20
pipe axis) be positioned at an angle of
= 45
-90
to the vertical plane
(Fig.5).
Fig.5. Recommended PEA positions when installing the flow meter
3.3. Requirements for the length of straight sections
3.3.1. If there are hydraulic resistances at the installation site, normal operation
of the flow meter is provided by straight sections of the pipeline before
the first and after the last one PEA in the stream. The minimum values of
the relative length of straight sections for different types of hydraulic re-
sistances are given in Table D.1 of Appendix D.
The length of the straight section L (mm) is determined by the for-
mula:
DN
N
=
L
,
where N is the relative length expressed by the number of DNs and shown
in Table D.1;
DN
– nominal diameter of CP, mm.
WARNING:
When measuring the reverse flow rate, all PEAs are the
first in the flow and the lengths of the straight sections must be deter-
mined from this position.
3.3.2. When installed in the pipeline in front of the primary flow straightener con-
verter (Appendix D), the straight input length of the CP can be reduced
by up to two times.
3.4. Installation on the pipeline
3.4.1. Before starting work on the pipeline in the place of installation of the flow
meter, fix pipe sections that may deviate from the coaxial position after
cutting the pipeline with clamps to the fixed supports.
WARNING:
Before installing the flow meter it is necessary to drain
the liquid and cover the section of the pipeline, where the installation
works will be carried out.
3.4.2. A section of the required length is cut out at the selected point of the liquid-
free pipeline, and counter flanges of the appropriate diameter are welded
to the pipe ends. Ensure the alignment and parallelism of the flanges,
between which the CP of flow meter is installed.
3.4.3. The flow meter should be installed in the pipeline, and the direction of the
arrow on the CP should coincide with the flow direction or the forward
direction for reverse flow. The joints between the flanges are sealed with
gaskets and the flanges are bolted together.
