IEC 61779-4:1998 pdf download – Electrical apparatus for the detectionand measurement of flammable gases -Part 4: Performance requirements for group ll apparatus indicating a volume fraction up to 100 % lower explosive limit

IEC 61779-4:1998 pdf download – Electrical apparatus for the detectionand measurement of flammable gases -Part 4: Performance requirements for group ll apparatus indicating a volume fraction up to 100 % lower explosive limit.
1.1 This part of lEG 61779 specifies requirements for group II (as defined in part I) portable. transportable and fixed apparatus for the detection and measurement of combustible gas or vapour concentrations with air. The apparatus, or parts thereof. may be installed or used in potentially explosive atmospheres, other than mines susceptible to firedamp (I.e. group I). The requirements and test methods applicable to the apparatus covered by this standard are specified in part I –
1.2 This standard is restricted to apparatus intended for the detection and measurement of combustible gas or vapour concentrations with air up to 100% lower explosive limit (LEL).
2 DefinItions
For the purpose of this part of lEG 61779, the definitions given in part 1 apply.
3 General requirements
The apparatus shall comply with the general requirements specified In part I and with the performance requirements specified in clause 4 of this standard.
Compliance shall be determined in accordance with the appropiate test requirements and methods, Including Initial calibration, specified In part 1.
It shall be verified that the contents of the manufacturer’s instruction manual are In accordance with the requirements specified in part 1.
4 Performance requirements
4.1 General
The normal conditions for tests are specified in 43 of part 1. Compliance shall be determined in accordance with the test methods specified in 4.4 of part I.
4.2 Uripowered storage
Alter being submitted to the conditions specified in 4.4.2 of part I. the apparatus shall meet the requirements specified in 4.3 to clause 5 of this standard.
4.3 CalIbration curve (not applicable to alarm-only apparatus)
4.3.1 CalIbration curve
Alter Initial adjustment with the standard test gas, each Individual indication In the three sets of indications (after correction using the manufacturer’s calibration curve, if necessary) obtained br each of the four gas volume ratios distributed over the measuring range, shall not differ from these volume ratios by more than ±5 % of the measuring range or ±10 % of the indicahon. whichever is the greater.
4.3.2 Response to gases other than the test gas
The apparatus indication (after correction using the manufacturer’s calibration curves, if necessary) obtained for each of the three 9d5 volume ratios of each as tested shall not differ from these volume ratios by more than ±7% of the measuring range or ±15 % of the indication. whichever is the greater.
4.4 Stability (continuous duty apparatus)
Continuous duty apparatus shall comply with the following requirements.
a) short-term stability
The short-term variation shall not exceed ±5 % of the measuring range or ±10 % of the indication, whichever is the greater.
b) long-term stability (fixed and transportable apparatus)
The long-term variation shall not exceed ±10 % of the measuring range or ±30 % of the indication, whichever is the greater.
C) long-term stability (portable apparatus)
The long-term variation shall not exceed ±5 % of the measuring range or ±10 % of the indication, whichever is the greater.
4.5 Stability (spot-reading apparatus)
The variation of the indication shall not exceed ±5 % of the measuring range or ±10 % of the indication, whichever is the greater.
4.6 Alarm
The alarm(s) shall operate during every cycle of the test. If a latching alarm is provided, the manual reset action shall be checked.
4.7 Temperature
The variation of the indication from that at 20 °C, over the specified temperature ranges. shall not exceed the following:
a) for portable or transportable apparatus where the control unit and the sensor are used In the same general environment, the variation over the temperature range —10 C to +40 °C shall not exceed ±5 % of the measuring range or ±10 % of the indication, whichever is the greater. Tests shall be carried out at temperatures of —10 C, 20 C and 40 C;
b) for fixed apparatus with remote sensors, where the control unit and sensor are not used in the same general environment, the following temperatures shall be applied:
1) Sensors
With the control unit under normal ambient test conditions, the sensor shall be tested in air and In the standard test gas at —25 C and .55 C. The variation shall not exceed ±10% of the measuring range or ±20 % of the indication, whichever is the greater.
2) Control units
With the sensor under normal ambient test conditions, the variation at +5 °C and +55 C shall not exceed ±5 % of the measuring range or ±10 % of the indication. whiChever iS the greater.