
Operating principle of the shut-off valve
Theshut-offdeviceisasafetydevicethatgoesoff
whenthepressurevalueinthedownstreampipe
increasesordecreasesbeyondtheprefixedcali-
brationvalues,cuttingautomaticallytheflowofthe
gas
Shut-off valve with screw reset
Thesedeviceconsistsofavalvebody10,acontrol
head,adiaphragmassembly4-15andastem–
valve plug assembly12 –18, which remain in a
balancedpositionthroughamechanicalballsys-
temTheshut-offvalveistriggeredwhenthepres-
surevalueinthecontrolchamber5,thatfromthe
downstreampipeflowintothischamberthrough
theimpulseintake14,increasesordecreasesbe-
yondtheestablishedpressurevalues,thusmoving
fromitsbalancingpositionthediaphragmassem-
bly4–15Thestem18connectedtothevalveplug
12triggersundertheforceofthespring13,coming
immediatelyintocontactwiththevalve8cutting
automaticallytheflowofthegas
NOTE:
The schematic section refers to a safety
valveinstalledofseries8500,buttheoperating
principle is valid even for other safety valves in-
stalledofseries8200and8300
34
34
SSV 8500
(for RB 4700 models with integrated SSV 8500)
Item Description
1
Screwingring
2
Cover
3
Vent
4
Diaphragm
5
Motorisationchamber
6
Flange
7
Valveplugplate
8
Valveorifice
9
inletchamber
10 Valvebody
11 Outletchamber
12 Valveplug
13 Valveplugspring
14 Diaphragmplate
15 Impulseintake
16 Balls
17 Maxcalibrationspring
18 Stem
19 Cover
20 Screwingring
21 Mincalibrationspring