Industrial Refrigeration Systems in Potentially Explosive Atmospheres

Introduction

Industrial refrigeration components are typically used in ammonia refrigeration systems. Some components are also used in related applications where locations are classified as hazardous areas. Danfoss has extensive experience supplying components to this business area, particularly in Europe. Due to new, more restrictive regulations, refrigeration components and systems must fulfill requirements for potentially explosive atmospheres as specified in the ATEX directive. Process Refrigeration Systems (PRS) are typically classified as hazardous areas, requiring ATEX compliance.

The ATEX 2014/34/EU directive is a European directive that specifies requirements for equipment intended for use in potentially explosive atmospheres. It is mandatory in all EU and EFTA member states.

Disclaimer

This application guide is based on European directives and standards to describe relevant solutions for industrial applications. Danfoss does not take responsibility for specific application solutions; the system designer is responsible for ensuring compliance with all relevant requirements.

Application Area for ATEX and Harmonised Standards

The ATEX directive and harmonised technical standards state requirements for:

• Design of equipment
• Manufacture of equipment
• Testing of equipment

Compliance with the ATEX directive ensures free movement of goods and equipment between EU member states and allows equipment to be put into service, provided there are no specific national requirements. The zone classification for the destination country must be approved by local authorities. If local authorities require a higher classification than the equipment is approved for, the system must not be used.

The ATEX directive does not cover operation; national laws apply when equipment is in use at the end-user's facility.

Gas Zones

Hazardous areas are classified into zones based on the likelihood of an explosive atmosphere being present:

Fig. 1 Gas zones

Scope of ATEX

The ATEX Directive includes:

• Mining and non-mining equipment
• Explosive atmospheres caused by gas and dust
• Electrical and non-electrical equipment
• Equipment (machines, devices, built-in instruments, mobile devices)
• Security systems (equipment that can stop/limit explosions)
• Components (parts without independent function)
• Security control and regulation devices used outside explosive areas that secure equipment in hazardous areas

The ATEX Directive excludes:

• Medical equipment for hospitals
• Equipment for use with explosive or unstable chemicals
• Household appliances and equipment for non-commercial surroundings
• Personal Protection Equipment
• Tankers and mobile offshore units
• Means of transport (except vehicles)

Equipment for mining industries and dust-related explosive atmospheres are not covered in this guide.

Non-mining equipment for potentially explosive atmospheres is classified into Equipment Group II, Categories 1, 2, and 3. Requirements depend on the equipment type.

Simple mechanical components like valves and filters, which do not contain potential ignition sources, are typically not covered by the ATEX directive. However, manufacturers must conduct and keep a risk assessment report to prove the equipment is safe.

Mechanical components with potential ignition sources, and electrically operated components, are covered by the ATEX directive and must be marked accordingly.

Fig. 2 ATEX requirements illustrate ATEX scope and related documentation.

The Explosion Triangle

The explosion triangle illustrates the principle of explosion, requiring fuel, oxygen, and an ignition source. Removing any one element eliminates the risk of explosion. In refrigeration systems, the risk of explosion is primarily considered for the exterior of the system. Internally, the system contains 100% refrigerant with no oxygen, thus posing no explosion risk.

Fig. 3 The explosion triangle.

The maximum concentration of flammable refrigerants in machinery rooms is limited, for example, to 20% of the Lower Flammability Limit (LFL).

Fig. 4 Flammable concentration, showing LFL and UFL for propane as an example.

Non-electrical and Electrical Equipment

Non-electrical Equipment

The risk analysis for non-electrical refrigeration equipment (valves, etc.) must focus on ignition sources. Risk assessments should be conducted according to EN/ISO 80079-36. Non-conductive materials (like plastic) that can create static electricity, magnesium content, and hot surfaces are potential ignition sources that must be analyzed and avoided. Simple components without these ignition sources are typically outside the ATEX directive's scope.

Electrical Equipment

Requirements for electrical equipment in hazardous areas are similar to previous legislation but more demanding. Two common methods of electrical protection are:

• Intrinsic Safety: This method ensures insufficient energy to cause ignition of a surrounding explosive atmosphere by an electrical spark or component heating. It is suitable for low power consumption equipment, often used for measuring devices.
• Encapsulation: Electrical components are fully encapsulated. This method is used for components with higher power consumption, like solenoid coils, but power consumption is also a limiting factor due to the risk of high surface temperature.

Fig. 5 Intrinsic safety protection method, illustrating EX-zone and Non-EX zone setups with Zener and isolation barriers.

Marking

Components within the scope of the ATEX directive must be CE-marked with the specific 'Ex' symbol. The marking details depend on the equipment type and include:

• CE mark
• CE Registration number of Notified Body
• Specific marking: Equipment Group (I or II), Equipment Category (1, 2, or 3), Nature of Atmosphere (G for Gas, D for Dust), Protection Type (e.g., 'd' for flameproof enclosure, 'm' for encapsulation, 'e' for increased safety, 'n' for non-flammable), Gas Group (IIA, IIB, IIC), Temperature Class (T1 to T6), and Protection Level (EPL Ga, Gb, Gc).

Fig. 6 Ex-marking details.

Documentation

Required documentation depends on whether the component has an ignition source. All ATEX-covered components must be supplied with a CE declaration of conformity. Non-electrical equipment without ignition sources, though not covered by the ATEX directive, requires a manufacturer's declaration confirming suitability and absence of ignition sources, along with a safety risk assessment.

Fig. 7 Documentation flowchart for ATEX requirements.

Equipment Group and Zones

Equipment in specified hazardous areas must meet certain requirements:

• Category 3 equipment: Suitable for Zone 2 and outside categorized areas.
• Category 2 equipment: Suitable for Zone 1, Zone 2, and outside categorized areas.
• Category 1 equipment: Suitable for Zone 0, Zone 1, Zone 2, and outside categorized areas.

Fig. 8 Category relations illustrating zone suitability.

Products Approved According to ATEX Directive

Danfoss offers various products approved according to the ATEX directive for different zones:

• Solenoid coil type BO and BZ: Approved for Zone 1 (Ex mb IIC T4 Gb).
• Pressure transducer type AKS 32, 32R, 33 & EMP2: Approved for Zone 2 (Ex nA IIA T3 Gc).
• Pressure transducer type MBS 4201 & 4251: Approved for Zone 0 (Ex ia IIC T6..T4 Ga).
• Gas detector Type GD Heavy Duty: Approved for Zone 1 (Ex db IIC T4 Gb).
• Pressure & Temperature switches RTxxxE: Approved for Zone 1 (Ex ia IIC T6..T1 Gb).

Fig. 9 Danfoss products approved according to ATEX directive.

Hazard Area Classification (Zone Classification)

Hazard area classification is a method of analyzing and classifying environments where explosive gas atmospheres may occur. It aims to determine the type of zone (0, 1, or 2) and the extent of the zone. Zone NE (negligible extent) may be used if ignition consequences are negligible.

Refrigerant systems are classified into zones based on risk. Factors influencing zone classification for flammable refrigerants include leak probability, leak rate, leak duration, leak form, leak pressure, refrigerant flammability levels, and ventilation rate.

For refrigeration systems, it's important to note:

• Potentially explosive atmospheres do not occur inside a refrigeration system due to the absence of oxygen (if designed and maintained per EN 378).
• Potentially explosive atmospheres can occur outside the refrigeration system.
• Systems with flammable refrigerants (e.g., Propane) require detailed assessment for possible leak sources.
• Systems with non-flammable refrigerants (e.g., CO₂) located in potentially explosive atmospheres do not increase the system's risk profile.

Note 1: The end-user is responsible for proper risk assessment and zone specification according to local legislation. The required ATEX approval level for components is defined by the zone requirements.

Note 2: Component manufacturers must document that their products released for use in potentially explosive atmospheres comply with requirements. For non-electrical equipment, an ignition assessment per EN ISO 80079-36 is required. For electrical equipment, an ATEX-type approval certificate valid for the application is necessary.

Common Standard for Determining Hazardous Zones Classification for Systems with Flammable Refrigerants

The common standard for determining hazardous zones classification is EN / IEC 60079-10-1. This standard involves several steps:

1. Identify sources of release.
2. Determine the release rate and grade of release based on frequency and duration.
3. Assess ventilation or dilution conditions and effectiveness.
4. Determine zone type based on release grade and ventilation/dilution effectiveness.
5. Determine the extent of the zone.

Typical release sources include leaks from flange connections, valve spindle seals, safety valves, and during servicing.

Note: EN/IEC 60079-10-1 provides formulas and tables for evaluating release rates and ventilation, which are helpful for system evaluation.

Sealing Materials

Special attention is needed for sealing materials, as some hydrocarbons are not compatible with commonly used O-rings. Propylene, for instance, is not compatible with CR-O-rings.

Fig. 10 Material compatibility (sealing material/O-rings).

Note 1: FPM O-rings are not available for temperatures below -40 °C.

Note 2: A '+' indicates compatibility; standard valves with Chloroprene O-rings can also be used.

ANNEX I: Equipment Groups and Temperature Classes - EXPLOSION PROOF SOLENOIDS

Electrical apparatus for hazardous areas are classified into groups (I for mining, II for non-mining) and subgroups (IIA, IIB, IIC) based on gas properties. Apparatus certified for a higher subgroup may be used in applications requiring a lower subgroup.

TEMPERATURE CLASS

Temperature classification is based on the maximum surface temperature of equipment. This temperature must be lower than the ignition temperature of the surrounding explosive atmosphere, with a safety margin.

¹⁾ The ignition temperature of a gas mixture must be higher than the maximum surface temperature, with a 10 to 20% safety margin.

The ignition temperature of dust clouds is generally 300-700 °C, while dust layers can ignite at lower temperatures (150-350 °C).

ANNEX II - Classification of Danfoss Industrial Refrigeration products

This annex provides an overview of Danfoss products, their compatibility with refrigerants, and ATEX approvals for different hazard areas and zones.

Note: Valve/refrigerant marked with (X) indicates compatibility; standard valves with Chloroprene O-rings can also be used.

ANNEX III - Manufacturer's declaration for potentially explosive atmospheres

This section contains a manufacturer's declaration from Danfoss A/S for industrial refrigeration products, confirming conformity with relevant directives and standards. It lists various valve types and their applicable refrigerants.

The declaration is valid for products listed and their released refrigerants as per Danfoss Product Store or Coolselector2.

Key Declarations:

• Stop Valves (SVA series): Conformity declared.
• Filters (FIA series): Conformity declared.
• Check Valves (NRVS, NRVA): Conformity declared.
• Pilot valve housing welded (CVH): Conformity declared.
• Regulating Valves (REG series): Conformity declared.
• Stop Check Valves (SCA series): Conformity declared.
• Check Valves (CHV series): Conformity declared.
• Overflow valves (OFV series): Conformity declared.
• Float Valves (HFI, SV series): Conformity declared.
• Pilots for ICS Valves (CVP series): Conformity declared.
• Safety Valves (SFA, SFV, BSV series): Conformity declared.
• Change Over Valves for Safety Valves (DSV): Conformity declared.
• Main Valves (ICS, ICLX, PMC): Conformity declared.
• Pilots for ICS Valves (EVM): Conformity declared.
• Electrically operated expansion valve (AKVA): Conformity declared.
• Solenoid Valves (EVRS, EVRST, EVRA, EVRAT): Conformity declared.

Valves with special O-rings compatible with specified refrigerants (Propylene):

• Main Valves (ICS 3E): Conformity declared.
• Pilot float valve (SV3E): Conformity declared.
• Pilots for ICS Valves (CVPE-M, CVPE-L, CVCE, EVME): Conformity declared.

For these valves, a hazard analysis confirms no potential ignition source under normal conditions, including malfunctions. These listed valves are not covered by the scope of ATEX Directive 2014/34/EU but can be used in categories II 3G (Zone 2) and II 2G (Zone 1).

Notes:

• Valves must be installed and maintained according to EN 378.
• End users should avoid electrostatic discharge.
• Electronic/Mechanical actuators/pilots require separate conformity assessment.
• Products are grouped based on refrigerant compatibility and sealing elements.

Reference to standards and directives: EN ISO 80079-36:2016, EN 378:2016.

ANNEX IV: Valves for HC-refrigerants

This annex lists specific Danfoss valves designed for Hydrocarbon (HC) refrigerants, along with their connector sizes, code numbers, and relevant pilot controls.

ANNEX V: ICS3E valves

Description: ICS3E valves are servo-operated valves belonging to the ICV (Industrial Control Valve) family. They are specifically designed for use with Hydrocarbon refrigerants and feature three pilot pressure connections.

Technical Data:

• Refrigerants: Selected HC, Propane R290, Propylene R1270, Ethane R170, Butane R600, Iso-Butane R600a.
• Temperature Range: -40 °C to 120 °C (-40 °F to 248 °F).
• Max. working pressure: 65 bar (943 psig).
• O-ring material: Fluorocarbon (Viton) compound for low-temperature applications.
• Marking: Valves are marked with the name "ICS3E". Dimensions and performance data are identical to the standard ICS (Literature no.: AI241186442033).

Material Specification:

ANNEX V: SV3E valves

Description: SV3E valves function as modulating liquid level regulators in refrigerating, freezing, and air conditioning systems for ammonia or fluorinated refrigerants. They are also suitable for Hydrocarbon refrigerants.

Technical Data:

• Refrigerants: Selected HC, Propane R290, Propylene R1270, Ethane R170, Butane R600, Iso-Butane R600a.
• Temperature Range: -40 °C to 120 °C (-40 °F to 248 °F).
• Max. working pressure: 28 bar (406 psig).
• O-ring material: Fluorocarbon (Viton) compound for low-temperature applications.
• Marking: Valves are marked with the name "SV3E". Dimensions and performance data are identical to the standard SV (Literature no.: AI175286419654).

Material Specification:

ANNEX V: CVPE valves

Description: CVPE valves are constant pressure pilot valves designed for high-pressure applications and are suitable for Hydrocarbon refrigerants.

Technical Data:

• Refrigerants: Selected HC, Propane R290, Propylene R1270, Ethane R170, Butane R600, Iso-Butane R600a.
• Temperature Range: -40 °C to 120 °C (-40 °F to 248 °F).
• Max. working pressure: 65 bar (943 psig).
• O-ring material: Fluorocarbon (Viton) compound for low-temperature applications.
• Marking: Valves are marked with the name "CVPE". Dimensions and performance data are identical to the standard CVP (Literature no.: AI248786497190).

Material Specification:

ANNEX V: CVCE valves

Description: CVCE valves are pressure-operated pilot valves with an external signal connection, used to indicate system reference pressure. They are suitable for Hydrocarbon refrigerants.

Technical Data:

• Refrigerants: Selected HC, Propane R290, Propylene R1270, Ethane R170, Butane R600, Iso-Butane R600a.
• Temperature Range: -40 °C to 120 °C (-40 °F to 248 °F).
• Max. working pressure: 65 bar (943 psig).
• O-ring material: Fluorocarbon (Viton) compound for low-temperature applications.
• Marking: Valves are marked with the name "CVCE". Dimensions and performance data are identical to the standard CVC (Literature no.: A1248786497190).

Material Specification:

ANNEX V: EVME valves

Description: EVME valves are pilot solenoid valves suitable for liquid, suction, and hot gas lines. They are also suitable for Hydrocarbon refrigerants.

Technical Data:

• Refrigerants: Selected HC, Propane R290, Propylene R1270, Ethane R170, Butane R600, Iso-Butane R600a.
• Temperature Range: -40 °C to 120 °C (-40 °F to 248 °F).
• Max. working pressure: 65 bar (943 psig).
• O-ring material: Fluorocarbon (Viton) compound for low-temperature applications.
• Marking: Valves are marked with the name "EVME". Dimensions and performance data are identical to the standard EVM (Literature no.: AI248786497190).
• Note: Solenoid coils must be EX approved.

Material Specification: