Performance Checks; Equipment Required For Performance Checks - GasTech D-Guard2 Operator's Manual

Observe the system readings derived from the detector's current loop output signal and check that

they are as expected. For instruments other than those monitoring oxygen, the current loop signal
level should be near 4.00mA (no background gas present). Oxygen monitors will have a baseline
signal current at approximately 17.37mA to 17.38mA. If the controller system has measurement
scaling applied to the detector's current loop signal, then the 4mA baseline current would represent
0.00 for all detector types except oxygen. For oxygen monitors, the readings should equate to around
20.9% volume.
Check that the detector readings are stable and representative of expected surrounding gas

concentrations.
If problems are observed during the commissioning process, they must be addressed before the

installation can be completed and the detector put into service.

10.2. Performance Checks

After the installation has been verified and the system has been powered up for at least 1 hour (ideally several
hours allow the sensors to fully settle), a 'bump' test to verify the detector's response to target gas must be
carried out.
Bump-testing must only be carried out by suitably trained personnel under permitted site conditions.
Carrying out bump-testing using non-approved or site inappropriate equipment could create a hazard
situation and increase the risk of injury. All equipment must be approved for use at the site / area
where the detector is installed and must be used only as instructed in its operational manual by
appropriately trained personnel.
Bump test procedures involve the use of toxic gases. The gas concentrations used for test and
calibration purposes are considered non-harmful over the time period for which testing is likely to
occur. It is however, the responsibility of the personnel carrying out commissioning to ensure that all
relevant occupational health and safety regulations are observed and that proper gas handling
procedures are followed.
These tests must only be performed by suitably trained personnel. Gastech makes the assumption
that personnel carrying out any procedure given in this manual are fully competent in the
use of toxic gases, gas cylinders, regulators and piping/hoses.

10.3. Equipment Required For Performance Checks

Purge Gas: 100%v/v nitrogen or clean instrument air.

Target Gas: To match detector type. Optimally balanced in air or with an instrument air content.

Purge gas and target gas must be contained in an appropriate cylinder fitted with a suitable regulator

providing a flow rate of between 0.5 to 1.0 litres/minute.
Appropriate hoses must be fitted to the cylinder, which may include PTFE types for certain 'sticky' gas

types such as chlorine, ammonia, nitrogen dioxide etc.
Target gas concentration must not be greater than the instrument's full scale reading

Target gas minimum concentration must not be less than 25% of the detector's full scale reading.

Service Tool.

Detector calibration plug.

Suitably approved digital multimeter with a traceable calibration.

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D-Guard
handling and