18
Fig.5. Recommended locations of PEA pair
2.3.3. Length requirements for straight pipe runs
2.3.3.1. For proper operation of the flow meter, before the first and the last PEA
with respect to the flow direction, there should be straight pipe runs of
corresponding length with the DN equal to the DN
of the CP. Table D.1
given in Appendix D shows minimum values of relative length of
pipeline straight runs that should be used for typical installations.
The length of the straight pipe run L (mm) is calculated as follows:
DN
N
=
L
×
,
where N is the relative length defined in the number of DNs and specified
in Table D.1;
DN
– CP nominal diameter, mm.
CAUTION!
While measuring the reverse flow, all the PEAs are in
upstream position, and the length of the straight pipe runs shall be
defined in view of this condition.
2.3.3.2. Any diaphragm or venturi type structure, as well as any valve, refer to
the type of hydraulic resistance specified in Appendix D as “control
valve”.
2.3.3.3. In case of mounting the straightening vane into the pipeline before the
measuring Pipe Section (Appendix E), reduction of straight pipe run
length is possible at the inlet of the CP up to two times. In this case, the
required length of the straight pipe run is defined on the base of site
survey, and the individual measurement technique shall be designed for
this structure.
2.3.4. Mounting the flow meter flanged type
on the pipeline
2.3.4.1. Before working on the pipeline at the CP mounting location, fix the pipe
sections that may tip out of their axes after cutting the pipeline.
CAUTION! Before mounting the flow meter, it is necessary to
cut off liquid flow in the pipeline section where the flow meter will
be installed, make sure that pressure is released and drain the liq-
uid.
2.3.4.2. Cut a pipe run of the required length at the selected liquid-free pipeline
section. Join the flow meter's flanges with the companion flanges pro-
vided in the delivery package and bolt them together. Make several tack
welds between the cut ends of the pipeline and companion flanges.
Then, remove the flow meter and finally weld the flanges to the pipeline.
