52 Weight of equipment and outfit EO

Because ships have increased comfort, weight of E&O has increased. Despite smaller crews, the weight of outfit has increased because:

1. Greater surface area and space required per man.

2. The incombustible cabin and corridor walls in use today are heavier than the earlier wooden walls.

3. Sanitary installations are more extensive.

4. Air-conditioning systems are heavier than the simple ventilation devices formerly used.

5. Heat and vibration insulation is now installed.

The weight of some equipment items has increased over time:

1. The weight of hatches:

(a) Owing to the application of steel in the lower decks.

(b) Owing to greater hatchway areas.

(c) Owing to the requirement for container stowage on the hatches.

2. More comprehensive cargo gear.

3. Fire prevention measures (CO2 units and fire-proof insulation).

In contrast, the hold ceiling is now lighter. Nowadays the side-ceiling of holds is normally omitted and instead of the bottom ceiling it is usually the actual inner bottom which is strengthened. This strengthening is included in the steel weight.

Two methods for subdividing the E&O components are commonly applied:

1. According to the workshops and the company departments which carry out the work.

2. According to the function of the components and component groups.

These or similar component subdivision methods—extended to cover machinery—provide a detailed and comprehensive basis for the whole operation (calculation, construction, preparation, procurement of material) at the shipyard.

Details of a ship's lightweight and its subdivision are rarely published. Neither is there a method to determine the weight of E&O. If no reliable data on the basis ship exists, published statistical values have to be used. These values may relate to a variety of component and ship sizes. What proportion of the ship's lightweight is made up by E&O depends to a great extent on the ship type and size.

Better estimates of E&O weights may be obtained if E&O is divided into general E&O and cargo-specific E&O. The shipyard can use larger databases to derive empirical estimates for the general E&O.

An exacter knowledge of the E&O weights can only be gained by breaking down the weight groups and determining each weight individually. This involves gathering information from the subcontractors. As this procedure is rather tedious, the degree of uncertainty for these weight groups remains generally larger than for steel weight.

The following are the main methods used to determine E&O weights:

1. The construction details are determined and then the individual weights summed. This also enables the centre of weight of this weight group to be ascertained. Furthermore, the method provides a sound basis for the calculation. This very precise method requires a lot of work. It is therefore unsuitable for project work. A comprehensive collection of unit weights for the construction details is also necessary.

2. The sum total of all E&O weights is determined by multiplying an empirical coefficient with a known or easily obtainable reference value. This method of attaining a combined determination of all E&O weights will produce sufficiently precise results only if data for well-evaluated 'similar ships' exist. Nevertheless, this method is by far the most simple. If no suitable basis ships and their data are available, the coefficients given in the literature can be used.

The coefficients depend on the ship type, standard of equipment and ship size. Where possible, the coefficients should be related to ship's data which produce a more or less constant value for the ship's size. The coefficient then depends only on ship type and standard of equipment.

On all types of cargo ships, the equipment weight increases approximately with the square of the linear dimensions. Reference values here are primarily area values, e.g. L • B or the 2/3 power of volumes. On passenger ships, however, the equipment weight increases approximately with the 'converted volume'.

Particularly suitable reference values are:

1. The 'converted volume'—including superstructure and deckhouses corresponding to the gross volume of tonnage measurement of 1982.

2. The steel weight.

Literature on the subject gives the following reference values:

1. The 'converted volume' L • B • D (Henschke, 1965).

2. The area (L • B • DA)2/3. Here, DA is 'depth-corrected to include the superstructure', i.e. the normal depth D increased by an amount equal to the superstructure volume divided by the deck area. The values scatter less in this case than for (1) (Henschke, 1952).

3. The area L • B. Here, too, the values are less scattered than for the reference value L • B • D. Weberling (1963) for cargo ships, Weberling (1965) for tankers and reefers, Watson and Gilfillan (1977).

4. The steel weight WSt.

5. The hold volume. Krause and Danckwardt (1965) consider not only summary weights, but also individual contributions to this weight group.

6. The hold volume associated with the deadweight.

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