The U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration (PHMSA) issued an amended corrective action order (CAO) that contains new and amended preliminary findings with respect to the April 29, 2016 failure of the Delmont Compressor Station pipeline section of the Penn-Jersey system, operated by Texas Eastern Transmission, LP (TET), a subsidiary of Spectra Energy (Houston, Texas). The CAO also requires additional corrective actions to be taken.
The amended CAO, dated July 19, 2016, states the cause of the failure in Salem Township near Delmont, Pennsylvania is unknown at this time, and the investigation is ongoing. The preliminary investigation of the failed pipe section, which was transported to an independent metallurgist for examination and failure analysis, identified evidence of external corrosion at circumferential welds at the failure site. The pattern of corrosion indicates disbondment of the coating material applied to the girth weld joints.
The failed pipeline (Line 27) is a 30-in (762-mm) diameter pipeline, constructed in 1981, that transports natural gas from the Delmont Compressor Station discharge in Salem Township, Pennsylvania, to Lambertville Station in New Jersey. The X65 grade, double submerged arc welded pipe, manufactured by United States Steel Corp., has a wall thickness of 0.404 in (10 mm) and is coated with fusion-bonded epoxy (FBE) with tape-coat coating at girth weld joints. It is one of four Penn-Jersey system pipelines in a common right-of-way near the scene of the failure.
The amended CAO outlines procedures for the exposure, testing, and remediation of Line 27, which include, among other things, exposure of Line 27 extending for at least two girth welds on either side of the failure site so it can be examined for corrosion, coating condition, concussive damage, and thermally impacted areas. If damage to the exposed pipe is discovered, additional pipe must be exposed until at least 10 feet of undamaged pipe is exposed and examined. Repairs or replacement of the pipe or coating will be done as necessary. Upon completion of pipe replacement and repairs, proper backfill will be added to ensure protection from stones and rocks. The CAO also calls for the restoration and verification of adequate cathodic protection for the area where the failure occurred.
Three adjacent pipelines, 24-in (609-mm) Line 12, 30-in Line 19, and 36-in (914-mm) Line 28 loop), run parallel to Line 27 in the vicinity of the failure. The CAO lists procedures for the exposure, examination, remediation, and restart of these pipelines as well, which include exposing these lines for at least two girth welds in both directions from the failure site and examining the girth welds and pipeline coating materials for damage caused by thermal and concussive forces. A broader exposure of each line will continue if associated damage is discovered, until 10 feet of undamaged pipe is reached and verified. Any needed repairs are to be guided by established Spectra procedures, and safe-operating-pressure calculations and remediation for any pits or other forms of anomalies found should be done using specified engineering permanent repair methods and design factors. Repair or replacement of the pipe or coating should be done as necessary.
Spectra Energy voluntarily made the decision, as a conservative and precautionary measure for confirming the system’s integrity, to conduct a thorough assessment along the entire Penn-Jersey pipeline system, which consists of four parallel pipes running from Delmont, Pennsylvania to Lambertville, New Jersey. This assessment includes reviewing inspection data, evaluating construction records, performing field investigations, and scheduling additional interior and exterior inspections. These field investigations include uncovering the pipeline in certain locations to inspect it from the outside.
The company says the work plan it developed as part of a thorough assessment of the entire Penn-Jersey system is well-aligned with the work described in the amended CAO and includes anomaly investigations, inline inspections, and hydrostatic testing. Many of the action items noted in the amended CAO have either begun or been completed.
According to Spectra Energy, a 2012 inline inspection of the line did not reveal areas requiring repair or remediation before the next inspection, and the company continues to investigate what factors may have contributed to the incident as well as support PHMSA’s ongoing investigation. The root cause analysis, it says, will likely be complete by early fall.
The pipe failure occurred around 8:13 a.m. EDT on April 29, 2016. At that time, TET personnel at the Delmont Compressor Station heard a loud explosion and the sound of natural gas being released from an undetermined location. The failure resulted in the release of 208,425 MCF (59,019 m3) of natural gas, which ignited and produced a crater ~30 ft (9 m) wide, 50 ft (15 m) in length, and 12 ft (3.7 m) deep and a burn zone with a radius of ~1/4 mile (0.4 km). The explosion caused ~24.5 ft (7.5 m) of 30-in pipe to be ejected and land ~100 ft (30 m) away from the rupture site.
Sources: PHMSA, phmsa.dot.gov; and Spectra Energy, spectraenergy.com.
