When a fired heater won't light or unexpectedly shuts down, the culprit is often much smaller than you think.
Based on industry experience, pilot burners account for a significant share of fired heater issues, making them among the most important components to understand and maintain.
In the latest educational video from Tulsa Heaters Midstream, we explain how pilot burners work, why they fail, and what operators can do to keep their fired heaters operating reliably.
Why Pilot Burners Matter
A pilot burner may be small, but it performs one critical job:
It safely ignites the main burner.
Without a reliable pilot:
- The main burner won't light.
- Startup procedures become more difficult.
- Downtime increases.
- Troubleshooting takes longer.
Unfortunately, pilot problems rarely happen at convenient times. Many operators know the frustration of dealing with an ignition issue late on a Friday, during bad weather, or over a holiday weekend.
Understanding your pilot system before problems occur can save valuable time when every minute counts.
How a Pilot Burner Works
Most modern fired heater pilots use a premix burner design.
Before ignition, fuel gas and combustion air are mixed inside a Venturi.
This creates:
- Excellent air-to-fuel mixing
- Stable combustion
- A clean blue pilot flame
- Reliable ignition performance
The pilot tip is manufactured from high-temperature alloys because it must withstand continuous exposure to extreme heat.
A properly adjusted pilot produces:
- A stable blue flame
- Even heating around the pilot tip
- Reliable ignition of the main burner
Why Is There a Second Flame?
Many operators notice a larger yellow flame near the pilot.
This comes from what's commonly called the raw gas dump.
Its purpose is simple:
Easier Main Burner Ignition
The larger flame gives the main burner a larger ignition source.
Better Flame Scanner Detection
A larger flame is easier for flame scanners to detect, reducing nuisance trips during startup.
How Modern Pilot Ignition Works
Older fired heaters often required operators to light pilots using handheld torches manually.
Today's systems typically use high-voltage spark ignition.
An ignition transformer sends approximately 10,000 volts through an ignition cable to a spark plug located near the pilot tip.
When the spark jumps the electrode gap, the premixed fuel-air mixture ignites.
The process is similar to the spark plug in an automobile engine—but designed for industrial fired heater applications.
The Most Common Pilot Burner Problems
1. Ignition Wire Shorts
The most common failure occurs when the high-voltage ignition system develops a short.
If power is reaching the ignition transformer but no spark is visible, the problem is often:
- Damaged insulation
- Cracked ceramic insulators
- Moisture intrusion
- Worn ignition cables
Even a very small insulation defect can prevent proper ignition.
2. Plugged Gas Spud
Pilot gas passes through a very small orifice before entering the Venturi.
Because the opening is extremely small, debris can easily block fuel flow.
Installing quality gas filters helps reduce this risk, but contamination can still occur over time.
3. Dirty Venturi
Dust, dirt, or oily residue can accumulate inside the Venturi.
When airflow becomes restricted:
- Air/fuel ratios change
- Ignition becomes unreliable
- Flame quality deteriorates
- Pilot performance decreases
Routine inspection and cleaning help prevent these issues.
Preventive Maintenance Pays Off
Instead of waiting for an unexpected shutdown, operators should regularly inspect:
- Ignition wiring
- Ceramic insulators
- Spark gap
- Pilot gas filters
- Venturi cleanliness
- Pilot flame quality
Simple inspections can prevent hours of downtime later.
The Bottom Line
Pilot burners may be one of the smallest components in a fired heater, but they have an outsized impact on reliability.
Understanding how they operate—and recognizing common failure points—helps improve startup reliability, reduce downtime, and simplify troubleshooting.
For anyone responsible for fired heater operation or maintenance, knowing your pilot system is time well invested.