UL 60079-33 Ed. 1-2021

Explosive Atmospheres - Part 33: Equipment Protection by Special Protection - Published Date: October 21, 2021

1 Scope This  part of IEC 60079  standard  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  standard  applies to • electrical equipment employing a method of protection not covered by any existing standard in the  IEC  UL  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.  • electrical equipment that may or may not also involve non-electrical ignition sources.  NOTE UL 80079-36 and UL 80079-37 apply to equipment that only involves non-electrical ignition sources.  This  part of IEC 60079  standard  is not intended for equipment that is covered by the scope of other IEC  UL  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  standard  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  UL  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  UL  60079-0. Where a requirement of this standard conflicts with a requirement of IEC  UL  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  UL  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. Where references are made to IEC and ISO standards, the referenced requirements found in these standards shall apply as modified by any applicable US National Differences for the standard (see Clause 2).