The present invention relates to an access assembly to provide access to the interior of a vessel and comprising: a base to extend through a sidewall of the vessel and having a tubular sealing portion providing a passageway axially extending therethrough, a pierceable sealing member arranged across the sealing portion to obstruct the passageway, at least one closure member axially displaceable relative to the base between a sealing position, in which the closure member completely obstructs and seals the passageway, and a leakage position, in which the closure member leakily obstructs the passageway.
