Page 313 - Introduction to Marine Engineering

Instrumentation and control 287

SF
Scale
Manometer
Tank 1 Tank 2
Vent
Vs ci Compressed
air supply
Worn ienhprirnl ./A.
bell Selector •
cock
Three way
cock
Figure 15.10 Pneumatic gauge

Flow measurement can be quantity measurement, where the amount of
liquid which has passed in a particular time is given, or a flow velocity
which, when multiplied by the pipe area, will give a rate of flow.

Quantity measurement
A rotating pair of intermeshing vanes may be used which are physically
displaced by the volume of liquid passing through (Figure 15.1 l(a)). The

Casing

Outlet
(a! Intermeshing vanes
Drive mechanism
Housing to scale reading

Support
Flow
\
Rotor
(b) rotating element Figure 15.11 Flow quantity measurement