Yokogawa EJA310A - Manual (Page 24)

IM 01C21D01-01E 5-1
5. INSTALLING IMPULSE PIPING
5. INSTALLING IMPULSE PIPING
5.1 Impulse Piping Installation
Precautions
The impulse piping that connects the process outputs to
the transmitter must convey the process pressure
accurately. If, for example, gas collects in a liquid-
filled impulse piping, or the drain of a gas-filled
impulse piping becomes plugged, the impulse piping
will not convey the pressure accurately. Since this will
cause errors in the measurement output, select the
proper piping method for the process fluid (gas, liquid,
or steam). Pay careful attention to the following points
when routing the impulse piping and connecting the
impulse piping to the transmitter.
5.1.1 Connecting Impulse Piping to the
Transmitter
(1) Connecting the Impulse Piping to the
Transmitter
Symbols “H” and “L” are shown on a capsule assem-
bly to indicate high and low pressure side. Connect the
impulse piping to the “H” side.
F0501.EPS
“H” and “L” are shown
Process connection
Process connector
Bolt
Figure 5.1.1 “H” and “L” Symbols on a Capsule Assembly
(2) Tightening the Process Connector Mount-
ing Bolts
After connecting the impulse piping, tighten the
process connector mounting bolts uniformly.
5.1.2 Routing the Impulse Piping
(1) Process Pressure Tap Angles
If condensate, gas, sediment or other extraneous
material in the process piping gets into the impulse
piping, pressure measurement errors may result. To
prevent such problems, the process pressure taps must
be angled as shown in Figure 5.1.2 according to the
kind of fluid being measured.
NOTE
• If the process fluid is a gas, the taps must be
vertical or within 45
° either side of vertical.
• If the process fluid is a liquid, the taps must be
horizontal or below horizontal, but not more
than 45
° below horizontal.
• If the process fluid is steam or other condens-
ing vapor, the taps must be horizontal or above
horizontal, but not more than 45
° above hori-
zontal.
[Gas]
Pressure
taps
Process
piping
[Steam] [Liquid]
45 °
45 °
45 ° 45 °
45 °
45 °
F0502.EPS
Figure 5.1.2 Process Pressure Tap Angle (For Horizontal
Piping)
(2) Position of Process Pressure Taps and
Transmitter
If condensate (or gas) accumulates in the impulse
piping, it should be removed periodically by opening
the drain (or vent) plugs. However, this will generate a
transient disturbance in the pressure measurement, and
therefore it is necessary to position the taps and route
the impulse piping so that any extraneous liquid or gas
generated in the leadlines returns naturally to the
process piping.
• If the process fluid is a gas, then as a rule the
transmitter must be located higher than the process
pressure taps.
• If the process fluid is a liquid or steam, then as a
rule the transmitter must be located lower than the
process pressure taps.