GE Becker HPP-5, Installation And Maintenance Manual

Becker HPP-5 High Pressure Positioner Maintenance and Operation Manual  |  4

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Open on Increasing Signal

The positioner is a force-balanced instrument that provides a 

control valve position proportional to the pneumatic input signal� 

The control valve will close on loss of input signal� The energy to 

operate the control valve is obtained from the differential between 

the supply and discharge pressures� In steady state, the forces 

imposed on the balance beam by the input signal diaphragm and 

the range spring are equal; therefore, the top and bottom balance 

valves of the positioner are at or near their closed positions� The 

cylinder top and bottom pressures are both equal to power gas, 

and the control valve is stationary� An increase in the input signal 

pressure results in the opening of the upper balance valve due to 

an imbalance in the beam forces� This decreases the pressure in 

the cylinder bottom, while the pressure in the cylinder top remains 

at power gas pressure� The control valve begins to open�

The actuator rod stretches the range spring, increasing its tension� 

This force, which opposes the force on the balanced beam caused 

by the increasing input signal, continues to increase until the 

balance beam forces are in equilibrium� At this point the valve is in 

the correct position for the applied input signal� The positioner has 

a sensitivity adjustment that permits a balance between greater 

accuracy (from a smaller deadband) and minimal bleed gas�

Your HPP-5 positioner will come factory adjusted for your 

particular application� The use of the adjustment procedures will 

be necessary upon installation of a rubber goods replacement kit 

or any other disassembly or reassembly of the positioner�

Adjustment Procedure

The sensitivity adjustment drum on one end of the positioner 

determines the sensitivity of the unit�

The variable orifices determine the stroking speed of the 

positioner�

Initial Adjustment

1� Adjust the supply regulator:

Adjust the supply regulator to the desired power gas pressure� 

Refer to the original invoice paperwork supplied with the product 

for the appropriate power gas pressure setting� It is imperative 

that adequate supply gas pressure be supplied to the regulator 

pilot to help ensure proper operation of the system and all 

accessories�

2� Adjust the adjustable orifices:

The adjustable orifices are used to control the volume of gas that 

is supplied to the HPP-5 positioner� The stroking speed of the 

system is proportional to the numerical value of the adjustable 

orifice� Adjustable orifice settings are typically equal for both 

orifices� However, a few applications may require unequal settings 

for each adjustable orifice� Set both orifices according to the table 

on page 5�

NOTE: To determine the cylinder bore, look at the model number 

stamped on the stainless steel tag on the top of the cylinder� The 

cylinder bore will be the second number in the alphanumeric 

model code� This one or two digit number will be the diameter in 

inches (for example, a unit with the model number 6H8F6FG-H4 

has an 8-inch bore)�