1. The Maritime Safety Committee approved the following amendments to MSC/Circ.677:
2. Member Governments are invited to apply the amendments to the Revised standards, as amended, to ships constructed on or after 1 January 2013 and to ships constructed before 1 January 2013, no later than the first scheduled dry-docking carried out on or after 1 January 2013.

The in-line pressure/vacuum relief valve is an automatic pressure/vacuum valve, which operates through the vapor header. It relieves pressure and vacuum during loading, discharge, voyage and ballasting.

In-line pressure vacuum relief valve is installed on cargo tanks, I.G. main etc.

The In-line pressure vacuum relief valve is a combined pressure/vacuum relief system, and it is designed for marine tankers and chemical tankers.

The In-line pressure vacuum relief valve is designed and constructed to comply with IMO MSC/cirs 677.

The materials for shall be selected for the stored-product service temperatures and pressures.

Also, the materials should be compatible with the product stored in the tank and with any products formed in the vicinity of the relief valve during filling and discharge.

Usually the materials are available in Aluminum, Carbon Steel, Stainless Steel grade 304, 316 and 316L to suit individual requirements.