Company:4Subsea AS Products:Marc Industries:Energy | Overview: Subsea drilling is conducted through a string of steel pipe called a rigid riser that runs from the oil rig to the blowout preventer (BOP). The primary purpose of the BOP is to cut off the flow of oil in the event of an emergency during drilling. The BOP may be connected to the subsea well directly, which consists of a string of vertical pipe running into the seabed down to the reservoir. The part of the well above (2-5 m) the seabed is called the wellhead system. This is the interface to the equipment to be connected to the subsea well. Alternatively, the BOP may be connected to a valve tree, which in turn is connected to the subsea well. The valve tree is used to control the flow of oil, and is usually called a Christmas tree. Challenge: The traditional approach to estimate
fatigue life for underwater applications is
based on the nominal stress at a given
location. The calculated stress is related
to test results through S-N curves, which
give a required amount of stress cycles
to cause fatigue failure. The results from a
fatigue test are plotted as stress (S) versus
number of cycles to failure (N), which gives
the S-N curve. However, fatigue testing
is expensive and time consuming so it is
usually possible only in certain cases.Benefits:
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