IM 01C25C01-01E
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 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 measure-
ment 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 Connec-
tions 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.EPS
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 Mount-
ing 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
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.)
5.1.2 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.
