This machine is constructed to meet the requirements of steamship
builders and is recognized and adopted by marine engineers of this and
of other countries as the standard design for this service and _for oil
tank steamer work_.
It will be observed, see Fig. 449, that its proportions are such
as to secure the advantages of large pumping capacity with unusual
compactness and moderate weight.
This pump is of the packed piston type, and has the valves so
arranged that the water pistons are always submerged, thus making it
particularly well adapted for long and difficult suction lifts such as
are met with in steamers carrying petroleum in bulk, and in steamers
having extensive systems of water ballast tanks.
[Illustration: FIG. 449.]
_The demands for water ballast service_ are generally met by the
following two sizes, as shown in the table below.