Solas solutions

Operators have several ways to meet IMO`s latest Solas requirement for venting cargo tanks.

Incidents like the rupture of an over-pressurised tank in a VLCC caused IMO to look again at the regulations concerning cargo tank venting. During the review the Australians highlighted an incident where a pressure/vacuum valve (pv valve) had stuck in the closed position and led to over-pressurisation of a tank during loading operations. To prevent such incidents happening again, IMO has added paragraph 1.2.3 to Regulation 59 of Solas (see box). In essence this requires tanker newbuildings with keel laying after 1 July 1998 to have either a secondary means of venting the cargo tanks or a pressure monitoring system. Existing tonnage must be modified at the first scheduled drydocking, but not later than July 2001.

It is possible to comply with the new regulations by adopting one of a number of strategies, some require additional equipment, others may not. “You have to look ship by ship to see what, if any, modifications are required,” says Norman Rattenbury, deputy head of piping systems for Lloyd`s Register.

He points out that vessels carrying a single cargo (such as a VLCC), may have a common inert gas main capable of venting the tanks. “Provided all cargo tanks are open to the IG main during cargo operations, the pv breaker on the main could be deemed as the second means of protection,” he says. In these cases a change of operating procedures may be all that is required to ensure compliance – this would have to be witnessed by class and flag to verify it. Some may vessels already conform to the new regulation as certain operators already specify two pv valves in each tank.