Vessels are classified into categories with increasing hazard potential in accordance with PED Annex II (see tables 1, 2, 3 and 4 below). The category is determined according to the procedure listed below. The determined category determines the possible conformity assessment procedures.
Vessels with only a low risk are not assigned to any category (see tables below). Good engineering practice (SEP) applies to them.
Procedure for determining the category for vessels
The pressure vessels are classified on the basis of:
- Fluid type (gas or liquid)
- their maximum allowable pressure PS [bar],
- their Volume V [Liter],
- the fluid group for which they are intended
Note 1: Vessels for super-heated water (temperature > 110° C are covered by table 2 below.
Note 2: Heat exchangers are considered to be vessels, exception:
Heat exchangers which consist of straight or bent pipes which may be connected by common circular header(s) made also from pipe are classified, and only if, the three following conditions are met:
– air is the secondary fluid,
– they are used in refrigeration systems, in air conditioning systems or
– in heat pumps,
– the piping aspects are predominant.
Note 3: Half-pipe coil or a similar “jacket” construction that heat or cool a vessel are to be classified as vessels.
Note 4: At gas-loaded accumulators, or other vessels with a flexible or non fixed membrane, are made up of two chambers with different fluids, the maximum allowable pressure (PS) and the total volume of the vessel shall be used for classification.
Note 5: If a vessel contains a gas and and liquid, the classification shall be on the basis of the fluid which requires the higher category. The total volume (V) of the vessel, shall be used to determine the category, not the actual volume occupied by the individual fluids at any particular time.
Note 6: If a pressure equipment has several pressure chambers, the categories for the individual chambers must be determined separately. The pressure chamber with the highest category is then decisive for the pressure equipment, e.g. heat exchangers
Note 7: Characteristics (hazardousness) of the solid (contain in gas fluid) should be considered as part of the hazard analysis and do not influence the classification of the vessel.
What are fluid groups?
Fluid group 1: Consisting of substances and mixtures, that are classified as hazardous
Fluid group 2: Fluids not falling into fluid group 1
Read more details about the allocation of fluids to the fluid groups
Tables for determination of vessel categories
| Tables for gaseous fluids | Tables for liquid fluids |
|---|---|
| Gaseous fluid: Means gases, liquefied gases, gases dissolved under pressure, vapours and also those liquids whose vapour pressure at the maximum allowable temperature is greater than 0,5 bar above normal atmospheric pressure (1013 mbar) | Liquids fluid: Means liquids having a vapour pressure at the maximum allowable temperature of not more than 0,5 bar above normal atmospheric pressure (1013 mbar) |
 Exceptionally, vessels intended to contain an unstable gas and falling within categories I or II on the basis of table 1 shall be classified in category III. |  |
 Exceptionally, portable extinguishers and bottles for breathing equipment shall be classified at least in category III. |  |
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Read more details about the allocation of fluids to the fluid groups
