Release and fire from a hydrogen pipeline

Early in the morning of (3:00 AM), the personnel on one of the companies on site reported a potential pipeline leak just south of the valve station. The potential leak was discovered due to bubbling water in the ditch. No visible hydrocarbon sheen was noted, indicating a probable non-hydrocarbon gas leak. Later in the morning, the personnel tested their area gas pipelines and determined that their company was not the source of the leak.
Later on the same day, another company tested their pipelines and determined that their hydrogen pipeline was the source of the leak. The line was de-pressurised and this caused the bubbling in the ditch to subside and eventually stop at noon.
The SCADA (Supervisory Control and Data Acquisition) system was functional and operating under normal conditions at the time of the incident. The pipeline pressure drop due to the failure was so small that it did not indicate on the control room SCADA screen at the pressure point adjacent to the leak area.

The leak resulted in 1.7 mmscf (ca. 4 t) of hydrogen was released to atmosphere, and the re-routing of the affected section lasted more than 6 months, the repair was expected after one year.

The pipeline section was in water. The loss of containment has been attributed to internal corrosion of pipeline materials.
The difficulty in accessing the location of the release could hint to a shortcoming of the design of the pipeline or to an error in the installation.

underground pipepine

DESCRIPTION OF THE FACILITY
The pipeline had been produced and installed in 1993, was made of carbon steel API 5L X42, with an epoxy coating.
Pipeline diameter = 10 inch (0.254 m), wall thickness = 0.25 in (6.4 mm)
It was at 5 metre depth.

No consequence for persons or environment. Maintenance costs incurred due to the partial replacement of the line.

The State railroad commission was called and notified of the leak at 12:55 am on November 13, 2018.
A plan was developed to isolate the line while minimising emissions from the plant reformer. An additional isolation valve on the affected pipeline the valve station was installed in order to isolate it from another hydrogen line.
Hydro-excavation was attempted to uncover the leak location but, due to soil instability, the depth of the excavation (over 25 foot), and its proximity to an interstate highway, the decision was made to abandon this activity and backfill the excavation.
A company expert in pipeline inspection and integrity was contracted to smart pig the affected pipeline section. Results from the in line inspection pig identified 5 areas of concern. All locations were at the bottom of the pipe and at low-lying areas. No property damage occurred due to the incident.
1700 thousand standard cubic feet went lost during the leak (unintentional release)