Impulse Piping - Emerson Rosemount 2151N Reference Manual

Reference Manual
00809-0000-4851 Rev AD
December 2023

Impulse Piping

Installation
The piping between the process and the transmitter must
accurately transfer the pressure to obtain accurate
measurements. There are five possible sources of error:
pressure transfer (such as obstruction), leaks, friction loss
(particularly if purging is used), trapped gas in a liquid line or
liquid in a gas line, and density variations between the legs.
The best location for the transmitter in relation to the process
pipe depends on the process itself. Use the following
guidelines to determine transmitter location and placement of
impulse piping:
Keep impulse piping as short as possible.
•
For liquid service, slope the impulse piping at least 1
•
inch per foot (8 cm per meter) upward from the
transmitter toward the process tap (see Figure 2-1 for
details).
• For gas service, slope the impulse piping at least 1
inch per foot (8 cm per meter) downward from the
transmitter toward the process tap (see Figure 2-1 for
details).
Avoid high points in liquid lines and low points in gas
•
lines.
• Make sure both impulse legs are the same
temperature.
• Use impulse piping of large enough diameter to avoid
friction effects and blockage.
Vent all gas from liquid piping legs and internal to
•
transmitter process flange.
Drain all liquid from gas piping legs and internal to
•
transmitter process flange.
When using a sealing fluid, fill both piping legs to the
•
same level.
• When purging, make the purge connection close to
the process taps and purge through equal lengths of
the same size pipe – avoid purging through the
transmitter.
Keep corrosive or hot process material out of direct
•
contact with the transmitter.
Prevent sediment deposits in the impulse piping.
•
Keep the liquid balanced on both legs of the impulse
•
piping.
Avoid conditions that might allow process fluid to
•
freeze within the process flange.
• Make sure the impulse piping is of adequate strength
to be compatible with anticipated pressure.
Rosemount 2151N
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