An Economical Pile-Handling Technique Using Dynamic Upend
Authors: Converse R.M. , Bhattacharjee S. , Chen J. , Windus J.W. , Raymond K.G. 
Published: October 2008

The paper presents a new, economical technique for upending relatively long, single piece piles. This technique was used successfully on four projects in the summer of 1989. The main features include eliminating pile closures and minimizing the amount of rigging needed to handle the piling. As soon as the pile is rotated to vertical, it is ready to be stabbed into the jacket.

INTRODUCTION

Pile installation has always been a significant cost in the installation of offshore platforms. With the advent of one-piece skirt piles to eliminate welding of piles offshore, the transport and handling of these large units has increasingly affected pile installation costs. While the value of mechanizing these operations has been recognized, the required investment has been inhibited by the small number of piling on a single project and the variable characteristics of the piles from one project to another. In 1988, McDermott Marine Construction received contracts to install four platforms in the Gulf of Mexico during the summer of 1989. Each platform had large one-piece skirt piles, three with 8-72 inch diameter battered piling, ranging from 380 feet to 425 feet in length, and the fourth with 484 inch diameter vertical piling, 400 feet long. This amount of booked work provided the impetus to evaluate new ways to handle this type of piling and justified a greater level of investment in mechanization than normally is the case. The result was a new, more mechanized method for handling large, one-piece piling. This paper presents the new method, traces its development, describes the marine and structural analyses employed, notes the major considerations in the design of the fabricated handling devices and discusses the offshore experience using this method.

THE METHOD

The resulting method, which is the subject of this paper, has the following features:Transport the large one-piece piles on a material barge.To begin a pile installation cycle, offload one pile using a specially designed spreader bar and place it onto two multipurpose supports attached to the side of the derrick barge.Insert an internal type elevator/gripper, horizontally, into the top of the pile and grip the pile.Slightly raise the hook to remove the pile load from the top end support.Rotate the top end support out from under the pile which simultaneously rotates a sling restraining arm into position above the pile.Release the bottom of the open-ended pile; whereupon, it floods freely and rapidly rotates to vertical while the top remains suspended from the derrick with slings that bear against the restraining arm.After the pile reaches vertical, check the accumulator charge on the gripper release system and stab the pile into the structure without further handling.

Please refer to Figure 1, "Pile Upend" for a diagram of the upend behavior.

DEVELOPMENT

Prior Art

The various techniques for handling large, one-piece piling, which the authors were aware of up to this time, can be grouped into three general categories:Upend a horizontally floating pile by controlled flooding: In this category, the piles usually achieve a floating position by (a) towing the floating piles to the site, (b) launching them off a material barge or (c) lifting them off a transport barge and setting them into the water.