4IIM2C - Ed 2 - May 2020
Working principle
Safety valve
M2 gas valve comprises two class A automac shut-
o valves, electrically operated.
Each operator consists of a plunger connected to a
rubber seal. A closing spring presses the seal against
the seat, and thus ensures the ghtness of the valve.
At rest, both safety valves are closed; thus gas cannot
ow beyond chamber ①.
When energized independently or simultaneously,
the coils generate a magnec eld which moves
up the plunger, and releases the gas flow from
chamber ① to chamber ② for valve V1 (from ③
to ④ for V2).
A power-on indicator on the plasc cover lights up
as valve V1 is energized.
When de-energized, each safety valve closes within
0.2 second.
Pressure regulator
The M2 gas valve pressure regulator is normally
closed type, pneumatically operated by a servo
system.
system. The servo system controls the main regulator valve opening to equilibrate – through a
diaphragm – the downstream pressure ③ to a setpoint adjusted by the screw S.
A small valve in the servo system supplies the main diaphragm chamber ⑤ with upstream pressure
picked from chamber ②. When regulated pressure falls below the setpoint, the servo diaphragm moves
down opening the servo valve. This results in a pressure increase of the main diaphragm chamber
which opens the main regulator valve, and thus increases the regulated pressure. In return, when
the regulated pressure exceeds setpoint, the servo valve closes. A calibrated orice, which creates
a permanent leakage between the main diaphragm chamber and the regulated pressure chamber,
allows for the pressure to decrease, and thus the main regulang valve to close.
This design allows for excellent precision when regulang the downstream pressure, regardless to
upstream pressure variaon or downstream ow changes.
It also plays a role to soen the burner ignion : the progressiveness of regulang valve opening
combines with servo valve system to damp pressure peaks during transient phases. In some cases, it
can be an eecve alternave to slow opening devices.
Flow adjustment
A seng screw, located on the valve V2, limits the opening stroke of plunger. It can be used to
nely adjust the maximum gas ow.
①
②
③④
⑤
V1 V2
S
