A Composite-Construction Egress System with High Temperature Protection
Authors: Lyons Robert A. , Haney Charles W. , McCormick W.H. 
Published: December 2007

Although many industrial scenarios require job functions to be carried out from elevated areas, traditional egress systems for safe emergency evacuation of personnel from elevated work places have been limited in their capabilities. This situation provided the stimulus for an oilfield service company to design the emergency evacuation system discussed in this paper for the sole purpose of enhancing safety during the course of operations on their hydraulic workover well servicing units. The technology used for its development, however, could be applied to other work situations requiring emergency evacuation from an elevated work area. The key component in the new composite evacuation system is the individual personnel enclosure that was designed using material technology developed for the aerospace industry to provide protection for each person after entry and during descent to the ground. The personnel enclosure is referred to as the emergency escape pod (EEP). The specific work place considered when developing this emergency evacuation system was the work basket on a hydraulic workover (or snubbing) unit.

The paper will first review the history of emergency evacuation from the work basket and will then discuss the innovative design features and testing that went into this composite evacuation system. Of particular interest will be the:–Materials and honeycomb construction that provide the light-weight heat insulating barrier.–Design features used for the system.–Finite element analysis methods used to structurally optimize the design.–Prototype testing that was conducted using a hydraulic workover unit.–Jet-fire testing conducted by an independent test laboratory to verify heat insulating properties.–Training methods used to insure personnel safety in use of the system.–Deployment of the systems to insure availability in locations with hydraulic workover units.

Although no evacuation system can guarantee personnel safety, testing and experience to date have shown that this system has the capability to significantly improve safety, even in worst case scenarios such as an accidental well blowout.

Introduction

Hydraulic workover (or snubbing) units are designed to move jointed pipe in a wellbore while high well pressure is present below the wellhead. The work basket, located on top of the hydraulic jack, is used as a personnel work platform. Various controls are located in the work basket, including those for the hydraulic jack assembly, stationary slip bowls, traveling slip bowls, counterbalance winches, diesel power unit, and blowout preventers. Typically, either three or four persons maintain control of the hydraulic workover unit while standing on the floor of the work basket. In spite of the many mandatory safety procedures and equipment that are employed, there are emergency conditions that can occur during service operations, including accidental well blowout, the unexpected release of hydrogen sulfide gas, a leaking blowout preventer assembly, an unexpected 'kick' from the pressurized well, and wellhead or casing failure. Personnel working in this environment, therefore, must have a reliable evacuation system that can quickly and safely transport them to the ground if an emergency condition should occur.

Fig. 1 shows the equipment components that make up the typical hydraulic workover assembly with the EEP's mounted to the work basket. The primary hydraulic workover components that mount on top of the wellhead include the following major items:–Blowout preventer assembly–Access window with pipe guides–Stationary window with slip bowls–Hydraulic jack assembly with guide tubes–Traveling slip bowls–Telescoping mast

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