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Mechanical engineering

Application of the directive 94/9/EC to Rotating Mechanical Seals

When a Mechanical Seal[1] is a Machinery Element and when an ATEX-Component


A mechanical seal is a device which prevents leakage of fluids along rotating shafts. Primary seal function is at right angles to the axis of rotation between one stationary ring and one rotating ring.


These are parts of machinery not defined within 94/9/EC.

Most mechanical seals are machinery elements. Typically these seals are:
• Catalogue mechanical seals and their parts, selected by the equipment manufacturer alone or with assistance from the mechanical seal manufacturer.
• mechanical seals stocked by the equipment manufacturer or end user for general applications
• mechanical seals used for applications where the service conditions are not closely specified
• non cartridge-seals and parts
• standard cartridge-seals.

Mechanical seals will also be machinery elements if a risk assessment by the mechanical seal or equipment manufacturer shows that the seal is not expected to be an ignition source even in the event of fault conditions.


The following definition is taken from the European Commission ATEX Guideline (Second edition).

The two defining elements for components are that they,
are essential to the safe functioning of equipment and protective systems with respect to explosion protection (otherwise they would not need to be subject to the directive);
• with no autonomous function (see 3.8) (otherwise they would have to be regarded either as equipment, protective system or as device according to Article 1.2).

Engineered mechanical seals maybe classified and sold as ATEX components. Typical examples are:
• Mechanical seals for specific applications where close co-operation between mechanical seal manufacturer and equipment manufacturer is required and will often result in a specifically designed mechanical seal.
• Mechanical seals for some category 1 equipment.

In this case the mechanical seal manufacturer shall supply sufficient information about the performance of the seal so that the equipment manufacturer does not need to repeat unnecessary efforts such as tests or calculations concerning the mechanical seal in order to ensure that the equipment complies with ATEX requirements. The equipment manufacturer shall supply sufficient information about the intended application and equipment.


A) Mechanical seal manufacturer:

Case 1: Mechanical Seals supplied as Machinery Element
It is normal practice that the manufacturer of mechanical seals supplied as Machinery Element provides complete documentation for safe use of his product i.e.:
instruction manual for incorporation into equipment, which shall include safety aspects and limits of operation.

Case 2: Mechanical Seals supplied as ATEX Components
Mechanical seals shall comply with article 8.3 of 94/9/EC ATEX Directive.
An ATEX component mechanical seal shall be supplied at least with the following information:
• all information/documentation given for case 1
• results of relevant calculations and/or tests that have been carried out
• a temperature rating as far as possible
• an indication of the category
• a list of ATEX essential safety requirements that the mechanical seal complies with
• what fault conditions have been considered for category 1 or 2 mechanical seal
• a close specification for intended use, for example gas group
• a certificate of conformity
• marking for components in accordance with the latest ATEX Guidelines

B) Equipment Manufacturer:

In all cases the equipment manufacturer is responsible for the entire package within his scope of supply and therefore it will be required to comply with article 8.1 of 94/9/EC ATEX Directive.

[1] This consideration paper does not consider mechanical seal control systems.

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