650
MODERN GASWORKS PRACTICE
there is some slight constructional defect, such as the grip being slightly larger than the cup, or if the two are not set to an exact circle. If the grip is slightly large the cup will not engage centrally, with the result that the grip is slightly
Fig. 400.—Square Cup and Grip. Early Design.
tilted and the guide rollers are, in turn, thrust hard over against the columns. The efEect will be noticed by a consideration of Fig. 401. The tendency can, of course, be minimized by additional guide rollers on the grip running on guides attached to the inner lift. Wlien properly constructed, the grip with the weight it carries should act as a support to the inner lift, and counter-act any tendency towards t.ilting.
When designing the cup and grip, sufficient widtli should be allowed so that riveting may be carried out with ease. The minimum width should be 8 inches. The cup sides and cup rows on the bell must be stouter than the normal side sheeting, and a beading, to increase rigidity, should be run all round at the base of the cup side. The stouter cup sheets will prove effective in meeting any corrosion duetothe changing level of the water in the lute. In addition, they avoid the undesirable practice of riveting very thin. sheets to the thick section of the cup or curb. The thickening up of these
plates enables the reduction to be effected in two steps. For the cup rows and cup sides | inch sheeting is common, while the beading, which may be either moulded or flat, varies from f inch to | inch thick ; but everything, of
course, depends upon the size of the holder.
The crown sheeting of gasholders varies from 14 gauge to 10 gauge in thickness (i.e. få inch to inch), depending entirely upon the size of the holder ; curb rows being, of course, thicker (| inch to | inch in medium-sized holders, and so much as | inch in large holders). As regards side sheeting, this varies from 12 gauge to 10 gauge in thickness ; curb, or cup and grip rows again being heavier. The side sheets of the top lift are occasionally thicker (sav 8 gauge) than those of succeeding lifts ; and it should be remembered that where joints between rolied sections and plates occur it is always advisable to use heavier plates, so as to avoid attaching a very thin section to a thick one, a practice generally followed by imperfect and leaky joints. The sheets employed should be as large as practicable,
1 L'
s1
Fig. 401.