Range Adjustment
Note:
There will be some interaction between
range and bias adjustments. It may therefore
be necessary to readjust the bias and re-check
the range after completing the following steps.
The range, or the amount of travel between the
lower and upper limits of the input signal, is set
with the
range spring
.
This range will typically
be 12 psi for a 3-15 psi system or 24 psi for a 6-
30 psi system. The limits of the range can be
defined as the initial point at which the instru-
ment signal to the
HPP-SB
creates full (equal
to the power gas pressure) or zero (depending
on the positioner and actuator action) output
pressure.
1.
After setting the bias for the start of the valve
travel, continue increasing the instrument
signal until full stroke of the valve is
achieved.
2.
The upper end of the range will be found
when the valve travel indicator reaches the
end of stroke AND the output pressure
gauges read full power gas or zero
(depending on the positioner and actuator
action). Be sure not to overshoot at this
point as any signal level above this upper
limit will show the same reading on the cyl-
inder gauges. This point is the highest end
of the range and the value may not neces-
sarily be equal to the desired upper range
HPP-SB Positioner
Adjustment
3.
If the range is less than desired (i.e. the
actuator reaches its full travel in less than
the specified input range), strengthen the
range spring
by winding it counterclock-
wise onto the
spring retainer
.
If the range
is greater than desired, weaken the
range
spring
by winding it clockwise. Repeat
adjustments until the desired range pro-
vides full or zero output pressure.
4.
If the desired range is not achieved after
making the above adjustments, readjust
the bias (per the previous instructions) to
allow proper range adjustment.
5.
It may be necessary to change the range
spring retainer
for some non-standard
ranges (refer to
Table 3
).
HPP-SB
8
September 1999
Note: For intermediate ranges, use the next size range spring.
Stroke (Part Number)
4
6
8
12
6
01-6288 01-6287 01-6287 01-6801
12
25-1151 25-1152 25-1153 25-1154
18
25-1599 25-1600 25-1601 25-1602
24
25-1218 25-1219 25-1220 25-1221
Spring Range
(psi)
Table 2
: Range Spring Configurations
Table 3
: Range Spring Retainer
Type
Typical Use
Short (01-2509 )
8” and 12” Stroke
Intermediate (11-2572 ) 6” Stroke
Long ( 01-2042 )
4” Stroke
Summary of Contents for HPP-SB
Page 19: ...HPP SB Positioner Instruction Manual HPP SB 19 September 1999...
Page 20: ...HPP SB 20 September 1999 HPP SB Positioner Appendix...
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