Page 68: of Offshore Engineer Magazine (Apr/May 2014)

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Subsea

Preventing

Experience can play a major role in the development of an efective fexible pipe integrity problems integrity management system (FIMS) and plan. Photos from Flexlife.

for fexibles

Unbonded fexible pipes have been deployed in the global oil and gas industry for more

By Stuart Mitchell, Flexlife to this issue because of the hydrostatic ne of the most common integrity support of the seawater around them. A than 30 years, and historically issues relating to fexibles can breach in a subsea fowline experiences they have proved their extreme

O be mechanical damage to the fewer corrosion problems, due to reduced outer sheath, or a failing of the venting oxygenation of the seawater and support reliability. However, like all long system leading to a pressure breach of the from the fowline’s cathodic protection serving products, they can outer sheath. (CP) system.

sufer integrity problems over

By contrast, risers do not enjoy the Globally, about 35% of all fexibles same near-sea surface hydrostatic sup- experience an issue of this kind. This time, and a lack of inspection or port. When over-pressurised, the outer problem particularly affects fexible risers maintenance can be one of the sheath of the riser will tend to burst at as opposed to fowlines. Given the num- the sea surface, or splash zone, where it ber of pipes that suffer outer sheath dam- biggest issues afecting their is least supported and where there is a age, and the history of failures in pipes performance.

higher incidence of oxygenated seawater leading to loss of containment around the and sporadic – or no support – from the world related to this, integrity is clearly

CP system. This can create signifcant an issue that needs to be addressed.

general corrosion problems and lead to a

During operation, a buildup of gases product which is unft for service. can occur within the annulus of the fex-

The service life of the riser can also ible that need to be vented. be reduced due to corrosion fatigue

Subsea pipelines are less susceptible

April 2014 | OE oedigital.com 70 000_OE0414_Subsea3-Flexlife.indd 70 3/22/14 9:04 PM