Installation of Ex isolation modules / Ex i isolation amplifiers

The mounting rail in the analyzer has a length of approximately 250 mm, with the number of installable components being limited.

The maximum installation height is approximately 95 mm; however, it is less in the area of the display (88 mm). The width must not exceed 80 mm.

The add-on devices must be approved for an ambient temperature of up to 60 °C; this temperature can be reached under extreme marginal conditions.

The label of the analyzer shows all types of explosion protection that the device itself and the components can have.

Installation must always be discussed with the competent experts.

Slots in the analyzer and the purging unit.

Ex i isolation amplifier, 7MB8000-3AB

The analog inputs and outputs of the analyzers are not intrinsically safe in the basic version.

The analog output can be supplemented later with an intrinsically-safe analog output (explosion protection type EEx ib II C or EEx ia II C). For this purpose, a suitable commercially available isolating transformer can be mounted on a rail in the device.

Technical data:

• Intrinsically-safe analog output
• mA isolating transformer without power supply
• For installing in the analyzer

Isolation amplifier, rail mounting

• Intrinsically-safe output EEx ia IIC
• Galvanic isolation

Technical data

Explosion protection

Isolating relay (signal outputs with external voltage supply) 7MB8000-4AA/-4AB

If the device has to be opened, it must be isolated at all poles from the mains cable, the binary inputs, relay outputs, analog inputs/ outputs, RS485 interface cable, and the PROFIBUS PA cables (not Ex i). For this purpose, isolating relays must be inserted. Intrinsically-safe circuits are excepted from this.

An isolating relay must be explosion-proof if it is to be set up in an area subject to explosion hazard.

Protective gas

• The fed-in gases are not flammable. Air from an area not subject to explosion hazard can be used as the protective gas (purging gas).
• Flammable gases or gas mixtures that are rarely or only briefly ignitable are fed in. The enclosure must be flooded with inert gas.
• Gas mixtures that are occasionally ignitable are introduced. As with b), the enclosure must be flooded with inert gas; in addition, the sample gas inlet and outlet must be equipped with flame arrestors.
• Explosive gas mixtures that are present in the long term or permanently must not be connected!

Flame arrestors

If the gas mixture to be measured sometimes has an explosive composition, flame arrestors must be installed in the sample gas inlet and, in certain circumstances, also in the sample gas outlet, in addition to the application already described with flammable sample gases.

The material of the flame arrestors must be resistant to the flow-type sample gas mixture. For this reason, they are available in two different versions:

• The detonation protection (Ex designation Ex IIG IIC) is used to prevent flashover in the case of unstable detonations and deflagrations of explosive gas or vapor/air mixtures of explosion group IIC.
• The flame arrestor consists essentially of a detonation-proof enclosure with gas connections and a ceramic sinter cartridge built into the housing (max. pore width: 80 µm) to prevent flashover.

It may be heated up to 150 °C and subjected to a pressure up to 3 bar (abs.).

Technical data

Differential pressure switch: 7MB8000-5AA

There must be a fail-safe guarantee that the sample gas pressure will never exceed 5 hPa under the purging gas pressure.

If this cannot be guaranteed on the plant side, a differential pressure switch must be mounted between the sample gas line and the purging gas line and connected electrically with the purging unit.

The differential pressure switch always has contact with the sample gas.

Technical data

• Differential pressure switch with magnetic spring contact
• Type 821.1
• Materials coming into contact with the sample gas: 1.4571
• Measuring range: -20 ... +20 hPa
• Trigger point: adjustable