Data Sheet
Bulletin 71.1:S200
8
Several S200 Series regulators have relief across the
diaphragm (Figure 5) to help minimize overpressure.
Any outlet pressure above the start-to-discharge
point of the nonadjustable relief spring moves the
diaphragm off the relief seat, allowing excess pressure
to bleed out through the screened stabilizer vent.
For extra protection, should emergency conditions
exist which prevent normal operation of the regulator
(for example, linkage becoming disconnected or disk
broken off), the relief stem contacts the underside of
the closing cap, limiting the rise of the relief. Since the
diaphragm continues to rise as downstream pressure
builds, it lifts off the relief, thereby opening the valve to
provide relief operation.
™
The Types S203, S203H, and S203P are available
with a True-Monitor
regulator, which is integral yet
acts independently of the main regulator. The monitor
provides equivalent overpressure protection when
compared to a standard two-regulator monitor setup.
If one regulator fails, the other regulator provides
control and overpressure protection. The monitor
construction provides the following important features:
—In DOT 192.197
paragraph “b” which states “or if the gas contains
material that seriously interferes with the operation
of service regulators, there must be suitable
protective devices to prevent unsafe overpressuring
of the customer’s appliances if the service regulator
fails.” The Type S203 is designed to address the
above issue and other common types of failures
found in service regulators, such as lever arm,
pusher post, and stem failures.
—Required
relief capacity is cut down without restricting total
regulator capacity. The internal token relief and
monitor work in combination to limit relief discharge
to atmosphere. The internal token relief also acts
as an alarm to indicate when the monitor is operating.
—
In the event of regulator failure, the monitor
regulator limits downstream pressure.
—
The monitor diaphragm and piston are in motion
under normal operating conditions, prepared to
provide overpressure protection when needed.
No manual reset procedure is required to return
the regulator to normal operation after relief of the
overpressure condition.
As downstream pressure registers under the
main diaphragm, it also registers on top of the
monitor diaphragm through the pitot tube located
near the body outlet. Under normal conditions
as downstream pressure uctuates due to load
changes, the main regulator disk and the monitor
piston move toward or away from the orice.
If downstream pressure begins to increase due
to main regulator failure, and if the downstream
pressure increases to 7 to 28 inches w.c. / 17 to
70 mbar above set pressure, the internal relief valve
begins to open to limit downstream pressure. At
the same time, the increasing pressure is sensed
on the monitor diaphragm (see Figure 7) causing
the monitor piston to move towards the orifice to
restrict the flow through the regulator to limit the
downstream pressure. While the monitor is in
operation, regardless of the downstream demand,
the token internal relief valve will continuously
operate due to the engineered bleed in the monitor
piston. This bleed allows a minimal amount of flow
to exhaust to atmosphere to notify the user that the
regulator is operating in monitor mode.
As downstream pressure drops back to normal, the
piston moves back away from the orice and the
internal relief valve closes, automatically allowing
normal operation again.
The combination of a restriction in the internal relief
valve and the monitor piston positioned near the inlet
side of the orice limits the maximum downstream
pressure and the related ow through the internal relief
valve to the values shown in Table 5 and Figure 8.
On installations requiring a minimum outlet pressure,
the Types S204 and S206 regulator (Figure 9) and
the Types S204H and S206H regulator with low outlet
pressure shutoff shuts the regulator off if the required
minimum outlet pressure cannot be maintained. With
the ow shut off, the possibility of gas accumulation
downstream of the regulator is minimized.
As downstream pressure drops under high demand or
because the inlet pressure is too low, the diaphragm
drops to its lowest position and the main disk moves to its
farthest position from the orice. This allows the spring in
the back disk assembly to seat the back disk against the
orice and shut off ow. This condition is maintained until
the regulator is manually reset by pulling upward on the
pusher post extension in the spring case.