1. Article 1 paragraph 2 (j) excludes pressurized equipment comprising casings or machinery from the scope of the PED
a) if this equipment is primarily dimensioned for loads other than pressure, i.e. for which pressure is not the significant design factor and
b) if it is primarily designed to move or rotate or fulfil other functions than pressure containment.
2. Such equipment may include
- engines including turbines and internal combustion engines;
- steam engines, gas/steam turbines, turbo-generators, compressors,
- pumps, actuating devices and curing moulds for tyres.
3. For such equipment, pressure can be considered as not being a significant factor, if other factors alone or together are more significant than pressure.
Other factors are, e.g.:
- dynamic loads with vibrations or very high number of cycles;
- thermal loads together with a complicated form of structure;
- stiffness of the structure because of external mechanical loads or requirements related to high weight;
- requirements related to low elongation, low change of diameter or low other deformation because of functional requirements to rigidity.
This shall be decided on a case by case basis, taking into accountestablished safe industrial practice.
4. An over-dimensioning as such shall not result in exclusion from the PED with regard to Article 1 paragraph 2 (j).
Note1:
No factor is included in the requirements of the PED. Any factor given in a guideline would therefore go beyond the PED and should be avoided.
Note 2:
If a factor were used to decide whether the requirements of the PED are applicable or not, overdimensioning could result in a case where pressure equipment need not fulfil the requirements of the PED. This is not acceptable.
Note 3:
To decide on the exception with a factor of overdimensioning would consequently result in the necessity of a detailed stress analysis, especially if this factor would have been connected to the primary membrane stress. This is far beyond the present established industrial practice.
Note 4:
Furthermore, there is a danger that the more important influences explained in paragraphs 1 to 3 of the above answer could be overlooked if the decision whether the pressure is a significant design factor were based on a factor of overdimensioning only.