Purpose

Awaiting the conclusion to the ongoing discussions in IMO regarding cargo vessels and the term “screw-down valve” in SOLAS Reg. II-1/12.5.1, this instruction is issued to give guidance for Norwegian vessels in this respect. 
Further noting that the International Association of Classification Societies (IACS) has submitted document SLF 51/3/4 in which it argues that butterfly valves provide a means as effective as screw-down valves for this purpose which is currently under discussion in the International Maritime Organization (IMO).

Application

This instruction is applicable to cargo vessels with a gross tonnage of 500 and above constructed on or after 1 January 2009.

References

Agreement of 1 June 2002 between the Ministry of Trade and Industry and ROs – annex I section 2.1.1.

Background

In accordance with SOLAS Reg. II-1/12.5.1, cargo vessels constructed on or after 1 January 2009 shall be fitted with a screw-down valve capable of being operable from above the freeboard deck if there is a pipe penetrating the collision bulkhead.
However, prior to 1 January 2009 subject requirement for cargo vessels was a suitable valve. The industry standard for some cargo vessels was to fit a remotely operated butterfly valve. It is also noted that for some types of cargo vessels it is not feasible to use a screw-down valve on the pipe penetrating the collision bulkhead due to the ships arrangement. 

Instructions to RO 

The NMA will accept the use of butterfly valves instead of screw-down valves in accordance with SOLAS Reg. II-1/12.5.1 on cargo vessels if the RO is satisfied that the butterfly valve in question and its arrangement provide a sufficient level of safety. However, the NMA has the following specific requirements to the system if the valve is remotely operated:
• The actuator shall be of a double acting type.
• When subject to loss of power, the actuator should remain in its current position.
• When subject to loss of power, the valve should be able to be manually operated.
If so deemed by the RO, no application for exemption of this arrangement needs to be forwarded to the NMA.