Instruction Manual

299H Series
5
Principle of Operation
!
WARNING
Since a pilot-operated regulator is
constructed of both a pilot and a main
valve, do not exceed the maximum inlet
pressure shown on the nameplate.
Letter keys in this section refer to Figure 2 unless
otherwise noted. Fast response and accuracy are
made possible by the amplifying effect of the pilot
and by the two-path control system. The function of
the pilot is to sense change in the controlled pressure
and amplify it into a larger change in the loading
pressure. Any changes in outlet pressure act quickly
on both the actuator diaphragm and the loading pilot,
thus providing the precise pressure control that is
characteristic of a two-path control system.
Upstream or inlet pressure is utilized as the operating
medium, which is reduced through pilot operation to load
the main diaphragm chamber. Tubing connects the inlet
pressure to the pilot. Downstream or outlet pressure
registers underneath the main diaphragm (E) and on top
of pilot diaphragm (F). There are three different versions
of pressure registration for the 299H Series.
Internal registration—Outlet pressure is registered
through the throat (J) to the main diaphragm chamber
and then through a small port (G) to the top of the
pilot diaphragm.
External registration—The throat (J) is blocked and a
downstream control line is connected to the pilot upper
diaphragm chamber or the actuator lower diaphragm
chamber. A small port (G) connects the two chambers.
Dual registration—The lower main diaphragm chamber
registers outlet pressure through the throat (J) and the
upper pilot diaphragm chamber registers downstream
pressure by using a downstream control line. The port (G)
between the chambers is blocked.
Type 299H
In operation, assume the outlet pressure is less than
the setting of the pilot control spring (A). The top side
of pilot diaphragm assembly (F) will have a lower
pressure than the setting of the control spring (A).
The control spring (A) forces the diaphragm assembly
upward, opening the pilot orice (C). Additional loading
pressure is supplied from the pilot orice to the top side
of the main diaphragm (E).
Type 299HS
E0072
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
July 2008
Type 299HS
LOADING PRESSURE
EXTERNAL REGISTRATION
INTERNAL REGISTRATION
Figure 2. 299H Series Operational Schematics (continued)
TYPE 299HS
INTERNAL REGISTRATION
E0069
E0070
EXTERNAL REGISTRATION
E0072
Type 299HS
E0072
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
July 2008
Type 299HS
LOADING PRESSURE
EXTERNAL REGISTRATION
INTERNAL REGISTRATION
Type 299HS
E0072
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
July 2008
Type 299HS
LOADING PRESSURE
EXTERNAL REGISTRATION
INTERNAL REGISTRATION
Type 299H Internal Registration
E0070
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
July 2008
Type 299H
LOADING PRESSURE
OUTLET
INLET
K
G
C
A
B
E
H
F
J
3/4 NPT
CONTROL LINE
CONNECTION
PILOT SUPPLY
SCREEN