Technical Specifications

ValVue Digital Communications Software Ver. 2.80
234
GE Oil & Gas
To create a custom characterization:
1. Click Custom and the Custom Characterization dialog appears.
2. Enter values in the Input Signal (%)/Position (%) fields from lowest to highest. If there is too
drastic a slope change the Invalid Segment dialog appears. Adjust values accordingly.
Figure 36 Invalid Segment
Input Signal (%)/Position (%) fields activate and appears.
3. Click Close and a dialog appears prompting you to save.
4. Click OK.
Custom Linearization
Two types of linkages are modeled: simple and compound. Most Masoneilan linkages use the
compound linkage system.
Simple Lever Type The simple lever has the pivot point (the potentiometer in the
SVi1000) mounted a fixed distance (L1) from the valve stem pickup
point. In order to compute the proper correction curve, the stroke
length, the distance from the pivot to the valve stem pickup point
and the valve position at horizontal must be entered. Clicking Simple,
entering a value and clicking OK computes the correction and dis-
plays the curve.
Compound Lever Type The compound lever linkage has two lever segments attached at one
end to the pivot and the other end to the valve stem pickup point. In
order to compute the proper correction curve, the user must enter
the stroke length, first lever segment length (L1), second lever seg-
ment length (L2), the distance from the pivot to the valve stem pickup
(L3), the valve position at horizontal. Clicking Compound, entering a
value and clicking OK computes the correction and displays the
curve.
Most Masoneilan linkages use a linkage with L3 equal to L1, i.e. the second lever arm is vertical
when the first lever arm is horizontal. The correction computation will correctly compute the
correction curve when L3 is not equal to L1, however L3 must be greater than 0 which requires
that the valve stem pickup not be lined up with the pivot and that the pickup be on the same
side of the pivot as the link between the first and second lever segments.