Underwater pipeline apparatus for delivering a pig unit through a seabed pipeline

摘要

The apparatus includes an inlet conduit (12) for coupling to a pipeline inlet port (14) at a location behind the pig unit (15) in its intended direction of travel, from said entry point to said exit point, having an opening (11) to the sea to admit pressurised water into the pipeline under the head of water above the pipeline and means to regulate flow of water through the inlet conduit into the pipeline to regulate the speed of delivery of the pig unit along the pipeline. The opening can be a fixed orifice (11) as shown or an isolating valve and a flow-limiting valve with variable choke. An intake filter and additive supply with pump may be provided. A boost pump, to drive the pig when the head is reduced, can be operated by a surface vessel.