Yokogawa EJA530A - Manual (Page 24)

IM 01C21F01-01E 5-2
5. INSTALLING IMPULSE 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.
(4) 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.
5.2 Impulse Piping Connection
Examples
Figure 5.2 shows examples of typical impulse piping
connections. Before connecting the transmitter to the
process, study the transmitter installation location, the
process piping layout, and the characteristics of the
process fluid (corrosiveness, toxicity, flammability,
etc.), in order to make appropriate changes and
additions to the connection configurations.
Note the following points when referring to these
piping examples.
• If the impulse piping is long, bracing or supports
should be provided to prevent vibration.
• The impulse piping material used must be compat-
ible with the process pressure, temperature, and
other conditions.
• A variety of process pressure tap valves (main
valves) are available according to the type of
connection (flanged, screwed, welded), construction
(globe, gate, or ball valve), temperature and
pressure. Select the type of valve most appropriate
for the application.
F0505.EPS
Tee
Stop valve
Stop valve
Drain valve
Drain plug
Union or flange
Union or flange
Tap valve
Figure 5.2 Impulse Piping Connection Examples