Steam boiler explodes
An explosion occurred in the combustion chamber of a high pressure oil-fired steam boiler. A faulty fuel solenoid may have contributed to an accumulation of fuel in the combustion chamber leading to an explosion of un-burned oil in the combustion chamber.
The boiler burner management system is a microprocessor-based control system designed to provide proper burner sequencing, ignition and flame monitoring protection for automatically fired burners. Along with the operating controls, it sequences the burner/blower motor, ignition and fuel valves to provide a safe pilot ignition and main flame burner operation.
BC Safety Authority’s investigation identified the following findings and contributing factors:
- The burner management flame control was sent to the manufacturer for analysis and its findings were submitted to BCSA. The manufacturer’s report did not find any malfunction with the control.
- Nozzles were found to be heavily covered in soot. A licensed BC Class A contractor inspected the burner nozzles and reported that they may have contributed to an ignition failure.
- Ignition electrodes were identified to be set too far apart and may have contributed to a delayed ignition. The flame controller was set to lock out the ignition sequence if it did not detect a flame within 10 seconds. The manufacturer’s report indicated there was no malfunction with the control.
- An inspection determined that a failure of the fuel solenoid valve on the fuel line from the fuel pump to the nozzles may have provided enough fuel for an explosive situation.
- One of the crew, a motor hand who was responsible for the blow‐downs of the boiler, did not possess a certificate of qualifications for that work and had only four hours of boiler operation instruction. This operator's training was not compliant with regulatory requirements.
- Logbook records for the time period reviewed did not include comments or observations of findings during daily checks. No one performing daily checks signed the logbook. There is no objective evidence in the logbook to support supervisor verification of personnel performing boiler related duties.
- Maintenance records showed that the boiler annual service was performed which included cleaning and a check of all burner controls, fuel lines, all electrical connections and all operating and safety controls as well as firing the boiler. The records did not identify any problems with the boiler.
The investigation is documented in our enhanced incident investigation report format.