Rapid Makeup Coupled Tendon Connection

Abstract

ABSTRACT This paper discusses the design, analysis, and operation of a threaded tendon connection that uses a coupling having dissimilar thread forms on the two ends. This allows makeup of the connection by a partial turn of rotation of the coupling while holding the tendon tubulars fixed. Also discussed in this paper are possible makeup tools and other features that can be incorporated into the connector. INTRODUCTION A TLP typically makes use of tendons, attached to the comer columns of the platform, to moor the platform. Current and proposed designs for TLP tendons make use of tubular steel members of roughly 24 to 30 inches in diameter having three-quarters of an inch to one and one-half inches wall thickness. These tendons also extend well over 1000 feet in length. Several methods exist for connection, transportation, and installation for the tendons. Tendons may be fabricated by welding pipe sections together on shore and floating the tendons to the installation site, where they are upended and installed. An alternative method is to deliver the tendon to the installation site, on a boat or barge, in sections. These sections can then be connected, using a derrick barge, and lowered into the water vertically as each section is added. In order to quickly connect the tendon sections, a mechanical connector must be incorporated on the ends of the tendon section. The requirement for this connector include:Vertical assembly of up to 240 feet length tendon joint.Structural strength equal to or greater than the pipe body.Sufficient fatigue life for the specific application.Operational characteristics which allow for ease of installation.Ability of the connection to seal the tendon from sea water in most cases. These requirements typically lead to classic designs of weld-on threaded joints which make use of a male member (commonly referred to as the pin) on one tubular joint, which makes up to a female member (commonly referred to as the box) on the mating joint. Makeup of the connection normally requires rotation of one of the tubular joints with at least several turns, while holding the other joint fixed. This is a difficult task when dealing with the long tendon joints, particularly when working on a derrick barge which may be moving considerably while floating in the ocean. Performing this task can also require a very large fixture for aligning and rotating the tendon section. There are also connectors available that snap together by forcing together male and female sections by using a hydraulic makeup tool to provide a high axial makeup force. These connectors usually make use of a shallow thread or annular grooves. This paper is not intended to address these type of connectors nor attempt to compare their load carrying capacities to this Rapid Makeup Coupled Connection. The connector being presented here makes use of a coupling that contains a different thread type on each end of the coupling. (See Figure 1.)