THE STORAGE OF GAS
643
In the example in question the maximuni tension was found to be 8'5 tons, therefore—
Diameter of tie bar = \ / v 4-71
= Vl’8 = 1-34 inches, or, say, a If inch or inch bar.
Round bars are to be preferred to other sections, such as flåts, tees or channels, in that they are more simply connected to the standards and are more adaptable for tension gear. Care should be taken, however, to ensure that the rods are tliickened at the screwed end, so that there is no loss in strength when the screw is cut. When connecting eyes are employed they must be of such design as to be of equal strength to the bar. The attachment of the eye to the standard should be such that the connecting pin is in double shear.
It will, of course, be understood that of the two diagonal ties in each panel only one is under stress at a time.
THE HOLDER BELL
In the design of the holder bell, particular consideration must be given to the
top curb (where side sheets and top sheets meet), the ring curb at the base of the top upper and lower edges of succeeding lifts.
lift, and the curbs at the
The top curb, owing to the gas pressure on the dorne, is by far the most highly stressed. The forces acting on it are shown in Fig. 393. They produce, as is seen, a compound stressing which tends either—
(«) To tear the top bodily away at the junction of side and dorne plates.
(&) To buckle the curb, side plates or dorne plates.
The function of the top curb is, therefore, to resist these tendencies, whilst an additiona] safeguard isprovided against the blowing-in of the side sheets by interposing vertical stift’eners at intervals around the cylinder. The resultant pressure of the gas on the interiør of the dorne, and the weight of the plates composing the dorne, will be such as to produce a pull in the plates, the direction of which pull will be at a tangent to the point under consideration. So far as the plates
Weight of Side Sheeting
Ftg. 393.--Forces on Top Curb. Note. —Resultant is always Horizontal, but HAS BEEN SHOWN SLIGHTLY OUT OF HORIZONTAL to bxplain Diagram.
forming the sides are concerned, the effect of the internal gas pressure is to produce a slight ring tension, but the plates are of necessity more than strong enough to copc with. this. The ring stress is transmitted to the curbs by the vertical