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11. Check for OFF: Measure the voltage to the heater at output terminals Lo and No, to verify the output is off.
12. Remove the wire bridge. Wait for 10 seconds for the temperature reading to return.
13. Press the RESET button.
14. Clear the alarms.
15. The HEATER LED is now on, and the ALARM and LIMITER LEDs are off.
16. Check for ON: Measure the voltage to the heater at output terminals Lo and No, to verify the output is on.
Clean up steps:
1. Return the control algorithm to its previous setting if it was changed to force the output on.
3.1.9 Test in the event of a fault
In the event of a system fault, the device is designed to fail safe whenever possible. If the limiter output does not close, even after
pressing the RESET button, check the Status of the Safety Limiter, and any active alarms in the supervisory software. If no issues
are indicated in these locations, or the error cannot be resolved by the installer, the unit may need to be replaced. See last page of
installation manual for contact information.
3.1.10 Determining safety integrity of the Elexant 5010i-LIM
The Elexant 5010i-LIM is a Type B system, as defined in IEC61508-2:2010. A sub-system is a Type B system when all of the following
apply:
1. The failure mode of at least one component that is used is not adequately defined.
2. The response of the sub-system in fault conditions cannot be completely determined.
3. No adequately reliable failure data, based on field experience is available for the subsystem, to support the assumed failure rates for
recognized and unrecognized hazardous failures.
The Elexant 5010i Limiter variant meets the requirements for Systematic Capability (SC) 2. The following table presents the achievable
Safety Integrity Level (SIL), depending on the Safe Failure Fraction (SFF) and the Hardware Fault Tolerance (HFT) for Type B safety-
related subsystems. The table below is valid for the Elexant 5010i-LIM:
SFF of an element
Hardware Fault Tolerance
0
< 60%
Not Allowed
60% - 90%
SIL 1
90% - 99%
SIL 2
≥ 99%
SIL 3
Table 3 - Maximum SIL for Type B with SC 2
The Elexant 5010i-LIM is at HFT of 0, SIL2 (90% - 99%) for Type B safety-related subsystems.
3.1.11 PFDavg safety function
The limiter temperature sensor and limiter electronics together form the safety related system that performs the safety function.
The "average probability of the hazardous failure of a safety function for the entire safety related system" (PFDavg) is divided among
the subsystems. An external device such as the temperature sensor, is specific to the installation, and shall in accordance with the
standards for the safety loop, be considered separately.
Type
SIL
1
Elexant 5010i-LIM
SIL 2
Table 4 - Safety Integrity Level
SIL = Safety Integrity Level
1
MTTR = Mean Time to Repair
2
HFT = Hardware Fault Tolerance
3
SFF = Safe Failure Fraction
4
1oo1 = One out of One
5
PFD = Probability of Failure on Demand
6
Architecture
MTTR
(hrs)
2
1oo1
8
5
1
SIL 1
SIL 2
SIL 3
SIL 3
Proof Check
HFT
SFF
Interval (years)
3
4
1
0 (1oo1)
97%
10
5
20
2
SIL 2
SIL 3
SIL 3
SIL 3
PFD
avg.
6
8.30E-05
8.18E-04
1.63E-03
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