The small diameter line which is used to discharge the last part of the cargo from the ship is called as MARPOL line.
As per MARPOL Annex 1, Regulation 30, “Every oil tanker delivered after 1 June 1982, required to be provided with segregated ballast tanks or fitted with a crude oil washing system, shall comply with the following requirements:
a) it shall be equipped with oil piping so designed and installed that oil retention in the lines is minimized; and
b) means shall be provided to drain all cargo pumps and all oil lines at the completion of cargo discharge, where necessary by connection to a stripping device. The line and pump draining shall be capable of being discharged both ashore and to a cargo tank or a slop tank. For discharge ashore a special small diameter line shall be provided and shall be connected outboard of the ship’s manifold valves.”
When cargo discharge has been completed, the contents in the pipeline should also be discharged ashore. As per MARPOL Annex, Regulation 30, the required arrangement for this operation is a stripping system which includes a separate, small diameter discharge line to the cargo manifold where it is connected to the manifolds of each individual cargo tanks and that connection will be situated on the pipeline of each individual cargo tank and placed after the manifold valve.
Note: Each cargo tank pipeline has a valve at its end at the manifold, this is known as the manifold of that particular cargo tank and that valve is known as the manifold valve of that cargo tank
Ref: MARPOL Consolidated Edition
