Functional Test; Functional Test Description; Functional Test Procedure - Raychem NGC-40-SLIM Manual

3�8 Functional test
The RAYCHEM NGC-40-SLIM units meet the requirements of SIL2 (see paragraph
3.13 for more details) accordingly to IEC 61508-1:1998 and IEC 61508-2:2000.
In this standard it 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 RAYCHEM NGC-40-SLIM 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 SIL level
NGC-40-SLIM 2
Table 4: Functional test
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.
3�9 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 the Limiter tripped LED
("Trip") on the display of the unit should not be lit. In case the Limiter tripped LED is
ON then the unit should be reset before the functional test is performed.
3�10 Functional test procedure
The following steps should be executed as part of the functional test. Repeat this
test for all sensors connected to the limiter module.
• Disconnect one of the leads of the temperature sensor of the limiter RTD.
• The red alarm LED "Trip" should light up 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 "Trip Reset" button is been pressed, the Limiter 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
• The red alarm LED "Trip" should light up 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 Limiter 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)
• Disconnect the RTD(s) from NGC-40-SLIM module.
• The red alarm LED "Trip" should light up and the output of the unit should
switch OFF.
• Connect decade boxes to the RTD terminals to simulate the measured
temperature. (The decade box simulates the resistance of the PT100 sensor)
• Set each of the decade box resistance values below the trip point resistance
value (for a relationship between PT100 resistance value and temperature curve
see appendix A).
• Reset the limiter. The limiter trip alarm will go away and switch the output on.
• Increase the resistance of decade box 1 up till 5 degrees below the limiter trip
point. The limiter shall not trip.
• Increase the resistance of decade box 1 slowly to 5 degrees above the limiter
trip point.
• The red alarm LED "Trip" should light up and the output of the unit should
switch OFF.
• Decrease the resistance of decade box 1 slowly to 5 degrees below the
limiter trip point.
Proof check Unit Lifetime
interval
1 year 25 years
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