Forfatter: A.-M.Inst.C E., George Frederick Zimmer
År: 1916
Forlag: Crosby Lockwood and Son
Sted: London
Sider: 752
UDK: 621.87 Zim, 621.86 Zim
Being a Treatise on the Handling and Storing of Material such as Grain, Coal, Ore, Timber, Etc., by Automatic or Semi-Automatic Machinery, together with the Various Accessories used in the Manipulation of such Plant
DISCHARGING BY MEANS OF SKIPS AND GRABS 399
In working two-rope grabs, cranes specially designed for the purpose should preferably
be employed in order to obtain the best results. As, when grabbing, the question of
output is generally of the first importance, it is obviously best, in order to make the
installation economical, to have a crane which will operate the grab at the highest speed,
even if the first cost be somewhat greater.
The “ Priestman ” grab crane, as shown in Fig. 562, has been designed to meet these
Fig. 563. Crane and Grab mounted on a Barge.
conditions. Normally seventy to eighty lifts can be made per hour, or probably nearly
twice the number obtainable with some ordinary cranes.
These appliances are used for discharging grain, coal and other heavy material, as
well as for dredging purposes. Generally speaking, the mechanical details are identical;
the cranes only differing in the way in which they are mounted according to the purposes
they have to serve. Thus they may either be fixed on quay walls, mounted on wheels, or