6
D5290 - 10 A SIL 3 Relay Output Module for NE Load G.M. International ISM0111-8
Application D5290S - SIL 3 Load Normally Energized Condition (NE) and Normally Energized Relay,
with interruption of only one load supply line
Normal state operation De-energized to trip operation
13
15
21
PLC
Output ON
24 Vdc
NE
Load
SIL 3
22
14
Service
Load
(Not SIL)
+ / AC
- / AC
13
15
21
PLC
Output OFF
0 Vdc
NE
Load
SIL 3
22
14
Service
Load
(Not SIL)
+ / AC
- / AC
Functional Safety Manual and Applications
2)
Description:
Input Signal from PLC/DCS is normally High (24 Vdc) and is applied to pins 1-2 or 3-4 in order to Normally Energize (NE) the internal relays.
Input Signal from PLC/DCS is Low (0 Vdc) during “de-energize to trip” operation, in order de-energize the internal relays.
The Load is Normally Energized (NE), therefore its safe state is to be de-energized; the Service Load is normally de-energized, therefore it energizes during
“de-energized to trip” operation.
Disconnection of the NE Load is done on only one load supply line.
The following table describes the status (open or closed) of each output contact when the input signal is High or Low.
Safety Function and Failure behavior:
D5290S is considered to be operating in Low Demand mode, as a Type A module, having Hardware Fault Tolerance (HFT) = 0.
In the 2nd Functional Safety application, the normal state operation of relay module is energized, with NE (Normally Energized) loads.
In case of alarm or request from process, the relay module is de-energized (safe state), de-energizing loads.
The failure behaviour of the relay module is described by the following definitions:
□ fail-Safe State: it is defined as the output load being de-energized;
□ fail Safe: this failure causes the system to go to the defined fail-safe state without a process demand;
□ fail Dangerous: failure mode that does not respond to a demand from the process (i.e. being unable to go to the defined fail-safe state),
so that the output load remains energized.
□ fail “No effect”: failure mode of a component that plays a part in implementing the safety function but is neither a safe failure nor a dangerous failure;
When calculating the SFF this failure mode is not taken into account.
□ fail “Not part”: failure mode of a component which is not part of the safety function but part of the circuit diagram and is listed for completeness;
When calculating the SFF this failure mode is not taken into account.
Failure rate date: taken from Siemens Standard SN29500.
Failure rate table:
Failure rates table according to IEC 61508:2010 Ed.2 :
PFDavg vs T[Proof] table (assuming Proof Test coverage of 99%), with determination of SIL supposing module contributes ≤10% of total SIF dangerous failures:
PFDavg vs T[Proof] table (assuming Proof Test coverage of 99%), with determination of SIL supposing module contributes >10% of total SIF dangerous failures:
Systematic capability SIL 3.
Operation Input Signal
Pins 1-2 or 3-4
Pins
13 - 21
Pins
14 - 22
Pins
13 - 15
NE Load (SIL3)
Pins 14 — - / AC Supply
Service Load (Not SIL)
Pins 15 — - / AC Supply
Normal High (24 Vdc) Closed Closed Open Energized De-Energized
Trip Low (0 Vdc) Open Open Closed De-Energized Energized
Failure category Failure rates (FIT)
λ
dd
= Total Dangerous Detected failures 0.00
λ
du
= Total Dangerous Undetected failures 1.60
λ
sd
= Total Safe Detected failures 0.00
λ
su
= Total Safe Undetected failures 191.40
λ
tot safe
= Total Failure Rate (Safety Function) = λ
dd
+ λ
du
+ λ
sd
+ λ
su
193.00
MTBF (safety function, single channel) = (1 / λ
tot safe
) + MTTR (8 hours) 591 years
λ
no effect
= “No effect” failures 209.60
λ
not part
= “Not Part” failures 0.00
λ
tot device
= Total Failure Rate (Device) = λ
tot safe
+ λ
no effect
+ λ
not part
402.60
MTBF (device, single channel) = (1 / λ
tot device
) + MTTR (8 hours) 283 years
MTTF
S
(Total Safe) = 1 / (λ
sd
+ λ
su
) 596 years
MTTF
D
(Dangerous) = 1 / λ
du
71347 years
λ
sd
λ
su
λ
dd
λ
du
SFF
0.00 FIT 191.40 FIT 0.00 FIT 1.60 FIT 99.17%
T[Proof] = 1 year T[Proof] = 14 years
PFDavg = 7.01 E-06 - Valid for SIL 3 PFDavg = 9.81 E-05 - Valid for SIL 3
T[Proof] = 20 years
PFDavg = 1.40 E-04 - Valid for SIL 3
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