A New Mechanical Pile Connector Speeds Offshore Contruction Projects
Authors: Hettinger F.L. 
Published: December 2007

During the past year, a new mechanical pile connector has been introduced to the offshore construction industry. This connector has been the culmination of an extensive development and fullscale testing program by Vetco Offshore, Inc. A family of driveable pile connectors has since been produced, ranging in size from 30" O.D. to 72" produced, ranging in size from 30" O.D. to 72" (762 mm to 1829 mm). Included in this family are standard releasable connectors and remote-releasable connectors for skirt pile applications, and a slightly modified design recommended for permanent pile applications. pile applications. Specifically designed for skirt pile and permanent pile applications, the pile connector permanent pile applications, the pile connector incorporates field-proven features that have been used on Vetco wellhead and riser connectors. The design phase included a finite element optimization and a fatigue analysis of the connector. Special anticorrosion considerations have been taken to ensure long life in the marine environment.

The connector was tested extensively at both in-plant and field facilities. These tests included tensile, pressure, bending, functional, and pile driving tests. Following the development tests, the connector was supplied to several users for actual field trials. Since the connector has been introduced to the offshore industry, it has been used in a variety of skirt piles and permanent pile applications. To date, the pile connector pile applications. To date, the pile connector has been supplied in 30", 40", 42", 48", 54" and 72" (762 mm, 1016 mm, 1067 mm, 1219 mm, 1372 mm and 1829 mm).

Introduction

It has been found that the handling, stabbing, and connecting of individual pile sections often represents a critical phase during offshore construction. These operations are particularly acute during heavy weather conditions. Considerations for men and machinery safety often dictate a work slowdown, or even a stoppage, until a suitable weather window is available.

In addition, a significant amount of time is consumed during pile welding operations. Weld time must include pile positioning, preheat, welding, cool-down, and inspection. For welding larger diameter, heavy-wall pipe sections, these welding operations become increasingly time consuming and expensive.

Recognizing these increased costs of offshore welding and rig time, Vetco has developed a mechanical connector for large diameter pile sections (Figure 1). The Vetco Pile Connector is a heavy-duty, driveable connector designed specifically for connecting sections of drive string, platform piling and other large diameter applications. it piling and other large diameter applications. it is a threadless connector and does not require rotation for makeup. When made up, the connector provides a strong, pressure-tight and rigid provides a strong, pressure-tight and rigid connection which efficiently transfers the driving energy throughout the length of the piling string. This results in a faster, more economic driving operation. Since the pile connector is preloaded during makeup, this condition greatly enhances the fatigue strength of the joint, ensuring that it has longer fatigue life than the basic pile section. The design and materials of the connector have been carefully considered to ensure that it has maximum corrosion resistance and is suitable for application in a permanent offshore installation.

During the pile connector design phase, experience gained from producing several other field-proven mechanical and hydraulic connectors was utilized. In particular, Vetco's long experience in marine drilling riser connectors and subsea hydraulic connectors was used to adapt several successful features to the pile connector.

This paper presents a technical description of the Vetco Pile Connector. In doing so, it describes the development of the connector from design through prototype testing and field application stages.