5 Operation
During operation there is very little to do with the detector other than performing the regular
Function test of the detector and cleaning of lens and mirror if dirty. The cleaning of the lens
and mirror is described in the chapter Maintenance and Function test is explained in the next
chapter.
5.1 Function test
Function test of the Detector can be performed by applying gas or using the Gas Free test kit.
This is a simple test carried out to make sure the gas detector will respond when exposed to
gas, often referred to as Bump testing the Detector. This test is typically performed on a
regular basis to verify the Safety Functions of the Detector. The bump test is used to confirm
the detector is responding to gas presence and generating the correct outputs as prescribed.
The Operator can select from one of the methods described below depending on the
configuration of the detector and local preferences.
It is recommended to perform the Function test in non-condensing ambient conditions.
Proof Test interval
The time between two periodical tests of the Detector Safety Function is from a Safety context
called the Test Interval. PG11 is certified in accordance with the standard IEC 61508 with a
SIL2 rating. If used in an 1oo2 configuration the PG11 is rated for SIL3.
A gas being released from a Gas cylinder will give a very small “gas cloud” that will be
diluted very quickly. This is challenging when testing a gas detector since the gas
reaching the gas detector will have a much lower concentration compared to what is
on the Gas cylinder. Especially if there are windy conditions it can be challenging to get
any gas to the detector with a small amount of gas coming from a Gas cylinder.
Therefore precautions have to be taken when testing a detector to get valid results.
For example using a 50 %LEL test gas and injecting it at 2 liters/min into a PG11 fitted
with Environment Shield using the “Gas test kit”, can result in a gas reading as low as
20 %LEL if there is windy conditions.
Please refer to the chapter “5.2 Perform a check of the Gas Detector accuracy” if a more
precise test is required.
Document 022-80036-OM Revision R03 Page 22 of 48
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