Yokogawa EJX115A - Manual (Page 25)

<4. Installing Impulse Piping>
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IM 01C25A01-01E
4. Installing Impulse Piping
4.1 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 line, or the drain of a gas-filled
impulse line becomes plugged, it 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 a transmitter.
4.1.1 Connecting Impulse Piping to the
Transmitter
(1) Check the High and Low Pressure
Connections on the Transmitter (Figure 4.1)
Symbols “H” and “L” have been placed on the capsule
assembly to indicate high and low pressure side. With
differential pressure transmitters, connect the high
pressure side impulse line to the “H” side, and the low
pressure side impulse line to the “L” side.
With gauge/absolute pressure transmitters, connect the
impulse line to the ‘H’ side.
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Process
connection
“H” and “L” are shown
Process connection
Process connector
Bolt
Differential Pressure Transmitter
Figure 4.1 “H” and “L” Symbols on a Capsule
Assembly
(2) Changing the Process Connector Piping
Connections (for differential pressure
transmitters)
The impulse piping connection distances can be changed
between 51 mm, 54 mm and 57 mm by changing the
orientation of the process connectors.
This is convenient for aligning the impulse line with a
process connectors.
57 mm 54 mm 51 mm
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Figure 4.2 Process Connector Impulse Piping
Connection Distances
(3) Tightening the Process Connector
Mounting Bolts
After connecting an impulse line, tighten the process
connector mounting bolts uniformly.
(4) Removing the Impulse Piping Connecting
Port Dustproof Cap
The impulse piping connecting port on the transmitter is
covered with a plastic cap to keep out dust. This cap must
be removed before connecting the line. (Be careful not
to damage the threads when removing this cap. Never
insert a screwdriver or other tool between the cap and
port threads to remove the cap.)
(5) Connecting the Transmitter and 3-Valve
Manifold (for differential pressure
transmitters)
A 3-valve manifold consists of two stop valves to block
process pressure and an equalizing valve to equalize
the pressures on the high and low pressure sides of the
transmitter. Such a manifold makes it easier to disconnect
the transmitter from the impulse piping, and is convenient
when adjusting the transmitter zero point.
There are two 3-valve manifold typs: the pipe-mounting
type and the direct-mounting type; care should be taken
with respect to the following points when connecting the
manifold to the transmitter.
 Pipe-Mounting Type 3-Valve Manifold
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Nipple
Nipple
Process
connector
Ball head
lock nut
Pipe
Ball head
lock nut
Process
connector bolts
50 mm(2-inch) pipe
Pipes
3-valve
manifold
Impulse piping
Vent plug
(optional)
Stop valve
(low pressure side)
Equalizing valve
(balancing)
Stop valve
(high pressure side)
Figure 4.3 3-Valve Manifold (Pipe-Mounting Type)
In
sta
llin
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pu
lse
P
ip
in
g
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