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Reg. 550

Bar stays and Firebox stays

 

Each bar stay or firebox stay shall be made from a solid rolled bar without weld in its length, except where it is attached to the plate it supports.

Bar stays which have been worked in the fire shall be subsequently annealed.

It is preferred that when the stay is in position in the boiler, its axis shall be normal to the plate it supports, but where this cannot be so arranged, then, if the stay is fitted with nuts, beveled washers shall be provided between the nuts and the plate.

Stays shall be secured to the plates they support by one of the following methods:-

a) Bar Stays

i) Plain bars, passing through clearing holes in the plates and welded thereto (see Figure XII/42).
ii)

Plain bars passing through clearing holes in the plates and fitted with washers on the outside, the stay and washers being welded to the plates in accordance with any one of the methods shown in Figures XII/43(a), XII/43(b), XII/44(a), XII/44(b), XII/45(a), XII/45(b).


Note:- Cleaning hole for the purpose of this regulation means a machined cylindrical hole having a diameter not exceeding that of bar stay by more than 2%.

b) Firebox Stays

i) Screwed stays, screwed through the plates and riveted over at each end to form substantial heads, or fitted with nuts, or the projecting ends fillet-welded as indicated in Figures XII/39 and XII/40.

It is recommended that where the stays are screwed, this shall be with a fine thread and the stays and holes shall be screwed with a continuous thread.

The stays shall be screwed with fine threads of not less than 11 threads per inch.

The screw threads on the stays shall be clean, free from checks or imperfections, of full depth, of a correct standard form and a good fit in the holes.

The middle portion shall preferably be turned down to the bottom of the thread.

ii)

Plain stays shall be strength welded to the plates (See Figures XII/41 and  Fig XII/41A).

NOTE:This form of attachment is also suitable for plain bar stays all dimensions are in mm attacment of firebox abd reversal chamber stays.


All screwed stays less than 14 inches long should preferably be drilled with a tell-tale hole 3/16 inch diameter to a depth of ½ inch beyond the inner face of the plate. Stays which are obscure on one side should preferably be made from hollow staybar.
 
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