Extractive continuous process gas analytics

Use of series 6 in hazardous areas

Depending on the application, the measuring device can include the following parts:

• Analyzer with Ex approval
• Ex p safety equipment (purging unit)
• Flame arrestors with Ex approval
• Ex i isolating transformer
• Isolating relay with Ex approval

Gas analyzers

Suitability-tested field analyzers of series 6 must be used to measure gases in hazardous areas.

The series 6 analyzers are approved in accordance with Ex type of protection "Pressurized enclosure Ex p" for Zone 1 and Zone 2. In addition, these analyzers must be connected to monitoring equipment which must also be suitability-tested.

Following purging of 5 minutes, the checking equipment ensures that no gas fumes can enter the enclosure, and accumulation of the sample gas in the enclosure is prevented. The volume flow during the purging phase is > 50 l/min. The protective gas is usually fed into the analyzer enclosure from a supply network via the monitoring equipment.

Exception: A pressurized enclosure is not required in Zone 2 for the measurement of gases whose composition always remains below the lower explosive limit (25% of LEL); in this case, it is sufficient for the field housing to have the restrictive breathing enclosure type of protection (type of protection Ex n R).

Category ATEX II 2G (Hazardous Zone 1)

Two variants of the Ex p pressurized enclosure are available for use in Zone 1:

• Pressurized enclosure with leakage loss
  (Bartec Ex p purging unit for compensation of losses from leaks is no longer available for order as of July 2021)
  The principle of this type of protection is based on prevention of ingress of the surrounding atmosphere or of the sample gas into the enclosure of the electrical equipment through overpressure in the device.
  Only the volume of protective gas that is required to maintain an overpressure of at least 50 Pa (recommended 5 hPa) above the sample gas pressure and at least 50 Pa (recommended 5 hPa) above the atmospheric pressure is fed into the enclosure. The maximum purging gas pressure is 165 hPa; this results in a maximum permissible sample gas pressure of 164 hPa or 160 hPa.
  If the sample gas is flammable or occasionally combustible, the analyzer enclosure must be additionally purged with inert gas (e.g. nitrogen). In these cases, you must additionally ensure that the internal enclosure pressure is at least 50 Pa (recommended 5 hPa) higher than the fail-safe-regulated sample gas pressure.
  If the pressure control of the sample gas is not fail-safe (= "double fault safety"), but only operationally safe (="single fault safety"), a differential pressure switch of the Ex p safety equipment must be used externally to signal if the sample gas pressure exceeds the purging gas pressure. This measure initiates a safety shutdown.
  With occasionally flammable sample gas mixtures, flame arrestors must be additionally mounted externally at the sample gas input and output of the analyzer (for OXYMAT and CALOMAT).
  Both the differential pressure switch and the flame arrestors come into contact with the sample gas and must therefore be made of corrosion-resistant material, if applicable.
  Prototype test certificate: PTB 00 ATEX 2022 X
  Device marking: II 2 G Ex px [ia] IIC T4
• Pressurized enclosure with continuous purging
  The principle of this type of protection is based on having continuous purging of the Ex p enclosure after the purge. It prevents ingress of the surrounding atmosphere and ensures that, for example, sample gas released through leaks is thinned to the extent that a combustible mixture cannot be created. The volume flow of the protective gas is fixed at 1 l/min and exceeds the maximum release volume by a factor of more than 100.
  Protective gas flows continuously through the enclosure with a volume flow of at least 1 l/min; in addition, the flow ensures that the enclosure pressure is increased to at least 50 Pa (recommended 5 hPa) higher than the atmospheric pressure.
  The max. permissible purging gas pressure is 165 hPa. The max. permissible sample gas pressure is equivalent to the permissible analyzer sample gas pressure.
  Prototype test certificate: German Technical Inspectorate 01 ATEX 1708 X
  Device marking: II 2G Ex px ia [ia] IIC T6 or T4 or T3 Gb.

The purging gas is monitored using Ex p monitoring equipment: This is a stand-alone device which is connected electrically and pneumatically to the analyzer. Explosion protection is only provided when both devices are combined (analyzer and purging unit, and possibly further measures) (see below).

Category ATEX II 3G (Hazardous Zone 2)

Two variants complying with Directive 2014/34/EU (94/9/EC) are available for use in Zone 2.

• Explosion protection through restrictive breathing enclosure
  The enclosure is sealed sufficiently to prevent the ingress of gas fumes. With this degree of protection, only sample gases may be fed in which are below the LEL (25% of the LEL).
  Prototype test certificate: German Technical Inspectorate 01 ATEX 1686 X
  Device marking: II 3 G Ex nR IIC T6 or T4 Gc
  It is not necessary to install a purging unit here.
• Pressurized enclosure with continuous purging
  The principle of the type of protection "Pressurized enclosure for category 3 equipment" is based on the measure that the penetration of potentially explosive atmosphere into the gas analyzer is prevented.
  Protective gas continuously flows through the enclosure with a volume flow of at least 1 l/min; furthermore, the flow results in an overpressure in the enclosure of at least 50 Pa (recommended 5 hPa) compared to atmospheric pressure.
  The max. permissible purging gas pressure is 165 hPa. The max. permissible sample gas pressure is equivalent to the permissible analyzer sample gas pressure.
  Prototype test certificate: German Technical Inspectorate 01 ATEX 1697 X
  Device marking: II 2/3G Ex pz [ia Ga] IIC T6 or T4 or T3 Gb/Gc
  The purging gas is monitored using Ex p monitoring equipment. This is a stand-alone device which is connected electrically and pneumatically to the analyzer. Explosion protection is only provided when these two devices (analyzer and purging unit) are combined. (See Purging unit below)
  The electronics of the analyzer may be exempt from the simplified pressurized enclosure. Multiple simplified pressurized enclosures may be pneumatically installed in series if required.

Category ATEX II 3D (Hazardous Zone 22)

Zone 22 concerns the so-called dust protection. This is the European successor to the previous German Zone 11. Zone 22 concerns the area in which, during normal operation, it is not expected that potentially explosive atmospheres occur in the form of a cloud of flammable dust in the air. Should such a cloud occur, however, then only briefly.

Prototype test certificate German Technical Inspectorate 03 ATEX 2278 X.
They receive the Ex marking II 3D IP65 T60°C or T65°C or T82°C or T130°C.

With this degree of protection, only sample gases may be fed in which are below the LEL (25% of the LEL).

Purging requirements for the USA and Canada

The continuous analyzers from Siemens with approvals for Class I, Div 2 never require purging in a hazardous area in accordance with Class I, Div 2 / Zone 2 under the aspect of area classification. All electronic and mechanical components are classified as "non-explosive" and can be used in environments in accordance with Class I, Div 2 / Zone 2. However, purging may be necessary for a specific application, depending on the type of sample gas and the respective analyzer model, in order to comply with the NEC and NFPA standards and to guarantee maximum possible safety as well as protection of the system. Additional measures are required in this case in coordination with the supervising authority:

NFPA 496 requirements for continuous gas analyzers and systems from Siemens

The NFPA 496 "Standard for Purged and Pressurized Enclosures for Electrical Equipment" describes in great detail and clarity the requirements for purging and for the pressurized enclosure for electrical installations depending on 1) the external hazardous area classification, 2) the classification/grading of the system, 3) the type of gas in the gas path, and 4) the expected discharge of gas (none/limited/unlimited).

It is assumed for the internal gas path of a continuous gas analyzer that it exhibits only low losses under normal conditions and uncontrolled losses in the case of a mechanical failure (abnormal conditions).

When connecting gases with flammable components (> LEL) to the gas path of an analyzer with a hermetically sealed enclosure, the flammable component can accumulate in the inside of the analyzer enclosure – even under normal conditions – beyond a limit for continuous explosiveness and change the area classification (inside the analyzer enclosure) from "General Purpose" (Universal) or Class I, Div 2 / Zone 2 to Class I, Div 1 / Zone 0. This can also occur under abnormal conditions in any type of analyzer enclosure (including NEMA 1).

Analyzers for installation in the field – O6F, U6F and C6F – have a sealed enclosure (IP65 / NEMA 4 equivalent in accordance with IEC/EN 60529 and NEMA Standards Publication 250). Only a small natural exchange of air takes place with the environment. In accordance with NFPA 496, a limited discharge of gas is to be expected under normal conditions, and an unlimited discharge under abnormal conditions.

Analyzers for 19" rack mounting – O6E, U6E, U/O6, C6E, U23, O61, O64 and FID6 – have an "open" enclosure (IP20 in accordance with IEC/EN 60529, no exact NEMA equivalent for IP20 available). A high natural exchange of air takes place with the environment unless the exchange is restricted. In accordance with NFPA 496, no discharge of gas is to be expected under normal conditions, but an unlimited discharge under abnormal conditions.

In the case of devices designed for general applications, it is assumed that they can ignite a potentially explosive gas mixture at any time, and therefore no type of hazardous atmosphere whatsoever may be present in the vicinity of these analyzers or within the enclosure at any time.

It is assumed that devices designed for Class I, Div 2 / Zone 2 cannot ignite a potentially explosive gas mixture under normal conditions (single fault safety), and these analyzers can therefore be used in an occasionally explosive atmosphere in the environment or within the enclosure in accordance with the definition of Class I, Div 2 / Zone 2. However, a frequent or permanent explosive atmosphere must be avoided since a simultaneous error occurring on the electrical components of the analyzer could constitute an ignition source.

When purging a continuous gas analyzer or when purging/venting a continuous gas analyzer system suitable for Class I, Div 2 / Zone 2 with instrument air or ambient air, and if failure of the safety vessel is not obvious, a leak detector (measurement in % of LEL) or similar equipment should be used in order to detect unlimited discharges under abnormal conditions and to avoid a frequent or permanent explosive atmosphere inside the analyzer or in its environment. The leak detector must be fitted at a location where the escaping sample gas can be measured before becoming too greatly diluted. The alarm limit of the leak detector must be set to a level which enables detection of a dangerous state with consideration of the fact that the discharged sample gas has most probably already been diluted before it reaches the sensor.

Use of SIPROCESS GA700 in hazardous areas

SIPROCESS GA700, family

Depending on the application, the measuring device can include the following parts:

• OXYMAT 7, ULTRAMAT 7, CALOMAT 7 with Ex approval
• Ex p monitoring equipment (purging unit)
• Flame arrestors with Ex approval
• Ex ec enclosure for Ex-19" rack units (cannot be ordered from catalog)

Gas analyzers

Performance-tested SIPROCESS GA700 analyzers can be chosen for measuring oxygen in hazardous areas.

The SIPROCESS GA700 analyzers are approved in the 19" rack unit enclosure variant designed according to Ex type of protection "Increased Safety Ex ec". The analyzer must be installed in an enclosure that meets the requirements of type of protection "Ex ec" according to EN/IEC 60079‑0 and EN/IEC 60079‑7

The OXYMAT 7 is approved in the "wall box" version in accordance with Ex type of protection pressurized enclosure "Ex p" for Zone 1 and Zone 2.

In addition, these analyzers must be connected to monitoring equipment which must also be suitability-tested.

Following purging of 10 minutes, the monitoring equipment ensures that no gas fumes can enter the enclosure, and accumulation of the sample gas in the enclosure is prevented. The volume flow during the purging phase is > 60 Nl/min. The protective gas is usually fed into the analyzer enclosure from a supply network via the monitoring equipment.

A pressurized enclosure is not required for variants in type of protection "Increased Safety Ex ec" for Zone 2 for the measurement of gases whose composition always remains below the lower explosive limit (25% of LEL).

With the Ex-d field device, Siemens presents an ATEX-approved and IECEx-approved analyzer for Zone 1. The field device comprises a field control unit and a field module.

The field control unit is approved in type of protection Flameproof Enclosure "Ex d" with integrated electronics, a connection enclosure in type of protection Increased safety "Ex e" and a keyboard with intrinsically safe protection type "Ex i". The field module with the module is certified for the type of protection Flameproof Enclosure "Ex d".

Category ATEX II 2G and IECEx (Hazardous Zone 1)

Two enclosure variants complying with Directive 2014/34/EU are available for use in Zone 1.

• Pressurized enclosure with continuous purging with px monitoring system
  The principle of this type of protection is based on having continuous purging of the Ex p enclosure after the purge. It prevents ingress of the surrounding atmosphere and ensures that, for example, sample gas released through leaks is thinned to the extent that a combustible mixture cannot be created. The volume flow of the protective gas is fixed at 1 l/min and exceeds the maximum release volume by a factor of more than 100.
  Protective gas flows continuously through the enclosure with a volume flow of at least 1 Nl/min; in addition, the flow ensures that the enclosure pressure is increased to at least 50 Pa (recommended 5 hPa) higher than the atmospheric pressure.
  The maximum permissible purging gas pressure is 110 hPa. The maximum permissible sample gas pressure for non-flammable gases is 3 000 hPa (abs.), but for occasionally explosive gases (Zone 1 gases) only 1 100 hPa (abs.).
  • Prototype test certificate: BVS 14 ATEX E 153
  • IECEx Declaration of Conformity: IECEx BVS 14.0104X
  • Device marking: II 2G Ex pyb ib IIC T4 Gb (in conjunction with a px monitoring system)
    The purging gas is monitored using Ex p monitoring equipment. This is a stand-alone device which is connected electrically and pneumatically to the analyzer. Explosion protection is only provided when both devices are combined (analyzer and purging unit, and possibly further measures).
• Ex-d field device
  The gas analyzer is provided for the analysis of non-flammable and flammable gases.
  Ignitable parts are located in an enclosure which is designed such that, in the event of an ignition, flashover of the explosion into the environment is prevented.
  The maximum permissible sample gas pressure for non-flammable gases is 3 000 hPa (abs.), but for flammable and occasionally explosive gases (Zone 1 gases) only 1 100 hPa (abs.).
  • EC type-examination certificate BVS 15 ATEX E 038 X
  • IECEx Declaration of Conformity: IECEx BVS 15.0030X
  • Example of device marking: II 2G Ex db e ib IIC T4 Gb

Category ATEX II 3G and IECEx (Hazardous Zone 2)

Three enclosure variants complying with Directive 2014/34/EU are available for use in Zone 2.

• 19" rack unit type of protection "Increased Safety Ex ec"
  The analyzer does not contain an ignition source. It must be installed in an enclosure that meets the requirements of type of protection "Ex ec" according to EN/IEC 60079‑0 and EN/IEC 60079‑7 Enclosure und analyzer must comply with at least IP54 and pollution degree 2 when assembled.
  • Prototype test certificate: BVS 18 ATEX E084 X and BVS 15 ATEX E 007 X
  • IECEx Declaration of Conformity: IECEx BVS 15.0007X
  • Example of device marking: II 3G Ex nA nC ic IIC T4 Gc
• Wall box, Ex protection through degree of protection "Increased Safety Ex ec"
  The analyzer does not contain an ignition source. With this degree of protection, only sample gases may be fed in which are below the LEL (25% of the LEL). It is not necessary to install a purging unit here.
  • Prototype test certificate: BVS 14 ATEX E 153X, BVS 14 ATEX E154 X
  • IECEx Declaration of Conformity: IECEx BVS 14.0104X
  • Example of device marking: II 3G Ex ec ib nC IIC T4 Gc
• Pressurized enclosure with continuous purging with py or px monitoring system
  Protective gas continuously flows through the wall box with a volume flow of at least 1 Nl/min; furthermore, the flow results in an overpressure in the enclosure of at least 50 Pa (recommended 5 hPa) compared to atmospheric pressure. This means that flammable and potentially explosive gases can also be measured. The max. permissible purging gas pressure is 110 hPa.
  • Prototype test certificate: BVS 14 ATEX E 153 X
  • IECEx Declaration of Conformity: IECEx BVS 14.0104X
  • Example of device marking: II 2G Ex pyb ib IIC T4 Gb (in conjunction with a py or px monitoring system)
    The purging gas is monitored using Ex p checking equipment. This is a stand-alone device which is connected electrically and pneumatically to the analyzer. Explosion protection is only provided when both devices are combined (analyzer and purging unit, and possibly further measures). In the case of flammable sample gases or sample gases above the LEL (25% of the LEL), a py¹⁾ or px purge must be used.

Category ATEX II 3D (Hazardous Zone 22)

Zone 22 concerns the area in which, during normal operation, it is not expected that potentially explosive atmospheres occur in the form of a cloud of flammable dust in the air. Should such a cloud occur, however, then only briefly.

• Prototype test certificate: BVS 14 ATEX E 153 X
• IECEx Declaration of Conformity: IECEx BVS 14.0104X

Example of device marking:

• II 2G/3D Ex pyb ib IIIC/IIC T65°C Dc/Gb (in conjunction with a py¹⁾ or px monitoring system).
  Flammable and potentially explosive gases can be introduced.
• II 3D Ex tc ib IIIC T65°C Dc
  With these degrees of protection, only sample gases may be fed in which are below the LEL (25% of the LEL).

¹⁾ For the measurement of flammable gases, a px monitoring system (option -E72) is recommended, since with py purge monitoring it must be ensured that remedial action is taken immediately in the event of malfunction.

Additional safety mechanisms for continuous gas analyzers for measuring explosive gases (internal explosion protection) for series 6

Although the IEC and EN regulations IEC 60079-10, EN 60079-10 (gas) do not specifically define the terms seldom, occasional, frequent, and permanent, the following interpretation is customary:

• Frequent or continuous: > 1 000 hours per year
  → a frequent explosive atmosphere corresponds to Zone 0 or Class I, Div 1
• Occasional: 10 to 1 000 hours per year
  → an occasional explosive atmosphere corresponds to Zone 1 or Class I, Div 1
• Seldom: < 10 hours per year
  → a rarely explosive atmosphere corresponds to Zone 2 or Class I, Div 2

The following additional safety mechanisms are recommended for continuous gas analyzers for measuring explosive gases (internal explosion protection). These requirements are based on the European ATEX approvals for analyzers.

Further important information

Material of gas paths

It is strongly recommended that you use gas paths made of metal for applications with flammable gases since such gas paths offer the greatest safety. This particularly applies to analyzers or systems which are purged with instrument air or ambient air since a potentially explosive atmosphere can be produced under abnormal conditions.

Additional reasons for purging analyzers

• Corrosive sample gases: Purging with air or inert gas is necessary to prevent the accumulation of corrosive gas inside the analyzer, whereby operators or service engineers could be injured or the analyzer unit could be damaged. The discharged purging gas should be released at a non-critical point (collective vent etc.)
• Toxic gases: Purging with air or inert gas is necessary to prevent the accumulation of toxic gas inside the analyzer, whereby operators or service engineers could be injured. The discharged purging gas should be released at a non-critical point (collective vent etc.) More information can be found in the OSHA regulations for handling toxic materials.

Differentiation of cases: Hazardous zones/danger through flammable sample gas (series 6)

Ex configurations – Main selection criteria (series 6)

Additional units, selection criteria (ATEX 2G)

Differentiation of cases: Hazardous zones/danger through flammable and potentially explosive sample gas (SIPROCESS GA700, OXYMAT 7, ULTRAMAT 7 and CALOMAT 7)

Wall-mounted device

¹⁾ The above-mentioned purging monitoring in py mode is permissible according to the certificate, but is explicitly not recommended by SIEMENS. As a manufacturer, we generally recommend the use of a purge monitor in px operation. The py operation requires immediate intervention by the operator in the event of failure or insufficient purging, since the Ex p system only provides an alarm and no automatic shutdown.

²⁾ For the measurement of flammable gases, a px monitoring system (option E72) is recommended, since with py purge monitoring it must be ensured that remedial action is taken immediately in the event of malfunction.

The evaluation regarding possible zone displacement must be performed by the operator on site in all cases.

OXYMAT 7 field device

Rack unit

Use of OXYMAT 6 in hazardous area and/or for measurement of flammable gases

- Combination not allowed

X Possible combination, no additional data required

o Not required

Ex configurations, possible combinations

¹⁾ Required under certain conditions: See table of Ex configurations, selection criteria

²⁾ Installation in additional enclosure required

³⁾ When using flammable gases and only in coordination with relevant authority

⁴⁾ When used in hazardous zone 22, it is prohibited to purge the analyzer and no flammable gases may be introduced

Use of ULTRAMAT 6 in hazardous area and/or for measurement of flammable gases

- Combination not allowed

X Possible combination, no additional data required

o Not required

¹⁾ Required under certain conditions; see table of Ex configurations, selection criteria.

²⁾ Installation in additional enclosure required

³⁾ When using flammable gases, only in coordination with relevant authority

⁴⁾ When used in hazardous zone 22, it is prohibited to purge the analyzer and no flammable gases may be introduced

Use of CALOMAT 6 in hazardous area and/or for measurement of flammable gases

X Possible combination, no additional data required

- Combination not allowed

o Not required

Ex configurations, possible combinations

¹⁾ Required under certain conditions; see table of Ex configurations, selection criteria

²⁾ Installation in additional enclosure required

³⁾ When using flammable gases, only in coordination with relevant authority

⁴⁾ When used in hazardous zone 22, it is prohibited to purge the analyzer and no flammable gases may be introduced

Use of ULTRAMAT 23 in hazardous area and/or for measurement of flammable gases

- Combination not allowed

o Not required/not defined

¹⁾ Required under certain conditions

²⁾ Installation in additional enclosure required

Use of OXYMAT 7 in hazardous area and/or for measurement of flammable gases or potentially explosive gases

- Combination not allowed

X Possible combination, no additional data required

o Not required/not defined

¹⁾ Variant "G" only

²⁾ Installation in an IP54 enclosure according to EN/IEC 60079-0 and EN/IEC 60079-7 with defined air exchange rate according to BVS 15 ATEX E 007 X and IEC-Ex BVS 15.0007X

³⁾ Gönnheimer Ex p purge monitoring (px)

Use of ULTRAMAT 7 in hazardous area and/or for measurement of flammable gases or potentially explosive gases

- Combination not allowed

X Possible combination, no additional data required

o Not required/not defined

¹⁾ Variant "G" only

²⁾ Installation in an IP54 enclosure according to EN/IEC 60079-0 and EN/IEC 60079-7 with defined air exchange rate according to BVS 18 ATEX E 084 X; BVS 15 ATEX E 007 X and IEC-Ex BVS 15.0007X

³⁾ Gönnheimer Ex p purge monitoring (px)

Use of CALOMAT 7 in hazardous area and/or for measurement of flammable gases or potentially explosive gases

- Combination not allowed

X Possible combination, no additional data required

o Not required/not defined

¹⁾ Variant "G" only

²⁾ Installation in an IP54 enclosure according to EN/IEC 60079-0 and EN/IEC 60079-7 with defined air exchange rate according to BVS 18 ATEX E 084 X; BVS 15 ATEX E 007 X and IEC-Ex BVS 15.0007X

³⁾ Gönnheimer Ex p purge monitoring (px)

Overview of the Ex certificates (series 6)

CP = Continuous Purging

LC = Leakage compensation

… -S = Special application

burn. = Flammable gases

nbrn. = Non-flammable gases

o = In progress

The certificates are available for download free-of-charge in various languages at:http://www.siemens.com/processanalytics/documentation