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Processing plant: Combating the cold

A lengthy freeze in 2009-10 hit a number of Norway’s land-based petroleum plants. Faulty design was the main reason for these problems, according to a PSA review.


This article was published in the publication "Safety - status and signals 2010-2011".

Many weeks of extreme cold allowed ice to build up in piping systems at various processing facilities last winter.

But this went unnoticed until pipes were wholly or partly plugged or pressure had built up.

The most serious incidents occurred at Kårstø north of Stavanger, Mongstad near Bergen and Nyhamna in mid-Norway.
Icing at all these facilities cut or eliminated flaring capacity.

This problem may have existed for a number of days before it was detected. Ice could also have reduced fl are system capacity in earlier winters, but melted before being discovered.

Testing

These experiences underline the importance of testing safety systems during cold spells, since most safety barriers in a process plant are passive in normal operation.

As happened with the flare systems, these barriers could be weakened or demolished without anyone realising it.

Tests are needed to establish that they remain intact.

Temperatures offshore were not as low as on land last winter, and relatively few incidents related to icing problems
were reported from NCS installations.

But fresh incidents occurred at Kårstø and Nyhamna this December.

They did not introduce any new factors, but underlined that the problem is not being adequately addressed.

The PSA will therefore continue to devote attention to the icing problem in 2011 in order to check that operators and the industry in general have amended winter test routines for safety.

This article was published in the publication "Safety - status and signals 2010-2011".