GE Becker HPP-5, Installation And Maintenance Manual

Becker HPP-5 High Pressure Positioner Maintenance and Operation Manual  |  6

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Bias Adjustment

For Standard (Non-Split Range) Systems:

1�   To increase the bias setting, increase tension on the range 

spring� This is accomplished by either raising the spring 

retainer or screwing the bias adjustment stud into the indica-

tor bar or tail rod� Note the two jam nuts tightened against 

one another to adjust the length of the stud� When properly 

adjusted, tighten the bias lock nut(s)�

2�  To decrease the bias setting, decrease tension on the range 

spring by either lowering the spring retainer or screwing the 

bias adjustment stud out of the indicator bar or tail rod� Note 

the two jam nuts tightened against one another to adjust the 

length of the stud� When properly adjusted, tighten the bias 

lock nut(s)�

For Split Range Systems (see Table 1)

3�   Find the bias adjustment screw (1/2-20 thread with 3/8 flats) 

on the end of the positioner opposite to the pneumatic signal 

input port� Loosen the jam nut located on the adjustment 

screw�

4�   To increase the bias setting, tighten the adjustment screw�

5�   To decrease the bias setting, loosen the adjustment screw�

6�   Holding the adjustment screw in place, tighten the jam nut 

against the positioner body�

Table 1. Adjustable Bias Springs

Table 2. Range Spring Configurations

Spring

(part number)

Range

(psig)

Green (20-2592)

1-6

Silver (25-1038)

2-11

Blue (25-1036)

4-20

Red (25-1037

8-30

Spring 

Range (psi)

Stroke (Part Number)

4”

8”

12”

14”

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

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 instrument signal to the HPP-5 positioner starts 

valve movement until the end of the valve stroke and full pressure 

differential across the cylinder output gauges�

1�   After setting the bias for the start of the valve travel,  

continue increasing the instrument signal until the valve 

stroke is completed and the cylinder output gauges show full 

power gas pressure differential�

2�   Be sure not to overshoot at this point as any signal level 

above this upper limit will show the same reading on the 

cylinder gauges� This point is the highest end of the range, 

and the value may not necessarily be equal to the desired 

upper range value�

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 counterclockwise 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 provides 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 

nonstandard ranges (refer to Table 3)�

Table 3. Range Spring Retainer

Type (part number)

Typical Use

Short (01-2509)

8” and 12” Stroke

Intermediate (11-
2572)

6” Stroke

Long (01-2042)

4” Stroke

Changing Positioner Action

To change the positioner from open on increasing signal to close 

on increasing signal, or vice versa, the following parts kits must be 

ordered:

To change open on increasing to close on increasing: Part 

#25-1444 plus an extension rod� The serial number of the actuator 

must be specified� The exact part number of the extension rod will 

vary based on the actuator stroke�

To change close on increasing to open on increasing: Part #25-

1289� Note: If converting a close on increasing signal positioner 

to open on increasing signal, the wide end of the tube may be 

shortened by 11/16 of an inch with a hacksaw instead of ordering 

Part #25-1289�

The stroke length of the actuator cylinder MUST be specified 

when ordering the above part numbers� If the actuator serial 

number cannot be found, the stroke length can be found from the 

regulator model number� The stroke length is the second letter in 

the model number� For example model 10H12L6FG-SR-S-HSB- 

40/35-100-O has a stroke length of “L”, or 12 inches (“L” is the 12th 

letter in the alphabet)�

Refer to the drawings in the Appendix for the following:

1�   Disconnect all supply lines, instrument line, and output line 

from the positioner�

2�   Remove the range spring at both ends and those items 

connecting it to the rod and the positioner feedback arm�