Principle Of Operation - Emerson Fisher LS200 Series Instruction Manual

The standard gas pressure devices (regulators
and safety shut-off devices) are those used in the
assemblies dealt with into EN 12186 and EN 12279
and their use has to be under the provisions into
ENs 12186 and 12279.
If additional pressure accessories (e.g. slam shut
controller) are needed, it is recommended to use
Emerson products.
Emerson will not be responsible for any possible
inefficiency due to installation of non-Emerson
production additional pressure accessories (e.g.
slam-shut controller).
An external downstream control line is required for
the operation of the regulator. A restriction collar is
available to reduce the flow capacity of the regulator.

Principle of Operation

Refer to the operational schematics in Figure 3. The
LS200 Series downstream pressure is registered
under the diaphragm via the external control line and
is used as the operating medium. Increased demand
lowers the downstream pressure and allows the
spring to move the diaphragm and stem assembly
down, opening the valve disk and supplying more gas
to the downstream system.
MONITOR
Figure 3b. LS200 Series Monitor Configuration Installation Schematic
5 x DN
10 x DN
REGULATOR
Decreased demand increases the downstream
pressure and moves the diaphragm and stem
assembly up, closing the valve disk and decreasing
the gas supply to the downstream system.
Boosting System
The LS200 Series incorporates a balancing diaphragm
and a boosting system. When the regulator is locked
up, inlet pressure is registered on the top of the disk
and on the bottom of the balancing diaphragm through
space between the stem and cage. Also, downstream
pressure is registered on the bottom of the disk and on
the top of the balancing diaphragm through a passage
in the stem.
When the trim is open, gas flows from the inlet over
the edge of the disk to the outlet. Under the disk,
there is little gas flow. The gas pressure is higher
than it is in the flow path where gas velocity tends to
lower the pressure. The higher pressure near the disk
is registered on the top of the balancing diaphragm
through the space between the stem and the cage.
This pressure registered on the top of the balancing
diaphragm aids downward disk travel and
compensates for spring and diaphragm effect. This
improves regulator rangeability and performance.
LS200 Series
7