PED and ATEX - can both directives apply for a pressure vessel?

[XL83NL]

This week had an inspection of a pressure vessel. As im not that into ATEX, I had question, as the vessel (an S&T HEX) had the ATEX zone classification on the nameplate, toghether with the CE mark en Ex-symbol.
Long story short, can any pressure vessel, like a simple column, reactor or shell in tube heat exchanger, designed and delivered under the PED, also fall under the ATEX directive, when it's main purpose is to contain pressure acc. article 1, para 2.1.1 of the PED?

‘Vessel’ means a housing designed and built to contain fluids under pressure including its direct attachments up to the coupling point connecting it to other equipment. A vessel may be composed of more than one chamber.

Please note Im only referring to the vessel itself, and Im not looking at any instruments which may be on the vessel (like a pressure switch) when the vessel is placed in an ATEX zone/environment.

 

[Caloooomi]

It is definitely a shell and tube and not an immersion bundle in a shell?

Was the heat exchanger supplied with additional equipment and sold as one? E.g. transmitters, pressure control devices?

If they had to take into account any additional requirements for protection against explosion / fires, then I can understand the Ex mark, but on it's own I'm not too sure...

 

[XL83NL]

No, not an immersion heater. Let's, for sake of simplicity, consider a vessel is ordered without ATEX, and doesn't have any protection means like a level switch or whatever. It's just a simple vessel with top, bottom, a shell and some nozzles. (We actually never buy our vessels with additional instruments).

Then such a case comes to my question: can a pressure vessel, ordered with no means of instrumental things, be considered to fall under the ATEX directive?

 

[Caloooomi]

Well, it depends... If the pressure vessel can be considered a possible source of ignition which would result in an explosion, then yes the ATEX Directive would apply.

For example, overheating, high surface temperature etc.

 

[XL83NL]

Agreed. But can it? Valves for example are exempt from ATEX. We have supplied vessels with a design over 700 deg C for use in ATEX environment; no need for ATEX certification on the vessel (which acted as a preheated for a steam methane reformer).

Thanks for your input so far, but I haven't found any answer yet that solve the question.

 

[Caloooomi]

Pressure Equipment Directive (PED) 97/23/EC is a single market directive similar to Directive 94/9/EC. Relatively few items of pressure equipment have their own source of ignition. There are a small number of examples of safety accessories which may be autonomous protective systems or, possibly, equipment. Flame arrestors have been judged to be pressure accessories in the sense of the PED. There are no additional requirements for the flame arrester element under the PED. PED specifically excludes from its own scope equipment classified no higher than Category I under Article 9 of PED but inside the scope of ATEX.

The Pressure Equipment Directive deals only with the pressure hazard and does not consider the prevention of and protection against explosions/inflammations, which are not triggered by pressure.
In most cases it is presumed that PED equipment does not have an own ignition source when it is properly installed according to the instructions of the manufacturer (including information about
maintenance and repair of the connecting devices, e.g. valves, flanges). If such PED equipment shows hot surfaces occurring during operation caused by the temperature of its content solely, it is
not applicable to consider this equipment under the ATEX Directive 94/9/EC.

Taken from:

https://www.ptb.de/cms/fileadmin/in...TEX_Guidelines_4th_Edition_September_2012.pdf

So in general, no, ATEX is not considered for most pressure vessels under PED. Probably still wise to do a hot surface check though!

 

[Hoxton]

I am a little surprised that a "bare" shell and tube heat exchanger is considered to fall under ATEX.

I do not have my files available, but Wikipedia shows "In very broad terms, there are three preconditions for the directive to apply: the equipment a) must have its own effective source of ignition; b) be intended for use in a potentially explosive atmosphere (air mixtures); and c) be under normal atmospheric conditions."

In general you must NOT apply CE marking unless a Directive applies, but the Technical File will contain the justification.

 

[XL83NL]

Its a long story as I mentioned. It wasn't considered to fall under the ATEX. It was purchased with the idea to reference the atex zone on the nameplate, so the end client knows in which zone the vessel can be used. Since the nameplate als bears the CE mark, suggestion is given the vessel itself is subject to and complies with the atex. This got me thinking when I noticed it during inspection, and made me pose the question.

The reference by caloomi is excellent, and I think the guidelines provide the answer. Thanks all.

 

[micalbrch]

CE mark does not mean ATEX. CE mark means compliance with an (any) European Directive which can be PED or ATEX (to name just two examples). And yes a pressure vessel can be subjected to ATEX. If it falls under PED than PED rules ATEX. If it does not fall under PED (as you know PED has exceptions) it can fall under ATEX.

 

[XL83NL]

Yes, but the CE mark together with the Ex mark means atex, doesn't it?

 

[micalbrch]

"Yes, but the CE mark together with the Ex mark means atex, doesn't it?" Yes, it does. But you must then also have a Declaration of Conformity from the manufacturer.

 

[XL83NL]

Hi all, thanks for the input. I think Ive gathered sufficient info. esp. the reference to the ATEX guidelines are useful.