7
3.2. Length requirements for straight pipe runs
3.2.1. For proper
flowmeter’s operation, before the first and the last PEA with
respect to the flow direction, there should be straight pipe runs of corre-
sponding length with the DN equal to the DN of the CP. The
“type” in-
stallation minimum values of relative length of the straight pipe runs for
various PEA installation configurations and types of hydraulic resistance
are shown in Table A.1 of Appendix A
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 speci-
fied in Table. A.1.
DN is the CP nominal diameter at the mounting location of
PEAs, mm.
CAUTION!
While measuring the reverse flow, all the PEAs are in
upstream position, and the length of the straight pipe runs shall be de-
fined in view of this condition.
3.2.2. In case of mounting the straightening vane into the pipeline before the
measuring section (Appendix D), reduction of straight pipe run length is
possible at the inlet of the CP up to two times.
3.2.3. For the flowmeter with PEAs mounted along the axis of the straight CP
of U-elbow type, the requirements for the length of the straight pipe runs
before and after the CP are not specified. The required technical and
metrological characteristics of the flowmeter are provided by the CP de-
sign of U-elbow type.
3.3. Requirements for placing the Secondary measuring
converter
The following conditions should be observed at the site of CS loca-
tion:
- Operation conditions in accordance with the requirements of the Opera-
tion Manual
- Option for connecting the CS to the protective earthing trunk line (neu-
tral earthing)
- Free access to the CS.
