Cla-Val X144 Technical Manual - Manual (Page 5)

SECTION 1: System Components and How They Work
1.1 - Theory of Operation
The X144 e-FlowMeter is an insertion vortex flowmeter based on a phenomenon which generates of a
succession of alternating swirls called Karman vortex street (Figure 1-1).
When the fluid meets an obstacle (called a bluff body) which is placed in parallel with the flow of the fluid it
divides the flow and generates small swirls or vortices alternately on both sides downstream of the obstacle.
The generation of the swirls is directly proportional to the speed of the fluid. The detached swirls generate
zones of variable pressure that are detected by the forces acting on a small piezoelectric crystal
encapsulated in the transmitter (Figures 1-2 and 1-3).
The X144 e-FlowMeter employs an innovative feature called the Swivel Measurement Cylinder which allows
for the proper distance between the bluff body and the sensor, while still retaining the capability of being
inserted into a tapping as small as 1/2-inch NPT.
2
Bluff Body
Sensor
Karman
Vortex
Street
Flow
Direction
Figure 1-1: Karman Vortex Street
Meter Bluff Body
Flow
Direction
Integral Sensor
Flow
Direction
Vortices
Measurement Cylinder
Figure 1-3
Figure 1-2
flow direction