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Reference Manual
00809-0200-4101, Rev AA
July 2008
2-15
Rosemount 2051
Impulse Piping The piping between the process and the transmitter must accurately transfer
the pressure to obtain accurate measurements. There are six possible
sources of impulse piping error: pressure transfer, leaks, friction loss
(particularly if purging is used), trapped gas in a liquid line, liquid in a gas line,
and density variations between the legs.
The best location for the transmitter in relation to the process pipe is
dependent on the process. 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 in./foot (8 cm/m)
upward from the transmitter toward the process connection.
• For gas service, slope the impulse piping at least 1 in./foot (8 cm/m)
downward from the transmitter toward the process connection.
• Avoid high points in liquid lines and low points in gas lines.
• Make sure both impulse legs are the same temperature.
• Use impulse piping large enough to avoid friction effects and blockage.
• Vent all gas from liquid piping legs.
• 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 (above 250 °F [121 °C]) process material out of
direct contact with the sensor module and flanges.
• Prevent sediment deposits in the impulse piping.
• Maintain equal leg of head pressure on both legs of the impulse piping.
• Avoid conditions that might allow process fluid to freeze within the
process flange.