Unbonded flexible pipe inspection issues and recommendations


Between 2002 and 2007 there were a number of failures of unbonded flexible pipelines giving rise to potentially serious hydrocarbon releases. HSE's Inspectors have discovered deficiencies in the maintenance regime for flexible pipe. Reasons for this appear to be:

  • a lack of knowledge and use of recognised good practice,
  • failure to implement a suitable verification scheme,
  • poor co-operation and communication between the pipeline operator and the installation duty holder.


Regulation 13 of the Pipelines Safety Regulations 1996 (PSR) requires the pipeline operator to ensure that a pipeline is maintained in an efficient state, in efficient working order and in good repair.

Regulation 17 of PSR and regulation 8 of the Offshore Installations and Pipeline Works (Management and Administration) Regulations 1995 (MAR) require pipeline operators and installation duty holders to co-operate with each other.

Regulations 19 to 21 and Schedule 7 of the Offshore Installations (Safety Case) Regulations 2005 (OSCR) require the installation duty holder to put into effect and maintain a verification scheme. This should cover safety critical elements including all hydrocarbon risers. It requires written schemes to be produced to ensure that these elements are suitable and remain in good repair and condition. There should be independent and competent assurance on ongoing suitability of flexible hydrocarbon risers.

Good practice guidance

The following good practice guidance is available:

  • API 17B Third Edition March 2002: Recommended Practice for Flexible Pipe
  • API 17J Second Edition Addendum 1 December 2002: Specification for Unbonded Flexible Pipe
  • 2001 UKOOA State of the Art Flexible Riser Integrity Issues
  • 2002 UKOOA Monitoring Methods and Integrity Assurance for Unbonded Flexible Pipelines.


Pipeline operators should implement good practice guidance or equivalent arrangements including:

  • establishing an integrity and condition monitoring programme based on:
    • evaluation of relevant failure modes,
    • assessment of risk attributed to each failure mode,
    • a range of complementary inspection/monitoring/testing techniques,
  • taking a whole lifecycle approach which should be established and implemented at design,
  • providing systems which detect any degradation at an early stage,
  • formally documenting and demonstrating best practice.

HSE Intervention Priorities

Continue communication and intervention work to help reinforce the adoption and use of recognised good practice for the inspection and maintenance of flexible pipe.

Targeted intervention of flexible pipe integrity management arrangements and practice, including coverage of associated verification issues.

Issue Date: 19 February 2008
Gas and Pipelines Unit

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Updated 2021-02-24