Reference Manual
Rosemount 3051N
FIGURE
GAS OR LIQUID SERVICE | GAS SERVICE | STEAM SERVICE |
Flow
Flow
Flow
Impulse Piping
The piping between the process and the transmitter must accurately transfer the pressure to obtain accurate measurements. There are several possible sources of 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 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 m) upward from the transmitter toward the
process connection.
•For gas service, slope the impulse piping at least 1 inch per foot (8 cm per 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.
•Keep the liquid head balanced on both legs of the impulse piping.
•Avoid conditions that might allow process fluid to freeze within the process flange.
