§249 バケットエレベーター

The question arises, how are bucket elevators to be treated within the framework of Directive 2014/34/EU especially in respect that in the surrounding area of bucket elevators potentially explosive areas are not necessarily present?

The intention of Directive 2014/34/EU is to avoid the ignition of potentially explosive atmospheres by equipment, protective systems and components. According to the potential hazards and the prevention measures the products are divided into categories.

Directive 2014/34/EU defines a potentially explosive atmosphere as an atmosphere, which could become explosive due to local and operational conditions. This means that the potentially explosive atmosphere is either present from the beginning or develops during the working process (e.g. in relation with the conversion of energy or the processing of materials).

In bucket elevators the potentially explosive area is limited in general by housings and/or sheathings, whereby a multiplicity of potential ignition sources can become effective due to construction, for example by rubbing and flapping sparks or by inadmissible heating.

An ignition hazard assessment should be carried out by the manufacturer of bucket elevators to analyse all the equipment related potential ignition sources able to ignite an explosive atmosphere (e.g. belts, buckets, angle wheels, drive units, regulating devices - see also EN 1127-1 for the list of ignition source) and take all preventive measures according to design, transported material, transport speed etc. under the aspect of the intended use of the equipment.

The necessary level of protection of equipment and components inside the housing (e.g. category) depends on the frequency and the occurrence of the explosive atmosphere inside this housing.

According to the necessary level of safety, depending on their incorporation in the housing and the disturbances or equipment faults, which have normally to be taken into account, some components (presenting a higher risk) might be assigned to categories different to the entire category of the bucket elevator. The document CEN/TR 16829:2016 prepared by Technical Committee CEN/TC 305 deals with bucket elevators that may handle combustible products capable of producing potentially explosive atmospheres of dust or powder inside the bucket elevator during its operation.

If some ignition sources cannot be avoided by the design of equipment or components, the manufacturer of the bucket elevator has to avoid the transmission of explosion to all the process.

The user/employer normally selects a bucket elevator based upon the category (related to internal zone) and then shall perform a risk assessment based upon the local circumstances. Such a risk analysis shall include the probability that ignition sources enter from outside but also the potential consequences of an explosion. Depending upon the acceptability of risks, in addition to preventative measures (based upon category of the bucket elevator) explosion protection measures may be needed.

The ATEX 'workplace' Directive 1999/92/EC, which deals with the minimum requirements for improving the level of health and safety protection of workers potentially at risk from explosive atmospheres, complements the responsibilities of manufacturers under Directive 2014/34/EU by setting out the responsibilities of user/employers.