Modern Gasworks Practice

THE STORAGE OF GAS © CO unnecessary, was firstinstal] ed in this country in 1888. At the time of its introduction there was much. discussion as to the stability of the design, and many engineers pronounced the system as dangerous. As holders of the kind have now been in operation for upwards of twenty-five years, there can be little doubt that with. proper precaution in design and supervision during working they are no more likely to fail than the guided types, whilst with modem improvements there is practically no limit, within reason, to the dimensions to which they may be constructed. Briefly, the principle of their operation is dependent upon the introduction of spiral guide rails affixed to the holder side, these acting in lien of the vertical standards and bracing of the more common type of holder. The spiral rails engage with rollers on the edge of the tank in such, a manner that the bell screws itseif up and down. The direction of the spiral may be either left-handed or right-handed, or successive Fig. 410.—Dual Guide Rollers ror. Spiral Holder. lifts may operate in. reverse directions as shown in Fig. 408. The rails on the(outer lift must be affixed to the exterior of the beil, but those on succeeding lifts may be either interior or exterior, although the latter are invariably employed. The holder seen in Fig. 408 is of the four-lift spiral type, operating in an annular brick tank. The Crown is iintriissed, being supported, when the bell is grounded, by a timber framing. It will be noticed that to the two lower lifts are attached twin spiral rails, which are desirable in all spiral holders of 250 feet diameter and upwards. (As the effect of frost might be attended by serious results, it is frequently the custom to instal an anti-freezing apparatus in connection with the water-lutes of modern holders.) It will be seen that it is the guide rollers which have to withstand the ordinary forces acting on the beil, and, through them, the forces are transnaitted to the upper tank curb. The curb has, accordingly, to be of particularly stout construc-tion, the more so if provision is made in the original strucfrure for the insertion of