Rosemount 4600, Справочное руководство

Страница: 15 / 68

Reference Manual
00809-0100-4022, Rev AA
July 2002
2-5
Model 4600
Impulse Piping
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, leaks, friction loss (particularly if purging is
used), trapped gas in a liquid line and liquid in a gas line.
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.
• Use impulse piping large enough to avoid friction effects and blockage.
• Vent all gas from liquid piping legs.
• 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 200 °F [93.3 °C]) process material out of
direct contact with the transmitter.
• Prevent sediment deposits in the impulse piping.
• Avoid conditions that might allow process fluid to freeze within the
process connector.