[2580]. Trough flooring.
Iron and Steel Plates.—It is essential to possess some knowledge of what sizes and weights are obtainable at ordinary prices, because it is frequently desirable to utilise the largest available, in order to save the cost of making joints. Frequently joints are made by riveting, not because they are wanted at all, but simply because they cost less than single plates would do. Information of this kind is only to be obtained from the price-lists of the iron and steel manufactures, which are supplied to the trade.
The meaning of “maximum dimensions” is thus:—Taking a 11⁄2″ plate, for example, the maximum dimensions of which are given in a list as 40′ in length by 10′ in width, it is not possible to get a plate measuring 40′ by 10′, for that would make a united area of 400′, and the list limit is 150′ area. But the area can be taken out either in length or in width, within the limiting length of 40′ and width of 10′. The maximum area divided by any length in feet not exceeding the maximum, will give the maximum width for that length; and the maximum area divided by any width in feet not exceeding the maximum, will give the maximum length for that width. Thus, 150′ area divided by the maximum length, i.e. 40, gives 3′ 9″ width of plate. Or 150′ divided by the maximum width, i.e. 10, gives 15′ length of plate. And for anything over these maximum dimensions special quotations have to be made. But no plate can be rolled to contain the greatest length and the greatest width at the same time.
Again, in reference to “extras,” many points have to be borne in mind. Thus, as regards shape, any departure from the rectangular form is an extra, as tapered plates, sketches, i.e. any irregular outlines, and also circles. The extra, under this head, may be about 25s. per ton. As regards thickness, plates under 1⁄4″ thick are an extra, rated at from 10s. to 20s. per ton more. As regards width and length, quite special terms are made, amounting to 5s. perhaps on each 3″, a serious item. And as regards weight, steel plates over about 40 cwt. are charged extra, at the rate of about 5s. per 5 cwt.
To give examples: The Steel Co. of Scotland roll steel plates from 1⁄16″ to 11⁄2″ thick, and from an area in the first case of 30′ to 150′ in the latter. The thicknesses advance by thirty-seconds in thickness up to 3⁄16″, by sixteenths up to 1⁄2″ and by eighths up to 11⁄2″. The following table will give an idea of their limiting sizes, which may be taken as fairly typical of steel plates in general. It will be seen that I have included only a few of the thicknesses named above.
| Maximum. | ||||||
|---|---|---|---|---|---|---|
| Thick- ness. | Length. | Width. | Area. | |||
| in. | ft. | in. | ft. | in. | ft. | |
| 1⁄8 | 22 | 0 | 5 | 0 | 50 | |
| 1⁄4 | 33 | 0 | 6 | 3 | 90 | |
| 3⁄8 | 38 | 0 | 7 | 4 | 100 | |
| 1⁄2 | 40 | 0 | 8 | 3 | 110 | |
| 3⁄4 | 40 | 0 | 9 | 3 | 140 | |
| 1 | 40 | 0 | 10 | 0 | 150 | |
| 1 | 1⁄4 | 40 | 0 | 10 | 0 | 150 |
| 1 | 1⁄2 | 40 | 0 | 10 | 0 | 150 |
David Colville and Sons roll plates from to 1⁄4″ to 11⁄2″ in thickness with an area of 80′ in the first and 140′ in the last; other sizes intermediate. But by special arrangement plates 1⁄4″ thick can be rolled to 140′ area, and 11⁄2″ of 170′. Thirty hundredweight is the limit of weight in ship plates, and 40 in boiler plates. Plates up to 61⁄2 tons weight each can be rolled at special prices. It is impossible to roll plates exactly to weight, and it is usual to allow a deviation of from 21⁄2 per cent. to 5 per cent. over weight for boiler plates, and under or over for ordinary plates.
The Parkhead Steel Works roll 1⁄16″ plates to a maximum area of 36′, 1⁄4″ plates to 70′, 1⁄2″ plates of 110′, 3⁄4″ plates of 140′, 1″ plates of 150′, and 11⁄4″ plates of 150′ area. The limiting weights are 20 cwt. for ship plates, and 40 cwt. for boiler plates. Above these 5s. per 5 cwt., or part of the same, is charged.
The Weardale Iron and Coal Co. roll steel plates from to 1⁄4″ to 11⁄2″ thick, with a maximum area of 60′ in the first, and 120′ in the second; 30′ is the maximum length, and 8′ the maximum width. Circular plates are also rolled from 5′ 6″ diameter of 1⁄4″ thick, to 8′ 6″ diameter in 11⁄2″ thick. All ordinary thicknesses, also intermediate between these, are rolled.
The limiting weights and dimensions of the steel plates of Bolekow, Vaughan and Co. are 18 cwt. 80 sq. ft. in area, 23′ in length, and between 12″ and 60″ in width. Extras are, for every hundredweight, or part of the same above 18 cwt., 10s.; for every foot, or part of a foot, above 23′ in length, 5s.; for every square foot above 80 sq. ft., 1s.