TL;DR
Duct burner ignition failure is usually a BMS permissive not met, a failed igniter, or low fuel gas pressure. Check the BMS permissive list first before touching the burner hardware.
What you might see
- duct burner ignition attempt fails with no flame confirmation
- UV or IR flame detector not confirming flame after igniter fires
- fuel gas pressure at the burner below normal
- burner management system (BMS) showing ignition lockout
Likely causes
BMS permissive not satisfied (purge not complete, oxygen in flue gas too low, fan not proven)
Faulty igniter plug or damaged igniter cable causing no spark
Fuel gas pressure below the minimum pressure switch setpoint
UV or IR flame detector contaminated or failed, not confirming a flame that is actually present
Required tools
- BMS permissive list on DCS or panel
- Fuel gas pressure gauge at burner inlet
- Replacement igniter plug (same specification)
- LOTO kit for fuel gas supply isolation
Safety first
- Never bypass the duct purge timer permissive. Igniting into an un-purged duct risks a deflagration.
- Always lock out the fuel gas supply before inspecting or replacing the igniter plug.
Procedure
- 1
Read the BMS permissive list on the control panel or DCS. Identify which permissive is blocking the ignition sequence.[1]
- 2
Verify the duct purge cycle has completed with adequate airflow time to satisfy the purge permissive.
Warning: Never bypass a duct purge permissive. An un-purged combustion duct can detonate on igniter spark if residual unburned fuel is present. - 3
Check the fuel gas supply pressure at the burner inlet isolation valve. Confirm the pressure is above the minimum pressure switch setpoint.
- 4
Attempt one ignition sequence from the BMS. If no spark is heard and the flame detector does not confirm, lock out the duct burner fuel supply.
- 5
With the fuel supply locked out and the duct adequately cooled, inspect the igniter tip for fouling or damage. Replace the igniter plug if the electrode gap is worn or the insulator is cracked.
- 6
Clean or replace the UV or IR flame detector if it is contaminated. Perform a functional test with a flame torch before returning it to service.
- 7
After repairs, perform a full BMS restart sequence and confirm ignition and flame hold.
Sources
Vogt Power Vogt-Nemag HRSG (Heat Recovery Steam Generator) general technical documentation, Vogt Power
HRSG duct burner management system operation and igniter maintenance, general power generation references (general)
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