Cap Blows off of Choke Body -- Man Burned

Effective Date: 4/30/1975

U.S. Department of the Interior
Minerals Management Service
Gulf of Mexico OCS Region

Notice No. 022

April 30, 1975

OCS Operations Safety Alert

Cap Blows Off of Choke Body--Man Burned

A fire recently occurred on a production platform when the cap of a well choke blew off.

As a result of the cap failure, natural gas filled the well bay and adjacent areas and ignited. The source of ignition was not definitely identified.However, several possibilities existed: mechanical spark, static discharge,engine exhaust/engine backfire.

The duration of the resulting flash fire was limited by actuation of the emergency shutdown system which closed in the well and shut off the gas flow feeding the fire. Only minor facility equipment damage resulted and first- and second-degree burns were sustained by one person who was in the well bay area putting the platform back on production at the time of the accident.

The operator's accident investigation and analysis discovered that the acme threads of the choke cap and body were worn and eroded. Thread checks on other choke assemblies revealed a substantial number which exhibited similar thread erosion. The problem was not isolated to any one field or type production even though most of the eroded threads were found on wells producing some water. To prevent any possible recurrence of this type accident, the operator plans to take the following action:

1. All choke body and cap threads will be brushed, inspected, and gauged, at regular intervals, and replaced if necessary.

2. Emphasis will be placed on lubrication of threads during the regular inspection interval with a thread lubricant having corrosion and erosion inhibiting qualities.

[signature] D.W. Solanas

Oil and Gas Supervisor

Field Operations

Gulf of Mexico Area