CompEx Practice Exam - Hazardous Area Certification and Safety

Comprehensive Question and Answer flashcards derived from the CompEx practice examination notes covering ATEX directives, Ex concepts, cable installation, ingress protection, temperature classes, and inspection standards.

What is the primary objective of European Directive ATEX 95?

To remove technical barriers to trade between member nations of the European Union.

Under ATEX 95 Directive, which equipment group and categories apply to non-mining gas or dust hazards?

Group II, Categories 1, 2, or 3.

What does the European Directive ATEX 95 specifically govern?

The design of equipment for use in potentially explosive atmospheres.

How does the installation standard BS EN60079-14 relate to IEC60079-14?

BS EN60079-14 is identical to IEC60079-14.

Which standard governs the installation of new equipment in potentially explosive gas atmospheres?

IEC60079-14.

Into which gas sub-division does Hydrogen fall?

IIC.

Into which gas sub-division does Acetylene fall?

IIC.

Into which gas sub-division does Ethylene fall?

IIB.

What is the temperature at which a gas/air mixture spontaneously ignites without an external ignition source called?

The ignition temperature.

What is the temperature at which a gas/air mixture ignites in the presence of an external ignition source called?

The flash point.

Which gas property dictates the selection of equipment's 'T' rating?

The ignition temperature of the gas.

What is the default design ambient temperature range for IEC 60079 equipment unless marked otherwise?

$-20^\text{o}\text{C}$ to $+40^\text{o}\text{C}$

What does the temperature classification ('T' class) of Ex equipment represent?

The maximum surface temperature reached by equipment in contact with flammable gas at maximum ambient conditions, which will not be exceeded in normal or specified fault conditions.

How many recognised temperature classes exist for Ex equipment?

6 (ranging from T1 to T6).

What is the maximum allowable surface temperature for equipment with temperature classification T5?

$$85^\text{o}\text{C}$$

How is Zone 0 defined regarding the presence of an explosive gas/air mixture?

An area in which an explosive gas/air mixture is present continuously, for long periods, or frequently.

How is Zone 1 defined regarding the presence of an explosive gas/air mixture?

An area in which an explosive gas/air mixture is likely to occur in normal operation occasionally.

How is Zone 2 defined regarding the presence of an explosive gas/air mixture?

An area in which an explosive gas/air mixture is unlikely to occur in normal operation, and if it does occur, will persist for a short period only.

What Equipment Protection Level (EPL) and Category correspond to Zone 0?

EPL 'Ga' (Category '1G').

What Equipment Protection Level (EPL) and Category correspond to Zone 1?

EPL 'Gb' (Category '2G').

What Equipment Protection Level (EPL) and Category correspond to Zone 2?

EPL 'Gc' (Category '3G').

In which locations can intrinsically safe equipment marked Ex 'ib' be used?

Locations requiring EPL 'Gb' or 'Gc' (Categories '2G' or '3G').

In which locations can intrinsically safe equipment marked Ex 'ic' be used?

Locations requiring EPL 'Gc' (Category '3G') only.

Where can equipment marked Ex 'ia' be safely installed?

Locations requiring EPL 'Ga', 'Gb', or 'Gc' (Categories '1G', '2G', or '3G').

Which type of protection offers the highest level of safety and integrity?

Ex 'ia'.

Where can type Ex 'n' equipment be installed?

Locations requiring EPL 'Gc' (Category '3G') only.

Where can type Ex 'd' flameproof equipment be installed?

Locations requiring EPL 'Gb' or 'Gc' (Categories '2G' or '3G').

What does the letter 'U' appended to a certificate number signify?

The item is a component intended for incorporation in certified Ex equipment.

What does the suffix 'X' on a certificate number indicate?

Special conditions apply for safe use; refer to documentation.

What does the CE marking on an item of equipment indicate?

Compliance with all applicable European Union directives.

Why is flameproof (Ex 'd') apparatus given that designation?

An internal explosion will not ignite an external gas atmosphere.

What is 'pressure piling' in flameproof Ex 'd' enclosures?

A phenomenon where ignition in one part of an enclosure causes a higher explosion pressure in another interconnected part.

What do the two numbers following 'IP' in an Ingress Protection rating refer to?

Protection against solid matter (first digit) and water (second digit).

Which protection concept uses internal overpressure to prevent external flammable gas from entering equipment?

Ex 'p' (Pressurisation).

What is the minimum Ingress Protection (IP) rating required for an Ex 'e' junction box?

IP54.

What does 'te' time represent for an Ex 'e' motor?

The time to disconnection for a stalled motor starting from hot operating temperature.

What explosion protection technique is represented by Ex nA?

Non-sparking apparatus.

What is the main function of safety units such as Zener Barriers?

To limit the maximum energy transferred from power supplies to equipment in the hazardous area.

What does 'Um' on an intrinsically safe apparatus label specify?

The maximum r.m.s. supply voltage that can be applied to non-intrinsically safe terminals (typically $250\text{ V}$).

What is the minimum clearance distance between bare I.S. terminal conductors and earthed metal?

$$3\text{ mm}$$

What is the minimum clearance distance required between adjacent terminals of different intrinsically safe circuits?

$$6\text{ mm}$$

What is the minimum clearance distance required between live parts of I.S. terminals and non-I.S. terminals in the same enclosure?

$$50\text{ mm}$$

What is the minimum cross-sectional area required for aluminium cables used in hazardous areas for non-I.S. circuits?

$$16\text{ mm}^2$$

What is the minimum clearance distance between flanged openings in Ex 'd' IIC apparatus and solid obstructions?

Not less than $40\text{ mm}$

What is the maximum allowable earth impedance for a Zener barrier earth connection?

Less than $1\text{ }\text{ohm}$

What minimum cross-sectional area copper conductor is required for single-wire earthing of a Zener barrier?

$$4.0\text{ mm}^2$$

What is the preferred identification color for intrinsically safe cables and equipment?

Light blue.

What is the maximum interval between periodic inspections for portable and transportable equipment?

6 months.

Which grade of inspection is required before equipment is brought into service upon handover?

Initial Detailed inspection.

What defines a Visual inspection in hazardous area maintenance?

An inspection which identifies defects apparent to the eye without using tools or access equipment.

At which grade of inspection is an Ex 'd' cable gland dismantled for examination?

Detailed inspection.

According to IEC 60079-14, what is the maximum allowable insulation resistance to protect new plastic-covered cable trays against static electricity?

Insulation resistance must not exceed $1\text{ G}\text{ohm}$