• Published: 14 Jan 2021

Near Miss - Casing stud failure on water injection pump

Casing stud failure image
Casing stud failure image

Cause & Consequence

  • Moving, flying or falling object

Description of Incident

Three operators were conducting a routine start of a water injection pump. One Operator was opening/monitoring the discharge. While carrying out the task a stud (fastener) from the pump casing failed and was projected in the air. The system was operating at 120bar at the time. The stud landed on the deck approximately 1.4 meters away from the Operator. The pump was stopped immediately, and the manual suction and discharge valves were closed. Water injection was shut down approximately 5 minutes later. The stud weighed 4.4kg.

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Good Practice Guidance

The incident in this safety alert is unusual, however it was a serious incident. The fastener that failed was one of the main pressure containing fasteners on an API 610 BB3 pump. Therefore, it is sensible to conduct a review of all other similar BB3 pump applications to see if there is a risk of a similar occurrence:

  1. Review pump length of time in service, has it been in service for 10 years plus without overhaul? This style of pump has a centre bearing that is lubricated with the pumped fluid.
  2. Conduct visual inspection of the pressure containment fasteners, what is the general condition, are they visibly badly corroded? It is not possible to assess the stud condition using NDT without removal of the nut.
  3. What is the pumped fluid? Is it corrosive if it is in contact with the pumps pressure containment fasteners?
  4. Is there a history of pump casing erosion, could this lead to corrosion/erosion of the pressure containment fasteners?
  5. Are there any planned maintenance routines in place to inspect or schedule pump overhaul?
  6. As part of pump overhaul, consider coating the two long casing fasteners to minimise corrosion/erosion effects if the pumped fluid does get to them, HVOF tungsten carbide suggested. This relates to fasteners 14 and 34 in this alert, the ones closest to the shaft and the last stage impeller. Only the area of the stud closest to the casing join requires additional protection.

If the answers to the above questions relating to your pumps cause concern, please take action to lower the risk. Possible risk reduction measures include the following;

  • Barrier off high risk areas or contain a fastener at risk of failing (short term).
  • Schedule/plan overhauls where required.
  • Put in place planned maintenance to inspect high risk pumps.

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