992
THE HONGKONG GOVERNMENT GAZETTE, DECEMBER 3, 1909.
For iron the constant in the formula to be reduced 10 per cent.
For vertical type, such as the fireboxes of vertical boilers, the constant is to be reduced ten per cent. for steel and twenty per cent. for iron.
(15.) For furnaces of the Adamson type with the distance between the flanges not exceeding (120T-12) the following formula may be used :—
10,500 × T
5 3 × D
where T-thickness of plate in inches.
L + 12 60×T
-W
L-length between centres of flanges in inches. D-outside diameter of furnace in inches.
W-working pressure..
and provided the rings are well and efficiently made.
(16.) The working pressure of steel furnaces of the ribbed, corrugated or suspension type may be ascertained by the following formula :-
where T-Thickness in inches.
14,000 × T
D
W
D-Smallest outside diameter of furnaces in inches.
W-working pressure.
(17.) The foregoing formula are to be used for steel furnaces the material of which is of boiler flanging quality with a tensile strength of 25 to 30 tons per square inch.
(18.) A greater compressive stress should not be allowed on steel tube plates than 14,000 lbs., which is that used in the following formula:-
(D-d) Tx 28,000
WXD
where D-least horizontal distance between centres of tubes in inches.
d-inside diameter of ordinary tube in inches. T-thickness of tube plate in inches.
W-width of firebox in inches.
For iron tube plates, for 28,000 write 18,000.
The strength of stays supporting flat surfaces is to be calculated from the smallest part and the stress is not to exceed the following limits :---
(19.) Iron stays under 11⁄2 inches diameter and welded stays, 6,500 lbs. per square inch, for solid stays above 14 inches 8,000 lbs. per square inch.
Steel stays under 11⁄2 inches diameter 9,000 lbs., per square inch, above 14 inches diameter 10,000 lbs. per square inch. No steel stays are to be welded.
Steel stay tubes when fitted with nuts 8,000 Ibs. per square inch, without nuts 7,500 Ibs. per square inch.
Iron stay tubes 7,000 and 6,500 respectively.
The Inspector is to remember that the boiler mountings including steam pipes, and apparatus connected therewith, other than the prime mover, form part of the boiler and they must ascertain the efficiency of such parts, by calculation and inspection, special attention being given to the safety valves.
(20.) The steam pipes of all boilers installed after the passing of this Ordinance shall be constructed of copper or wrought-iron.
In existing boilers cast-iron pipes need not be objected to provided, on examination, they are found to be sound and to comply with the requirements as regards drainage, &c., similar to copper or wrought iron pipes.