Yokogawa EJA115 - Manual (Page 22)

<4. Installing Impulse Piping>
20
IM 01C22A01-01E
4) Now tighten the nuts and bolts securely in the
following sequence:
Process connector bolts
→ transmitter-end ball head
lock nuts → 3-valve manifold ball head lock nuts →
3-valve manifold mounting bracket U-bolt nuts
Direct-Mounting Type 3-Valve Manifold
1) Mount the 3-valve manifold on the transmitter. (When
mounting, use the two gaskets and the four bolts
provided with the 3-valve manifold. Tighten the bolts
evenly.)
2) Mount the process connectors and gaskets on the top
of the 3-valve manifold (the side on which the impulse
piping will be connected.)
Bolts
Process
connector
Gasket
Gasket
Process
connector
Bolts
Stop valve
Stop valve
3-valve manifold
3-valve
manifold
Equalizing valve
Equalizing
valve
Stop valve
Impulse
piping
Impulse
piping
Stop valve
F0404.ai
Figure 4.4 3-Valve Manifold
(Direct-Mounting Type)
4.1.2 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 4.5 according to the kind of
fl
uid being measured.
NOTE
• If the process fl uid is a gas, the taps must be
vertical or within 45° either side of vertical.
• If the process fl uid is a liquid, the taps must be
horizontal or below horizontal, but not more than
45° below horizontal.
• If the process fl uid is steam or other condensing
vapor, the taps must be horizontal or above
horizontal, but not more than 45° above horizontal.
[Gas]
Pressure
taps
Process
piping
[Steam] [Liquid]
45°
45°
45° 45°
45°
45°
F0405.ai
Figure 4.5 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 fl uid is a gas, then as a rule the
transmitter must be located higher than the process
pressure taps.
• If the process fl uid is a liquid or steam, then as a
rule the transmitter must be located lower than the
process pressure taps.
(3) Impulse Piping Slope
The impulse piping must be routed with only an upward or
downward slope. Even for horizontal routing, the impulse
piping should have a slope of at least 1/10 to prevent
condensate (or gases) from accumulating in the pipes.
(4) Temperature Difference Between Impulse
Piping
If there is a temperature difference between the high and
low impulse piping, the density difference of the fl uids
in the two lines will cause an error in the measurement
pressure. When measuring fl ow, impulse piping must be
routed together so that there is no temperature difference
between them.