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The University of Southampton
Rifi An Enterprise Consultancy Unit

Case Study: Failure investigation of sleeve and cage components from a subsea choke valve

Objective: To provide an informed opinion on the original condition / composition of sintered carbide materials from which the choke valve was manufactured and identify the mechanism of failure.


  • Choke valves were failing below the designed service life.
  • The failure of the valves was causing major delays during production.
  • There were concerns about the metallurgical properties of the materials used for the manufacture of the choke valves.
  • It was imperative to establish the mechanism causing the failure of the valves: was it material dependent or due to operational inconsistencies?
  • What we did

  • Detailed visual assessment of the damaged inner walls of the sleeve was conducted.
  • Samples were examined using both optical and scanning electron microscopes, including energy dispersive X-ray analysis.
  • It was demonstrated that failure of the subsea choke valves was material related and resulted from subsurface cracks in the tungsten carbide (WC-Co) matrix, causing the sleeve to delaminate and fracture.
  • Impact

  • The findings of this study have led the client to consider alternative materials for the manufacture of the subsea choke valves.
  • According to the client, the potential cost saving to their business by the recommendation of this work is in the region of £1M - £2M per day avoiding unnecessary shut downs.
  • SEM image of choke valve
    SEM image of choke valve
    Damaged choke valve
    Damaged choke valve

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