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PED Fluid group for Acids

PED Fluid group for Acids

PED Fluid group for Acids

Does anybody have experience on how to categorize concentrated acids or bases in the PED fluid group system?

In the PED text at http://ped.eurodyn.com/directive/directive_article...
there’s a reference to 67/548/EEC which includes corrosive fluids as being dangerous, however there is no mentioning of those in the PED. It seems reasonable to me to argue that e.g. concentrated nitric acid is not healthy for people, but it is mainly classified as corrosive, harmful and irritant which is not necessarily the same as toxic. Some of my colleagues believe it is then a group 2 fluid, and the same response have apparently been heard at the local Notified Body although not in writing.

Can it be said that not all fluids defined as dangerous in 67/548/EEC are group 1 when the PED text refers specifically to it?

“A dangerous fluid is a substance or preparation covered by the definitions in Article 2 (2) of Council Directive 67/548/EEC of 27 June 1967 on the approximation of the laws, regulations and administrative provisions relating to the classification, packaging and labelling of dangerous substances …..

Group 1 comprises fluids defined as:
- explosive,
- extremely flammable,
- highly flammable,
- flammable (where the maximum allowable temperature is above flashpoint),
- very toxic,
- toxic,
- oxidizing.

The 67/548/EEC text is found at

Any links to interpretations etc. will be appreciated


RE: PED Fluid group for Acids

The PED is pretty global and a lot of terms are extremely
open to interpretation. We supply flexible hoses to the chemical industry and from a safety point of view we use
for highly corrosive fluids the group 1 classification.
For a number of products this could prove to be difficult,
but for our products it is workable in practise and this
point of view is shared by a number of plant engineers.

Best Regards

RE: PED Fluid group for Acids

It is worth noting that if the vapour pressure at design temperature is greater than 0.5 bar then it must be classed as a gas not a liquid.

RE: PED Fluid group for Acids

Thanks for the responses

I may have picked a bad example, but lets just stick with Nitric Acid.

The Danish Environmental Protection Agency have a (danish)list of dangerous substances and their classification:
Here's some of the data for Nitric Acid:
CAS number:7697-37-2
conc.>=70% Classification:O;R8 C;R35
20%<=konc.<70% Classification:C;R35
5%<=konc.<20% Classification:C;R34

As you can see at concentrations below 70% nitric acid is not classified oxidising, neither toxic although I wouldn't dream of drinking it. Another example is sulphuric acid which also have no O (for oxidising) or T (for toxic)

I looked in a list the EU on transport of dangerous goods also at http://europa.eu.int/eur-lex/pri/en/oj/dat/2004/l_...
and found also no O or T.

My question is:
If I look up an acid and do not find a T or O (or anything about flammable/explosive), is the fluid then group 2 even when it is categorized dangerous according to 67/548/EEC?

It may be that some companies specify in their safety data sheets that these acids are Toxic and/or oxidising but this just leads to another question:

Is there another database reckognized by the EU where one might search for hazard classifications? (for example 96/49/EC, annex A and B)?


RE: PED Fluid group for Acids

Not all substances categorized dangerous according to 67/548/EEC are group 1.
Only de substances classified as per article 2 (2) of that Directive. Classsification and symbols are not the same.
Look guideline 2/7 in ped website.
You mustn't over-categorized an equipment.

Regards from Barcelona
G. García

RE: PED Fluid group for Acids


I understand your point, and I have seen guideline 2/7 - but I don't see that this provides the full answer (or maybe I just don't understand it fully?)

According to article 2 (2) in 67/548/EEC dangerous substances include those which are harmful, corrosive or irritant.

The PED text refers to article 2(2) AND lists all of the "hazard types" from article 2(2) EXCEPT those which are harmful, corrosive or irritant.

So what to do with a substance that is classified corrosive or harmful (thus dangerous) but not in the PED listing?

Take 60% nitric acid as an example (Corrosive)


RE: PED Fluid group for Acids

As far as I know, a dangerous fluid not within types of danger refer to in article 9 point 2.1 is group 2.

Regards from Barcelona
G. García

RE: PED Fluid group for Acids

Thanks Garcia

This corresponds to what I have heard, although only second hand which was my reason for starting this thread.

What I'm looking for is anywhere to find that  clarification in writing - links etc.


RE: PED Fluid group for Acids

I have now got an e-mail (in danish) from the danish member of the PED committee.

It confirms the response from Garcia and states clearly that only those dangerous fluids specifically mentioned in article 9 shall be group 1.

I suggested to him that a new guideline was issued, but the committe tend to think that guideline 2/7 provides the answer so it might not come.


RE: PED Fluid group for Acids

I wonder, have You tried to determine the category of your pressure device before discussing the fluid danger class?

We always check both applicable tables (Class I and Class II) for the device. If, and only if, there is a difference in the output category, we determine if the fluid is class I or class II.

If there is no difference, always choose class I (it's better for you to take the worst case).
There is not very much difference between modules, excepted A-A1 (which are a lot simpler), so the difference (in my humble opinion) exists only where those two modules are applicable.

If the difference exists, I suggest you to take Class I fluid anyway. The directive clearly states that toxic, extremely toxic, flammable, extremely flammable, etc. fluids are class I.
Think about this. Drinkable water is probably the only fluid you can suppose is class II without doubt.

Hope this helps.

Che Dio ce la mandi buona, o almeno ce la mandi- Massimiliano Eusebi

RE: PED Fluid group for Acids


I must say I disagree with you in that one should categorize a fluid higher than required.

Obviously ANY piping system must be designed and installed in in a safe and sound manner (i.e. Sound engineering Practice - SEP)

The PED categorization (I,II,III for piping) is made to separate more dangerous systems from less dangerous, and the rules are harmonized throughout the EU.

These rules are good in the sense that they do not prevent you from using your common sense and make a safe plant, but they are also used to define common sense for engineers and authorities of different opinions.

Typically the higher category - the higher cost for the manufacturer/owner.

As engineers it is our job to make a safe system for a low cost. An owner may decide to be more strict than specified in the PED, but otherwise we should not "overcategorize" as Carcia says.

My question was if all acids are category 1 (and I thought they were) and the answer was NO! as you can see. For us this means that kilometres of pipes in our new plant will be according to SEP instead of Category I, and this means a hell of a lot for both cost and time. (We will still make a safe system off course)


RE: PED Fluid group for Acids

Then I must say Sorry for the misleading information.
Hope I will do better next time.

Che Dio ce la mandi buona, o almeno ce la mandi- Massimiliano Eusebi

RE: PED Fluid group for Acids

Just to confirm that dangerous fluids as understood by the PED are NOT the same as all those listed in article 2 (2) in 67/548/EEC, a revision to guideline 2/7 has been proposed and will be discussed in the work group on January 19.

The proposal is as follows:


WPG 2/7rev

Proposed revision of guideline as adopted on 29 June 2000

Pressure equipment directive 97/23/EC

Commission’s Working Group “Pressure”

Proposal related to: Articles 9.2.1, 9.2.2
Question:    Article 9 classifies fluids with reference to Article 2 (2) of Directive 67/548/EEC. Does this mean that all fluids classified as dangerous are group 1 ?
Answer:    NO, only those fluids cited in Article 9 paragraph 2 of the Pressure Equipment Direc-tive (PED) are to be classified as group 1. According to Directive 67/548/EEC they have one or more of the following risk phrases:
    - R2, R3 for explosive
    - R12 for extremely flammable
    - R11, R15, R17 for highly flammable
    - R26, R27, R28, R39 for very toxic
    - R23, R24, R25, R39, R48 for toxic
    - R7, R8, R9 for oxidising.

    For flammable fluids, see guideline 2/20.

Note 1:    The reference to the directive 67/548/EEC is used for the definitions of the risks of the substances. Annex I of this directive is not exhaustive whatever the version is. The fact that a substance is not listed in Annex I of this directive does not imply its classifica-tion in Group 1 or 2. It is advisable then to refer to the safety data sheet supplied with the product in accordance with the directive 91/155/EEC to identify whether the risks of Group 1 are included or not.
Note 2:    Fluids which have the symbol T or T+ are not necessarily group 1. As an example, fluids that are classified carcinogenic may have the symbol T. However, they don’t be-long to Group 1 fluids of the PED because they are not classified toxic (e.g. 2-naphtylamine salts, index no. 612-071-00-0). In directive 67/548/EEC, the symbols and classification are not the same. The symbols are defined in article 6 of Directive 67/548/EEC (article 16 of amendment 79/831/EEC) and this article is not mentioned in Article 9 of the PED. Classification and symbols are listed separately in the lists of fluids, Directive 93/21/EEC, and amendments.

  Accepted by WPG on:    2004-12-16

  Accepted by Working Group "pressure" on:



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