THE STORAGE OF GAS
651
for the jointing is then reduced to a minimum and the labour of riveting is lessened. On. the other hånd,
smaller plates and, therefore, more liberal riveting have a tendency to stiften up the whole shell.
The most
modern forms oi the cup and grip are seen in Figs. 402, 403, and 404, the las t-named being of the bent-plate type and showing the method of usingthe riveting tool at inaccessible
Joint
cover
Landing blocks 6"*1" r£
(/o xaVu
Fig. 403.
places. The extension of the upper portion of the grip plate shown in Fig. 403 ensures greater safety against the possibility of biowing. In connection with the design shown in Fig. 400, it should be mentioned that trouble is frequently experienced with the dip plates landing on top of the bolt heads which fix the bottom roller carriages to the horizontal channel, and also on the joint covers. The difficulty is avoided by placing landing blocks round the cups about every two feet (see Fig. 403). These blocks are of iron, being usually 6 inches by 1 inch. for an 8-iiich channel.
The thinner sheets of the gasholder beil are usually riveted up cold with | inch livets at a pitch of 1 inch, or inch rivets at 1| inch pitch. Curb and such rows have stifter
Hr; g
rivets at a slightly greater pitch, but all rivets-