At a glance
- Required: design and build in accordance with sound engineering practice and supply adequate instructions for use (Art. 4(3)).
- Not allowed: a CE marking under the PED, and no EU declaration of conformity — no procedure was carried out, so there is nothing to declare.
- National in-service rules continue to apply; whether an inspection duty exists is a separate, national question.
What Article 4(3) says
Article 4(1) sets thresholds for pressure vessels, fired or heated equipment, piping and accessories. If your equipment stays below them, Article 4(3) requires it to be designed and manufactured in accordance with the sound engineering practice of a Member State in order to ensure safe use. The equipment is accompanied by adequate instructions for use, and it does not bear the CE marking referred to in Article 18.
The abbreviation SEP is common across the industry. It is not a category: there is no category zero and no "category SEP". It is a separate regime next to categories I to IV.
In practice
What you do
- design and build in accordance with sound engineering practice: a substantiated calculation, material with certificates, qualified welding, a tightness test
- supply adequate instructions for use — a hard requirement of Art. 4(3) itself
- make your name and address traceable on the equipment or in the documents
What you do not do
- affix a CE marking under the PED — Art. 4(3) rules that out
- draw up an EU declaration of conformity under Annex IV — no procedure was carried out
- refer to a module or certificate — they do not exist here; a supplier's declaration of your own is fine
The interpretation of "sound engineering practice" in the left column is a statement of practice; the directive leaves the interpretation to the Member State.
The nuance on the CE marking
The equipment may well carry a CE marking under other legislation that applies to it at the same time — machinery legislation, for example, or the low-voltage rules. The marking then belongs to that legislation and not to the PED. That is precisely why the EU declaration of conformity states, per piece of legislation, what the conformity refers to.
If you want to give the buyer something anyway, provide a supplier's declaration that says what was done and that states explicitly that the equipment falls under Article 4(3). An EU declaration of conformity under Annex IV is not appropriate here: it belongs to a completed module, and there is none.
Three misunderstandings
"Article 4(3) means the PED does not apply"
No. The equipment falls within the scope of the directive; only the conformity assessment and the CE marking are absent. If your equipment really falls outside the directive, that is one of the exclusions of Article 1(2) — a different thing altogether.
"So no in-service inspection either"
That is a separate, national question. In the Netherlands, for instance, the general user obligations of the pressure equipment decree continue to apply — instructions in Dutch, proper maintenance, use as intended. See the page on operating pressure equipment in the Netherlands.
"Below the threshold is below the threshold"
The threshold applies to the equipment as placed on the market, with the PS and temperature you assign yourself. A manufacturer who picks a generous PS for margin can push himself into category I. Conversely, a PS chosen tightly to stay below the threshold is a design decision you must be able to defend, including to an insurer.
What a buyer may expect from you
There is no file requirement in the PED, but there is a buyer who wants something in hand. In practice a professional buyer asks for four things, and this is also what an insurer will request after an incident:
- the strength calculation or the design rule used, with the PS and TS applied;
- the material certificates of the pressure-bearing parts;
- the evidence of the tightness or pressure test, with the test pressure used;
- the instructions for use, including the limits within which the equipment may be operated.
That list follows from practice, not from Article 4(3); it is the experience-based point that most often makes the difference between a discussion and a completed delivery. For a reasonable test pressure, see the page on the minimum test pressure.
Frequently asked questions
May I affix CE to Article 4(3) equipment?
Not under the PED. Article 4(3) states explicitly that this equipment does not bear the CE marking referred to in Article 18. If other Union legislation applies that does require a CE marking, the marking belongs to that legislation and the declaration must show what it refers to.
Must I draw up an EU declaration of conformity under Article 4(3)?
No. An EU declaration of conformity under Annex IV belongs to a completed conformity assessment procedure. Under Article 4(3) there is none. A supplier’s declaration of your own, stating what was done and that the equipment falls under Article 4(3), is common and prevents discussion.
What does "sound engineering practice of a Member State" mean concretely?
The directive does not define it and leaves it to the Member States. In practice it comes down to a demonstrable, repeatable way of working: a substantiated strength calculation, certified material, welding by qualified people and a tightness test. That is a statement of practice, not a legal definition.
Is Article 4(3) the same as "outside the PED"?
No. Article 4(3) equipment falls within the scope of the directive but below the thresholds of Article 4(1). Outside the directive is only what Article 1(2) explicitly excludes, or what has a maximum allowable pressure of 0.5 bar or less.
Does Article 4(3) equipment need in-service inspection?
That does not depend on Article 4(3) but on national law. In the Netherlands the designation follows the Annex II table and category, so without a category there is no designation — but the general user obligations continue to apply.
Are you really below the threshold?
The free tool checks your PS, V or DN against Article 4(1) and shows how much room remains before category I starts.
Run the free check or see the full report