Yokogawa EJX115A - Manual (Page 26)

<4. Installing Impulse Piping>
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IM 01C25A01-01E
1) Screw nipples into the connection ports on the
transmitter side of the 3-valve manifold, and into
the impulse piping connecting ports on the process
connectors. (To maintain proper sealing, wind sealing
tape around the nipple threads.)
2) Mount the 3-valve manifold on the 50 mm (2-inch)
pipe by fastening a U-bolt to its mounting bracket.
Tighten the U-bolt nuts only lightly at this time.
3) Install the pipe assemblies between the 3-valve
manifold and the process connectors and lightly
tighten the ball head lock nuts. (The ball-shaped ends
of the pipes must be handled carefully, since they will
not seal properly if the ball surface is scratched or
otherwise damaged.)
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)
NOTE
After completing the connection of the transmitter and
3-valve manifold, be sure to CLOSE the low pressure
and high pressure stop valves, OPEN the equalizing
valve, and leave the manifold with the equalizing valve
OPEN.
You must do this in order to avoid overloading the
transmitter from either the high or the low pressure
side when beginning operation.
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
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 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 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.
(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.