5
DYNAMIC PRESSURE
Consider the sections of pipe depicted in the sketch below. In sketch (A) the
pressure as read by the E30 when water fl ows will be less than the pressure read
by the pressure gauge. The difference between the two readings will be directly
related to the fl ow velocity and the ratio of the two pipe diameters. The E30 will
see the pressure as lower than that seen by the pressure gauge. This is due to
the higher velocity through the small pipe and thus lower pressure than the
pressure in the larger pipe where the velocity is lower. In sketch (B) both the
pressure gauge and the E30 will read the same pressure since the velocity is
constant between the two tapping points. In sketch (C) the E30 will read the
dynamic pressure as higher than the pressure as read by the pressure gauge.
This is the reverse of the situation in sketch (A)
Note that in a static situation with no fl ow the pressure gauge and the E30 will
read the same pressure in all three pipe confi gurations.
Careful consideration should therefore be given to the location of the tapping
point. When water is fl owing the tapping points location will effect the pressure
reading and thus what the E30 actually displays.
A
B
C
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