Flexible Riser Inspection

Flexible risers rely on multiple layers to provide pressure containment, tensile strength and protection against the subsea environment. The outer sheath prevents seawater from entering the annulus, where the steel armour wires are located.

Damage to the outer sheath can allow seawater to enter the annulus, increasing the risk of armour wire corrosion and potentially affecting the riser’s long-term integrity.

Detecting annulus flooding and understanding its condition are therefore important parts of flexible riser integrity management, helping operators identify potential concerns and determine whether further investigation or monitoring is required.

Water depth can influence the acoustic response of a flexible riser. As external pressure increases, the normally unbonded layers are compressed, changing how acoustic energy travels through the riser structure.

These differences need to be considered when interpreting inspection data, particularly when assessing annulus flooding and other condition indicators.

TSC Subsea has developed inspection methods and data interpretation techniques for both shallow and deepwater applications, supported by qualification testing and offshore experience at water depths exceeding 2,000 metres.

This experience allows us to account for variations in riser construction and operating conditions when assessing annulus condition.

External insulation can make it more difficult to assess the condition of a flexible riser without removing protective materials.

TSC Subsea has developed and qualified ART inspection methods for insulated flexible risers, allowing annulus condition to be assessed through suitable insulation systems without removing the insulation or outer sheath.

This enables operators to obtain information about potential annulus flooding while reducing the need for intrusive inspection and associated preparation work. Inspection suitability is assessed against the specific riser construction, insulation materials and thicknesses.