1. Basic Information

Question 1

What does ATEX 95 (94/9/EC) relate to?

Answer 1

The ATEX equipment directive. It relates to places where dusts or flammable gases may be present.

Concerns equipment and protective systems in potentially explosive atmospheres. Introduced into british law and mandatory by July 2003. Applies to both electrical and mechanical equipment.

It is intended to remove barriers to trade by ensuring that the quality of equipment, wherever it is manufactured in the EU, meets rigorous essential safety requirements.

Question 2

What does ATEX 137 (1999/92/EC) relate to?

Answer 2

It addresses the safety where there is a danger from potentially explosive materials. It relates to places where dusts or flammable gases may be present.

Defines requirements for worker safety and details both employer and employee requirements.

Introduced into british law and mandatory by July 2006.

It is aimed at ensuring the health and safety of workers whilst in their place of work. This directive categorises the work place into zones. Zones provide a measure of the probability of the presence of a dangerous mixture with air of any flammable gas or combustible dust.

Zones used with flammable gases are 0, 1 and 2 (other than mining applications). Zones used with combustible dusts are 20, 21 and 22.

Question 3

What are the employers basic duty?

Answer 3

To provide a safe place in which to work and to employ competent people.

Question 4

What are the employees basic duty?

Answer 4

To exercise diligence and care whilst undertaking allotted tasks and not to intentionally or recklessly interfere with or misuse anything provided in the interests of health, safety or welfare.

Infringement may result in legal action. It applies to both gas and dust.

Question 5

What regulation does DSEAR transpose into law?

Answer 5

ATEX 137.

Question 6

What do technicians need to do in order to undertake work in a potentially explosive atmosphere?

Answer 6

They need to prove competence which can be demonstrated as a basic competence by the possession of a current CompEx certificate in the appropriate units.

Question 7

What is required before undertaking any work?

Answer 7

A permit to work is required. Different companies operate different systems.

Question 8

Do you need to isolate?

Answer 8

Recognised procedures are to be followed to ensure that equipment to be worked on is not ‘live’. Exceptions to this may be where intrinsically safe circuits are involved. Therefore instruments/meters approved for such an operation are used.

Question 9

What condition must tools be in?

Answer 9

Tools are to be in a sound condition, free from defects and suitable for use in potentially explosive atmospheres. The judgement as to the suitability of tools and instruments may require formal risk assessment.

Question 10

What equipment is prohibited?

Answer 10

Matches or other forms of ignition are prohibited from being carried into potentially explosive atmosphere, except n exceptional circumstances where their use is covered by a ‘fire permit’.

However, battery operated pacemakers, watches, certain hearing aids and certified intrinsically safe equipment and instruments are permitted in hazardous areas.

Question 11

What are the two relevant ATEX directives and what are their purposes?

Answer 11

ATEX 95 and 137. Remove technical barriers to trade with the EU and outlines essential technical and safety requirements with which products must comply.

Question 12

Briefly explain knowledge, skills and competencies of a responsible person.

Answer 12

General understanding. Practical and working understanding.

Question 13

Briefly explain knowledge, skills and competencies of a operative person.

Answer 13

General understanding and familiarity. General understanding of Inspection and Maintenance (IEC 60079-17). Familiarity with selection and erection of equipment (IEC 60079-14).

Question 14

Briefly explain knowledge, skills and competencies of a designer person.

Answer 14

Detailed knowledge.

Question 15

A verification dossier shall be prepared for every installation, containing:

Answer 15

• Area classification drawing
• Instructions for erection and connection
• Instructions for electrical equipment with suffix X
• Descriptive document for IS systems.
• Equipment declaration of conformity.
• Information necessary for inspection.
• Details of relevant calculations.
• Details of repairs.
• Gas/Vapour classification.
• Temperature class or ignition temperature.
• External influences and ambient temperature.
• Equipment suitability e.g. temperature rating, type of protection, IP rating, corrosion resistance.
• Material characteristics
• Types and details of wiring systems.
• Cable entry systems.
• Drawings and schedules of circuit identification.

Question 16

What three things are need for a fire?

Answer 16

Fuel, heat/source of ignition, oxygen.

Question 17

What stamp on equipment?

Answer 17

Ex in hexagon.

Question 18

What is IEC 60079-14

Answer 18

Standard ofr electrical installations.

Question 19

What is IEC 60079-17

Answer 19

Inspection and maintenance.

Question 20

What is the flash point?

Answer 20

Lowest temperature at which a liquid in an open vessel will give off sufficient concentration of vapours to form an ignitable mixture with air. Fire hazards are often based on its flash point.

Question 21

What is ignition temperature?

Answer 21

Once the flammability range has been reached, the vapours will ignite at the proper ignition temperature. The ignition temperature of a substance is the lowest temperature necessary to cause the vapour to burn in the absence of the heat source.

If the vapour-air mixture is confined and there is an ignition source, an explosion will result.

The ignition temperature is often misleading because it is a relatively large number often in the hundreds of degrees.

However, only takes a short duration of contact with a potential ignition source to reach this temperature and ignite the vapour.

Question 22

What is a temperature classification?

Answer 22

Temperature classification is based on the maximum temperature which any relevant part of the apparatus (which may be in contact with explosive atmosphere) will reach, when operating within normal design ratings at an ambient temperature not exceeding 40degC. Suitable equipment must have a T class LOWER than the ignition temperature of the gas.

Tested range -20 - +40 unless stated. (Ambient?).

Question 23

Describe IP ratings.

Answer 23

First digit refers to protection against solid matter. Second against liquid. Minimum of IP54 for ATEX. IP54 unless otherwise stated.

Question 24

What is an Ex component?

Answer 24

A part of electrical apparatus for use in potentially explosive atmospheres which is not intended to be used alone in such atmospheres and requires additional certification when incorporated into electrical apparatus or systems intended for use in potentially explosive atmospheres. I.e. a type d push button switch. type e terminal block, some glands.

They are marked with the symbol U.

Question 25

What are the steps for selection of equipment?

Answer 25

• determine zone classification.
• select type of protection for that zone.
• Ensure equipment is certified for the relevant gas group.
• Ensure temperature class of the equipment is below the ignition temperature of the gas.
• Ensure suitable for environment.