Explosive atmospheres – Part 33: Equipment protection by special protection “s”

This part of IEC 60079 gives the specific methodology for the assessment and testing, and requirements for marking of electrical equipment, parts of electrical equipment and Ex components with special protection “s”.

This part of IEC 60079 applies to

• electrical equipment employing a method of protection not covered by any existing standard in the IEC 60079 series,

• electrical equipment employing one or more recognized types of protection where the design and construction is not fully compliant with the standard for the type of protection,

• electrical equipment where the intended use is outside the parameters of the scope of the standard for the type of protection.  This part of IEC 60079 is not intended for equipment that is covered by the scope of other

IEC 60079 equipment standards unless

• it is clearly demonstrated that compliance with the type of protection is not feasible, and

• additional measures are applied to establish an equivalent equipment protection level.

This part of IEC 60079 for special protection “s” is applicable to Group I, Group II and Group III and for equipment protection levels Ma, Mb, Ga, Gb, Gc, Da, Db and Dc, as defined in IEC 60079-0.

Certain specific guidance for assessment and testing are provided in the annexes to this standard.

This standard supplements and modifies the general requirements of IEC 60079-0. Where a requirement of this standard conflicts with a requirement of IEC 60079-0, the requirement of this standard shall take precedence.

NOTE 1 This standard may be used where equipment requires a higher EPL than the underlying protection techniques provide. Additional control measures or additional design and test requirements would be applied.

NOTE 2 Parts of equipment that can be designed and tested to standardized techniques should be so designed.

Only those parts where conformance with essential safety requirements is achieved through alternative controls should be considered for special protection “s”. Equipment similar in attributes and performance to other equipment within a particular type of protection should be reviewed first to that method of protection prior to being considered for the use of Ex ”s”’. Some parts of IEC 60079 allow a degree of variance from the equipment requirements and where determined to be close enough by independent verifiers, then it is preferable to prescribe to the original type of protection.