nVent RAYCHEM Elexant 4010i/4020i User Manual
RAYCHEM-AR-H60624-40X0iOpsManual-EN-1905
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8. Check for ON: Measure the voltage to the heater at the limiter contactor output relay, to verify the
output is on.
9.
Install a wire bridge between TB1 position 10 and TB2 position 12 to simulate a short across the
limiter RTD (sensor). Wait about 10 seconds for the short to be detected.
10. Result: The red Alarm LED lights up and the Output LED of the unit switches off. The Safety Limiter
page shows “TRIPPED!” in the status box.
11. Check for OFF: Measure the voltage to the heater at the limiter contactor output relay, to verify the
output is off.
12.
Remove the wire bridge. Wait for 10 seconds for the temperature reading to return.
13.
Press the TRIP RESET button.
14. Clear the alarms.
15. The orange Output LED is now on, and the red Alarm LED is off.
16. Check for ON: Measure the voltage to the heater at the limiter contactor output relay, to verify the
output is on.
Clean up steps:
1. Return Intelligent Limiting to its original setting.
2. Return the control algorithm to its previous setting if it was changed to force the output on.
4.1.10 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 TRIP RESET button, check the RTD Status and Switch Status of
the Safety Limiter in the Safety Limiter’s Maintenance page, and any active alarms. 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 Section 1.3 for nVent Customer Care contact information.
4.1.11 Determining Safety Integrity of the Elexant 4020i-Mod-IS-LIM
The Elexant 4020i-Mod-IS-LI 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 4020i 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 4020i-MOD-IS-LIM:
SFF of an element
Hardware Fault Tolerance
0
1
2
< 60%
Not Allowed
SIL 1
SIL 2
60% - 90%
SIL 1
SIL 2
SIL 3
90% - 99%
SIL 2
SIL 3
SIL 3
≥ 99%
SIL 3
SIL 3
SIL 3
Table 12 - Maximum SIL for Type B with SC 2
The Elexant 4020i-MOD-IS-LIM is at HFT of 0, SIL2 (90% - 99%) for Type B safety-
related subsystems.
4.1.12 PFDavg Safety Function
The limiter temperature sensor, limiter electronics and the limiter relay 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 an external power contactor installed in a panel is specific to the installation, and shall in
accordance with the standards for the safety loop, be considered separately.
