A machinery handling combustible gas or dust, does need an ATEX marking?
Article 1 of directive 2014/34/UE defines the field of application to:
(a) equipment and protective systems intended for use in potentially explosive atmospheres;
(b) safety devices, controlling devices and regulating devices intended for use outside potentially explosive atmospheres but required for or contributing to the safe functioning of equipment and protective systems with respect to the risks of explosion;
(c) components intended to be incorporated into equipment and protective systems referred to in point (a).
This implies that all machineries physically entering into a classified zone according to directive 99/92/CE (zone 0, 1, 2, 20, 21, 22) must be marked ATEX in compliance to the directive (art. 1 point a)).
In addition, the machines not intended to be installed in ATEX zone but that represent by themselves a source of emission explosive atmosphere, must be marked ATEX since they classify the installation zone.
The latter represent a wide variety of situation in the market.
Let consider, for instance, flavour feeder ethanol-based in the food industry, or paint dispenser solvent-based, dispenser of combustible dust and so on…
These machineries can emit liquid, vapour or dust capable to generate a potentially explosive atmosphere. When it is necessary to avoid an ATEX compliance process, it is possible to equip the machine with explosion prevention systems such as ventilation, dilution, confinement or other methods that reduce the probability of ATEX formation to negligible values.
These functions represent the protection method in compliance to the requirement 1.5.7 of directive 2006/42/CE and must satisfy the related performance level accordingly. However, such functions are covered by article 1 point b) of directive 2014/34/UE.
These non-ATEX machineries featuring safety functions related to the risk of explosion must be ATEX in the whole channel components (input-logic-output). These components, since outside a classified zone could belong to the less expensive class of ATEX components (namely II 3GD); however they shall respect the reliability requirement (PL or SIL).
Internal and external ATEX marking of machineries.
Directive 2014/34/UE does not require any ATEX marking of internal parts. This because only the external parts can eventually come into contact with ATEX.
If it can be excluded a release of flammable or explosive substances from the inside, ATEX directive is not applicable.
However a manufacturer can classify an internal zone for information purposes (let consider isolator or glovebox where the user can insert objects, substances or devices).
Nevertheless the machinery directive guarantees that all machinery placed on the marked are compliant with respect to the risk of explosion, since this is included in the essential health and the safety requirements.