The term pressure-bearing housing refers to an envelope in which fluid under pressure (PS > 0,5) is contained or transported (volume V > 0).
Therefore, a product whose only pressure-bearing surface is a flange or screwed fitting is not a pressure accessory but is a component of an item of pressure equipment under the Pressure Equipment Directive (PED) when used on such equipment.
Typical examples of components which are not pressure accessories: Level Switch, Flush Mounted Pressure Transmitter and Thermowell.
Note:
This does not apply to such devices when employed in a safety function.