Safety Functions; Design Features; Calculation Of The Mttf For The Electrical And Pneumatic Part Of The Valve System - Emerson AVENTICS AV Notice D'instruction

Pneumatics wiring diagram
1V3-1V8
K1
1V1
14
14 12
X X
3
X
1
X
5 X
R X
Fig. 7: Pneumatics wiring diagram, example 1
K1 Valve terminal system
1V3 – 1V8 Not drawn
1V1 – 1V16 Not drawn
0V1 Main air valve
Complete valve system with external components
1 2 3
3
1 2
Fig. 8: Valve system and external components
1 Bus coupler
3 Valves (not in the safety circuit)
5 Pneumatic supply plate, - no monitor-
ing (UAoff) required, no active elec-
tronics installed
7 Safety module, corresponds to block
2 in the safety-related block diagram

3.4.2 Safety functions

Safety-related prevention of unexpected start-up from the rest
position, with the option of personal rescue.
In this documentation, only the pneumatic control component is shown as a sub-
system. For the complete safety function, additional safety-related control com-
ponents (e.g. guards and electrical logic) must be added as subsystems.
• Severity of injury = S2
• Hazardous point is within the accessible area and the operator cannot free
himself
• exhausting must not cause any additional hazard
• as the personal rescue 2V1, 2V2, 3V1 and 3Vn are fully functional after emer-
gency stop, i.e. after exhausting the 3/2 directional control valve in the air
preparation unit, and have no influence on the safety function, they are not
taken into account in the calculation.
This can only be implemented by the following circumstance:
• Only in a state without pressure
• After active emergency stop by 2V1 (a 2V1 can supply several 2V2), this must
be mounted close to the hazardous point
• Provide a joint personal rescue for cylinder groups (a 2V2 can exhaust several
cylinders)
Functional description of switching PL c, d, e_Kat-3_02 when used in a
manual workplace
• Movements are redundantly controlled by main air valve 0V1 and working
valve 1Vn
• Valve 0V1 must be actuated constantly, so that 1Vn can be actuated
AVENTICS™ AV | R412018148-BAL-001-AB | English
PLr = e
1V2 1V9
12 14 12
14
X
3
1
5 X
R
X
G
14 0S1
0V1
1V1 – 1V8 Valves outside the safety-related
control chain
1V9 – 1V16 Valves for actuators with PL
0S1 Position detection of 0V1
4 5
4 5
7
7 8 8
2 Pneumatic supply plate
4 Electrical supply plate - corresponds
to block 4 in the safety-related block
diagram
6 Valves (safety circuit) - corresponds
to block 5 in the safety-related block
diagram - the electrical part of the
valves (valve driver) corresponds to
block 4 in the safety-related block di-
agram
8 Main air valve corresponds to block 6
and 7 in the safety-related block dia-
gram
• the sole failure of 1 of the mentioned valves does not jeopardize the safety
function
• all valves are actuated cyclically in the process
1Vv11-1V16
• the function of the main air valve 0V1 is monitored by a valve position query
0S1
1V10
• the function of the working valve 1Vn is indirectly detected during the process
12
by the switches nS1 and nS2
• the accumulation of undetected faults can lead to a loss of the safety function
• in case of danger due to stored energy (pressure, mass, spring), additional
measures are required

Design features

• Basic and proven safety principles as well as the category B requirement are
met
• Main air valve 0V1 is moved to the safe switching position by a spring
= e
r
• Working valve nV1 has a locked center (zero overlap) with spring centering
• the safe switching position is reached for both valves after the control voltage
is removed
• signal processing of the valve queries and monitoring is carried out in a single-
channel PLC control
6 6
• Control ON and loading door closed:
– Main air valve 0V1 is switched and voltage is applied to the valve system
• Automatic mode ON and loading door open:
– there is no voltage applied at main air valve 0V1 and at the valve system
• Setup operation and safety door bridged with key switch:
– there is no voltage applied at main air valve 0V1 and at the valve system
– the pneumatic line between main air valve 0V1 and working valve nV1 is
exhausted
– Movements are only possible with additional consent switch
– the consent switch switches the main air valve 0V1 and voltage is applied
at the valve system
– Dangerous movements without additional measures with justification are
only permitted with the safety door closed
Calculation of the probability of failure and service life
Required service life:
20 years / 320 days / 24 h / 10 sec. cycle time (nop = 2764800 cycles/year)
• Valve 0V1 B
• Valve nV1 B
3.4.3 Calculation of the MTTF for the electrical and pneumatic part
of the valve system
Fig. 9: Relevant components for calculating the MTTF
4 Electrical supply plate with UAon
monitoring, corresponds to block 4 in
the safety-related block diagram
6 Valves (safety circuit) corresponds to
block 5 in the safety-related block di-
agram the electrical part of the valves
(valve driver) corresponds to block 4
in the safety-related block diagram
See g 6. Reliability values
It follows:
• Electrical supply plate (4) MTTF = 854 years
• UAoff monitoring (5) MTTF = 1094 years
= 79.2 million (IS12-PD)
10D
= 39.6 million (AV05) or valve nV1 B
10D
4
4
5 Pneumatic supply plate with UAoff
10 Valve driver board, 4x
and see g Fig. 9
= 105.8 million (AV03)
10D
10 10
10
MTTF
6 6
5
5
for the electrical part
D
monitoring, the electrical function =
UAoff monitoring corresponds to
blocks 4 and 8 in the safety-related
block diagram
18