Step-by-step Guide to Fired Heater Startup and Shutdown Procedures

Introduction

Fired heaters—also known as process heaters or furnaces—are critical assets in refineries, chemical plants, and other industrial facilities. They provide high-temperature heat for processes such as crude oil distillation, catalytic reforming, and steam reforming. Startup and shutdown of these heaters must follow strict procedures to prevent accidents, equipment damage, and unplanned downtime. Even a minor deviation can lead to tube failures, thermal shock, or combustion instability. This guide outlines the essential steps for safe and reliable fired heater startup and shutdown, covering both normal and emergency scenarios. Operators should always consult their specific equipment manuals and site-specific operating procedures, as heater designs vary.

Preparation Before Startup

Thorough preparation prevents many common problems. Before lighting any burner, complete the following checks:

Mechanical and Structural Inspection

Inspect refractory lining for cracks, spalling, or gaps. Damaged refractory can lead to hot spots and structural damage.
Check tubes for signs of creep, bulging, corrosion, or external fouling. Tube integrity is paramount.
Verify that all access doors, observation ports, and explosion doors are closed and secure.
Ensure the stack is clear of obstructions; check for debris or birds' nests that could impede draft.

Instrumentation and Controls

Calibrate and test all thermocouples, pressure transmitters, and flow meters. Confirm readings match known values.
Verify that safety shutdown systems (flame scanners, high-temperature trips, low-fuel-pressure trips) are functional and not bypassed.
Test the burner management system (BMS) per manufacturer recommendations. Cycle check valves and actuators.
Confirm that fuel gas (or oil) supply pressure and quality meet specifications. Remove any condensate from gas lines.

Utility Systems

Ensure instrument air, cooling water, and steam (for atomization or soot blowing) are available at adequate pressure.
Verify that electrical supplies to fans, pumps, and control panels are on and stable.
For forced-draft or induced-draft heaters, test damper operation and fan rotation direction.

Safety and Area Preparation

Confirm that fire-fighting equipment (extinguishers, fire monitors) is accessible and inspected.
Ensure all personnel in the area understand that startup is in progress. Gas tests may be required in confined spaces.
Review the startup sequence with the operations team. Assign roles for burner observation and remote panel monitoring.

Step-by-Step Startup Procedure

Always follow the manufacturer's startup sequence outlined in the equipment manual. The steps below are a general guideline for typical natural-draft and forced-draft fired heaters.

1. Purge the Heater

Purging removes any combustible gas or vapor from the firebox and flue gas path. Run the forced-draft fan (or natural draft with dampers open) for at least five air changes of the heater volume, or as required by NFPA 86 and local codes. Confirm with an oxygen analyzer that the oxygen concentration in the firebox is at least 20% by volume before lighting any burner.

2. Verify Pilot Burner Operation

If the heater uses a pilot burner, open the pilot fuel valve and ignite the pilot manually or via an ignition transformer. The pilot must produce a stable, proven flame before opening the main burner fuel valve. Check the flame scanner response; a false flame signal can cause serious issues.

3. Light the Main Burner(s)

With the pilot established, open the main burner fuel valve slightly. Introduce fuel gradually while monitoring for ignition. If ignition does not occur within a few seconds, close the fuel valve immediately and repeat the purge cycle. NEVER attempt to relight a burner that has failed without purging again. Adjust primary air registers to achieve a stable, blue flame with minimal yellow tipping.

4. Warm-Up Phase (Heat Soak)

After lighting the burner(s), do not increase the firing rate too quickly. The heater components—tubes, refractory, and casing—must warm up uniformly to avoid thermal shock and stress cracking. Follow the manufacturer's warm-up curve, typically holding at a low fire rate for 30 minutes to an hour. Monitor tube metal temperatures and refractory surface temperatures. Record all readings.

5. Increase Heat Load Gradually

Once the heater has stabilised at low fire, increase the fuel flow stepwise, allowing temperatures to equalize at each step. Continue until the desired process outlet temperature is reached. Adjust excess oxygen levels to maintain optimal combustion (usually 2–4% O2 for gas-fired heaters, 3–5% for oil-fired). Check draft at the radiant section outlet; maintain a slight negative pressure (typically −0.05 to −0.15 in. w.c.) to prevent flame puffing.

6. Final Checks and Handover

When the heater is at normal operating conditions: verify all safety trips are armed, confirm that tube skin temperatures are within limits, inspect burner flames (all tips should be stable green/blue, no impingement on tubes), and log steady-state parameters. Hand over to shift operations with clear notes on any anomalies observed during startup.

Step-by-Step Shutdown Procedure

Shutdown can be planned (normal) or emergency. Both require careful control of temperature and fuel.

Normal (Planned) Shutdown

Reduce heat input gradually – Lower the fuel flow stepwise while maintaining stable combustion. Avoid abrupt fuel cuts that could cause backflow or explosion. Over 15–30 minutes, bring the heater to low-fire condition.
Turn off the burner(s) – Once at low fire, close the main burner fuel valve. If pilots are used, close the pilot fuel valve after confirming the main flame is extinguished. The flame scanner should indicate loss of flame.
Purge the firebox – After burner shutdown, continue to run the fan (or maintain natural draft) for at least 5 minutes to clear any residual combustible gases. This is critical before opening any doors.
Allow natural cooling – Do not force cool the heater with excessive draft or water spray. Thermal shock can crack tubes and refractory. Monitor cooling rates; typical maximum is 50°C per hour for the first few hours.
Isolate and blind – Once cool enough (usually below 150°C tube skin temperature), close manual block valves and install positive isolation (blinds or removable spools) on fuel and process lines. This ensures safety for maintenance.
Secure auxiliary systems – Turn off fans, purge steam, and lock out electrical panels.
Final inspection and records – Conduct a visual inspection of the firebox, tubes, and refractory. Record any abnormalities, such as cracked tubes or fallen refractory. Update heater inspection database.

Emergency Shutdown (ESD)

An emergency shutdown may be triggered by high tube skin temperature, low flow, fire, or a process upset. The sequence is typically automated but manual intervention may be needed.

Activate ESD – The BMS immediately closes all fuel block valves and isolates the heater. If the ESD is not automatic, the operator must manually hit the emergency stop.
Maintain purge – Do NOT immediately stop the fan. Continue purging for at least 5 minutes to sweep combustibles out of the system.
Isolate process fluids – If the process continues to flow, the heater tubes may become heat sinks; close the process inlet/outlet isolation valves if safe to do so.
Evacuate and assess – Ensure all non-essential personnel leave the area. Use gas detectors to check for leaks. Only re-enter when cleared by safety.
Post-emergency – Do not attempt to relight the heater until the cause of the emergency is identified and corrected. A root cause analysis should follow.

Troubleshooting Common Startup and Shutdown Issues

Problem	Possible Cause	Corrective Action
Flame instability / blow-off	Low fuel pressure, high draft, or fuel composition change	Check fuel pressure, adjust damper, verify fuel quality
Delayed ignition (explosion risk)	Inadequate purge, fuel valve leaks, pilot too weak	Stop, purge for 5 minutes, fix leaks, strengthen pilot
Excessive tube metal temperature during warm-up	Firing rate too high, low process flow, burner misalignment	Reduce fire, increase flow, realign burner tips
Smoke at stack during startup	Insufficient air, oil burner atomization poor	Increase primary air, clean oil nozzle and strainer
Hot spots in refractory	Localized overheating, damaged lining	Shut down and repair refractory section

Safety Best Practices and Compliance

Adhering to industry standards reduces risk. Key references include NFPA 86 (Standard for Ovens and Furnaces), API Recommended Practice 556 (Fired Heaters and Steam Generators), and local occupational safety regulations. Critical safety practices:

Lockout/Tagout (LOTO) – Always apply LOTO to fuel valves, fans, and electrical disconnects during maintenance shutdowns.
Personal Protective Equipment (PPE) – Wear hard hat, safety glasses, flame-resistant clothing, and heat-resistant gloves when near a fired heater. Use hearing protection near fans.
Continuous gas monitoring – Install fixed combustible gas detectors in the heater area and test portable detectors before entry.
Regular training and drills – Conduct annual simulator training for startup/shutdown sequences and emergency response. Document all drills.
Preventive maintenance – Follow manufacturer’s maintenance schedule for burners, safeguards, and refractory. Replace flame scanners before the end of their service life.
Documentation – Keep a log of every startup and shutdown, including temperature ramps, pressure changes, and any alarms. This data helps identify trends and prevent failures.

Conclusion

Fired heater startup and shutdown procedures are not routine checklists; they are critical safety operations that require discipline, knowledge, and vigilance. By systematically preparing, purging, gradually warming, and then cooling down, operators can protect equipment integrity and prevent accidents. Understanding both normal and emergency sequences ensures that even under unexpected conditions, the team can respond correctly. For further reading, consult OSHA guidelines on industrial furnaces and the U.S. Department of Energy industrial heating resources. Regular training and adherence to these procedures will keep fired heaters operating safely and efficiently for years.