SC156

SC
SC
156
156

(June 2002)(cont)(Rev.1
Oct 2018)(Rev.2
Jan 2021)(Rev.3
July 2024)

Doors in watertight bulkheads of cargo ships
and passenger ships
Application
This unified interpretation pertains to doors located in way of the internal watertightsubdivision boundaries and the external watertight boundaries necessary to ensurecompliance with the relevant subdivision and damage stability regulations.
This unified interpretation does not apply to doors located in external boundaries above
equilibrium or intermediate waterplanes.
The design and testing requirements for watertight doors vary according to their location
relative to the 1) equilibrium waterplane or intermediate waterplane at any stage of assumed
flooding and or 2) bulkhead deck or freeboard deck.
This UI applies to ships subject to certification under SOLAS, MARPOL, ICLL, the IBC Codeand the IGC Code in accordance with SOLAS II-1/Reg. 4.1 and Reg.4.2 as amended byresolution MSC 474 (102).
Small cargo vessels not subject to damage stability requirements are not required to comply
with the full scheme1.
Footnote:
1 Doors in watertight bulkheads of small cargo ships, not subject to any statutory subdivision and damage stability

requirements, may be hinged single action doors arranged to open out of the major space protected. They shall be
constructed in accordance with the requirements of the classing society and have notices affixed to each sidestating, "To be kept closed at sea".

Note:
1. This UI SC 156 is to be uniformly implemented by IACS Members and Associates from 1
January 2003.
2. Rev.1 of this Unified Interpretation is to be applied by Members on ships contracted forconstruction on or after 1 January 2020 (in the absence of a building contract, the keel ofwhich is laid or which are at a similar stage of construction on or after 1 July 2020) or
delivered on or after 1 January 2024.
3. The “contracted for construction” means the date on which the contract to build the vessel
is signed between the prospective owner and the shipbuilder. For further details regarding
the date of “contract for construction”, refer to IACS Procedural Requirement (PR) No. 29.
4. Rev.2 of this Unified Interpretation is to be applied by Members on ships contracted forconstruction on or after 1 July 2021 (in the absence of a building contract, the keel ofwhich is laid or which are at a similar stage of construction on or after 1 January 2022)
or delivered on or after 1 July 2024.
5. Rev. 3 of this Unified Interpretation is to be applied by Members on ships contracted
for construction on or after 1 July 2025 (in the absence of a building contract, the keelof which is laid or which are at a similar stage of construction on or after 1 July 2025)
or delivered on or after 1 January 2028.

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SC156

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156(cont)

1.

Definitions

For the purpose of this UI the following definitions apply:
Watertight: Capable of preventing the passage of water in any direction under a design
head. The design head for any part of a structure shall be determined by reference to its
location relative to the bulkhead deck or freeboard deck, as applicable, or to the mostunfavourable equilibrium/intermediate waterplane, in accordance with the applicablesubdivision and damage stability regulations, whichever is the greater. A watertight door isthus one that will maintain the watertight integrity of the subdivision bulkhead in which it islocated.
Equilibrium Waterplane: The waterplane in still water when, taking account of flooding due
to an assumed damage, the weight and buoyancy forces acting on a vessel are in balance.
This relates to the final condition when no further flooding takes place or after cross flooding
is completed.
Intermediate Waterplane: The waterplane in still water, which represents the instantaneous
floating position of a vessel at some intermediate stage between commencement andcompletion of flooding when, taking account of the assumed instantaneous state of flooding,the weight and buoyancy forces acting on a vessel are in balance.
Sliding Door or Rolling Door: A door having a horizontal or vertical motion generally
parallel to the plane of the door.
Hinged Door: A door having a pivoting motion about one vertical or horizontal edge.
2.
Structural Design
Doors shall be of approved design and substantial construction in accordance with therequirements of the classing society and shall be of a strength equivalent to that of thesubdivision bulkheads in which they are fitted.
3.
Operation Mode, Location and Outfitting
Doors shall be fitted in accordance with all requirements regarding their operation mode,
location and outfitting, i.e. provision of controls, means of indication, etc., as shown in Table
1 below. This table is to be read in conjunction with the following general notes: For
passenger ships the watertight doors and their controls are to be located in compliance withSOLAS II- 1/13.5.3 and II-1/13.7.1.2.2.
3.1

Frequency of Use whilst at sea

Normally Closed
Kept closed at sea but may be used if authorised by the Master. To be closed again after use.
Permanently Closed
Such doors shall remain closed at sea. The time of opening such doors in port and of closing
them before the ship leaves port shall be authorised by the Master and entered in the logbook. Should such doors be accessible during the voyage, they shall be fitted with a device
to prevent unauthorised opening.

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SC156

SC
156(cont)

Used
Kept closed at sea, but may be opened during navigation to permit the passage of passengers
or crew, or when work in the immediate vicinity of the door necessitates it being opened as per
SOLAS II-1/22.3. The door shall be immediately closed after use.
3.2

Category of watertight doors for passenger ships

Category B
A watertight door that may be opened during navigation when work in the immediate vicinity ofthe door necessitates it being opened, according to SOLAS regulation II-1/22.3. The door must
be immediately closed when the task which necessitated it being open is finished.
Category C
A watertight door that may be opened during navigation to permit the passage of passengers
or crew, according to SOLAS regulation II-1/22.3. The door must be immediately closed whentransit through the door is complete.
Category D
A watertight door that shall be closed before the voyage commences and shall be kept closed
during navigation.
1.

A watertight door of a width of more than 1.2 m in machinery spaces as permitted by
SOLAS regulation II-1/13.9. The door shall remain closed during navigation except in caseof urgent necessity at the discretion of the master according to SOLAS regulation II-1/22.4.

2.

Additionally, watertight doors fitted in watertight bulkheads dividing cargo between deck
spaces in accordance with SOLAS regulation II-1/13.8.1 or dividing cargo spaces inaccordance with SOLAS regulation II-1/14.2, shall be closed before the voyagecommences and shall be closed during navigation according to SOLAS regulation II1/22.5.

3.3

Type

Power operated, sliding or rolling2
Power operated, hinged
Sliding or Rolling
Hinged3.4

Control

3.4.1

Local

POS
POH
S
H

All doors, except those which are to be permanently closed at sea, are to be capable of being
opened and closed by hand (and by power, where applicable3) locally from both sides of thedoors, with the ship listed to either side.
For passenger ships, the angle of list at which operation by hand is to be possible is 15 degrees.
For cargo ships, the angle of list at which operation by hand is to be possible is 30 degrees.

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156(cont)

3.4.2 RemoteWhere indicated in Table 1, doors are to be capable of being remotely closed by power fromthe bridge4 for all ships, and by hand also from a position above the bulkhead deck forpassenger ships as required by SOLAS II-1/13.7.1.4 13.6.1.4. Where it is necessary to start
the power unit for operation of the watertight door, means to start the power unit is also to
be provided at remote control stations. The operation of such remote control is to be inaccordance with SOLAS II-1/ 13.7.1 to 13.7.4. For tankers, where there is a permanent
access from a pipe tunnel to the main pump room, in accordance with regulation II-2/4.5.2.4
the watertight door shall be capable of being manually closed from outside the main pumproom entrance in addition to the requirements above.
3.5

Indication5

3.5.1 Where shown in Table 1, position indicators are to be provided at all remote operating
positions for all ships and provided locally on both sides of the internal doors for cargo ships,
to show whether the doors are open or closed and, if applicable, with all dogs/cleats fully andproperly engaged.
3.5.2 The door position indicating system is to be of self-monitoring type and the means fortesting of the indicating system are to be provided at the position where the indicators are
fitted.

Footnotes:
2 Rolling doors are technically identical to sliding doors.
3 Arrangements for passenger ships shall be in accordance with SOLAS II-I/ 13.6.1.4 and 13.6.1.5and regulation II-

1/13-1.2 for cargo ships
4 Arrangements shall be in accordance with SOLAS II-1/ 13.6.1.5 for passenger ships and 13-1.2 for cargo ships
5 Refer to SOLAS II-I/Reg.13, 13-1, 15-1 and 17-1, IEC 60092-504, IMO International Code on Alarms andIndicators 2009)

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156(cont)

3.5.3 A diagram showing the location of the door and an indication to show its position shallbe provided at the central operating console located at the navigating bridge. A red light shallindicate the door is in the open position and a green light shall indicate the door is in theclosed position. When the door is closed from this remote position, the red light shall flash
when the door is in an intermediate position. This applies to passenger ships and cargoships.
3.5.4 Signboard/instructions should be placed in way of the door advising how to act when
the door is in "doors closed" mode.
3.6

Alarms6

3.6.1 For passenger ships, failure of the normal power supply of the required alarms
shall be indicated by an audible and visual alarm at the central operating console at thenavigation bridge. For cargo ships, failure of the normal power supply of the required
alarms shall be indicated by an audible and visual alarm at the navigation bridge.
3.6.2 All door types, including power-operated sliding watertight doors which are to becapable of being remotely closed are to be provided with an audible alarm, distinct from anyother alarm in the area, which will sound whenever such a door is remotely closed.
For passenger ships the alarm shall sound for at least 5 s but not more than 10 s before thedoor begins to move and shall continue sounding until the door is completely closed. In thecase of remote closure by hand operation, an alarm is required to sound only while the door
is actually moving. In passenger areas and areas of high ambient noise, the audible alarms
are to be supplemented by visual signals at both sides of the doors.
3.6.3 All watertight doors, including sliding doors, operated by hydraulic door actuators, eithera central hydraulic unit or an independent hydraulic unit for each door is to be provided with alow fluid level alarm or low gas pressure alarm, as applicable or some other means ofmonitoring loss of stored energy in the hydraulic accumulators. For passenger ships this alarm
is to be both audible and visible and shall be located on the central operating console at thenavigation bridge. For cargo ships, this alarm shall be both audible and visible and should belocated at the navigation bridge.
3.7

Notices

As shown in Table 1, doors which are normally closed at sea but not provided with means ofremote closure, are to have notices fixed to both sides of the doors stating, “To be kept
closed at sea”. Doors which are to be permanently closed at sea are to have notices fixed toboth sides stating, “Not to be opened at sea”.
3.8

Location

For passenger ships the watertight doors and their controls shall be located in compliancewith regulations II-1/13.5.3 and II-1/ 13.6.1.2.2.

Footnotes:
6 Refer to SOLAS II-I/Reg.13, 13-1, 15-1 and 17-1, IEC 60092-504, IMO International Code on Alarms andIndicators 2009)

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SC1564.

SC
156(cont)

Fire Doors

Watertight doors may also serve as fire doors but need not be fire-tested if fitted on cargoships or if fitted below the bulkhead deck on passenger ships. However, such doors fitted
above the bulkhead deck on passenger ships shall be tested to the FTP Code in accordancewith the fire rating of the division they are fitted in. If it is not practicable to ensure self-closing,means of indication on the bridge showing whether these doors are open or closed and anotice stating ‘To be kept closed at sea’ can be alternative of the self-closing.
Where a watertight door is located adjacent to a fire door, both doors shall be capable ofindependent operation, remotely if required by SOLAS ll-1/ 13.7.1 to 13.7.3 and from bothsides of each door.
5.

Testing

Doors which become immersed by an equilibrium or intermediate waterplane, are to be
subjected to a hydrostatic pressure test.
For large doors intended for use in the watertight subdivision boundaries of cargo spaces,
structural analysis may be accepted in lieu of pressure testing. Where such doors utilise
gasket seals, a prototype pressure test to confirm that the compression of the gasket
material is capable of accommodating any deflection, revealed by the structural analysis, is tobe carried out.
Doors above freeboard or bulkhead deck, which are not immersed by an equilibrium orintermediate waterplane but become intermittently immersed at angles of heel in therequired range of positive stability beyond the equilibrium position are to be hose tested.
5.1

Pressure Testing

5.1.1 The head of water used for the pressure test shall correspond at least to the headmeasured from the lower edge of the door opening, at the location in which the door is to be
fitted in the vessel, to the bulkhead deck or freeboard deck, as applicable, or to the mostunfavourable damage waterplane, if that be greater. Testing may be carried out at the factoryor other shore based testing facility prior to installation in the ship.
5.1.2 Leakage Criteria
5.1.2.1The following acceptable leakage criteria should apply
Doors with gaskets
Doors with metallic sealing

No leakage
Max leakage 1 litre/min.

5.1.2.2 Limited leakage may be accepted for pressure tests on large doors located in cargospaces employing gasket seals or guillotine doors located in conveyor tunnels, in accordancewith the following7(P + 4.572) • h3
Leakage rate(litre/min) =6568

where: P = perimeter of door opening (metres)
h = test head of water (metres)
5.1.2.3 However, in the case of doors where the water head taken for the determination of thescantling does not exceed 6.10 m, the leakage rate may be taken equal to 0.375 litre/min if
this value is greater than that calculated by the above-mentioned formula.
Footnotes:
7 Published in the ATM F 1196, Standard Specification for Sliding Watertight Door Assemblies and referenced in

the Title 46 US Code of Federal Regulations 170.270 Door design, operation installation and testing

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5.1.3 For doors on passenger ships which are used at sea or which become submerged by
the equilibrium or intermediate waterplane, a prototype test shall be conducted, on each sideof the door, to check the satisfactory closing of the door against a force equivalent to a waterheight of at least 1 m above the sill on the centre line of the door8.
5.2

Hose Testing

5.2.1 All watertight doors shall be subject to a hose test in accordance with UR S14.2.3 after
installation in a ship. Hose testing is to be carried out from each side of a door unless, for a
specific application, exposure to floodwater is anticipated only from one side. Where a hose
test is not practicable because of possible damage to machinery, electrical equipment
insulation or outfitting items, it may be replaced by means such as an ultrasonic leak test or
an equivalent test.

Footnote:
8 Arrangements for passenger ships shall be in accordance with SOLAS Reg. II-1/13.5.2

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SC156
Table 1: Doors in Internal Watertight Bulkheads and External Watertight Boundaries in Cargo Ships and Passenger Ships

SC156(cont)

A. Door in Internal Watertight Bulkhead
I. Passenger Ships

Position(1)
Below Bulkhead Deck

1.

2.

3.

4.

5.

Regulation

CategoryType

RemoteClosureRemoteIndication

6.
Audible/VisualClosing
Alarm

7.

8.

NoticeComments

SOLAS II-1/10，
13.4, 13.5.1, 13.5.2,
13.6.1 to 13.6.8,
13.7.1, 13.7.3,
13.7.4, 16.2, 22.1
and 22.3

B, C

POS

Yes

Yes

Yes (local)

No

SOLAS II-1/10，
13.8.1, 13.8.2, 16.2,

D

S, H

No

No

No

Yes

D

POS

Yes

Yes

Yes (local)

No

D

S, H

No

Yes

No

Yes

For guidance regarding
watertight doors on
passenger ships which
may be opened during
navigation, see IMO
MSC.1/Circ.1564.

22.2, 22.5 and 22.13

SOLAS II-1/10, 13.9,
22.2 and 22.4
SOLAS II-1/10

and14.2

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SC156(cont)(2)
At or above bulkheaddeck and below the
worst intermediate or
final equilibrium
waterline(3)
At or above bulkheaddeck, and above theworst intermediate
and final equilibrium
waterlines, but
immersed in therequired range of
positive stability.

SOLAS II-1/10， 16.2,
17.2, 22.1,
and 22.3

B, C

POS

Yes

Yes

Yes (local)

No

For guidance regarding
watertight doors on
passenger ships which may
be opened during navigation,
see IMO MSC.1/Circ.1564.
See Explanatory Note toRegulation 17.2 of
Res.MSC.429(98)/Rev.2.

SOLAS II-1/17.3

N/A

POS,
POH

Yes

Yes

Yes
(local)May remain open, but shallalways be ready to be
immediately closed.
No
See Explanatory Note toRegulation 17.3 of
Res.MSC.429(98)/Rev.2.

SOLAS II-1/17.3

N/A

S, H

No

Yes

No

Yes

Normally closed.
If hinged, this door shall beof single action type.
See Explanatory Note toRegulation 17.3 of
Res.MSC.429(98)/Rev.2.

(4) At or above
bulkhead deck on
ro-ro passenger
ships.

SOLAS II-1/171.1.1 to 17-1.1.3,
22.8, 23.3 to 23.9

N/A

S, H

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No

Yes

Yes
(remote/local)Yes

Permanently closed. The
Administration may permit
some accesses to beopened in accordance withReg. II-1/23.6 and
23.8.

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SC156

II. Cargo Ships

SC156(cont)
1.
Position relative to
freeboard deck
Regulation

SOLAS II-1/10, 13-1.2,
16.2 and 22.1，22.3,
MARPOL I/28.3,
ICLL66+A.320 1988
Protocol to ICLL66,
IBC and IGC

2.

3.

Frequencyof UseType
while at sea

Used

POS

4.

5.

RemoteClosureRemoteIndication

Yes

Yes

6.

7.

Audible / Visual
Closing Alarm Notice

Yes (local)

8.

Comments

No

If hinged, this door shallbe of single action type.

(1)
Below

SOLAS II-1/10, 131.3,16.2 and 24.4,
MARPOL I/28.3,
ICLL66+A.3201988
Protocol to ICLL66, IBC
and IGC

Norm.
Closed

S, H

No

Yes

No

Yes

SOLAS II-1/10, 13-1.4, 131.5, 16.2, 22.2, 22.13,
24.3, and 24.4, MARPOL
I/28.3, ICLL66+A.3201988
Protocol to ICLL66, IBC
and IGC

Perm.
Closed

S, H

No

No

No

Yes

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Under ICLL66, hinged
doors separating amain machinery spacefrom a steering gearcompartment musthave the lower sill
above the Summer
Load Line.

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SC156

SC156(cont)SOLAS II-1/10, 131.2,16.2, and 22.1，22.3,
MARPOL I/28.3,
ICLL66+A.320
1988 Protocol to ICLL66, IBC
and IGC

Used

POS

Yes

Yes

Yes (local)No

If hinged, this door shall beof single action type.

(2)
At or above

SOLAS II-1/10, 13- 1.3,
16.2 and 24.4, MARPOL
I/28.3, ICLL66+A.3201988
Protocol to ICLL66, IBC and
IGC

Norm.
Closed

S, H

No

Yes

No

Yes

Under ICLL66, hinged
doors separating a mainmachinery space from asteering gearcompartment must havethe lower sill above theSummer Load Line.
Under MARPOL I/28.4.3,
hinged watertight doors
may be acceptable inwatertight bulkhead in the
superstructure.

SOLAS II-1/10, 13-1.4, 131.5, 16.2, 22.8, 24.3 and24.4, MARPOL I/28.3,
ICLL66+A.3201988
Protocol to ICLL66, IBC and
IGC

Perm.
ClosedS, H

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No

No

No

Yes

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B. Doors in External watertight Boundaries below equilibrium or intermediate waterplane(cont)
1.
Position relative tobulkhead deck or
freeboard deck

Regulation

2.
Frequencyof Usewhile at
sea

3.

4.

5.

Type

RemoteClosureRemoteIndication

Perm.
Closed

S, H

No

Yes

6.

7.

8.

Audible / Visual
Closing Alarm

NoticeComments

No

Yes

I. Passenger Ships
(1)
Below

SOLAS II-1/15.10,
16.2,
22.7 and 22.13
SOLAS II-1/16.2, 17.6,
22.8 to 22.13(2)
At or above

Norm.
Closed /Perm.
ClosedSOLAS II-1/16.2,
17-1, 23.3, 23.5,
23.6 and 23.8

Norm.
Closed /Perm.
ClosedSOLAS II-1/15.10,
15- 1.2 to 15-1.4,
16.2, 22.7, 22.12,
22.13 and 24.1

Perm.
ClosedSOLAS II-1/15-1.2
and 16.2

Norm.
ClosedSOLAS II-1/15-1.2 to
15-1.4, 16.2, 22.8
and 24.1

Perm.
Closed

S, H

No

Yes

No

Yes

S, H

No

Yes

Yes
remote/local

Yes

S, H

No

Yes

No

Yes

If hinged, normallyclosed door shallbe of
single action
type.

II. Cargo Ships
(1)
Below

S, H

No

Yes

No

Yes

S, H

No

Yes

No

Yes

(2)
At or above

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If hinged, normallyclosed door shallbe of
single action
type.

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SC156(cont)End ofDocument

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