ABSTRACT

Snap Lay? is a method of laying rigid steel pipelines using mechanical connectors to join spoolpieces together. This paper outlines its applications including the laying of pipe from a barge or constructions vessel, laying from an drilling rig and laying pipe by snapping spools together on the seabed. Finally the paper will review the most recent installation of two kilometers of twenty four inch diameter pipe on the Harding field for BP.

INTRODUCTION

Snap Lay? is a pipelay system which can fundamentally changes the way in which oil field are developed because it offers new opportunities in the configuration and installation of pipelines. An alliance to promote Snap Lay? was formed by SubSea Offshore, Hunting Oilfield Services and Uglands Offshore which offers a complete installation capability SnapLay projects will normally be led by SubSea Offshore.

The Merlin? Connector

The heart of the Snap Lay?system is the Merlin? Connector. The connector has been in use for over twelve years primarily in conductor and casing applications but it was also used as the connection medium for the tendons for the Shell Auger and Mars TLP's in the Gulf of Mexico (Figure 1) the Merlin? is a box and pin type of connector with a series of parallel teeth on the outside of the pin and a corresponding set on the inside of the box (figure 2) (It should be noted that these are not threads and no rotation is required for make-up). Each component has a nib and recess which form the sealing elements. The connector is currently produced in sizes ranging from 16 to 48′ but larger and smaller diameters are possible. There are over two thousand Merlins?in use and there is an exhaustive history of testing to draw on (figure 3 shows a pipe test piece with an early Merlin type connector being tested and demonstrating that the connector is stronger than the pipe).

Connector Operation

The connectors are welded onto the pipe spools as shown in Figure 4. The method of make-up is shown in Figure 5. The pin is inserted into the box until the nibs on both components engage on the corresponding profiles prior to the entry into the sealing recess. The teeth are configured such that they will not engage until the final make up position a makeup clamp is fitted around the two connector components and a hydraulic injection line is installed. Hydraulic fluid is injected into the void bounded by the two nib/profile seals. The effect of this injection is to compress the pin and expand and with an axial force of up to 400 tons the two components are forced together until the nibs engage in the recess. The hydraulic pressure is then released and the teeth engage. This makeup sequence is fully reversible.

Once made up clamp and hydraulic line are removed and plugs fitted. The connector offers four metal to metal seals between the bore of the pipe and the surrounding environment with each nib forming a metal to metal seal on its inner and outer faces.

This content is only available via PDF.
You can access this article if you purchase or spend a download.