Maritime and Coastguard Agency
OPERATIONAL ADVICE NOTE
Revision: 01
Fire Protection & Stability
Document
number:
OAN 726
Date:
12 October 2010
Passenger Ships and Cargo Ships
Fixed Pressure Water Spraying Systems and the
drainage of vehicle, special category and ro-ro spaces
Distribution
HQ & MO
Target
document
Expiry date
MSIS 12 Fire Protection Arrangements, Chapter 3
22 February 2011
Information
1.
The purpose of this OAN is to clarify the MCA application of SOLAS with regard to
SOLAS Chapter II-2 Regulation 20.6 and associated MSC.1/Circ.1320 in respect of the
protection of vehicle, special category and ro-ro spaces.
Background
2.
On 1st January 2010, Resolution MSC.256(84) introduced changes to SOLAS Chapter
II-2 Regulation 20 regarding the protection of vehicle, special category and ro-ro
spaces. Guidance notes have also been developed by the IMO and released as
MSC/Circ.1320.
The revised regulation II-2/20.6.1.4 requires the provision of
enhanced drainage and pumping arrangements so as to prevent the build up of free
surface on vehicle, special category, and ro-ro spaces, different for passenger and
cargo ships respectively. These requirements are applicable to ships constructed on
or after 1 January 2010. Ships constructed on or after 1 July 2002 and before 1
January 2010 are to comply with the previously applicable requirements of paragraph
6.1.4, as amended by resolution MSC.99(73).
3.
In addition the new regulation II-2/20.6.1.5 requires all ships with closed vehicle and roro spaces and special category spaces, where fixed pressure water spraying systems
are fitted, to be provided with means to prevent blockage of the drainage
arrangements. Existing ships will have to comply with 6.1.5 by the first survey after 1
January 2010.
4.
SOLAS Chapter II-2 Regulation 3 defines the following:
Vehicle spaces - are cargo spaces intended for carriage of motor vehicles with fuel in
their tanks for their own propulsion.
Special category spaces - are those enclosed vehicle spaces above and below the
bulkhead deck, into and from which vehicles can be driven and to which passengers
have access. Special category spaces may be accommodated on more than one deck
provided that the total overall clear height for vehicles does not exceed 10 m.
Ro-ro spaces - are spaces not normally subdivided in any way and normally extending
to either a substantial length or the entire length of the ship in which motor vehicles
with fuel in their tanks for their own propulsion and/or goods (packaged or in bulk, in or
on rail or road cars, vehicles (including road or rail tankers), trailers, containers, pallets,
demountable tanks or in or on similar stowage units or other receptacles) can be
loaded and unloaded normally in a horizontal direction.
Cargo spaces - are spaces used for cargo, cargo oil tanks, tanks for other liquid cargo
and trunks to such spaces.
Closed ro-ro spaces - are ro-ro spaces which are neither open ro-ro spaces nor
weather decks.
Closed vehicle spaces - are vehicle spaces which are neither open vehicle spaces nor
weather decks.
Open ro-ro spaces - are those ro-ro spaces which are either open at both ends or have
an opening at one end, and are provided with adequate natural ventilation effective
over their entire length through permanent openings distributed in the side plating or
deckhead or from above, having a total area of at least 10% of the total area of the
space sides.
Open vehicle spaces - are those vehicle spaces which are either open at both ends or
have an opening at one end and are provided with adequate natural ventilation
effective over their entire length through permanent openings distributed in the side
plating or deckhead or from above, having a total area of at least 10% of the total area
of the space sides.
Actions
5.
Noting that SOLAS Ch II-2, Reg 20.6.1.4 and Reg 20.6.1.5 plus MSC.1/Circ.1320
make application to “…closed vehicle, ro-ro spaces and special category spaces…”.
6.
The UK interpretation is that the aforementioned Regulations and guidelines are
therefore currently applicable separately to "closed vehicle" spaces, "ro-ro" spaces and
"special category" spaces. Since “closed” only relates to vehicle spaces it means that
SOLAS Ch II-2, Reg 20.6.1.4 and Reg 20.6.1.5 plus MSC.1/Circ.1320 are applicable to
all ro-ro spaces (both "open ro-ro spaces" and "closed ro-ro spaces").
7.
Notwithstanding the above interpretation. The MCA believe that IMO may not have
given enough consideration to precisely defining the applicability of SOLAS Ch II-2,
Reg 20.6.1.4, Reg 20.6.1.5 and MSC.1/Circ.1320. The majority of ‘space’ definitions
currently in SOLAS Ch II-2 Reg 3 appear to relate more to ventilation requirements
rather than the drainage of any water accumulation and consequent stability issues.
The potential for water to accumulate in any vehicle, ro-ro or special category space
fitted with a fixed pressure water spraying system, possibly causing a loss of stability,
is a serious safety concern. In order to address this matter and until IMO are able to
look at this issue in closer detail, MCA are of the opinion that the aforesaid Regulations
and Guidance should be applicable to anywhere where fixed pressure water-spraying
systems are fitted and where there is the possibility of water accumulation.
8.
The intention of SOLAS Ch II-2, Reg 20.6.1.4, Reg 20.6.1.5 and MSC.1/Circ.1320 is to
avoid large quantities of water accumulating on deck during the operation of water fire
fighting systems. Surveyors should therefore ensure that whatever arrangement is
finally accepted that this goal is achieved.
Freeing Ports
9.
The minimum drainage capacity as calculated in MSC.1/Circ.1320 may be achieved in
spaces above the bulkhead deck through the use of scuppers, freeing ports or a
combination thereof. The requirements of SOLAS II-2 Regulation 20 paragraph 6.1.5.
as elucidated in paragraph 5 of MSC.1/Circ.1320 are not applicable to freeing ports
and thus protective gratings are not required. It is to be noted that the fitting of gratings
to freeing ports may be detrimental to their effectiveness.
Guidance on the application of 6.1.5 to existing vessels
10.
Paragraph 5 of MSC.1/Circ.1320 provides the following guidance on the protection
arrangements required by SOLAS II-2 Regulation 20 paragraph 6.1.5:
5 Protection of drain openings
5.1 An easily removable grating, screen or other means should be installed over each
drain opening in the protected spaces to prevent debris from blocking the drain. The
total open area ratio of the grating to the attached drain pipe should be at least 6 to 1.
The grating should be raised above the deck or installed at an angle to prevent large
objects from blocking the drain. No dimension of the individual openings in the grating
should be more than 25 mm.
5.2 No grating or screen is required when a fixed mechanical system is provided to
unblock the drainage system, or when other than a gravity drain system is provided
with its own filter.
5.3 A clearly visible sign or marking should be provided not less than 1,500 mm above
each drain opening stating, “Drain opening – do not cover or obstruct”. The marking
should be in letters at least 50 mm in height.
11.
The following points provide guidance on the number of drain openings required to be
fitted with means of protection and other considerations that may apply to existing
vessels.
12.
Number of drain openings to be protected - The number and capacity of drain
openings to be protected should be calculated according to the procedure outlined
below in steps a to d:
a. The drencher pump capacity is calculated from the requirement to provide
water application at 3.5 l/m2 for low deck height spaces and 5 l/m2 for high deck
height spaces for the two largest adjacent drencher sections. (IMO Resolution
A.123(V) adopted 1967).
b. The drainage requirement is calculated using the requirements in force at the
time the ship was built. If these are not known then the drainage capacity is to
be taken as 125% of the sum of the drencher pump capacity for the entire space
plus the capacity of two fire hoses (four if carrying dangerous goods).
c. The quantity of water each drain opening is able to remove should be
calculated. This calculation will involve the physical dimensions of the drain, its
elevation above the discharge point, the nature of the drainage pipe and valve
arrangement and minimal water on deck to offer a pressure head. Account
should be taken of head losses in the arrangement.
d. Using the above the minimum number of drain openings which should be
protected may be calculated. Any drains fitted in excess of this requirement are
not required to have protection fitted, unless drainage cannot be obtained under
normal drencher test conditions with these drainage openings temporarily
closed (i.e. they may be excess in numbers or capacity, but are essential to
provide adequate drainage).
13.
The protected drain openings should be evenly distributed fore and aft, port and
starboard.
14.
In respect of drain opening protection arrangements and design: i.
Due to variations in design to meet differing situational requirements it is
impractical for MCA to recommend any fixed design or designs over another. It
will be for the shipyard/vessel owner to submit their designs for review and
acceptance by MCA.
ii. Each drain opening which is protected in order to comply with the regulation
must be fitted with an easily removable raised grating that complies with the
requirements of 5.1 of MSC Circ. 1320. The total open area ratio of the grating
to the drain pipe should be at least 6:1.
iii. The grating should be designed in such a way that the effectiveness of the
existing drain is not reduced and to minimise any sill created by the design. If
the design of the protection is such that there is any doubt about the retained
effectiveness of the drain, then a practical test should be carried out whereby
the drain is boxed off and a known quantity of water discharged through the
drain without the protection in place and then with. There should be no
difference in the time or quantity of water discharged.
iv. Where the protection is fitted to a drain in way of vehicle movements, the
protection should be designed to withstand the point loads exerted by the
maximum vehicle axle weight. This load should be transferred to the deck
without causing excessive point loads. The arrangement of the protection may
provide for openings at the ships side or similar protected location to be led to
the existing drain. Confirmation of the acceptability of any proposed
arrangements with regard to deck strength should be obtained from the relevant
Class Society.
15.
Drain openings which have been identified as excess to the required drainage capacity
may be left un-protected. During testing of the efficacy of the drainage system (see
point 14 below) these drains should be temporarily blanked to emulate the situation
where they are all blocked and only the protected drain openings remain for drainage.
The un-protected drains should not be permanently blanked off.
16.
The revised arrangements will be tested as part of the usual drencher and fire hose
testing regime at both PSSC and SEC renewal. Drainage requirements are expected
to be met with any unprotected drain openings temporarily blanked off.
17.
Each case will need to be considered individually by MCA. When satisfied with the
arrangements the MCA Marine Office dealing with the survey will issue a letter to the
ship confirming acceptance.
Author
Branch Head of Ship Safety
Paul Owen
Authorised by
Branch Assistant Director Seafarers & Ships
Paul Coley