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A gas well installation suffered a loss of containment when a gland nut and lockscrew assembly was ejected from a wellhead while the well was under pressure, shortly before commencing tubing installation. The release of gas resulted in a fire which caused the death of a field service technician.

Lockscrews are commonly used in surface wellhead equipment to mechanically energize or retain internal wellhead components. Lockscrews are not standardized across the industry, so manufacturers’ procedures should always be used for operations that may require manipulation of lockscrews. Work involving gland nut and lockscrew assemblies should be done under the supervision of qualified service personnel from the wellhead equipment provider who have access to the operational procedures, key dimensions, and torque ratings necessary for correct use. Operators should consider working with their wellhead equipment and service providers to validate the integrity of gland nut and lockscrew assemblies that are exposed to wellbore pressure in the field by taking the following steps:

1. Verify adequate engagement of gland nuts;
2. Confirm lockscrew assemblies’ torque values are consistent with manufacturer’s specifications;
3. Inspect lockscrew assemblies for any debris or damage such as scarring or bending;
4. Follow manufacturer’s procedures if checks show any of the above are inconsistent with the manufacturer’s specifications;
5. Conduct a pressure test to rated maximum working pressure to ensure gland nut and lockscrew assemblies have pressure integrity;
6. Consider isolating gland nut and lockscrew assemblies from wellbore pressure by having tubing hangers and adapters installed;
7. Reinforce with relevant personnel training and the use of procedures to address hazards associated with performing work on wellhead assemblies exposed to wellbore pressure; and
8. Review and implement appropriate engineering and well design controls (physical design of equipment) and administrative controls (procedures) to address the hazards of work involving gland nut and lockscrew assemblies.

These same validation steps should be taken prior to commencing any well work during which gland nut and lockscrew assemblies will be exposed to wellbore pressure.

Safety Alert number: 256
IOGP Safety Alerts http://safetyzone.iogp.org/

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