PHMSA Advisory Bulletin: Hard Spot Identification and Evaluation
Over the weekend PHMSA published an Advisory Bulletin to notify pipeline operators about evaluating their assets for the existence and threat of hard spots in the pipe body. PHMSA has concluded that the susceptibility comes from the plate and pipe manufacturing and is broader than previously thought. Hard spots may affect multiple pipelines manufactured before 1970.
As defined by PHMSA:
A hard spot is a defect that is created at the time the steel plates are rolled during the pipe manufacturing process. A localized increase in hardness produced during the hot rolling of steel plates as a result of localized cooling can form a hard spot. Localized hardening may also occur through the unintentional quenching during the manufacturing process or by cold work. Although hard spots are more prevalent in plate-formed pipe, seamless pipe can also be susceptible to hard spots when poor controls in the manufacturing process result in material property variations, including hardness.
In order to help operators understand the scope of the potential issue, PHMSA has provided the following general guidance:
Hard spots are a stable threat themselves but can be reactivated by coating degradation, soil chemistry, or increased hydrogen exposure/hydrogen cracking
Hard spots should be evaluated on all pre-1970s pipe, irrelevant of service (gas, hazardous liquid, and carbon dioxide).
Operators should collect and analyze data associated with hard spot MFL ILIs and follow industry best practices regarding hard spots when evaluating ILI data
Operators may leverage enhanced technology to allow for better data analysis on historic ILI runs
According to the Advisory Bulletin operators should:
Review all records to determine if Traceable, Verifiable, and Complete (TVC) and if the pipe manufacturer, steel plate manufacturer, and date of manufacture can be clearly identified
Determine if pipe in systems is susceptible to hard spots
Determine if those pipeline systems have experienced integrity issues
Develop and implement an enhanced assessment program for material hardness anomaly validations
Re-evaluate existing ILI data for feature identification
Continue sharing information regarding the destabilization of hard spots
Hardness can be evaluated in any condition. The following industry standards may provide a baseline for evaluations:
ASTM E92 Standard Test Methods for Vickers Harness of Metallic Materials
ASTM E10-18 Standard Test Methods for Brinell Hardness of Metallic Materials
ASTM E18-22 Standard Test Methods for Rockwell Hardness of Metallic Materials
Hard spots, if not identified and mitigated, pose a threat to the integrity of the pipeline from interacting threats such as coating degradation, soil chemistry, and/or increased hydrogen exposure, which can result in hydrogen-induced cracking. Pipeline operators should consider expanding their hard spot threat evaluation to all pipe manufactured prior to 1970, regardless of manufacturer; collecting and analyzing data associated with hard spot magnetic flux leakage in-line inspection tools; and following industry best practices when conducting in-line inspection data analysis.
You can read the full Advisory Bulletin here.