NORTHERN NATURAL GAS CO
gas_transmission Incident —
Incident Information
| Report Date | — |
| Operator | NORTHERN NATURAL GAS CO |
| Commodity | — |
| Pipeline Type | gas_transmission |
Location
| State | |
| Coordinates | 41.71717, -93.59099 |
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
ON NOVEMBER 11, 2014, AT APPROXIMATELY 0632 AN UNINTENTIONAL RELEASE OF GAS VENTED FROM A RELIEF VALVE AT THE GAS METERING STATION IN ANKENY, IOWA. A CALL FROM A CITIZEN WAS REPORTED TO NORTHERN JUST AS THE GAS CONTROL SYSTEM WAS ABLE TO CONFIRM A DROP IN INLET PRESSURE AT THE METERING STATION. NORTHERN DISPATCHED TECHNICIANS TO THE SITE AND VERIFIED THE 6-INCH RELIEF VALVE WAS VENTING GAS. THE STATION WAS BY-PASSED AT 0808 AND THE RELIEF VALVE STOPPED VENTING. AN INVESTIGATION CONCLUDED THAT THE METER STRAINER WAS FILLED WITH DEBRIS LIKELY FROM A CONSTRUCTION PROJECT TO REPLACE THE RELIEF VALVE AT THE STATION IN MAY OF 2014. THE REGULATOR DID NOT LOCK-UP FAST ENOUGH WHEN THE FLOW DECREASED AND THE PRESSURE WAS ABLE TO BUILD UP BETWEEN THE REGULATOR AND STRAINER TO REACH THE SET POINT OF THE RELIEF VALVE. ONCE THE RELIEF VALVE STARTED TO VENT, THERE WAS SUFFICIENT FLOW TO KEEP THE REGULATOR OPEN. THE STRAINERS WERE CLEANED, WHICH ALLOWED NORMAL FLOW, AND THE SYSTEM WAS RETURNED TO SERVICE.
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.