===+=========+===============+================+=======+========
No.| Size |Suction fitted |Discharge fitted|Stroke.|Size
|piston. | for. | for. | |pulleys,
| | | | |in.
---+---------+---------------+----------------+-------+--------
1 |2 in.| 1 in. pipe| 1 in. pipe | 3 in. |16 × 4
2 |2-1/2 „ | 1 „ „ | 1 „ „ | 3 „ |16 × 4
3 |3 „ | 1-1/4 „ „ | 1-1/4 „ „ | 3 „ |16 × 4
4 |2 „ | 1-1/4 „ „ | 1-1/4 „ „ | 6 „ |18 × 4
5 |2-1/2 „ | 1-1/4 „ „ | 1-1/4 „ „ | 6 „ |18 × 4
6 |3 „ | 1-1/2 „ „ | 1-1/2 „ „ | 6 „ |18 × 4
---+---------+---------------+----------------+-------+--------
[Illustration: FIG. 206.]
Fig. 206 exhibits two independent pumps. The description of the pump
shown in Fig. 205 will apply to the left-hand pump which is _a boiler
feed pump_. The improvement consists in the addition of another pump at
the right-hand side; this is a _suction force pump with an air chamber_
and is used to draw water from a well and discharge it into a tank from
which it is taken by the other pump and forced into the boiler, as
occasion requires.
These two pumps work simultaneously, being driven from the same shaft
with cranks set opposite each other. Like the pump previously described
this has a tight and loose pulley. The larger sizes are geared, having
a pinion on the pulley shaft and a spur wheel on the crank shaft.
These two pumps represent a high service and a low service, the
left-hand pump working under high pressure, against that in the boiler
and the right one against the head of water in the tank. Each pump
has its own separate connections—one or more—to suit the required
conditions.
The right-hand pump is double acting; the plunger-rod is guided by a
steadiment which holds it in line and preserves this alignment and the
power is transmitted through a forked connecting rod. The Table below
refers to both these pumps.