Table 3 Flexible riser inspection and monitoring techniques suggested by API 17B and the failure modes (FM) covered by each method.
Monitoring method | Description | FM covered |
|---|---|---|
Visual inspection (internal and external) | Assessment of leakage or visible deformation or damage to pipe or outer sheath | 1, 4, 5, 6, 8, 9 |
Pressure test | Pressure applied to pipe and decay measured as a function of time. Leakages or anomalies identified | 1, 2, 5 |
Destructive analysis of removed samples | Prediction of the state of aging or degradation | 8, 9 |
Load, deformation and environment monitoring | Measured parameters include wind, wave or current environment, vessel motions, product temperature, pressure and composition, and structural (or flexible pipe) loads and deformations | 7 |
Nondestru- ctive testing of pipes in service | Radiography to establish the condition of steel tensile armor and pressure armor layers in service | 2, 3, 4, 6, 7 |
Gaging operations | Gaging pigs to check for damage to the internal pipe profile | 1, 8, 9 |
Spool Piece | To predict the state of aging or degradation of the internal pressure sheath | 8, 9 |
Test pipe | Use of a flexible test pipe in series or in parallel with the flow which is periodically removed for destructive or nondestructive testing | 8, 9 |
Annulus Monitoring | Measurement of annulus fluid (pH, chemical composition, volume). Prediction of degradation of the steel pressure armor or tensile armor layers or the aged condition of the internal pressure sheath or susceptibility of annulus environment to such degradation | 7, 9 |