efficiency to see gross firing rate, useful heat output, and losses in a pressure-jet petroleum burner.
Equation Used
The calculator multiplies oil flow rate by fuel heating value to estimate gross firing rate. It then applies combustion efficiency to estimate useful heat output: useful heat = GPH x BTU/gal x eta.
- Fuel flow is the nozzle rating or actual oil flow in gallons per hour.
- Heating value is entered in BTU per gallon for the fuel oil.
- Efficiency is applied to gross fuel heat to estimate useful delivered heat.
The Petroleum Burner in Action
A petroleum burner does three things in sequence — pressurise the oil, shred it into droplets, and meter the right mass of air to burn those droplets clean. The pump (usually a Suntec A-series gear pump on small units) lifts oil to 100-300 psi and forces it through a nozzle with a swirl chamber upstream of a sharp-edged orifice. The swirl spins the oil into a thin conical sheet, the sheet breaks into droplets at the orifice exit, and a flame retention head shapes the air pattern around the spray cone so the droplets vaporise and burn before they hit cold steel. If the nozzle bore wears even 0.05 mm oversize, the spray angle widens, droplets get larger, and you'll see soot streaks on the boiler tubes within a week.
Why build it this way? Because liquid hydrocarbons don't burn — only their vapour burns. The whole job of a petroleum burner is to turn liquid into vapour fast enough to keep up with the air being pushed through it. Atomisation is the rate-limiting step. Pressure jet burners (residential and small commercial) handle this with hydraulic pressure alone. Steam atomising and air atomising burners (industrial, marine, heavy fuel oil applications) use a second fluid — steam at 60-150 psi or compressed air — to shear the oil at the nozzle tip, which lets you burn high-viscosity residual fuel that a pressure jet would never atomise.
The failure modes are predictable. Carbon build-up on the nozzle tip narrows the orifice and skews the spray pattern — you'll smell unburned oil and see a yellow flame instead of a clean orange-yellow. A clogged oil filter starves the pump and the flame goes lazy. Wrong air-to-fuel ratio (target around 14:1 by mass for No. 2 oil, with 10-15% excess air) produces either soot at low excess or wasted heat up the stack at high excess. And on heavy fuel oil systems, drop the preheat below 100°C and the viscosity climbs past 20 cSt — the nozzle can't atomise it and the flame stalls.
Key Components
- Fuel Pump: A positive-displacement gear pump pressurises oil to 100-300 psi for pressure jet burners, or up to 1,000 psi on industrial units. Suntec, Danfoss, and Webster dominate the residential market. The internal regulator must hold pressure within ±5 psi at the nozzle to keep droplet size consistent.
- Burner Nozzle: A precision-machined swirl chamber and orifice rated in GPH at 100 psi (e.g. a Delavan 0.85-80°B flows 0.85 GPH with an 80° hollow cone). The orifice tolerance must hold within 0.025 mm — anything looser changes spray angle and droplet size enough to soot the heat exchanger.
- Flame Retention Head: A slotted disc that meters primary air around the spray cone and creates a recirculation zone to anchor the flame. Beckett AFG and Riello 40 series are the common references. The gap between the head and the nozzle face sets the air swirl — typically 3-6 mm, and 1 mm off spec will lift the flame or push it into the chamber wall.
- Combustion Air Blower: A forward-curved fan delivers 50-200 CFM at 1-2 inches water column for residential burners. Mass flow is what matters — you need roughly 14 lb of air per lb of oil for stoichiometric combustion of No. 2, plus 10-15% excess.
- Ignition Transformer & Electrodes: A 10-14 kV transformer fires a continuous arc across two electrodes positioned 4-5 mm apart, just outside the spray cone. Modern units use a solid-state igniter rated for 20,000+ ignition cycles. Electrode gap drift of even 1 mm causes intermittent lockouts on cold mornings.
- Oil Preheater (heavy fuel only): An electric or steam-traced heater that holds No. 6 residual oil at 100-130°C to drop viscosity below 20 cSt at the nozzle. Without it, heavy fuel atomisation fails completely. Marine auxiliary boilers and large industrial plants run preheat as a hard interlock — no preheat, no fire.
- Flame Sensor: A cadmium sulfide cell (cad cell) on residential burners or a UV scanner on industrial units. The sensor must see flame within 4 seconds of ignition or the controller drops out and locks. Cad cell resistance under flame should read below 1,600 Ω — drift above 5,000 Ω and you'll get nuisance lockouts.
Real-World Applications of the Petroleum Burner
Petroleum burners run anywhere fuel oil makes more economic sense than gas — remote sites without pipeline access, marine vessels, mobile equipment, and any plant burning waste oil or heavy residual fuel. The burner you pick depends on the oil grade and the firing rate. Small pressure jet burners (0.5-3 GPH) heat homes and small commercial buildings. Mid-range industrial burners (5-50 GPH) fire bakery ovens, asphalt plants, and grain dryers. Steam atomising burners on heavy fuel oil (50-500+ GPH) run marine auxiliary boilers, refineries, and stationary power plants.
- Marine: Aalborg Mission OL marine auxiliary boilers on bulk carriers fire Saacke or Oilon steam-atomising burners on No. 6 heavy fuel oil at 200-400 kg/hr, with steam atomising at 8 bar and oil preheat to 130°C.
- Asphalt Production: Astec Double Barrel asphalt plants use Hauck StarJet or Eclipse RatioMatic oil burners rated 30-150 million BTU/hr to dry and heat aggregate to 150°C in the drum.
- Residential Heating: Beckett AFG and Riello 40 F series pressure jet burners fire Buderus and Burnham cast-iron oil boilers at 0.6-2.0 GPH on No. 2 fuel oil — common across rural New England and Atlantic Canada.
- Industrial Drying: GSI and Mathews Company grain dryers in the Canadian prairies run Carlin EZ-Pro burners on diesel during harvest when natural gas service isn't available at the bin site.
- Steam Power: Cleaver-Brooks CBLE firetube boilers with Webster JBS burners fire 50-200 BHP on No. 2 oil for hospital steam plants and food processing facilities.
- Cement & Lime Kilns: FLSmidth Duoflex and Pillard Rotaflam burners fire rotary cement kilns at 10-200 MW on heavy fuel oil, petcoke, or alternative fuels with multi-channel air staging.
- Waste Oil Heating: Clean Burn and Lanair shop heaters run modified pressure jet burners on filtered used motor oil at 0.85-2.0 GPH in automotive and fleet maintenance shops.
The Formula Behind the Petroleum Burner
Sizing a petroleum burner comes down to matching firing rate to heat load. The core calculation converts nozzle flow (GPH) at the rated pressure into delivered heat (BTU/hr) using the fuel's heating value and the combustion efficiency. At the low end of the typical residential range (0.50 GPH on No. 2 oil), you're around 70,000 BTU/hr — barely enough for a tight 1,500 sq ft house. At the nominal mid-range (0.85 GPH) you're at 119,000 BTU/hr, the sweet spot for most North American oil-fired homes. Push to 1.50 GPH and you're at 210,000 BTU/hr — territory where the heat exchanger must be sized to absorb the heat, otherwise stack temperature climbs past 250°C and efficiency drops fast.
Variables
| Symbol | Meaning | Unit (SI) | Unit (Imperial) |
|---|---|---|---|
| Q | Delivered heat output | kW | BTU/hr |
| GPH | Nozzle flow rating at rated pressure | L/hr | gallons/hr |
| P | Actual pump pressure at nozzle | kPa | psi |
| Prated | Nozzle rating pressure (always 100 psi for US nozzles) | kPa | psi |
| HV | Heating value of fuel (138,500 BTU/gal for No. 2 oil, 150,000 for No. 6) | MJ/L | BTU/gal |
| η | Combustion efficiency (typically 0.78-0.87 for modern burners) | — | — |
Worked Example: Petroleum Burner in a remote logging-camp bunkhouse heating retrofit
A 14-cabin remote logging camp on northern Vancouver Island replaces a propane heating system with a centralised No. 2 fuel oil boiler. The camp manager picks a Carlin EZ-Pro 102CRD burner on a 250,000 BTU/hr-rated cast-iron boiler, fires it with a Delavan 1.10-80°A nozzle, and sets the Suntec A2VA-7116 pump to 140 psi for slightly elevated firing rate. Fuel is No. 2 heating oil at 138,500 BTU/gal. The combustion technician measures 82% steady-state combustion efficiency on a Bacharach analyser. They need the actual delivered heat output to confirm the boiler is sized correctly for the cabin loop loads.
Given
- GPH = 1.10 gal/hr at 100 psi
- P = 140 psi
- Prated = 100 psi
- HV = 138,500 BTU/gal
- η = 0.82 —
Solution
Step 1 — correct the nozzle flow for actual pump pressure. Nozzle output scales with the square root of pressure ratio:
Step 2 — calculate nominal delivered heat at the operating point:
Step 3 — at the low end of typical operation, drop pump pressure to the rated 100 psi and the nozzle flows the rated 1.10 GPH:
That's a 23,000 BTU/hr swing just from pump pressure — meaningful when sizing the boiler and the cabin loop. At the high end, pushing the same nozzle to 200 psi (the practical ceiling before atomisation degrades and you risk pump seal failure on a Suntec A2VA):
But push above 180 psi and droplet size starts dropping below 20 µm — not a problem in itself, except the flame gets shorter, hits the front wall of the combustion chamber, and you start seeing localised hot spots and refractory damage within a season.
Result
Nominal delivered heat at 140 psi is 147,800 BTU/hr. That's a comfortable 60% load on the 250,000 BTU/hr boiler — exactly where you want a multi-cabin loop running, with headroom for cold snaps. The range from 124,950 BTU/hr at rated pressure to 176,650 BTU/hr at 200 psi shows how much trim authority pump pressure gives you on a single nozzle, but the sweet spot sits around 130-150 psi where atomisation is clean and pump life isn't compromised. If your stack analyser shows lower output than predicted, check three things in order: (1) air shutter setting drifting open and pulling excess air past 20% — efficiency tanks above that; (2) heat exchanger soot fouling adding 30-50°C to stack temperature, which directly drops η; or (3) a partially plugged oil filter starving the pump so actual nozzle pressure sits well below the gauge reading at the pump outlet.
When to Use a Petroleum Burner and When Not To
Picking between a petroleum burner, a gas burner, and a solid fuel system comes down to fuel availability, firing rate, turndown, and capital cost. Here's how the real numbers compare on the dimensions that drive the decision.
| Property | Petroleum Burner (oil) | Natural Gas Burner | Solid Fuel (coal/biomass) |
|---|---|---|---|
| Firing rate range | 0.5 GPH to 500+ GPH (70k BTU/hr to 70M BTU/hr) | 30k BTU/hr to 500M+ BTU/hr | 100k BTU/hr to 1 GW+ utility scale |
| Turndown ratio | 3:1 typical, 10:1 with steam atomising | 5:1 standard, 20:1 with modulating | 2:1 for stoker, 4:1 for fluidised bed |
| Combustion efficiency | 78-87% (residential), 85-92% (industrial) | 80-95% | 65-85% |
| Fuel energy density | 138,500 BTU/gal (No. 2), 150,000 (No. 6) | 1,030 BTU/ft³ at line pressure | 8,000-13,000 BTU/lb |
| Capital cost (residential) | $2,500-4,500 burner + tank | $1,500-3,000 burner only | $5,000-15,000 with feed system |
| Service interval | Annual nozzle + filter, 1-2 hr | 2-3 year tune-up | Daily ash + weekly cleaning |
| Site requirements | 275-1000 gal tank, no pipeline needed | Gas service or LP tank | Fuel storage building, ash handling |
| Best application fit | Off-grid, marine, heavy industrial, waste oil | Urban/suburban with gas service | Utility power, large industrial process heat |
Frequently Asked Questions About Petroleum Burner
That's a classic late-stage atomisation failure — and it's almost always the cut-off behaviour of the pump's solenoid valve, not the nozzle itself. When the burner shuts down, the solenoid is supposed to close sharply at full pressure so the spray cone collapses instantly. If the solenoid is weak or the pump pressure has drifted low (below 100 psi on a 100-psi-rated nozzle), the oil dribbles for half a second after spark cuts and you get unburned droplets coking on the chamber walls. Next ignition cycle, those coke deposits flash off as soot.
Pull the pump pressure gauge during shutdown — pressure should drop from operating pressure to zero in under 0.5 seconds. If it bleeds down slowly, replace the cut-off solenoid or the whole pump.
Spray angle has to match the combustion chamber geometry, not the firing rate. A wide 90° cone fits a short, wide chamber — typical of older cast-iron boilers like a Burnham V8. A narrow 70° cone fits a long, narrow chamber like a modern three-pass like a Buderus G115. Put a 90° nozzle in a long chamber and the cone hits the side walls, droplets impinge on cold steel, and you get soot streaks. Put a 70° nozzle in a short chamber and the flame stretches past the chamber back wall into the flue collector, overheating it.
Default to whatever the boiler manufacturer specifies on the burner data plate. The 80° hollow cone is the most common compromise and works in roughly 70% of residential installations.
No, you've got too much excess air. CO₂ in the flue is a direct proxy for excess air on oil — stoichiometric combustion of No. 2 produces about 15.5% CO₂, and you lose 1% CO₂ for every 10-12% excess air. At 10% CO₂ you're running roughly 50% excess air, which is dragging cold air through the chamber and out the stack. Efficiency is probably sitting around 75% instead of the 83-85% the burner is capable of.
Close the air shutter in small increments while watching smoke spot. Aim for trace smoke (Bacharach 0-1) at maximum CO₂, then back off the shutter just until smoke is zero. You should land at 11-12.5% CO₂ on a clean burner.
Yes for kerosene, qualified yes for diesel. Kerosene (K-1) is essentially No. 1 fuel oil — slightly lighter than No. 2, atomises easier, and burns cleaner. Most Beckett and Riello burners list kerosene as an approved fuel with a small nozzle size adjustment (drop one size because kerosene's lower viscosity means the same nozzle flows more volume).
Highway diesel works mechanically but the ULSD specification has lower lubricity than heating oil. Suntec and Danfoss pumps depend on fuel lubricity for the gear set — extended diesel operation will wear the pump within 2-3 seasons. If you're running diesel as an emergency stopgap, fine. If it's your year-round fuel, add a lubricity additive at 1,000 ppm or expect to replace pumps regularly.
Preheat lag. No. 6 residual fuel oil has a viscosity of 200-700 cSt at room temperature — completely unatomisable. The preheater needs to bring the oil to 100-130°C to drop viscosity below 20 cSt before the nozzle can shred it into burnable droplets. On a cold start, the line oil between the preheater and the burner gun is also cold, and your first 30-60 seconds of firing pushes that cold slug through the nozzle.
Fix is either a recirculation loop that keeps preheated oil moving past the burner gun continuously, or a longer pre-purge with the preheater on but the burner off until inlet oil temperature stabilises. Marine auxiliary boilers solve this with a continuous warm-up loop and a dedicated diesel oil pilot for cold light-off, switching to HFO once the system is hot.
You probably sized correctly for design day (-20°C outdoor in many North American climates), but oil burners only modulate by switching on and off — single-stage burners run at one fixed firing rate. In shoulder season, design-day load is maybe 30% of capacity, so the burner short-cycles. Each cycle wastes the purge and warm-up energy and chases the thermostat above setpoint.
Two real fixes: drop one nozzle size to reduce firing rate (a 1.00 GPH down to 0.85 GPH cuts output 15%), or add outdoor reset on the boiler control to lower water temperature when outdoor temp rises, which lengthens cycle times. Don't oversize for design day — for oil, sizing right at calculated heat loss with no safety factor is correct. The factor is already baked into the calc.
References & Further Reading
- Wikipedia contributors. Oil burner. Wikipedia
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