Types of protection

Information about the use of the markings
The markings used below for non-electrical equipment and dust explosion protection are still under discussion. For this reason they have to be treated as provisional.

• Mechanical strength in accordance with a defined safety factor to withstand internal explosion pressure
• As an orientation value, it may be assumed that inside the sphere approx. 0.8 MPa (8 bar) can be generated and that this sphere used as an EEx d enclosure must be able to withstand a pressure of 1.2 MPa (12 bar).
• Any gap between two parts of the enclosure must be kept so narrow and long that hot gas flowing out will not be able to ignite any potentially explosive atmosphere which may be present in the explosion hazard zone.
• The parameters for the gaps preventing the transmission of the ignition, width/length, are different for the explosion hazard subgroups II A, II B and II C. The most stringent requirements with regard to the gap parameters apply to enclosures in explosion hazard subgroup II C.

Applications

• Equipment where, during normal operation, sparks, electric arcs and/or hot surfaces are generated such as switchgear, slip rings, collectors, adjustable resistors, fuses or lamps, andheating cartridges.

The following LEUZE sensors are suitable for such applications:

• ILS 50 (category II 2G / II 2D)
• COMPACT EX1 (category II 2G / II 2D)
  
  

Important design parameters

• Free internal volume ≤20 cm³
• The encapsulation must permit a permanent temperature of the ≥10 K compared to the maximum operating temperature
• Limited to AC 690 V and 16 A.

Applications

• Contact systems
  
  

Important design parameters

• Free internal volume ≤20 cm³
• The encapsulation must permit a permanent temperature of ≥10 K compared to the maximum operating temperature
• The combination of the parts is tightly sealed or
• The design of the contacts will extinguish any incipient flame
• Limited to AC 254 V and 16 A.
• L and C are part of the test.
• Explosion hazard subgroups II A, II B and II C are to be treated differently.

Applications

• Contact systems
  
  

• Housing strength; the enclosing, flushed housing must withstand 1.5 times the overpressure experienced during normal operation.
• Flush before commissioning the electrical equipment.
• Shut-down or alarm if the flushing gas flow or overpressure fails.

Applications

• Equipment where during normal operation sparks, electric arcs or hot surfaces are generated and complex industrial equipment (controls) which must be operated in explosion hazard zones protected by this type of ignition protection.
• Large machines, slip ring or collector motors, switch cabinets and control cabinets and analytical apparatus.
  
  

Important design parameters

• The important difference from the pressurised enclosure is the restriction to a housing where no internal sources are available and no flammable gases or vapours can be released.
• Housing strength.
• Flush before commissioning the electrical equipment.
• Shut-down or alarm if the flushing gas flow or overpressure fails.

Applications

• Equipment where during normal operation sparks, electric arcs or hot surfaces are generated and complex industrial equipment (controls) which must be operated in explosion hazard zones protected by this type of ignition protection.
• Analytical apparatus without internal sources.
  
  

• The filling such as sand, glass balls etc. has to fulfil specific requirements, as must the housing design. The filling must not be able to leave the housing, neither during normal operation, nor as the result of electric arcs or other processes inside the powder-filled enclosure.

Applications

• Capacitors, electronic assembly groups or transformers which are used in an explosion hazard zone. Often components where sparks or hot surfaces occur but whose functioning is not affected by the finely grained filling.
  
  

• Stipulated, insulating liquids, e.g. oil
  Protection of the liquid from contamination and moisture.
• Assurance and possibility of monitoring that the oil level is safe
  - when heated up or cooled
  - for identification of leaks
  
• Restricted to non-portable devices

Applications

• Large transformers, switchgear, starting resistors and complete starting controllers.
  
  

• For uninsulated, live parts, special protective requirements apply.
• Air and creepage gaps are made wider than is generally the case in industry.
  Special conditions apply to the IP protection degree to be adhered to.
• For windings, their construction, mechanical strength and insulation, higher requirements apply and the windings must be protected from increased temperatures.
• Minimum cross sections are stipulated for winding wire, the impregnation and reinforcement of coils and for thermal monitoring devices.

Applications

• Installation material such as junction boxes, connection cabinets for heating systems, batteries, transformers, ballasts and cage motors.
  
  

Important design parameters

• For uninsulated, live parts, special protective requirements apply.
• Air and creepage gaps are specified.
• Special requirements must be fulfilled by certain types of equipment.

Applications

• Installation material such as junction boxes, connection cabinets, rotating electrical machines, special fuses, lamps, cells and batteries, transformers and low energy equipment.

The following LEUZE sensors are suitable for such applications:

• BR 96 EX n (category II 3G / II 3D)
• PKR 18 (category II 3G / II 3D)
• KONTURflex EX (category II 3G / II 3D)
• COMPACT EX2 (category II 3G / II 3D)
  
  

• Encapsulation:
  - Breakdown strength
  - Low water absorption
  - Resistance to various influences
  - Potting must be of the stipulated thickness all round
  - Cavities are only permitted to a limited extent
  - As a rule the potting is only penetrated by the cable entries
  
• The load on the components is limited or reduced
• Increased clearance between live parts

Applications

• Static coils in ballasts, solenoid valves or motors, relays and other control gear, of limited power and complete PCBs with electronic circuits.
  
  

Important design parameters

• Sealed by means of a melting process e.g.:
  - Soft solder
  - Hard solder
  - Welding
  - Fusing of glass and metal

Applications

• Spark generating equipment
  
  

Important design parameters

• It must be impossible to open the equipment during normal operation, internal free volume ≤100 cm³
• External connections, terminals or cables must be available
• Cast seal must permit permanent operating temperature ≥10 K compared to the maximum operating temperature
• It must not be possible for elastic seals to become mechanically damaged under normal operating conditions; they must maintain their sealing properties over the service life of the equipment

Applications

• Contact systems, static coils in ballasts, solenoid valves or motors and complete PCBs with electronic circuits.
  
  

Important design parameters

• It must be impossible to open the equipment during normal operation, internal free volume ≤100 cm³
• External connections, terminals or cables must be available
• It must not be possible for elastic seals to become mechanically damaged under normal operating conditions; they must maintain their sealing properties over the service life of the equipment

Applications

• Contact systems, static coils in ballasts, solenoid valves or motors and complete PCBs with electronic circuits.
  
  

Important design parameters

• Minimum degree of protection in accordance with IEC/EN 60529 ? IP 6X
• Consideration of dust accumulating on the surface and reduction of permissible surface temperature with dust layer ≥5 mm are possible.

Applications

• Various equipment where during normal operation sparks, electric arcs or hot surfaces occur and complex industrial designs (controllers) which by means of this type of ignition protection can be utilised in explosion hazard zones.
  
  

• Use of certain components for electrical and electronic circuits
• Lower permitted load on the components than in ordinary industrial applications with regard to
  - voltage related to electric strength
  - current related to heat
• Voltage and current, including a safety margin, are kept permanently so low that no impermissible temperatures can occur, and, in the event of open circuit or short-circuit, sparks and electric arcs possess so little energy that they are unable to ignite a potentially explosive atmosphere.
• An impression of this protection type is provided by the fact that potentially explosive atmospheres of subgroup IIA require only a few hundred µW and those of subgroup IIC only 10µW for ignition.

Applications

• Measuring and monitoring instrumentation and control
• Sensors working on the basis of physical, chemical or mechanical principles and at limited power
• Actuators working on the basis of optical, acoustic and, to a certain extent, mechanical principles.

The following LEUZE sensors are suitable for such applications:

• BR 92 Ex (category II 2G / II 3D)
  
• VS 403 (category II 3G / II 3D)
  
  

Important design parameters

• The requirements to be fulfilled by the circuit and the loads on the components are lower than those for the intrinsic safety type of ignition protection.
• Also with regard to errors, lower requirements apply.

Applications

• Measuring and monitoring instrumentation and control
• Sensors working on the basis of physical, chemical or mechanical principles and at limited power
• Actuators working on the basis of optical, acoustic and, to a certain extent, mechanical principles.
  
  

Important design parameters

• The powerloss in the housing may, if it contains sparking components, only lead to a temperature increase compared to the surrounding of ≤10 K.
• Equipment with these housings must allow monitoring of the vapour tightness and tightness after installation and maintenance.
• The allocation to the temperature class by the external surface temperature applies to all housings with and without sparking components.
• It must not be possible for elastic seals to become mechanically damaged under normal operating conditions; they must maintain their sealing properties over the service life of the equipment.
• Cast seals must permit a permanent operating temperature ≥10 K compared to the maximum operating temperature

Applications

• Switchgear, measuring and monitoring instrumentation and information systems and devices
  
  

Important design parameters

• The requirements for the housing material are the same as for the other types of protection. (see e.g. EN 50014)
• The components have to be selected in such a way that heat generation e.g. from friction is not possible.
• The friction occurring during normal operation must not lead to electrostatic charging or spark generation.
• The constructive requirements should be checked with regard to possible ignition sources similarly to that described for EN 1127-1.

Applications

• Currently only few experiences are available, as this standard is only available as a draft.
  
  

Important design parameters

• Under construction - must be observed.

Applications

• None yet known on the basis of the current development of the standard.