Drain apparatus for a subsea pipeline

A drain apparatus for use in a subsea gas pipeline to remove liquid from a multiphase flow in the subsea gas pipeline, the drain apparatus comprising:

• a first channel for carrying a multiphase flow comprising liquid and gas phases, the first channel comprising open ends configured to be connected to open ends of the subsea gas pipeline so as to install the drain apparatus inline with the subsea gas pipeline;
• and
• liquid extraction means for extracting the liquid phase from the multiphase flow in the first channel, such that the multiphase flow exiting a dry side of the first channel contains less liquid than the multiphase flow entering a wet side of the first channel;
• and
• at least one injection port configured to inject a hydrate inhibitor on the dry side of the first channel such that, in use, the hydrate inhibitor is carried in the multiphase flow along the subsea gas pipeline downstream of the drain apparatus,
• wherein an internal diameter of the first channel is substantially the same as an internal diameter of a subsea pipe arranged to carry the multiphase flow in the subsea gas pipeline, such that a pig travelling along the subsea pipe can pass through the first channel.