M10
Instruction Manual
24
4.5 HOW TO AVOID AIR POCKETS IN THE PIPELINES
This paragraph is intended to help the designers and users of electromagnetic flowmeters to create the best
installation layout that guarantees optimum performance of the meter, taking into particular consideration
the problem of the presence of air pockets in the pipe.
Fig. 30 Pumping stations with flowmeters and vent valves
What are the problems caused by the air pockets entrapped in any flowmeter?
The presence of air pockets can cause serious reading errors or strong instability. In this case, the
flowmeter could go into Error mode.
How are air pockets removed, or moved away from the flowmeter?
The air pocket inside a pipe always moves toward the top of the pipe, and it is assumed that the air will
always move if the flow passes along a horizontal pipe, but this is not the case. Instead, a specific water
speed is required to move the air; the greater the diameter of the pipe, the higher the airspeed is required
to move it away from the flowmeter.
Typically, most installations of flowmeters are simply sized on the diameter of the tube or on the flow rate
in the pipe, which means that the speed is often less than 0.5 m/s, which can be very problematic if the
air pockets occur.
As an example in a pipe with zero gradients, these are the specific water speeds necessary to move
away the air pockets detected in the tube:
DN50 → 0.4 m/s
DN150 → 0.7 m/s
DN300 → 1 m/s
DN600 → 1.5 m/s
To Next Page
Loading...