GE MN-ValVue-v2-8-IOM Manuel de service télécharger pdf (Page 628)

100

101

ValVue Digital Communications Software Ver. 2.80

628

GE Oil & Gas

Pressure

Units

You can select the units in

which

the actuator pressure is reported.

Selections are psi, bar, or kpa.

Position Fault

Limits

You can configure how position errors are handled. A position error

occurs when the valve position differs from the requested position

(from the input signal in normal operating mode or the manual set-

point in manual mode) by more than the Position Error Band for more

than the Position Error Time 1. When this occurs, a status flag is set

which is reported during the next HART message (only that a flag is

set is reported. You can send a Read Status message to find out the

cause of the status flag). If the error persists for Position Error Time 2,

the valve is put in failsafe position. This latter action may be disabled

by unchecking the Enable box next to the Time 2 entry.

For practical considerations, Time 2 (if enabled) must be larger than

Time 1 by at least 2 seconds. Time 1 should be at least as long as the

time required to open the valve fully or unnecessary position errors

are reported. The maximum time is 327 seconds.

Characterization

Control valves are often

characterized

to give a specific

relation-

ship

between

flow

capacity (Cv) and percent opening

the

valve.

The valve can

characterized

with special purpose trim or with

the SVI positioner. Several

characterizations

are

available:



Linear:

Causes the valve to open

proportionally

with the

input signal. This option should be selected if non-linear trim

is used in the valve.



Equal Percentage (50)

and

Equal Percentage (30):

Two

equal

percentage

characterizations

are available, one with R=50

and the other with

R=30.

 Quick Opening: The quick opening

characterization

is the

inverse of the Equal Percentage (50)

characterization

curve



Custom Configuration:

Selecting

this option

displays

additional

dialog where

you can enter or draw a

custom

characterization

curve. The

curve

can have up to nine

points and points in between are linearly

interpolated.

Air Action: Air-to-Open

Air-to-Close

You must select whether the valve is an air to open valve or an air to

close valve. This selection determines whether an increasing signal

opens or closes the valve.

Actuator Type:

Single/

Double

Selects the actuator type

single acting or double acting. This is

available

only on SVI2

Version

1.2.2 and later.

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GE MN-ValVue-v2-8-IOM Manuel de service Page 628

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