Branch Barrier Valve for Subsea Application

ABSTRACT A new type subsea repairable pipeline branch barrier valve, invented by TOTAL & STATOIL, has been developed by CAMERON based on the ram type blowout preventer principle. This valve can be serviced by diverless techniques without interrupting the production of the pipeline. The branch barrier valve concept has been proven through extensive testing to be reliable and provide increased safety for the operator. This paper explains this concept and reports results of testing. INTRODUCTION The need for a reliable subsea pipeline valve has long been a particular concern to the offshore petroleum industry. The trend towards deepwater development has promoted an increasing need for such equipment. Thus operators, such as TOTAL, STATOIL and MOBIL were driven to seek new concepts for a valve which could be serviced without closing or flooding the pipeline. This subsea valve design is based on the proven technology of the subsea ram type blowout preventer (B.O.P.). This new valve has design features using hydraulically actuated closing mechanisms and remote control functions. Testing, maintenance and repair may be performed subsea without interruption of the production flow and without seawater flooding of the pipe line. In addition, a diverless workover tool was designed by NORCEM COMEX SUBSEA to perform all the necessary functions for a diverless bonnet change out operation. The factory acceptance tests were performed successfully in January 1987. Actual field use will begin in the summer of 1987 in the Norwegian North Sea by TOTAL and STATOIL. Design Criteria The general design features and criteria of the valve are summarized as follows:Valve bore size range: 7" thru 36"Working pressure: Up to 2175 PS? (150 bar)Working temperature: °0 thru 50°CTransported medium: Oil, Gas, condensate, and seawater (before start up of pipe line)End connections: Flanged or weld endDiverless construction for water depth application to 300m maximum.Accept all bidirectional pipeline pigs.Test sealing mechanisms without interruption of the production flow.Valve body design for a 20 year life. GENERAL For development and testing, a 16", 150 Bar (2175 PSI) working pressure subsea valve was used to study the feasibility for construction of valves ranging from 7" to 36" bore with working pressures up to 2175 PSI. The valve test program included a significant number of cycles at pressures varying from full working pressure of the valve, to low pressure gas tests. The valve itself has three types of components: one body, two bonnets and two rams. The 16" valve (8700 Kg total weight) consists of a body with a frame to locate the workover tool (3650 Kg) and two bonnets with rams (2525 Kg each) A remote control system is also assembled onto the valve.