Dummy hot stab ejected during leak investigation

What happened?

A high potential near miss occurred when a dummy hot stab was ejected at 20,000psi. Personnel were out of the direct line of fire but within 1-2 meters of the skid.  Issues of weeping tubing on a skid had been identified and required investigation. The required ‘Blue Logic’ dummy stab was not readily available, and it was decided to use a ‘Seanic’ dummy stab manufactured to the same design code (API 17H) and thought to be interchangeable. A maximum test pressure of 20,000psi was applied in 1,000psi increments and had been held for 30 seconds when there was a loud noise, and the hot stab was ejected from the receptacle. The hot stab was propelled 6 metres before striking the ground and then travelling another 2 metres before coming to rest. At the time of the failure personnel were not directly in line of fire but there were people less than 2 metres from the travel path of the object.

What went wrong

• The wrong hot stab was used. A misalignment of 0.75mm between the hot stab and receptacle (invisible to the naked eye) failed at 8000psi during the test. Subsequent tests confirmed the ‘Seanics’ dummy hot-stab and the ‘Blue Logic’ receptacle are incompatible;
• There was no J Lock in place to secure the hot stab;
• Procedures not followed:
  • The operation was not conducted within the expected Safe System of Work (SSoW) process;
  • There was no documented Task Risk Assessment (TRA), Permit to Work (PTW) or Toolbox Talk (TBT) for this activity;
  • A Factory Acceptance Test document which includes the test steps was not referred to.
  • No Management of Change (MOC) was conducted to establish the safe application and authorization for the use of the ‘Seanics’ dummy hot stab;
• Barriers
  • Although barrier tape had been used to define an exclusion zone, this was not at sufficient distance from the test and five persons were located to the side of the test within 1-2 meters of the path of the flying object;
  • No blast barriers were used.

Recommendations

• During pressure tests, ensure that:
  • ONE single person is nominated as responsible;
  • Only essential personnel are present, that an exclusion zone is established at safe distance and that blast screens are positioned where appropriate;
  • The test procedures are clearly explained to all involved and that they all confirm their full understanding;
  • A safe system of work is fully implemented and maintained throughout the duration of the test;
  • Correct test fittings are confirmed securely attached, hoses secure, equipment has been maintained and is within the expected range of the pressure test;
  • Any monitoring during pressurization is conducted from a remote or safe position;
  • If leaks are experienced the system is fully depressurized before investigating;
  • If possible, test when there is minimum personnel or vehicle density or movement.
• Whenever possible request the supply of and use hot stabs and receptacles from the same manufacturer.

Members may wish to refer to

• Stored pressure: Corrosion coupon plug ejected from pressurised pipeline
• High potential near miss: working on pressurised pipeline
• Fatality: Stored pressure release