PD CEN/TR 15281:2006

Foreword
1 Scope
2 Normative references
3 Terminology and abbreviations
   3.1 Terminology
   3.2 Abbreviations
4 Inert gases
5 Influence of the oxygen concentration on explosive atmospheres
   5.1 General
   5.2 Gas and vapour explosions
   5.3 Dust explosions
   5.4 Hybrid mixtures
   5.5 Mists
   5.6 Influence of process parameters
6 Methods of Inerting
   6.1 General
   6.2 Pressure swing inerting
   6.3 Vacuum-swing inerting
   6.4 Flow-through inerting
   6.5 Displacement inerting
   6.6 Maintaining inert conditions
7 Inerting systems
   7.1 General introduction
   7.2 Inert gas supply
   7.3 Monitoring and control system
   7.4 Methods
8 Reliability
   8.1 Demands for safety critical equipment
   8.2 Inerting systems
9 Personnel and environmental protection
10 Information for use
Annex A (informative) Oxygen monitoring technology
Annex B (informative) Equations for pressure-swing inerting
Annex C (informative) Calculations for flow-through inerting
Annex D (informative) Addition of solids to an inerted vessel
        using a double valve arrangement
Annex E (informative) Addition of solids down a charge-chute to an
        open vessel
Annex F (informative) Examples on inerting specific items of process
        equipment
Annex G (informative) Prevention of diffusion of air down vent pipes
Bibliography

Discusses the requirements for absolute inerting. Inerting is used to influence the ignition and explosion characteristics of an explosive atmosphere.

Inerting is a measure to prevent explosions. By feeding inert gas into a system which is to be protected against an explosion, the oxygen content is reduced below a certain concentration until no explosion can occur. The addition of sufficient inert gas to make any mixture non-flammable when mixed with air (absolute inerting) is only required in rare occasions. The requirements for absolute inerting will be discussed. Inerting may also be used to influence the ignition and explosion characteristics of an explosive atmosphere.

The guidance given on inerting is also applicable to prevent an explosion in case of a fire.

The following cases are not covered by the guideline:

• admixture of an inert dust to a combustible dust;

• inerting of flammable atmospheres by wire mesh flame traps in open spaces of vessels and tanks;

• fire fighting;

• avoiding an explosive atmosphere by exceeding the upper explosion limit of a flammable substance.

Inerting which is sufficient to prevent an explosion is not a protective measure to prevent fires, self-ignition, exothermic reactions or a deflagration of dust layers and deposits.