NORTHERN NATURAL GAS CO — Gas transmission and gathering — incident on 2014-11-11

Current as of 2014-11-11 Government source

Pipeline and Hazardous Materials Safety AdministrationOfficial agency material

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Gas transmission and gathering incident in ANKENY, POLK County, IA. Reported cause: EQUIPMENT FAILURE. Reported consequences: 0 fatalities, 0 injuries, 3990 NATURAL GAS released, $0 reported property damage. Operator-reported incident data submitted to PHMSA, generally within 30 days. Records may be supplemented or corrected and do not represent final agency causal findings.

Report number: 20140121.

Operator ID: 13750.

Reported incident date: 11/11/2014 6:32.

Location detail: 736031

Cause detail: MALFUNCTION OF CONTROL/RELIEF EQUIPMENT

Cause detail: 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.

PHMSA trend classification: not significant, not serious.

PHMSA standardized cause: EQUIPMENT FAILURE — MALFUNCTION OF CONTROL/RELIEF EQUIPMENT.

PHMSA indexed costs: $18,435 reported total cost, $12,697.453 in 1984 dollars, $15,778.518 in current-year dollars.

PHMSA trend flags, standardized causes, and indexed costs are analytical fields added to operator-reported incident data. They do not represent final agency causal findings.

This material provides agency context. It does not replace binding regulatory text, and its legal effect depends on the underlying authority and facts.