Compex - Protection Types

Question 1

What is Ex d protection?

Answer 1

Ex d — Flameproof (Explosion-proof)

Principle: Enclosure withstands an internal explosion and cools escaping gases so they don’t ignite the outside atmosphere.

Question 2

What is Ex e protection?

Answer 2

Ex e — Increased Safety (now Ex eb for Zone 1, Ex ec for Zone 2)

Principle: Prevents arcs/sparks and limits temperature by design.

Use: Terminals, junction boxes, luminaires, drivers.

Question 3

What is Ex i protection?

Answer 3

Ex i — Intrinsic Safety (Ex ia/ib/ic)

Principle: Limit energy (U/I/C/L) so no spark or hot surface can ignite.

Grades: ia (Zone 0), ib (Zone 1), ic (Zone 2).

Use: Instrumentation loops, transmitters, HMIs, field sensors.

Question 4

What is Ex p protection?

Answer 4

Ex p — Pressurization/Purging (Ex pxb/pyb/pzc)

Principle: Maintain protective gas overpressure or purge flammable gas/dust from an enclosure.

Use: Large panels, analyzers, motors.

Notes: Monitoring of pressure/purge time; interlocks/alarms usually required.

Question 5

What is Ex m protection?

Answer 5

Ex m — Encapsulation (Ex ma/mb/mc)

Principle: Potting compound encapsulates ignition-capable parts.

Use: Coils, solenoids, small electronics.

Notes: Good for compact devices; repairs typically not permitted.

Question 6

What is Ex n protection?

Answer 6

Ex n (legacy Zone 2 concept) — migrated in modern standards:

Ex nA Non-sparking → Ex ec
Ex nL Energy-limited → Ex ic
Ex nR Restricted-breathing → Ex nr

Use: Zone 2-only equipment; check latest marking.

Question 7

What is Ex q protection?

Answer 7

Ex q — Powder/Quartz Filling

Principle: Fill enclosure with powder to quench arcs/sparks.

Use: Instrument transformers, capacitors.

Question 8

What is Ex o protection?

Answer 8

Ex o — Oil Immersion

Principle: Live parts submerged in oil to prevent ignition.

Use: Transformers, some switchgear.

Notes: Niche; maintenance must preserve liquid integrity.

Question 9

What is Ex op protection?

Answer 9

Ex op — Optical Radiation (for fiber optics)

Ex op is (intrinsically safe), Ex op pr (pressurized), Ex op sh (interlocked/contained beam path).

Use: Fiber systems in Ex areas

Question 10

What are the types of protection allowed in gas zone 0?

Answer 10

• Intrinsic safety: Ex ia
• Encapsulation: Ex ma
• Optical (inherently safe): Ex op is
• Special protection: Ex s (if certified as Ga)

Question 11

What is Ex s protection?

Answer 11

Ex s — Special Protection (IEC 60079-33)

Principle: Certified by special assessment where no existing type fits.

Use: Unique equipment; rely on certificate details.

Question 12

What are the types of protection allowed in gas zone 1?

Answer 12

• Flameproof: Ex d
• Increased safety (Zone 1 level): Ex en
• Intrinsic safety (Zone 1 level): Ex ib
• Encapsulation (Zone 1 level): Ex mb
• Pressurization/purging (Zone 1 level): Ex pxb, Ex pyb
• Powder filling: Ex qb
• Oil immersion: Ex ob
• Optical (protected or interlocked): Ex op sh, Ex op pr
• Special protection: Ex s (certified as Gb)

Question 13

What are the types of protection allowed in gas zone 2?

Answer 13

• Increased safety (Zone 2 level): Ex ec (modern replacement for Ex nA)
• Intrinsic safety (Zone 2 level): Ex ic
• Encapsulation (Zone 2 level): Ex mc
• Pressurization/purging (Zone 2 level): Ex pzc
• Oil immersion (Zone 2 level): Ex oc
• Powder filling (Zone 2 level): Ex qc
• Restricted breathing / flow restriction: Ex fr (modern replacement for Ex nR)
• “Ex n” legacy types (e.g., nA, nC, nR) may appear on older equipment; today these map mainly to Ex ec or Ex fr.