Structural damage incidents as a result of overpressure in iquid cargo tanks have been increased
Gard P&I Club issued Loss Prevention Circular No.08-11 regarding clearing of shore pipelines following cargo operations at terminals.
Over the years, Gard has seen some extensive structural damage incidents as a result of overpressure in the liquid cargo tanks during loading operations. Such damages result in time consuming and costly repairs and unfortunately, for reasons unknown, the frequency of such incidents has increased, despite ship procedures addressing the risks involved.
In Gards experience such incidents often occur during the loading operation phase when shore pipelines are being cleared, either by line blowing or by pigging1. In one such incident, failure to maintain close communication with the terminal and a lack of ship personnels attention to and awareness of the hazards related to an unattended open manifold valve during shore pipeline clearing operations seem to be the main causes.
After the completion of loading of one tank and initial clearing of the line, the terminal requested the re-opening of the manifold valve for further blowing of the cargo line. The line was then left open and the ship reportedly did not receive any further information from the terminal. Some five hours after the request for the re-opening of the manifold valve, a bang was heard on deck and cargo was seen emitting from the tank vent. The results were significant damage to the transverse bulkheads between the tanks and cargo mixing between tanks.
The purpose of this circular is therefore to highlight the main issues involved in order to minimize the risk of pollution and damage to the cargo tanks during cargo operations involving clearing of shore pipelines.
You can view the Circular by clicking here.
Source: Gard P&I Club