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ATEX

The cleaning of tanks that contained flammable materials can be hazardous. A tank emptied of such liquids often still contains trace vapours and this vapour residue is often explosive. Indeed, an empty or part-filled tank normally represents a greater explosion risk than a full one. Further to this the solvents used in many industrial cleaning processes are themselves flammable and potentially explosive when in a vapour state. So even if the initial tank contents represented no such risk the use of solvents to clean the tank may create a potential explosion risk.



ATEX represents the European guidelines in minimising the risk of triggering an explosion in such environments. Any equipment used within such an environment must conform to ATEX guidelines.



What requires an ATEX stamp?

In short any piece of equipment that could potentially generate heat, build up static, create a spark or in any other way trigger an explosion. Essentially this means that any object with moving parts of any kind must be ATEX approved if it is to be used within explosive environments.



What this means for tank cleaning equipment is that all rotary spray balls and impingement cleaners must have an ATEX approval that corresponds to the class of environment they are to be used in – typically closed environments like tanks we be zone class 0 and so tank cleaners need to conform to the highest ATEX standards (see below for details on classes).



ATEX classes

Level 0 – The explosion risk is continuous or likely to persist for long periods of time under normal operation.

Level 1 – The explosion risk is likely to occur under normal operation occasionally.

Level 2 – An explosion risk us unlikely to occur under normal operation but occasionally it might.



Hazard types

ATEX zones are further separated into two types of explosion hazard category dust and vapour/gas.

Equipment used in any such environments must conform to the relevant design, manufacturing and quality guidelines set out for each environment.



SNP Tank cleaners and ATEX



Static nozzles and manifolds

These nozzles have no moving parts and so would not be classed as “equipment”, as such they do not need to be rated for ATEX. However if these nozzles are added to a tank then an ATEX risk assessment still needs to be made on the whole assembly i.e. the tank and cleaning nozzles counts as an assembly. With static nozzle systems the only feasible explosion risk would come from a build-up of static charge on the nozzle so as long as the nozzle is made from a conducting material that is earthed then ATEX compliance will be met. Essentially this means that plastic nozzles of all kinds should be avoided even in static nozzle systems.



Rotary fan nozzles

These nozzles have moving parts so even though they are fluid driven with no electrical components they still require ATEX certification. The full HWS range of nozzles is certified for use in Zone 0 atex environments.  In contrast the HWP range of PTFE nozzles is not suitable for any ATEX zone because PTFE can potentially build up a static charge as such these tank cleaners should never be used in an explosive environment.



Rotary jet cleaners

The Orbitor range of tank cleaners are certified for ATEX zones 0 and above meaning they are suitable for use in cleaning highly explosive environments. The complexity of the Orbitor machine, when compared to simple rotary fan nozzles, means that some design modifications needed to be made to ensure ATEX compliance and so the ATEX versions of the Obritors have a slightly different design to standard Orbitors.



Tank Washing Engineering Considerations

Tank Washing Nozzle Designs

Tank Wash Nozzle Selection Table