3Printed in Italy - EE163/0704
3- Operation
The VMM type valve is a safety shutting device using
auxiliary power supply.
The first valve (A) is a fast opening solenoid valve that is
safety. When it is de-energized, the spring pushes on
the seal disc, keeping the gas passage closed. Now, the
inlet chamber is under the gas line pressure, and it
forces on the disc too, improving the seal.
When the coil is powered the valve opens rapidly,
against the strength of the spring and gas pressure.
If the power supply is shut off, the valve rapidly closes,
interrupting the gas flow.
Equally, the second valve (B) may be a fast opening or a
slow opening solenoid valve to adjust the gas flow, with
a first adjustable fast stroke and a second adjustable
slow stroke (see the Service Instruction Section).
It is possible connect a third by-pass valve (C), which
performs by driver stage or to obtain a second fast
(slow) stroke or both.
4- Accessories
A fine mesh filter is provided, to prevent dirty
contamination of the seal seat. However, an external
strainer must be installed upstream of the unit.
Each pressure chamber is provided with bilateral G1/4"
gauges, to connect min/max adjustable pressure
switches, leakage tester or other gas equipments.
On request, valves are supplied with a G1/8” connection
on the bottom, to installed a closed position indicator
micro switch. An adapting rod is provided too.
WARNING
The assemblage of any accessories could exclude
the fitting of other devices.
5- Coil features
The continuous service (100% ED) causes inevitable coil
heating, depending of working environment. This
situation is absolutely normal and has not to worry. To
improve the coil cooling, install the unit allowing free air
circulation.
Valve is provided with a power saving electronic device.
It has two stages of operation: full power is supplied to
the coil while the valve is opening; low power is supplied
while the valve is open.
Coil and terminal box are provided with suitable gaskets,
to avoid water and dirty contamination (see the Service
Instruction Section).
Fig. 2
6- General information
Backpressure sealing is compliant with the Class A:
the maximum backpressure admitted, with leakage
within the EN161 requirements, is 150mbar.
Maximum torsional stresses admitted are compliant
with the Group 2 of the EN161 standard.
Recommended testing pressure is 1500 mbar Max.
All components are design to withstand any
mechanical, chemical and thermal condition
occurring during typical service.
Effective impregnation and surface treatments has
been used to improve mechanical sturdiness,
sealing and resistance to corrosion of the
components.
Valves are suitable for use with air and non-
aggressive gases included in the 1, 2 and 3 families
(EN 437).
Materials in contact with gas:
•Aluminium
•Brass
•Stainless steel
•Plated steel
•Anaerobic adhesive
•Nitrile rubber (NBR)
•Polytetrafluoroethylene (PTFE)
1 = Adjustable pressure switch (Min)
2 = Adjustable pressure switch (Max)
3 = Valve leakage tester
4 = Limit switch
5 = Limit switch
6 = Burner pressure gauge
A = First valve
B = Second valve
C = By-pass valve
X = Inlet chamber
Y = Middle chamber
Z = Outlet chamber
