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.
It can be attached to other pressure equipment for example by bolting, brazing, soldering or welding.
It has a specific operational function (or functions), which could be for example: measurement, change the mechanical characteristics of the fluid flow, taking a sample, removal of sediment or gas. It does not necessarily have moving parts.
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 article 4.3. Such pressure accessories do not have to satisfy the essential requirements but only sound engineering practice.
Typical pressure accessory
Typical examples are: valves, pressure regulators, measurement chambers, pressure gauges, water gauge glasses, filters, expansion joints (devices containing one or more bellows) and manifolds. flame arresters and flash back arrester (if they do not exceed Category I)
Typical no pressure accessory
The following examples are not pressure accessories:
- safety valve (a safety accessory)
- cover, collar, gasket, flange, bolt (components of a pressure equipment)
- sight glass with its frames (components of a pressure equipment)
- Y-shape or similar fittings (piping components)
- Level Switch,
- Flush Mounted Pressure Transmitter and
- Thermowell.
