Chapter 3 Functional descriptions
44 SMSO-2-02.03- 15.07.03
3.2.10 Safety valve
The safety valve is a stop valve where on the input side there
is pressure and on the output side there is no pressure. Safety
valves form part of a multi-level safety concept to protect the
instant heater and steam generator from overheating and from
bursting under over-pressure. The safety valves are fitted
either into the supply pipe or into the hot water / steam pipe for
the instant heater / steam generator. Overpressure caused by
water expansion is diverted into the drip tray. This type of
valve can be fitted to any position because the spring always
keeps the closing element on the valve seat.
Function
The closing element is pressed onto the valve seat by means
of spring-resistance. If the water pressure on the inlet side
exceeds the closing pressure of the spring, the valve opens
and water flows through. Since overpressure can never occur
on the outlet side, the opening pressure is dependent on the
spring-resistance only. Safety valves must never be disman-
tled and their springs must never be replaced. Screw connec-
tions on the safety valve housing are coated with lead seal
coating, which would be broken if the valve were dismantled.
Special feature Take note of the direction of installation
Pressure relief valve
1 Housing (in two parts, screw connection)
2 Valve seat
3 Flat packing in closing element
4 Closing element
5 Pressure spring (depending on opening pressure)
DANGER TO LIFE / MATERIAL DAMAGE
Safety valves can only comply with
their safety functions if they are in-
stalled in the correct direction of flow.
Incorrectly installed valves can cause
the pressure to rise too high and the in-
stant heater or steam generator to
burst. Life-threatening injuries and ma-
terial damage could occur. When
installing a safety valve make sure that
it is installed in the correct direction.
Safety valves must not be disassem-
bled, decalcified and reassembled.
Do not use valves with damaged lead
seal coating .
Technical data
Opening pressure: Nominal: 11 bar
Maximum: 12 bar
Maintenance
Most frequent faults
Calcium deposits or soiling: continual flow of water as a
result of calcium or dirt particles on the flat packing or on
the valve seat.
Pressure spring fatigue: The opening pressure decreases
under a brewing pressure of 7.5 bar thus causing
incorrect dosing (insufficient quantity of product
dispensed).
Check
Service technicians must not open safety valves. If you sus-
pect that such a valve is malfunctioning (traces of calcium
etc.) or if a safety thermostat is triggered, the safety valve
must be replaced.
Service intervals
After 45,000 coffees or after 12 months operation, or if a
safety thermostat triggers, replace the following:
the complete safety valve
Drawing symbol Illustration
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