Atest Gaz Sigma SmArt, User Manual

Page: 12 / 84

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in the case of reactive substances – such as HCl, Cl
2
– note the danger of adsorption of a particular
substance on the sensor surface, particularly in humid environments,
the probability of deposition of dust, grease and other "clogging" substances, especially on the
sinter of the gas inlet to the measuring chamber, which may lead to the inhibit of the detector,
probability of occurrence of hot vapours of liquid substances at ambient temperature – which
constitutes a danger of condensation of this substance on the sensor – as a result, it may lead to
the inhibit of the detector,
ambient temperature – ambient temperature should be in line with the values declared by the
manufacturer (or see table 7). Especially during the start-up of the technological installation and in
the case of technological failures, attention should be paid to whether there is any temporary
exceeding of the temperature range, and when it occurs – please contact the manufacturer,
if the detector operates at an ambient temperature higher than the maximum permissible
ambient temperature, the efect may be twofold:
• a thermal detector failure can occur, or
• the detector may become a potential source of ignition for potentially explosive atmospheres,
danger of flooding the detector with water or other substance – it may lead to the inh ibit of the
detector,
when mounting on the outside of the building the detector should not be exposed to direct
environmental conditions, it is necessary to apply the relevant water-splash shield or weather
housing,
the oxygen content in the environment – especially in the case of catalytic detector (pellistor
type), oxygen content less than 18% significantly reduces the sensitivity of the detector.
On the other hand, it should be borne in mind that the admission of explosion-proof equipment
concerns atmospheres of oxygen concentration up to 21%. In larger concentrations the device
loses its explosion-proof properties and can become a source of ignition.
the presence of other gaseous substances which can cause:
• false alarms – e.g. the presence of aerosols in the case of semiconductor gas detectors – see
appendix [4],
• pollution of the detector – e.g. the presence of silicone can cause damage to catalytic detector
– see appendix [5],
• crossover efect – the sensor also reacts to other gases, e.g. an electrochemical sensor of
carbon monoxide can also react with hydrogen – see appendix [6],
• masking efect – a reaction of the sensor to the working gas can be reduced in the presence of
other interfering gases (e.g. in the presence of nitrogen dioxide, the sensor of sulphur dioxide
reacts weaker to the working gas).
vibrations – may reduce the explosion protection, therefore, in case of such a situation, it is
necessary to include appropriate recommendations for more frequent inspections in the project
documentation (e.g. more frequent survey inspections of the extent corresponding to visual
inspections up close are recommended).
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User's Manual: POD-009-ENG R07