Pressure accessories are classified into categories according to increasing hazard potential in accordance with PED Annex II. The category is determined according to the procedure listed below. The determined category determines the permissible conformity assessment procedures.
Pressure accessories with only a low risk are not assigned to any category. Sound engineering practice (SEP) applies to them.
Definition of pressure accessories
Pressure accessories are devices with an operational function and having pressure-bearing housings such as valves, expansion joints, filters etc.. Pressure accessories intended for pressure equipments such as vessels, pipings and fired or otherwise heated pressure equipment including where such equipment is incorporated into an assembly.
Note 1: Condensate trap is generally considered as a pressure accessory, placed on the market with CE marking where appropriate. However, a condensate trap specifically designed and manufactured as a part of a given item of piping may be assessed as part of the whole piping and, in that case, is not subject to individual CE marking.
Note 2: Silencers subjected to a back-pressure higher than 0,5 bar (for example outlet silencer of a booster) are submitted to the directive as pressure accessories.
Procedure for determining the category for pressure accessories
The pressure accessories are classified on the basis of:
- Fluid type (gas or liquid)
- their maximum allowable pressure PS [bar],
- their volume V [L] or their nominal size DN1, as appropriate,
- the fluid groups for which they are intended.
Where both the volume and the nominal size are considered appropriate, the pressure accessory shall be classified in the highest category.
1 In the absence of DN in the standards, it shall be assumed that DN corresponds to the internal diameter in millimetres for circular products or the diameter in millimetres of the equivalent flow section for non-circular products. In case of pressure accessories this assumption is made regardless of the diameter of the connection (which is usually expressed by DN).
The appropriate table for vessels (Table 1, 2, 3, and 4) or piping (Table 6, 7, 8, and 9) is to be used to determine the conformity assessment category with follow steps:
- Go to table 1, 2, 3, or 4 and determine category based on volume (category X on flow chart)
- Go to table 6, 7, 8, or 9 and determine category based on DN (category Y on flow chart)
- Compare the categories X and Y and the highest of the two categories is valid for the selection of the conformity assessment procedure
