British Wreck Commissioner's Inquiry
Day 21
Report of Bulkheads Committee
To the Right Honourable sir Michael E. Hicks -Beach, Bart., M.P., President of the Board of Trade.
Sir, - In your minute of the 7th March, 1890, you requested us to consider and report upon the following matters, viz.: -
1. As to the manner in which ships shall be subdivided so that they may float in moderate weather with any two compartments in free connection with the sea; and what Rule there should be as to the proportion of freeboard of the watertight deck next above, to which such bulkheads are attached, as shall be sufficient to enable the ship so to float.
2. As to the description of ship to which such should apply in regard to size, or what difference, if any, as between paddle or screw steamers, or sailing ships, or as to ocean voyagers, or cross -channel steamers.
3. Upon the construction and fitting of watertight bulkheads, with a view to their being able to sustain the necessary strain, particularly when the ship is rising and falling in a seaway without shoring or other adventitious aid, should it so happen that two adjoining compartments are in free communication with the sea, regard being given to the support of any 'tween decks abutting thereto.
4. In what manner the surveyors of the Board of Trade can best determine the sufficiency of such bulkheads?
5. Under what restrictions may passageways be permitted through such bulkheads, as closeable by portable plates, or so-called watertight doors, self-acting or otherwise; and what precautions are necessary as to openings in longitudinal bulkheads to enable the water to pass freely or under control from one side to the other, in case of the ship showing signs of instability, as might readily be the case should she be struck on a transverse bulkhead, and two compartments, both on one side, be in free communication with the sea.
6. Whether a transverse compartment divided into two by a longitudinal bulkhead, should be treated as one or as two compartments.
7. What particulars, drawings and calculations should be furnished by the owners of ships to the Board of Trade when they desire to take advantage of the following paragraph in the Rules made under the merchant Shipping (Life-Saving Appliances.) Act, 1888 (51 and 52 Vict. Cap. 24.): -
(13.) Watertight Compartments.
When ships are divided into efficient watertight compartments so that with any two of them in free communication with the sea, the ship will remain afloat in moderate weather, they shall only be required to carry additional boats or life rafts of one-half of the capacity required by paragraph (f.) Class 1, Division A, of these Rules.
8. Whether independently of the precise requirements of the foregoing paragraph the Committee have any recommendations to make with reference to bulkheads which would, in their opinion, contribute to the safety of life at sea.
In approaching these questions we found that but little definite information existed concerning them; and although we have had much valuable and interesting evidence from several well-known experts, we thought it necessary to have recourse to actual experiments, carried out under our own supervision, in order to obtain the information contained in Appendices A and b to our report. These experiments have been proceeding continuously for about a year, and our endeavour has been to arrange the results in a practical form.
As regards the sizes and classes of vessels assigned to the several grades of subdivision, in our reply to para. 2 we may observe that our conclusions in this respect are the result of much deliberation, and are based on what we deem a fair adjustment as between loss from broken stowage on the one hand, and the greater safety on the other, resulting from improved subdivision. In judging of this matter, we have supplemented our own practical knowledge with reports and evidence from representative shipowners and shipbuilders, as to the minimum length of hold admissible in various trades.
We now proceed to answer the questions categorically: -
1. Vessels may be considered able to float in moderate weather with any two adjoining compartments in free communication with the sea, if fitted with efficient transverse watertight bulkheads, so spaced that when two such compartments are laid open to the sea, the uppermost watertight deck to which all the bulkheads extend, and which we will call the bulkhead deck, is not brought nearer to the water surface than would be indicated by a line drawn round the side at a distance amidships of 3/100ths of the depth at side at that place below the bulkhead deck, and gradually approaching it towards the ends where it may be 3/200ths of the same depth below it. This line we may call the margin-of-safety line.
With longitudinal bulkheads in combination with transverse bulkheads the vessels should not, under the above conditions, list so as to bring the deck on either side below the water level. Vessels in which the bulkheads do not extend to a continuous deck require a modification of the margin-of-safety line, as to which see appendix A.
The arrangement of plane transverse bulkheads necessary to satisfy the above condition, May be determined with the aid of the curves and tables in Appendix A, or by separate calculations in accordance with the assumptions made in that Appendix.
These curves and tables show the maximum spacing of such bulkheads permissible in vessels of various descriptions and under various conditions at any point in the length measured along the loadline from the foreside of the stem to the afterside of the sternpost, in connection with any given freeboard measured from the bulkhead deck. The freeboard to be used is not necessarily that required under the merchant Shipping Act, 1890, but may be any freeboard which, on the application of the ship-owner, May be registered by the Board of Trade. Such freeboard we will call the bulkhead freeboard, and the corresponding loadline the bulkhead loadline. With the tables so arranged it is, we submit, unnecessary for us to frame Rules with regard to the proportion of freeboard in relation to the size of the vessel.
The tables have been constructed for vessels carrying coal cargoes, but it will be obvious that a vessel whose bulkheads are spaced on the assumption that she carries a cargo of coal, will not be able with equal safety to carry an equal weight of a cargo of greater density - say, pig iron.
There are thus two methods of proceeding, either of which would enable the condition specified in the boards question to be fulfilled, viz.:
(1.) bulkheads must be spaced for cargoes of some specified density, and the vessel will then be able to take full cargoes of such or any less density; or
(2.) bulkheads must be spaced for some average cargo, and when a cargo of greater density is carried, the vessel must have a greater freeboard, Ie., Must carry a less weight.
With a view to measuring the effect which difference in the density of the cargo has upon the spacing of the bulkheads, a series of experiments were carried out for a sailing vessel with cargoes of salt and iron, as well as of coal. No table has been prepared giving the spacing of the bulkheads suitable for the two former cargoes, but the curves deduced from the experiments are shown in conjunction with that for the coal cargo, and similar curves can be approximately deduced for cargoes of intermediate densities (Diagram 1.)
It is obvious from an examination of the curve for the iron cargo, that to require such a spacing of bulkheads in sea-going cargo vessels as would fulfill the conditions of the board's question under all circumstances of loading, would cause the holds to be too short for general trade. We recommend, therefore, that the arrangement of bulkheads in the vessels specified in the several grades, be fixed on the assumption that the cargo spaces in each, contain cargo such as coal, occupying 47 cubic feet to the ton, sufficient with the full complement of bunker coals on board to immerse the vessel to the bulkhead loadline, and so distributed as a whole that she may float on an even keel. Such cargo we have assumed to admit water to 40 cubic feet in every 100 cubic feet of the space it occupies.
In order that the advantage resulting from efficient subdivision of vessels by means of bulkheads may not be nullified by insufficient regard being given to dangers connected with openings in vessels' sides, we recommend the adoption of the following precautions in regard thereto: -
(a.) That all coaling and cargo ports in a vessel's side below the bulkhead deck be efficiently closed and made secure before the vessel puts to sea, and be not opened except when she is coaling or taking in or discharging cargo.
(b.) That there be no sidelights or ports the sills of which are nearer the bulkhead loadline than 12 inches.
(c.) That all sidelights fitted in coal bunkers and bunker holds be fixed. That the glass in such sidelights have a thickness of not less than one-half of their clear diameter, be enclosed in a sufficiently strong frame, and be recessed not less than 1 inch within the outer surface of the shell plating. That sidelights the sills of which are at a distance from the bulkhead loadline less than one-fourth of the bulkhead freeboard be not opened at sea except when, through the consumption of coal or otherwise, the vessel has lightened so much as to make the freeboard to the sills of the sidelights greater than one-fourth of the bulkhead freeboard, and in that case the provisions of sub-section (d.) may be held to apply. That ventilators in the vessel's side capable of closing automatically in case of submersion as well as by hand may be fitted, provided the sill of the opening on the inside be not within 2 feet of the loadline, but that any such automatic arrangement should be examined at least once a week, and if not in order it should be closed.
(d.) That all other sidelights and ports below the bulkhead deck be of sufficient strength. They may be fixed or capable of being opened, but in the latter case the sidelights as well as the ports, if any, should not be adapted to be opened by passengers, they should be closed before the vessel puts to sea, but may be opened during the voyage by the master's special orders if the sill be not less than one-fourth of the bulkhead freeboard above the loadline. The time of and reason for opening, and also the time of closing such sidelights and ports, should be noted in the official logbook. All sidelights, except those immediately under the bulkhead deck, and bullseye sidelights should be fitted with hinged metal covers.
(e.) That sidelights immediately under the bulkhead deck may be capable of being opened by passengers provided they be arranged to close automatically in case of submersion as well as by hand.
(f.) That notwithstanding the foregoing provisions to the contrary sidelights and ports immediately under the bulkhead deck, May be under the control of the crew or passengers, and need not be arranged to close automatically, provided the freeboard for the purpose of bulkhead spacing is measured not from the bulkhead deck, but from a line 3/100ths of the depth amidships below the line of the sills of any such sidelights and ports
(g.) That all other openings in a vessel's side below the bulkhead deck, such as scupper and sanitary pipes, etc, be fitted with efficient non-return valves, and that these be carefully examined before sailing on each voyage.
2 Although all vessels, whatever their length, can be subdivided so as to be able to float in moderate weather with any two adjoining compartments in free communication with the sea, yet if small vessels were subdivided to that extent their holds would be so reduced in length as to impair their value for commercial purposes. Having regard therefore to the exigencies of trade, we recommend that the following six grades be adopted according to which certain vessels should be fitted with bulkheads in the manner indicated in Appendix A, viz.: -
FIRST GRADE.
- Vessels subdivided throughout their lengths so that they may float in moderate weather with any two adjoining compartments in free communication with the sea.
This grade should apply to: -
(a.) Sea-going steam vessels whether paddle or screw which have passenger certificates under the merchant Shipping Act, and which are not less than 425 feet in length.
(b.) Cross -channel steamers, irrespective of their length, whose principal employment is the carriage of passengers, or passengers and mails - as, for instance, those running between Holyhead and Dublin or Kingstown, Dover and Calais, Folkestone and boulogne, Newhaven and Dieppe, Liverpool and Isle of Man.
SECOND GRADE.
- Vessels subdivided throughout their length so that they may float in moderate weather with any two adjoining forebody compartments, or with any one afterbody compartment, in free communication with the sea. A compartment, the fore end of which does not extend more than a quarter of its length forward of the centre of the vessels length may be treated as an afterbody compartment.
This grade should apply to sea-going steam vessels which have passenger certificates under the merchant Shipping Acts, and are less than 425 feet but not less than 350 feet in length.
THIRD GRADE.
- Vessels subdivided throughout their length, so that they may float in moderate weather with any adjoining two of the three foremost compartments or with any one of the other compartments, in free communication with the sea.
This grade should apply to sea-going steam vessels which have passenger certificates under the merchant Shipping Acts, and are less than 350 feet, but not less than 300 feet in length.
FOURTH GRADE.
- Vessels subdivided throughout their length, so that they may float in moderate weather with the two foremost compartments, or with any one of the other compartments in free communication with the sea.
This grade should apply to: -
(a.) Sea-going steam vessels which have passenger certificates under the merchant Shipping Acts, and are less than 300 feet in length.
(b.) Sea-going sailing vessels, irrespective of their length, which carry more than fifty passengers in all, or a greater number of passengers, cabin and other, than in the proportion of one statute adult passenger to every 33 tons of the registered tonnage of such ships.
FIFTH GRADE.
- Vessels subdivided throughout their length, so that they may float in moderate weather with any one compartment in free communication with the sea.
This grade should apply to: -
(a.) Sea-going steam vessels not having passenger certificates under the merchant Shipping Acts and being not less than 300 feet in length.
(b.) Sea-going sailing vessels not coming under the fourth grade, and being not less than 275 feet in length.
SIXTH GRADE.
- Vessels subdivided in the forebody, so that they may float in moderate weather with any one of the forebody compartments in free communication with the sea.
This grade should apply to: -
(a.) Sea-going steam vessels not having passenger certificates under the merchant Shipping Acts and being less than 300 feet, but not less than, 260 feet in length.
(b.) Sea-going sailing vessels not coming under the fourth grade and being less than 275 feet, but not less than 225 feet in length.
Every vessel coming under any of the above categories should have her foremost bulkhead at a distance from the stem, Measured along the loadline, not less than 5/l00ths of the ship's length.
By way of illustration of the above we give in Appendix A (Diagram 2.) some examples of possible subdivision in vessels of various lengths, according to the grades to which they belong.
3. Bulkheads forming watertight compartments may be considered of sufficient strength to withstand the strain, particularly when the vessel is rising or falling in a sea-way, without shoring or other adventitious aid, if constructed in accordance with the table of scantlings given in Appendix B, regard being had to the support of any 'tween decks or other permanent structure abutting thereto. Such bulkheads should be efficiently secured to the outside plating by means of frames or angle -irons, and also to the deck to which they extend.
4. The surveyors of the Board of Trade may accept the designs and scantlings contemplated in the tables above referred to as a standard of sufficiency, but other modes of construction may be allowed provided that it be shown to the satisfaction of the Board of Trade that the strength will not be less than it would have been if the bulkheads had been constructed as in Appendix B. In all cases regard is to be had to any collateral support given by decks, partial decks, longitudinal bulkheads, bunkers, trunkways, etc.
5.We recommend that any passage ways through such bulkheads should be subject to the following conditions, viz: -
(a.) That all openings in watertight bulkheads be fitted with efficient watertight doors. That portable plates be inadmissible except in the engine room space, and that an entry be made in the ship's logbook wherever such a plate is removed, and also when it has been efficiently replaced, and that such entry be afterwards copied in the official logbook.
(b.) That all doors forming part of watertight bulkheads - except such as are already shut - be closed before the vessel puts to sea, and be closed subsequently at least once in every twenty-four hours while on the voyage, and the fact entered in the official logbook. In addition we recommend that watertight door drill be a preliminary to the usual fire and boat drill.
(c.) That a watertight door may be self-acting or otherwise, but should be workable from above the bulkhead deck, and have an index showing whether such door is open or closed, except in the case of double doors the mechanical arrangement of which necessitates one being closed before the other can be opened, and in the case of doors which are only used when the vessel is loading or discharging cargo, or at a port or place of call; such doors should be closed under the supervision of the Officer in charge of the vessel before she is cleared for sea, and an entry to that effect made in the ship's logbook at the time, and signed by the said Officer, a copy of such entry being afterwards made in the official logbook.
(d.) That openings in watertight bulkheads through which coal may be worked during the voyage, be fitted with approved double doors as described above, or any equally safe arrangement. In no case should a watertight door be considered as forming part of a watertight bulkhead when coal, which may be passed through it while the vessel is at sea, is liable to rest against it.
6. A compartment subdivided by one or more longitudinal bulkheads should be treated as one compartment only, unless the owners satisfy the Board of Trade that the vessel will not have her stability seriously reduced, or list, so that any part of the bulkhead deck at the side is under water, in the event of the space between a longitudinal bulkhead and the vessel's side, or of two such adjoining spaces on the same side of the vessel being open to the sea. If the Board of Trade be not satisfied in the above respect trimming valves should be fitted to each such longitudinal bulkhead, each valve being workable from above the bulkhead deck, and having an index showing whether it is open or closed.
7. Owners desiring to take advantage of any exceptions made in favour of efficiently subdivided vessels should furnish the Board of Trade with the following particulars and drawings: -
(a.) Longitudinal elevation in section showing the sheer, the bulkheads, the bulkhead deck, and any other decks proposed.
(b.) Plan and elevation of each bulkhead, showing recesses and doors, if any, with their positions marked, together with details of the appliances for opening and closing them.
(c.) Proposed bulkhead freeboard and corresponding loadline; also the lines of the sills of the sidelights between the bulkhead deck and the bulkhead loadline.
Where bulkheads are constructed as specified in Appendix B they may be regarded as of sufficient strength without further calculation.
8. We recommend that each watertight compartment intended for occupation by crew or passengers should be provided with some independent means of escape, other than by watertight doors, available under all circumstances. Having regard to the great additional safeguard which such subdivision as we recommend would provide against loss not only by collision or stranding, but also by fire, we would suggest that the Board of Trade might well offer a larger concession than that mentioned in Section 7 of the Reference to this Committee, as an inducement to owners to subdivide their vessels to the extent that we have indicated under the several grades. We therefore submit that in such case owners might be relieved of the obligation to carry any part of the additional boats, rafts, and other life-saving appliances required by the Rules issued by the Board of Trade under the merchant Shipping (Life-Saving Appliances.) Act, 1888."
