12737-1909-Draft-Rules-under-the-Steam-Boilers-Ordinance-1909 — Page 7

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THE HONGKONG GOVERNMENT GAZETTE, DECEMBER 3, 1909.

It is expected that all rivet holes in new steel boilers are drilled in place. In the case of the rivet holes being formed by punching the Inspector must submit the case for the special consideration of the Government.

The pressure of new boilers by calculation will of necessity be affected unless reasonable proof of inspection during construction be produced to the satisfaction of the Government.

(7.) Flat Surfaces :-

The working pressure allowed on the flat surfaces of boilers made from steel plates may be found from the following formula :-

C (T+1)2 S-6

W

where T--Thickness of plate in sixteenths of an inch.

S-Surface supported in square inch.

W-Working pressure.

C-Constant according to the following circumstances.

C-130 when the plates are not exposed to the impact of heat or flame and the st are fitted with nets and washers, the latter being at least three times the diameter stay and two-thirds the thickness of the plates they cover. If the diameter of n washers be at least two-thirds the pitch of the stays and the thickness not less than plates they cover the constant may be increased to 195. If doubling strips are fitted of + same thickness as the plate they cover and not less in width than two-thirds the pitch of t stays the constant may be increased to 210. If doubling plates cover the whole of the fl surface the constant may be increased to 265.

C-115 when the stays are free from the impact of heat or flame and the stays are fitted with nuts only.

C-75 when the plates are free from the impact of heat or flame and the stays are screwed into the plates and riveted over.

C-80 when the plates are exposed to the impact of heat or flame and steam in contact with the plates and the stays fitted with nuts and washers, the latter being at least three times the diameter of the stay and two-thirds the thickness of the plates they cover.

C-70 when the plates are exposed to the impact of heat or flame and steam in contact with the plates and the stays fitted with nuts only.

C-105 when the plates are exposed to the impact of heat or flame with water in contact with the plates and the stays screwed into the plates and fitted with nuts.

C-70 when the plates are exposed to the impact of heat or flame with water in contact with the plates and the stays screwed into the plates and having the ends riveted over to form substantial heads.

C=40 when the plates are exposed to the impact of heat or flame and steam in contact with the plates with the stay screwed in the plates and having the ends riveted over to form substantial heads.

For iron boilers reduce the constants for riveted stays nine per cent. and the constants for nutted stays twenty per cent.

When a circular flat end is bolted or riveted to a cylindrical shell S in the formula equals the area of the square inscribed in the bolt or rivet circle.

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(8.) In steel flat surfaces of irregular form of staying or where the staying is con- tinuous or with stays secured by rivets as in the end plates of Lancashire or Cornish boilers

C (T+1) 2 -W.

2 R2 -6

Where Rthe radius of a circle passing through at least three points of support. In such cases C in the formula is as follows:-

:-

-For staying as described under Section (7), the constants given to meet any particular case may be taken.

furnaces.

C-115 for gusset staying.

C-210 for point of support at shell plate.

-170 for point of support at furnace edge.

C-210 in way of bottom manholes when points of support consist of shell and

For iron boilers reduce the constants twenty per cent.

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