<5. Installing Impulse Piping>
5-1
IM 01C25C01-01E
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 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.
5.1.1 Connecting Impulse Piping to the
Transmitter
(1) Check the High and Low Pressure
Connections on the Transmitter (Figure 5.1)
The letters H and L on the capsule assembly
indicate the high and low pressure sides. For
liquid level measurement in an open tank, the low
pressure side measures atmospheric pressure.
For a closed tank, connect the impulse line to the
low pressure side of the transmitter to measure the
pressure in the tank.
F0501.ai
H and L appear here
Low pressure
connection
Process connector
Bolt
Figure 5.1
H and L Symbols on a Capsule
Assembly
(2) Tightening the Process Connector
Mounting Bolts
After connecting the impulse line, tighten the
process connector mounting bolts uniformly.
(3) Removing the Impulse Piping Connecting
Port Dustproof Cap
The impulse piping connecting port of the
transmitter may be 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.)
5.1.2 Routing the Impulse Piping
(1) 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.
(2) Preventing Freezing
If there is any risk that the process fluid in the
impulse piping or transmitter could freeze, use a
steam jacket or heater to maintain the temperature
of the fluid.
NOTE
After completing the connections, close the
valves on the process pressure taps (main
valves), the valves at the transmitter (stop
valves), and the impulse piping drain valves,
so that condensate, sediment, dust and other
extraneous material cannot enter the impulse
piping.
