Functional Test; Functional Test Description; Functional Test Procedure; Test In The Event Of A Fault - nVent Raychem NGC-20-C-E Installations-, Betriebs- Und Wartungsanleitung

4.5 Functional test

The NGC-20-CL-E units are meeting the requirements of SIL2 (see paragraph 4.6 for more details) accordingly to IEC 61508-1:2000 and
IEC 61580-2:2000 In this standard is stipulated that in order to guarantee safe and reliable operation the units need to be subjected
to a functional test at regular intervals. In the case of the NGC-20 limiter this is set at 12 months (1 year) intervals. These tests must
be performed according to the guidelines provided. When the operational lifetime has expired, the systems no longer conform to the
requirements of their SIL certification.
Type
NGC-20-CL-E
Table 3: Functional test

4.5.1 Functional test description

In general the functional test always starts from the "normal" state, meaning that there should not be any alarms present on the unit
and that the limiter tripped LED (Lim Tripped) on the display of the unit should not be lit. In case the Lim Tripped LED is ON than the
unit should be reset before the functional test is being performed. Apart from the scheduled test intervals a functional test is to be
performed after every malfunction of the system and each time the limiter set point has been changed.

4.5.2 Functional test procedure

The following steps should be executed as part of the functional test:
• Disconnect one of the leads of the temperature sensor of the limiter RTD. (RTD 3 limiter)
• The red alarm LED "Lim tripped" should light up momentary and the output of the unit should switch OFF.
• Re-establishing the sensor connection has no immediate effect. Switch off the mains supply of the unit and leave the power off for
one minute. Powering up the unit again should not reset the limiter.
• After the Limiter reset button is been pressed the Lim Tripped alarm will go away and switch the output on. (Assuming the measured
temperature is below the set point temperature and there are no other faults)
• Install a wire bridge, short cutting the limiter sensor terminals marked with R+ and R- (RTD 3 Limiter)
• The red alarm LED "Lim tripped" should light up momentary and the output of the unit should switch OFF.
• Removing the wire bridge has no immediate effect.
• Switch off the mains supply of the unit and leave the power off for one minute. Powering up the unit again should not
reset the safety limiter.
• Only after the Limiter reset button has been pressed will the Lim Tripped alarm go away and switch the output on. (Assuming the
measured temperature is below the set point temperature and there are no other faults)

4.5.3 Test in the event of a fault

In the event of a system fault, the instrument switches off the load. This condition is indicated by the LED "Lim tripped" which will light
up. The fault is signalled simultaneously by the alarm relay which changes state. Press the reset button (at least 2 sec) until the "Lim.
Tripped" LED dims. If the safety circuit remains open, the system and the probe circuit have to be checked. Press the reset button again.
If the instrument remains inhibited after pressing the reset button the unit should be replaced.

4.6 Safety Integrity level

The safety integrity level of the NGC-20 is SIL2. The SIL level can be achieved by determining the following safety
related parameters:
1. PFDavg: The average probability of the hazardous failure of a safety function when it is demanded;
2. HFT: The hardware fault tolerance;
3. SFF: The fraction of non-hazardous (i.e. safe) failures
See for details on the NGC-20-CL-E table Table 4.
18 | nVent.com
SIL level
SIL 2
Proof check interval
1 year
Unit Lifetime
25 years