Technical Specifications

ValVueFF Software Interface to FVP

GE Energy

Position Limits Frame

Use the Position Limits frame (Figure 74) parameters to limit the valve, force the valve to

close tightly or open fully at specified positions, and to set the trip points of the limit

switches (DI block). You can also activate a warning when a deviation lasts longer than

Time 1 or to force the valve to it's failsafe position if the deviation lasts longer that Time 2.

CAUTION Position Limit parameters are powerful tools to alter the valve

performance to be non-linear. Use them with caution and only

when the process requires special performance.

When Tight Shutoff below is configured to a positive value,

small flows are not controllable.

Tight Shutoff Below

(TSB)

If the valve Target Position is less than this value, the valve is

forced to fully close. A value of -10 removes this function from the

normal travel range, unless the calibration of valve travel has

been readjusted. Set this between 1 and 3 to minimize seat leak-

age.

Full Open Above

(FOA)

If the valve Target Position is more than this value, the valve is

forced to fully open. A value of 110 removes this function from the

normal travel range.

Position Lower Limit The valve Target Position must not be less than this value. This

prevents the valve from closing. Use only when required by the

control strategy. A value of -10 removes this function from the

normal travel range.

Position Upper Limit The valve Target Position must not exceed this value. A value of

110 removes this function from the normal travel range.

CAUTION Use of Full Open Above at values less than 110 can result in

rapid increase in flow rate if input reaches this value. Use with

extreme caution.

Near Closed Value The threshold below which the valve is considered near closed.

Near Closed is useful for estimating when to change the valve

trim. This value does not effect valve travel it is used only for

reporting the time that valve is near the seat.

Determining Values to Disable Tight Shutoff Below, Full Open Above, and Limits

If Travel Limits have been readjusted after performing Find Stops, then the values that

disable the Tight Shutoff Below, Full Open Above, Position Lower Limit, and Position

Upper Limit functions must be determined by testing the limits. To disable these functions,

set them 10% above the full open mechanical stop position or 10% below the fully closed

mechanical stop position.