NORTHERN NATURAL GAS CO
gas_transmission Incident — — January 2, 2022
Incident Information
| Incident Date | January 2, 2022 |
| Operator | NORTHERN NATURAL GAS CO |
| Commodity | NATURAL GAS |
| Pipeline Type | gas_transmission |
Location
| State | |
| Coordinates | 40.96695, -95.93022 |
Cause
| Cause | EQUIPMENT FAILURE |
| Subcause | MALFUNCTION OF CONTROL/RELIEF EQUIPMENT |
Casualties
| Fatalities | 0 |
| Injuries | 0 |
Costs
| Property Damage | $300 |
| Emergency Response | $0 |
| Other Costs | $0 |
Location Map
Incident Narrative
"ON JANUARY 2, 2022, AT 1800 HOURS, THE OPERATOR WAS NOTIFIED BY A PASSERBY OF A LOUD NOISE NEAR THE OMAHA 1ST BRANCH LINE REGULATOR. TECHNICIANS ARRIVED ON SITE AND FOUND A RELIEF VALVE VENTING AT APPROXIMATELY 1920 HOURS. PRESSURE WAS VERIFIED TO BE NORMAL (SETPOINT 460 PSIG) DOWNSTREAM OF THE REGULATORS. TECHNICIANS ISOLATED THE RELIEF VALVE AT 1930 HOURS AND RETURNED THE RELIEF VALVE TO SERVICE AT 0030 HOURS JANUARY 3, 2022. INVESTIGATION CONCLUDED THAT MOISTURE BUILDUP IN THE RELIEF VALVE PILOT SENSE LINE STARTED FREEZING DUE TO AMBIENT TEMPERATURES, CAUSING ICE TO FORM IN THE SENSE LINE AND INCREASE PRESSURE TO THE PILOT ASSEMBLY. THIS ICE BUILDUP CAUSED THE RELIEF TO VENT BELOW THE SETPOINT. ADDITIONALLY, A SLIVER OF MATERIAL PREVENTED THE SEAL ON THE RELIEF VALVE TO CLOSE. THE SITE WAS CHECKED REGULARLY FOR REOCCURRENCE WITH NO NEW CONCERNS FOUND. THE INVESTIGATION WAS SHARED WITH OTHER TEAMS TO EVALUATE SIMILAR SCENARIOS."
About This Pipeline Incident
Pipeline incident data is reported to the Pipeline and Hazardous Materials Safety Administration (PHMSA). All significant incidents involving fatalities, injuries, or property damage over $50,000 must be reported.