Open On Increasing; Adjustment Procedure - GE Becker HPP-5 Installation And Maintenance Manual

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