Watertight Bulkheads

A. General

1. Watertight subdivision

1.1 All ships are to have a collision bulkhead, a stern tube bulkhead and one watertight bulkhead at each end of the engine room. In ships with machinery aft, the stern tube bulkhead may substitute the aft engine room bulkhead.

1.2 For ships without longitudinal bulkheads in the cargo hold area the number of watertight transverse bulkheads should, in general, not be less than given in Table 11.1.

Table 11.1 - Number of watertight transverse bulkheads

1.3 One or more of the watertight bulkheads required by 1.2, may be dispensed with where the transverse strength of the ship is adequate. The number of watertight bulkheads will be entered into the Register.

1.4 Number and location of transverse bulkheads fitted in addition to those specified in 1.1 are to be so selected as to ensure sufficient transverse strength of the hull.

1.5 For ships which require proof of survival capability in damaged conditions, the watertight sub-division will be determined by damage stability calculations. For oil tankers see Section 24, A.2., for passenger vessels see Section 29-I, C., for special purpose ships see Section 29-II,.C., for cargo ships of more than 100 m in length see Section 36 and for supply vessels see Section 34, A.2. For liquefied gas tankers see Rules for Ships Carrying Liquefied Gases in Bulk, Volume IX, Section 2, for chemical tankers see Rules for Ships Carrying Dangerous Chemicals in Bulk, Volume X, Section 2.

2. Arrangement of watertight bulkheads 2.1 Collision bulkhead

2.1.1 A collision bulkhead shall be located at a distance from the forward perpendicular of not less than 0,05 L_c or 10 m, whichever is the less, and, except as may be permitted by the Administration, not more than 0,08 L_c or 0,05 L_c + 3 m, whichever is the greater

2.1.2 Where any part of the ship below the waterline extends forward of the forward perpendicular, e.g., a bulbous bow, the distance x shall be measured from a point either:

– at the mid-length of such extension, i.e. x = 0,5 @ a

– at a distance 0,015 Lc forward of the forward perpendicular, i.e. x = 0,015 @ Lc, or

– at a distance 3 m forward of the forward perpendicular, i.e. x = 3,0 m whichever gives the smallest measurement.

The length L_c and the distance a are to be specified in the approval documents.

2.1.3 If 2.1.2 is applicable, the required distances specified

in 2.1.1 are to be measured from a reference point located at a distance x forward of the F.P.

Fig.11.1 - Location of collision bulkhead

2.1.4 The collision bulkhead shall extend watertight up to the bulkhead deck. The bulkhead may have steps or recesses provided they are within the limits prescribed in 2.1.1.

2.1.5 No doors, manholes, access openings, or ventilation ducts are permitted in the collision bulkhead below the bulkhead deck.

2.1.6 Except as provided in 2.1.7 the collision bulkhead may be pierced below the bulkhead deck by not more than one pipe for dealing with fluid in the forepeak tank, provided that the pipe is fitted with a screwdown valve capable of being operated from above the bulkhead deck, the valve chest being secured inside the forepeak to the collision bulkhead. The Administration may, however, authorize the fitting of this valve on the after side of the collision bulkhead provided that the valve is readily accessible under all service conditions and the space in which it is located is not a cargo space. All valves shall be of steel, bronze or other approved ductile material. Valves of ordinary cast iron or similar material are not acceptable.

2.1.7 If the forepeak is divided to hold two different kinds of liquids the Administration may allow the collision bulkhead to be pierced below the bulkhead deck by two pipes, each of which is fitted as required by 2.1.6, provided the Administration is satisfied that there is no practical alternative to the fitting of such a second pipe and that, having regard to the additional subdivision provided in the forepeak, the safety of the ship is maintained.

2.1.8 Where a long forward superstructure is fitted the collision bulkhead shall be extended weathertight to the deck next above the bulkhead deck. The extension need not be fitted directly above the bulkhead below provided it is located within the limits prescribed in 2.1.1 or 2.1.3 with the exception permitted by 2.1.9 and that the part of the deck which forms the step is made effectively weathertight. The extension shall be so arranged as to preclude the possibility of the bow door causing damage to it in the case of damage to, or detachment of, a bow door.

2.1.9 Where bow doors are fitted and a sloping loading ramp forms part of the extension of the collision bulkhead above the bulkhead deck, the ramp shall be weathertight over its complete length. In cargo ships the part of the ramp which is more than 2,3 m above the bulkhead deck may extend forward of the limits specified in 2.1.1 or 2.1.3 Ramps not meeting the above requirements shall be disregarded as an extension of the collision bulkhead.

2.1.10 The number of openings in the extension of the collision bulkhead above the bulkhead deck shall be restricted to the minimum compatible with the design and normal operation of the ship. All such openings shall be capable of being

closed weathertight.

2.2 Stern tube and remaining watertight bulkheads

2.2.1 Bulkheads shall be fitted separating the machinery space from cargo and accommodation spaces forward and aft and made watertight up to the bulkhead deck. In passenger ships an afterpeak bulkhead shall also be fitted and made watertight up to the bulkhead deck. The afterpeak bulkhead may, however, be stepped below the bulkhead deck, provided the degree of safety of the ship as regards subdivision is not thereby diminished.

2.2.2 In all cases stern tubes shall be enclosed inwatertight spaces of moderate volume. In passenger ships the stern gland shall be situated in a watertight shaft tunnel or other watertight space separate from the stern tube compartment and of such volume that, if flooded by leakage through the stern gland, the bulkhead deck will not be immersed. In cargo ships other measures to minimize the danger of water penetrating into the ship in case of damage to stern tube arrangements may be taken at the discretion of the Administration.

3. Openings in watertight bulkheads

3.1 General

3.1.1 Type and arrangement of doors are to be submitted for approval.

3.1.2 Regarding openings in the collision bulkhead see 2.1.5 and 2.1.10.

3.1.3 In the other watertight bulkheads, watertight doors may be fitted.

Watertight doors required to be open at sea are to be of the sliding type and capable of being operated both at the door itself, on both sides, and from an accessible position above the bulkhead deck. Means are to be provided at the latter position to indicate whether the door is open or closed, as well as arrows indicating the direction in which the operating gear is to be operated.

Watertight doors may be of the hinged type if they are always intended to be closed during navigation. Such doors are to be framed and capable of being secured watertight by handle-operated wedges which are suitably spaced and operable at both sides.

3.1.4 On ships for which proof of floatability in damaged condition is to be provided, hinged doors are permitted above the most unfavourable damage waterline for the respective compartment only. Deviating and additional requirements hereto are given in Chapter II-1, Reg. 13-1 of SOLAS (as amended by MSC.216 (82)).

3.1.5 For bulkhead doors in passenger ships, see Section.29-I, C.

3.1.6 Watertight doors are to be sufficiently strong and of an approved design. The thickness of plating is not to be less than the minimum thickness according to B.2.

3.1.7 Openings for watertight doors in the bulkheads are to be effectively framed such as to facilitate proper fitting of the doors and to guarantee perfect watertightness.

3.1.8 Before being fitted, the watertight bulkhead doors, together with their frames, are to be tested by a head of water corresponding to the bulkhead deck height. After having been fitted, the doors are to be hose- or soap-tested for tightness and to be subjected to an operational test. Deviating and additional requirements hereto are given in Chapter II-1 Reg. 16 of SOLAS as amended.

3.2 Hinged doors

Hinged doors are to be provided with rubber sealings and toggles or other approved closing appliances which guarantee a sufficient sealing pressure. The toggles and closing appliances are to be operable from both sides of the bulkhead. Hinges are to have oblong holes. Bolts and bearings are to be of corrosion resistant material. A warning notice requiring the doors to be kept closed at sea is to be fitted at the doors.

3.3 Sliding doors

Sliding doors are to be carefully fitted and are to be properly guided in all positions. Heat sensitive materials are not to be used in systems which penetrate watertight subdivision bulkheads, where deterioration of such systems in the event of fire would impair the watertight integrity of the bulkheads.

The closing mechanism is to be safely operable from each side of the bulkhead and from above the freeboard deck. If closing of the door cannot be observed with certainty, an indicator is to be fitted which shows, if the door is closed or open; the indicator is to be installed at the position from which the closing mechanism is operated.

3.4 Penetrations through watertight bulkheads

Where bulkhead fittings are penetrating watertight bulkheads, care is to be taken to maintain water tightness by observation of Chapter II-1 Reg. 12 of SOLAS as amended. For penetrations through the collision bulkhead, 2.1.6 is to be observed.

B. Scantlings

1. General, Definitions

1.1 Where holds are intended to be filled with ballast water, their bulkheads are to comply with the requirements of Section 12.

1.2 Bulkheads of holds intended to be used for carrying ore are to comply with the requirements of Section 23, as far as their strength is concerned.

h = distance from the load centre of the structure to a point 1 m above the bulkhead deck at the ship side, for the collision bulkhead to a point 1 m above the upper edge of the collision bulkhead at the ship side.

For cargo ships with proven damage stability see Section 36, E.2.

For the definition of "load centre" see Section.4. A.2.1.

c_p, c_s= coefficients according to Table 11.2

f =

R_eH = minimum nominal upper yield point [N/mm²] according to Section 2, B.2.

Table 11.2 - Coefficients c_p and c_s

For the definition of "constraint" and "simply supported", see Section.3. D.1.

2. Bulkhead plating

2.1 The thickness of the bulkhead plating is not to be less than :

t = [mm]

t_min = [mm]

For ships with large deck openings according to Section.5, F.1.2, the plate thickness of transverse bulkheads is not to be less than:

t = c @ + t_K [mm]

where

)R = distance from the mid of hold before to the mid of hold aft of the considered transverse bulkhead or supporting bulkhead [m]

a, b = spacing of stiffeners [m]

t_K = corrosion addition [mm] according to Section 3, K.

R_eH = nominal upper yield stress of material [N/mm²] according to Section 2, B.2.

F₁ = correction factor according to Section 3, F.1.

c = 13 in general

= 15 below z = 0,2 H and above 0,8 H and generally in the fore ship before x/L = 0,8

2.2 In small ships, the thickness of the bulkhead plating need not exceed the thickness of the shell plating for a frame spacing corresponding to the stiffener spacing.

2.3 The stern tube bulkhead is to be provided with a strengthened plate in way of the stern tube.

2.4 In areas where concentrated loads due to ship manoeuvres at terminals, may be expected, the buckling, strength of bulkhead plate fields directly attached to the side shell, is to be examined according to Section 9, B.4.4 and 4.5.

2.5 When determining the bulkhead scantlings of tanks, connected by cross-flooding arrangements, the increase in pressure head at the immerged side that may occur at maximum heeling in the damaged condition shall be taken into account.

3. Stiffeners

3.1 The section modulus of bulkhead stiffeners is not to be less than:

W = [cm³]

3.2 In horizontal part of bulkheads, the stiffeners are also to comply with the rules for deck beams according to Section 10.

3.3 The scantlings of the brackets are to be determined in dependence of the section modulus of the stiffeners according to Section 3, D.2. If the length of the stiffener is 3,5 m and over, the brackets are to extend to the next beam or the next floor.

3.4 Unbracketed bulkhead stiffeners are to be connected to the decks by welding. The length of weld is to be at least 0,6 x depth of the section.

3.5 If the length of stiffeners between bulkhead deck and the deck below is 3 m and less, no end attachment according to 3.4 is required. In this case the stiffeners are to be extended to about 25 mm from the deck and sniped at the ends. (See also Section 3, C.3.)

3.6 Bulkhead stiffeners cut in way of watertight doors are to be supported by carlings or stiffeners.

4. Corrugated bulkheads

4.1 The plate thickness of corrugated bulkheads is not to be less than required according to 2.1. For the spacing a, the greater one of the values b or s [m] according to 4.3 is to be taken.

4.2 The section modulus of a corrugated bulkhead element is to be determined according to 3.1. For the spacing a, the width of an element e, [m] according to 4.3 is to be taken. For the end attachment see Section 3, D.4.

4.3 The actual section modulus of a corrugated bulkhead element is to be assessed according to the following formulae:

W = t @ d [cm³]

where, carling or similar elements can not be fitted in line with the web strips

W = t @ d (d + t) [cm³]

e = width of element [cm]

b = breadth of face plate [cm]

s = breadth of web plate [cm]

d = distance between face plates [cm]

t = plate thickness [cm]

" 45E

Fig. 11.2 Element of corrugated bulkhead

4.4 For watertight bulkheads of corrugated type on ship according to Section 5, G. See Section 23, E.

5. Primary Supporting Members 5.1 General

Primary supporting members are to be dimensioned using direct calculation as to ensure the stress criteria according to 5.3.1 for normal operation and the criteria according to 5.3.2 if any cargo hold is flooded.

Regarding effective breadth and buckling proof in each case Section 3, E. and F. has to be observed.

In areas with cut-outs 2nd-order bending moments shall be taken into account.

5.2 Load assumptions 5.2.1 Loads during operation

Loads during operation are the external water pressure, see Section 4, and the loads due to cargo and filled tanks, see Section 17, B.1.7, Section 21, G. and if relevant depending on the deck opening Section 5, F.

5.2.2 Loads in damaged condition

The loads in case of hold flooding result from 1.3 considering Section 36, D.2.

5.3 Strength criteria 5.3.1 Load case "operation"

With loads according to 5.2.1 the following permissible stresses are to be used :

F_v =

#

^[N/mm2]

FN = normal stress, FN

#

^[N/mm2]

J = shear stress, J

#

^[N/mm2]

k = material factor according Section 2, B.2.

If necessary Section 5, F.2. shall be observed in addition.

5.3.2 Load case "hold flooding"

The thickness of webs shall not be smaller than:

t_w = [mm]

J_perm= 727 [N/mm²]

Q = shear force [kN]

h_w = height of web [mm]

a, b = lengths of stiffeners of the unstiffened web field, where h_w

$

b

#

a

5.3.3 Dimensioning of Primary Supporting Members

For dimensioning of primary supporting members plastic hinges can be taken into account.

This can be done either by a non-linear calculation of the total bulkhead or by a linear girder grillage calculation of the idealized bulkhead.

When a linear girder grillage calculation is done, only those moments and shear forces are taken as boundary conditions at the supports, which can be absorbed by the relevant sections at these locations in full plastic condition.

The plastic moments [kNm] are calculated by:

M_p =

c = 1,1 for the collision bulkhead

= 1,0 for cargo hold bulkheads The plastic shear forces [kN] are calculated by :

Q_p =

For the field moments and shear forces resulting thereof the sections are defined in such a way that the condition F_v

#

^R_eH

is fulfilled.

The plastic section moduli are to be calculated as follows:

W_p = A_i @ e_pi [cm³]

e_pi = distance [mm] of the centre of the partial area A_i from the neutral axis of the yielded section. The neutral axis shall not be taken in a position lower than the lowest point of the web.

A_i = effective partial area [mm²] considering Section.3, F.2.2.

In this connection the area A_s of webs transferring shear shall not be taken into account.

That part of the web height related to shear transfer shall not be less than:

)h_w = h_w @

t_wa = as built thickness of the web

$

^t_w

Where girders are built up by partial areas A_i with different yield stress R_eHi the plastic moments are calculated by:

M_p = [kNm]

The plastic shear forces are:

Q_p = [kN]

6. Watertight longitudinal structures

The plating and stiffeners of watertight longitudinal structures shall be dimensioned according to Table 11.2, column "Other bulkheads".

C. Shaft Tunnels

1. General

1.1 Shaft and stuffing box are to be accessible. Where one or more compartments are situated between stern tube bulkhead and engine room, a watertight shaft tunnel is to be arranged. The size of the shaft tunnel is to be adequate for service and maintenance purposes.

1.2 The access opening between engine room and shaft tunnel is to be closed by a watertight sliding door complying with the requirements according to A.3.3. For extremely short shaft tunnels watertight doors between tunnel and engine room may be dispensed with subject to special approval.

In this connection see also SOLAS 74, Chapter II-1, Regulation 11/8 as amended.

1.3 Tunnel ventilators and the emergency exit are to be constructed watertight up to the freeboard deck.

2. Scantlings

2.1 The plating of the shaft tunnel is to be dimensioned as for a bulkhead according to B.2.1.

2.2 The plating of the round part of tunnel tops may be 10 % less in thickness.

2.3 In the range of hatches, the plating of the tunnel top is to be strengthened by not less than 2 mm unless protected by a ceiling.

On container ships this strengthening can be dispensed with.

2.4 The section modulus of shaft tunnel stiffeners is to be determined according to B.3.1.

2.5 Horizontal parts of the tunnel are to be treated as horizontal parts of bulkheads and as cargo decks respectively.

2.6 Shaft tunnels in tanks are to comply with the requirements of Section 12.

Section 12

In document BKI Vol II 2014 (Rule for Hull) (Page 166-174)