The PSA has since been informed that the quality deviations of certain pipe components made of duplex and super duplex steel mentioned in our earlier message seem to have been caused by insufficient temperatures for part of the of piping components batch during the solution heat treatment process.
To PSA’s current knowledge, a major manufacturer of such fittings installed a new heat treatment furnace in 2006. The manufacturer did use a non adequate method of stacking the pipe fittings (Tees, bends and elbows of less than 4” in diameter) in baskets to be treated in the furnace.
This has probably resulted in an insufficient annealing temperature for parts of each batch (approx 10 to 20% has been reported). Thus, the inter-metallic phases/Fe-Cr+precipitates will not be properly dissolved. This again can explain the impaired material toughness and reduced pitting corrosion resistance measured. Charpy-V toughness values in the range of 10-15 Joule have been measured as an effect of the amount, distribution and density of inter-metallic phases.
The PSA regards this as a safety risk.
We have now asked relevant companies of the Norwegian oil and gas industry to check whether such quality variations of pipe fittings exist on their installations and facilities.
Furthermore, we have asked the companies to make an assessment of which risk factors are involved and to implement required corrective or mitigating actions, should such impaired pipe components be identified. The PSA has been informed that an investigation of possible inter-metallic phases by field microscopy on relevant pipe fittings in Norway is currently underway.
The PSA has encouraged the industry to ensure experience transfer and to share as much information on the issue as possible. Furthermore, we have informed our colleagues, who are with safety authorities of other countries about this matter.
Being the relevant Norwegian statutory regulator, we are unfortunately not in a position - nor do we have the capacity - to respond to all the many detailed queries, which we have lately received from all over the world with regard to this issue.
However, updates will be posted on our website as soon as they become available at: www.psa.no.
Contact person in the PSA:
Discipline leader Ole Jacob Næss, structural integrity