NORTHERN NATURAL GAS CO
gas_transmission Incident —
Incident Information
| Report Date | — |
| Operator | NORTHERN NATURAL GAS CO |
| Commodity | — |
| Pipeline Type | gas_transmission |
Location
| State | |
| Coordinates | 42.43854, -91.28763 |
Cause
| Cause | EQUIPMENT FAILURE |
| Subcause | — |
Casualties
| Fatalities | 0 |
| Injuries | 0 |
Costs
| Property Damage | — |
| Lost Commodity | — |
| Public/Private Damage | — |
| Emergency Response | — |
| Environmental Remediation | — |
| Other Costs | — |
Location Map
Incident Narrative
A NEAR-BY RESIDENT REPORTED A NOISE AT THE EARLVILLE, IOWA, COMPRESSOR STATION AT 19:30 HOURS ON 4/4/15. OPERATIONS RESPONDED AND AND FOUND THE FISHER 399 FUEL RUN RELIEF VALVE VENTING. OPERATIONS ISOLATED THE FUEL RUN TO STOP THE VENTING GAS. INVESTIGATION FOUND THE FISHER 6356EBH RELIEF VALVE PILOT WAS NOT HOLDING THE SET POINT AND OPERATING PREMATURELY. OPERATIONS REPLACED THE FISHER 6358EBH-5 PILOT WITH A NEW ASSEMBLY. THE NEW ASSEMBLY WAS TESTED AND VERIFIED AT THE SET POINT OF 450 PSIG. DISASSEMBLY OF THE FISHER 6358EBH PILOT DISCOVERED A FAILED O-RING UNDER THE DIAPHRAGM. THE FAILED O-RING IS ATTRIBUTED TO THE PREMATURE OPERATION OF THE RELIEF VALVE. A TREND OF THE FUEL RUN PRESSURE WAS REVIEWED AND A PRESSURE DROP WAS OBSERVED AT 15:52 HOURS ON 4/4/15. WE DETERMINED THIS WAS THE TIME THAT THE RELIEF VALVE STARTED VENTING. THE SCADA SYSTEM HAD A HIGH ALARM SET AT 490 PSIG AND THE PRESSURE NEVER EXCEEDED 435 PSIG, SO NO ALARM NOTIFICATION WAS RECEIVED. THE ALARM HAS BEEN ADJUSTED TO 425 PSIG TO PREVENT FUTURE OCCURANCES WITH NO ALARM NOTIFICATIONS.
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.