Honeywell HON 5020 User And Maintenance Manual page 14

Pressure sections in
HON 640a pilot series
How the HON 640a pilot
works
HON 5020 gas pressure regulator with HON 640a / HON 642a pilot
Figure
 The inlet pressure is conveyed into the pilot through the filter.
 The outlet pressure is conveyed into the pilot from the other side and produces a force
component that acts on the double diaphragm system from above.
 The pilot's set screw is used to tighten the pilot spring, producing a force component
that acts on the double diaphragm system from below.
 The force components being exerted on the double diaphragm system are used by the
system in order to compare the setpoint and the process value. Depending on the gas
pressure and on the set setpoint, the double diaphragm system's position inside the pi-
lot will vary slightly. This position change will result in a small/large gap between the
stationary nozzle and the deflector plate being cleared inside the double diaphragm
system. The dynamically regulated gap between the nozzle and the deflector plate is
used to build up the motorization pressure inside the double diaphragm system.
 The motorization pressure causes the gas pressure regulator being operated to open
and close as appropriate.
 The pilot's amplifying valve is used to set the speed of the motorization pressure
changes.
Color Meaning
Inlet pressure
Motorization pressure
Outlet pressure
Atmospheric pressure
Description
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