Heater coil failures in midstream operations are not “normal maintenance.” If your fired heater coils are rupturing every 18 months or failing every three years, that’s not bad luck — it’s a heater design problem.
At Tulsa Heaters Midstream, we regularly see operators replacing coils over and over in older heaters from competitors. The real issue isn’t the coil itself; it’s the heater geometry, flame control, heat flux, and material selection that create premature coil failures.
Let’s break down what’s actually causing heater coil failures, and how to fix them for good.
Why Heater Coils Fail in Midstream Operations
In fired heaters, the burner is the heart of the system, but the coil is where heat transfer happens. If the coil fails, your heater is down — and downtime costs serious money.
The most common causes of heater coil failure in midstream facilities include:
- Excessive tube metal temperature (TMT)
- Poor radiant box design
- Flame impingement on convection tubes
- High heat flux due to undersized radiant sections
- Improper coil spacing
- Corrosion from flue gas condensation
- Inadequate metallurgy for operating conditions
If your heater design is wrong, coil failures are guaranteed — no matter how many times you replace the tube bundle.
Elastic Failure vs. Rupture Failure in Heater Coils
Heater coil failures typically occur in two ways:
1. Elastic Failure (Most Common in Midstream Heaters)
Elastic failure happens when pressure and temperature exceed the material’s design limits. In midstream fired heaters, coils should operate within this elastic region — not near rupture conditions.
Poor heat transfer modeling or incorrect tube metal temperature predictions can push coils into failure even when pressure appears normal.
2. Rupture or Creep Failure (More Common in Refinery Furnaces)
In refinery heater design, coils may be intentionally designed closer to rupture limits for long-term operation (e.g., 100,000-hour creep life).
Midstream heaters should never operate in rupture failure territory.
If your midstream heater coils are rupturing repeatedly, your heater design is fundamentally flawed.
The #1 Design Flaw: Radiant Box That’s Too Small
One of the biggest causes of heater coil failure is an undersized radiant box.
When the radiant section is too small:
- The flame cannot be fully contained
- Flames extend into the convection section
- Shock tubes experience extreme temperatures
- Tube metal temperatures spike
- Coil rupture becomes inevitable
Flame impingement on tubes is one of the fastest ways to destroy heater coils.
If the flame touches the convection tubes, you’re dramatically exceeding design assumptions — and your heater coil life drops from decades to months.
High Heat Flux: Too Much Fire, Not Enough Surface Area
Another major cause of fired heater coil failure is excessive heat flux.
This happens when:
- The radiant section is too small
- There isn’t enough heat transfer surface area
- The coil geometry is too compact
- The heater design concentrates too much heat in one location
High heat flux = higher tube metal temperature = faster failure.
Proper heater design spreads heat evenly across sufficient coil surface area to keep tube metal temperatures within safe limits.
Coil Spacing Matters More Than You Think
Tightly wound coils are another hidden failure point.
When coils are too close together:
- Radiant heat cannot reach the back side of the tube
- Heat transfer becomes uneven
- The flame-facing side overheats
- Localized hot spots form
- Coil rupture risk increases
Proper coil spacing allows radiant energy to reflect off refractory walls and evenly heat the entire circumference of the tube.
Uniform heat transfer dramatically increases heater coil life.
Corrosion: The Silent Killer of Heater Coils
Not all heater coil failures come from overheating. Corrosion can destroy coils from the outside in.
Common Corrosion Causes:
- Low process inlet temperatures
- Flue gas condensation
- Carbonic acid formation on tube surfaces
- Frequent heater cycling (on/off operations)
- Poor post-purge procedures
When flue gas moisture condenses on coils, corrosion accelerates, especially in tightly wound radiant sections. Over time, the metal thins and fails under pressure.
Fixing the Problem Without Buying a New Heater
If replacing the entire fired heater isn’t an option right now, there are still ways to extend heater coil life:
Upgrade Coil Metallurgy
Instead of replacing carbon steel coils with the same material:
- Upgrade to low-chrome alloys
- Consider 304 stainless steel coils for high-temperature durability
Yes, stainless costs more — but replacing coils every 18 months costs far more in downtime, labor, and lost production.
Improve Heat Transfer Geometry (When Possible)
- Add heat transfer surface area
- Reduce heat flux where feasible
- Improve flame containment
- Adjust coil spacing during rebuilds
Improve Startup & Shutdown Procedures
- Proper post-purge to remove moisture
- Avoid repeated cold starts
- Prevent condensation-related corrosion
Heater Coils Should Last Decades — Not Years
A properly designed fired heater coil should last 20 to 30 years, not 18 months.
If your facility is on a constant cycle of heater coil replacement, the problem is not your maintenance team, it’s your heater design.
Stop Paying for the Same Heater Coil Failure Over and Over
Repeated heater coil rupture is a design failure, not normal wear and tear. Tulsa Heaters Midstream designs fired heaters so that coils:
- Stay within elastic failure limits
- Avoid flame impingement
- Maintain safe tube metal temperatures
- Deliver long-term reliability
- Reduce downtime and replacement costs
If your heater coils keep failing, it’s time to fix the root cause — not just replace the symptom.
Ready to Stop Coil Failures for Good?
If your fired heater coils are rupturing, leaking, or failing prematurely, Tulsa Heaters Midstream can help you identify the design flaw and engineer a long-term solution.
Stop replacing coils. Start fixing the problem.