Equipment protection by special protections Ex s

About the protection  

Special protection ‘s’ allows certification and testing for design of a product that cannot comply in full with recognised types of protection.  

It is also relevant where the standards for the recognized types of protection do not cover the required operating conditions. For example, outside normal atmospheric temperature and/or pressure and/or oxygen concentration or, used in hybrid mixture of dust and gas. 

Testing to standards  

The International Standard IEC 60079-33 or Australian/New Zealand Standard AS/NZS 60079.33 specifies the basic method on how the compliance can be achieved. It is applied in conjunction with the general requirements standard IEC 60079-0 or AS/NZS 60079.0. 

Testing techniques  

Here are some techniques that Ex s can be achieved, using one or a combination:   

• containment of internal explosion 

• exclusion of explosive atmosphere 

• avoidance of ignition sources 

• energy limitation, both sparking and thermal 

• dilution. 

Documentation required from the manufacturer 

Here are some documents the manufacturer needs to provide:  

• details of considerations given to the possibilities for design to the recognised types of protection (or combination of types of protection), before proceeding to special protection 

• aspects that are covered by the standards for any recognised type of protection applied, for those aspect that are not covered by verification to recognised types of protection 

• drawings that provide full specifications and details relevant to Ex s protection 

• draft ignition hazards assessment, which is used to develop required test plan 

• Failure Mode and Effects Analysis (FMEA). 

Ignition hazards assessment  

The ignition hazards assessment needs to identify all potential ignition sources that can occur and list control measures that are applied to reduce the likelihood of a potential ignition source becoming an effective ignition source.  

Here are some possible ignition sources:  

• sparks 

• electrical arcs 

• high surface temperatures 

• static electricity 

• radio frequency electromagnetic waves 

• electromagnetic waves including optical radiation 

• ionizing radiation 

• ultrasonic. 

Levels of protection  

Levels of protection ‘s’ is divided into three Levels of protection based on the risk of the electrical equipment becoming an ignition source in an explosive dust or gas atmosphere:  

1. ‘sa’ - EPL Ma, or Ga, or Da, “very high” level of protection, where equipment is not a source of ignition in normal operation, during expected malfunctions or during rare malfunctions 
2. ‘sb’ - EPL Mb or Gb or Db, “high” level of protection, where equipment is not a source of ignition in normal operation or during expected malfunctions 
3. ‘sc’ - EPL Gc or Dc, “enhanced” level of protection, where equipment is not a source of ignition in normal operation. 

Getting the test results

The results of our testing are presented in a test report that is endorsed by our local Australian laboratory accreditation body, NATA (National Association of Testing Authorities, Australia).

When product sample testing, design assessment (Ex test report) and quality assessment (quality assessment report) are successfully completed, an Ex Certificate of Conformity (IECEx or ANZEx) is issued by TestSafe.

Help and support

Complete our online enquiry form.

Call: +61 (2) 4724 4900

Email: testsafe@safework.nsw.gov.au

Mail us at: PO Box 592, Richmond, NSW 2753 Australia.