beh188
Mechanical
- Mar 30, 2009
- 99
The Pressure Equipment Directive (PED) requires that certificates of specific product control are required for "Main Pressure-Bearing Parts" in categories above I. This requirement is confusing to me for products such as a valve, where you have several components that are pressure bound. Are some "Main parts" while others are only pressure bound? The PED guidelines offer interpretations 7.6 and 7.8, which do not really clarify the issue. Any thoughts on how to differentiate between main and normal pressure bound parts? When wouldn't a failure of a pressure bound part cause a sudden release of pressure?
Gudeline 7.6
Question: The 2nd paragraph of section 4.3 of Annex I gives requirements for
the main pressure-bearing parts. How are they defined?
Answer: The main pressure-bearing parts are the parts, which constitute the
envelope under pressure, and the parts which are essential for the integrity
of the equipment.
Examples of main pressure-bearing parts are shells, ends, main body
flanges, tube sheet of exchangers, tube bundles.
The materials for these main pressure-bearing parts of equipment of
categories II to IV shall have a certificate of specific product control (see
Guideline 7/5).
See also guideline 7/8 for bolting parts (fasteners).
Guideline 7.8
Question: What are the certificates required for bolting parts?
Answer: The bolting parts (screw, nut, stud, etc) are joining components.
When these components contribute to the pressure resistance, their
materials shall fulfil the relevant requirements of annex I, section 4.
Regarding section 4.3 of Annex I, a bolt is not considered to be a main
pressure bearing part unless its failure would result in a sudden discharge
of pressure energy.
When bolts are used as
− main pressure bearing parts a certificate of specific product control is
required (unless the item of pressure equipment itself is in Category I)
− pressure bearing parts a test report is sufficient,
− non pressure bearing part a certificate of compliance is sufficient.
(refer to guideline 7/5).
Gudeline 7.6
Question: The 2nd paragraph of section 4.3 of Annex I gives requirements for
the main pressure-bearing parts. How are they defined?
Answer: The main pressure-bearing parts are the parts, which constitute the
envelope under pressure, and the parts which are essential for the integrity
of the equipment.
Examples of main pressure-bearing parts are shells, ends, main body
flanges, tube sheet of exchangers, tube bundles.
The materials for these main pressure-bearing parts of equipment of
categories II to IV shall have a certificate of specific product control (see
Guideline 7/5).
See also guideline 7/8 for bolting parts (fasteners).
Guideline 7.8
Question: What are the certificates required for bolting parts?
Answer: The bolting parts (screw, nut, stud, etc) are joining components.
When these components contribute to the pressure resistance, their
materials shall fulfil the relevant requirements of annex I, section 4.
Regarding section 4.3 of Annex I, a bolt is not considered to be a main
pressure bearing part unless its failure would result in a sudden discharge
of pressure energy.
When bolts are used as
− main pressure bearing parts a certificate of specific product control is
required (unless the item of pressure equipment itself is in Category I)
− pressure bearing parts a test report is sufficient,
− non pressure bearing part a certificate of compliance is sufficient.
(refer to guideline 7/5).
