According to the definition, a pressure accessory means a device with an operational function and having an identifiable pressure-bearing housing – i.e. the device has a function additional to that of containing pressure.
The pressure related hazard is identified in relation with the operational function of the pressure accessory., it is covered by PED.
The pressure-related hazard must be determined in relation with the operating function of the pressure accessories and is then covered by the PED as a pressure-retaining piece of equipment.
Examples for valves :
- Where a valve is intended to be used as the sole mean of isolation of the content of an item of pressure equipment from the atmosphere, or from downstream equipment which is not designed to withstand the upstream pressure, the internal parts of the valve which contribute to the isolation must satisfy the relevant essential safety requirements in PED Annex 1 ;
- Where a valve is intended to be fitted between a pressure vessel and pressure piping and both are designed to contain pressure, no pressure related hazard exist in relation to the operational function of the valve, therefore internal parts of the valve do not have to satisfy the relevant essential safety requirements in PED Annex 1.
The intended use of the valve shall be described in the operating instructions, and where it is to be used as a sole mean of isolation, it shall meet the essential safety requirements of the PED.
Classification
In accordance with annex II point 3, pressure accessories have to be classified using the appropriate table(s) of annex II on the basis of their PS, their V and/or DN, and the group of fluids for which they are intended. Pressure accessories with low PS, volume and/or DN will therefore fall under the requirements of PED article 4 par. 3. Such pressure accessories do not have to satisfy the essential requirements but only sound engineering practice.
