Hydrocarbon Processing - August 2022 - 27

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FIG. 5. The Option D configuration features an external feedback line connected to the pilot
regulator, delivering downstream pressure feedback.
through the dynamic control outlet loop.
In FIG. 1, this system is labeled Option
B and shows much more robust pressure
control than Option A (the spring-loaded
regulator). The amount of droop is reduced,
as represented by the flatter flow
curve. It is clear that dome regulators
equipped with pilot regulators can manage
pressure more accurately over a wide
range of flows. In most instances, standard
dome-loaded regulators are employed
with confidence that significant pressure
drops will not occur. However, even this
system can be improved.
Option C: External feedback line connected
to a dome-loaded regulator.
Additional accuracy can be achieved by
adding external feedback to a dome-loaded
regulator, as shown in FIG. 4. External
feedback is sent to the regulator by connecting
a tube from the downstream process
line back to the sensing area of the
dome-loaded regulator.
The external feedback line provides
more precise feedback on pressure levels
within the system instead of depending
solely on the pressure levels in the regulator
itself as is seen in standard domeloaded
regulators. In FIG. 1, this system is
shown as Option C, where some droop is
still observed despite a flatter flow curve
than either a spring-loaded regulator or a
dome-loaded regulator.
Option D: External feedback line connected
to a pilot regulator. In FIG. 5, the
final option connects the
external feedback
line directly to the pilot regulator instead
of the dome-loaded regulator. This
enables the pilot regulator to make highly
accurate adjustments to pressure in the
dome-loaded regulator's chamber based
on actual downstream pressure. Then, the
dome-loaded regulator can compensate by
changing its outlet pressure.
When system flow demands rise in
this configuration, pilot regulators monitor
lower pressures with the aid of the external
feedback line. If pressures drop, the
pilot regulator increases the pressure inside
the dome, which maintains the proper
downstream set pressure. The feedback
loop allows continuous, automatic
adjustments that keep the system stable
and working at optimal performance. In
FIG. 1, this is represented by Option D,
which clearly has the least droop and the
broadest flow range.
Minimizing droop. All regulators will
exhibit droop, but the right system configuration
can minimize it by keeping the
pressure constant as flow changes. Work
with your regulator supplier to design the
right system for your application.
SHAJI ARUMPANAYIL is a Product Manager
for Swagelok Company.
Hydrocarbon Processing | AUGUST 2022 27
BR22_0002_Markenrelaunch_Anzeige_Achema_55x255_LA11.indd 108.07.22 09:49
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Hydrocarbon Processing - August 2022

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