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Leak on main oil line caused by faulty valve stem

  • What happened?

    Whilst attempting to start exporting hydrocarbons, there was a leak from a main oil line.

    The leak was caused by a failing valve stem packing on the main oil line export pump recycle flow loop.

    There was a loss of primary containment with high potential.

    This resulted in a platform muster, emergency shut down (ESD) and a report to the Environmental Product Division (EPD).

    82 kg of hydrocarbons were released, resulting in an oil sheen.

    What happened - icon
  • Why did it happen?

    The flow valve was washed out due to high speed flowrates, erosive particles, high pressure drop and constant use. This caused unconstrained flow through the recycle line.

    Normally two pumps were in service. One pump had been offline for a few months due to maintenance.

    • During start-up, both pumps were online to re-instate the offline pump.
    • The high speed through the combined recycle line was transferred to the flow control valve on the second pump, causing loose gland nuts to unscrew.
    • The force of this energised the packing, creating a leak path for the fluids.

    It is believed that the gland nuts might have been loose when received from the manufacturer, and the valve was installed as received.

    Repeated issues with flow transmitters led operators to believe that flow readings were inaccurate.

    Why did it happen - icon
  • What did they learn?

    Review inspection and monitoring regimes.

    Review quality assurance (QA) checks and define QA expectations from vendors.

    Consider implementing a QA checklist for offshore crew.

    Review work instruction for gland packing tightening during valve commission and installation.

    Check that instruments are not out of range for current operating conditions.

    What learn - icon
  • Ask yourself or your crew

    What hazards weren’t considered when the pump was put back into service?

    What quality assurance checks should you carry out before re-instating an offline pump?

    How do you know that the equipment is fit to use as received from the manufacturers? What tests do you need to run?

    How can you check if flow readings are accurate?

    What should you do if you discover an oil leak?

    Ask your crew - icon
Published on 21/09/20 411 Views 1 likes

Whilst attempting to start exporting hydrocarbons, there was a leak from a failing valve stem packing on the main oil line export pump recycle flow loop. Courtesy of IOGP