Siemens SIPROCESS GA700 Compact Operating Instructions page 156

Connecting
4.3 Gas connections
Conditions
It is essential that you observe the following conditions for trouble-free operation:
● When tightening union nuts on the gas couplings, use a suitable open-ended spanner to
achieve correct counterlocking; otherwise the danger exists that the gas path will leak.
● If the protective gas is exhausted, the pressure drop over the exhaust air line at a flow of
60l/min must not switch off the Ex px safety equipment in the pre-purging phase or the
analyzer during the operating phase. To achieve this, the exhaust air line must be
dimensioned accordingly (e.g. the length of the exhaust air line may be about 20 m with an
internal diameter of G 1").
● The pre-purging time which can be set on the Ex px safety equipment (10 min with a
protective gas flow of 60 l/min) must not be undershot!
● Sample gas must not be supplied to the analyzer until the pre-purging phase has ended.
● OXYMAT 7: Before supplying sample gas, the microflow sensor must be safely purged by
reference gas. Therefore the reference gas must also be connected (pre-purging period =
10 min) when the Ex px safety equipment is switched on. The reference gas pressure must
always be 2 bar ± 0.1 bar above the sample gas pressure.
Ex px safety equipment
Example
If you are using Ex px or Ex pz safety equipment with the wall-mounted device, you will find
the information relevant for installation and operation in the corresponding manufacturer
documentation.
The electrical and pneumatic connection diagrams described in the sections below refer to the
example of the pressurized enclosure system "F870S-HD" distributed by
Gönnheimer Elektronik GmbH:
→ Figure 4-7 Pneumatic connection of the safety equipment - Example (Page 53)
→ Figure 4-8 Electrical connection of the safety equipment - Example (Page 54)
If you are using purging gas equipment from other manufacturers, contact your Siemens
service partner, if necessary.
Minimum requirements
In principle, any Ex px safety equipment with a type examination certificate to ATEX can be
used. This safety equipment must have at least the following features:
● A safety level of at least Category 3 to EN ISO 13849-1 for monitoring during pre-purging,
and a safety level of at least Category 1 to EN ISO 13849-1 for monitoring during operation,
or a transferable safety level from another comparable international standard.
● Adjustable pre-purging phase; protective gas flow must be ≥ 60 l/min
● Limiting of protective gas pressure during the pre-purging phase: < 100 hPa
● Connection of protective gas lines: 10 mm or 3/8" diameter from/to analyzer
● Inlet pressure for protective gas supply: 0.2 ... 0.4 MPa
50
Devices in explosion-proof design
Compact Operating Instructions, 05/2015, A5E35134047-02