Emerson 3051S Dokumentacja Pobierz pdf (Strona 22)

Reference Manual

00809-0200-4801, Rev CA

July 2010

Rosemount 3051S Series

2-8

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, liquid in a gas line, density variations

between the legs, and plugged impulse piping.

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 SuperModule 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.3

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Emerson 3051S Dokumentacja Strona 22