VEGA VEGADIF 34 … 51 - Manual (Page 43)

VEGADIF 34 … 51 43
20094-EN-030731
5.2 Impulse lines
The impulse lines are used for pressure trans-
mission from the pressure tapping points to
the transmitter. The following regulations must
be observed for running the impulse lines so
that the measured pressure reaches the
measuring cell unaltered:
- Lines with 12 x 1.5 mm or larger should be
used (see e.g. DIN 19 210, impulse lines for
flow measuring systems).
- The tube material must be corrosion resist-
ant, suitable for the measured product.
- The impulse lines must be as short as pos-
sible and must be grounded; avoid bend-
ing.
- The impulse lines must have a gradient of at
least 10 % (10 cm per meter); this prevents
buildup in the impulse lines.
- Ensure that the whole measurement system
(transmitter, high and low side impulse lines
etc.) is installed in the same aggregate
condition, corresponding to the process
aggregate condition and should be inde-
pendent of the ambient temperature.
- Both impulse lines should have the same
temperature (the differential pressure meas-
urement is density-dependent); hence the
impulse lines must be routed close together;
if necessary insulate or couple thermally.
- If necessary, the impulse lines should be
fastened with pipe clamps.
- We recommend connecting the impulse
lines via block or multiple valve blocks to the
transmitter; this ensures simple mounting
and dismounting of the transmitter without
interrupting the process.
Installation connections
Connection of the impulse lines
The impulse lines must be cleaned before
connecting to the transmitter:
- in applications with gases blow through with
compressed air.
- in applications with liquids use a suitable
cleaning liquid.
Contamination such as e.g. welding or pickling
residues must not penetrate the process
flanges (measurement errors!).
Before connecting to the transmitter, the im-
pulse lines to the block valves or valve block
must be tested for leaks.
The impulse line with the higher pressure must
be connected to the plus side of the transmit-
ter, the impulse line with the lower pressure to
the minus side of the transmitter.
Connection of impulse lines directly to the
transmitter
In this case the following connection options
exist:
- with cutting ring threading (non-soldered
bolting) to the 1 /
4
“ NPT, 1 /
2
“ NPT or R
C
1 /
4
“ NPT
inner threads of the process fittings to the
transmitter.
- with separate oval flange adapter to the
1 /
2
“ inner thread.
Connection of the impulse lines to the
valve block
The impulse lines are connected with cutting
ring threading (non-soldered bolting) to the
1 /
4
- 18 NPT inner thread of the valve block.