nVent RAYCHEM Elexant 4010i/4020i User Manual
RAYCHEM-AR-H60624-40X0iOpsManual-EN-1905
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4.1.6
Main Output Interlock
When the safety limiter output is off, for any reason, an internal signal overrides the output of the main
output switch, to force it off. The main output can only be switched on if the limiter temperature sensor is
connected, and the measured temperature is below the limiter set point. There is no user action required
for this feature, and it cannot be disabled.
Although the limiter overrides the main output, the heater must be connected such that both outputs can
disconnect power from the heater. Bypassing one of these outputs does not allow the system to achieve
a SIL2 safety rating for this element.
4.1.7
Internal Diagnostic
The internal power to the limiter circuit is continually monitored by the limiter microprocessor. Any
detected instability is reported to the user via an alarm on the product GUI. There is no known effect
on the safety function in the presence of a detected power failure. As a precaution, if the limiter power
failure warning is persistent or recurring regularly, follow the instructions in Section 4.1.14– Response to
Fault Conditions.
4.1.8
Functional Test
The Elexant 4020i Safety Limiter units meet the requirements of SIL2 (see Section 4.1.12 PFDavg Safety
Function for more details) as set out in IEC61508:2010. In accordance with this standard, units are
subjected to a functional test after commissioning and at regular intervals, in order to guarantee safe
and reliable operation. The test interval for the safety limiter can be set to 1, 10 or 20 years, depending on
the application. The functional test procedure is described in Section 4.1.9 – Functional Test Procedure.
Conformance to the SIL certification is limited to the 20-year lifetime of the unit.
Type
Safety Integrity Level Systematic Capability
Proof Check Interval Unit Lifetime
4020i-Mod-IS-LIM
SIL 2
SC 2
1, 10, or 20 years
20 years
Table 11 - Functional Test
4.1.9
Functional Test Procedure
The functional test is performed after commissioning and at regular intervals over its operational
lifetime, to ensure it is still capable of carrying out its intended safety function. This check requires a
voltmeter capable of reading the output heater voltage, and a short length of wire (5 cm / 2 in).
Setup the functional test using these steps:
1.
Disable Intelligent Limiting.
2. Reset any limiter-related trips.
3. Clear all alarms.
4. Status on main screen of the GUI is “Normal”.
5.
Ensure the controller output (and the Output LED) are on. The Control Mode can be switched to
“Always ON” if required.
6. Setup check: Measure the voltage to the heater at the limiter contactor output relay, to verify the
output is ON.
Execute the functional test by performing the following steps:
1.
Disconnect one of the limiter RTD leads (sensors).
2. 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.
3. Check for OFF: Measure the voltage to the heater at the limiter contactor output relay, to verify the
output is off.
4.
Reconnect the limiter RTD (sensor). Wait about 10 seconds for the temperature reading to return.
5.
Press the TRIP RESET button.
6. Clear the alarms in the Alarms screen.
7. The orange Output LED is now on, the red Alarm LED is off.
