Statoil is looking at placing a separate protection device upstream of choke valves. Choke valves are normally located downstream the wing valve on the Christmas tree or downstream pipeline block valves for satellite production systems, and are designed to control the flow to a certain flow coefficient (Cv) determined by how far the valve is opened. This protection device will look somewhat like a flow straightener or a flow conditioner, and is currently named “Brick Stopper”. However the intention of Brick Stopper is not to straighten the flow, but to protect the choke valve from impacts of large objects. There are some challenges related to the design of the Brick Stopper: the holes need to be optimised in terms of reducing the pressure loss versus stopping heavy objects; and material selection and hardfacing need to take both erosion and impact into consideration. A qualification program will be launched when an optimized design has been concluded. The intention of this program is to take impacts, erosion and fatigue into account. Impact loads will be selected high enough to avoid need for future qualifications of the same size and pressure class. The qualification program will also aim to consider long-term effects. Design of the Brick Stopper will be described in the piping detail standard (PDS) when the qualification is finalized, enabling anyone to produce the Brick Stopper based on Statoil’s design. Impact testing of the choke valves will still be required, but impact loads will be reduced and easier to standardize.
