1.1.1 This Published Document specifies requirements for the design, construction, inspection, testing and
verification of compliance of new unfired fusion welded pressure vessels. The materials of construction are
specified in Section 2. The term “pressure vessel” as used in this specification includes branches up to the
point of connection to the connecting piping by bolting, screwing or welding, and supports, brackets or other
attachments directly welded to the pressure containing shell. The term “unfired” excludes vessels that are
subject to direct generated heat or flame impingement from a fired process. It does not exclude vessels subject to electrical heating or heated process streams.
1.1.2 In addition to the definitive requirements this specification also requires the items detailed in 1.5 to
be documented. For compliance with this specification, both the definitive requirements and the documented items have to be satisfied.
1.1.3 This specification applies only to pressure vessels manufactured under the survey of a competent engineering Inspecting Authority or Organization. The competent engineering Inspection Authority or Organization shall either be:
a) a notified body appointed by a member state of the European Union for the Pressure Equipment Directive 97/23/EC for the range of activities covered by this specification; or
NOTE Within the UK the United Kingdom Accreditation Service (UKAS) acts on behalf of the regulating authority in accrediting inspection bodies.
b) accredited to BS EN 45004, to Type A independence criteria, for inspection in the subject matter of this
specification; or
c) accredited by an organization authorized by the local Regulatory Authority in countries outside the EU
and in circumstances where the Pressure Equipment Directive 97/23/EC does not apply.
The intent of this requirement is regarded as satisfied where inspection is carried out by competent
personnel of a separate engineering inspection department maintained by the purchaser of the vessel
(in which case Type B independence criteria shall be met). An inspection department maintained by the
manufacturer does not satisfy this requirement except:
a) that specific responsibilities may be delegated at the discretion of the Inspecting Authority or Organization; or
b) in the case of vessels for the manufacturer’s own use and not for resale.
This specification applies only to vessels made by manufacturer’s who can satisfy the Inspecting Authority
or Organization that they are competent and suitably equipped to fulfil the appropriate requirements of
this specification.
The requirements for testing and inspecting serially manufactured pressure vessels are given in Annex V.
In all other respects the appropriate requirements in the specification apply.
Glass lined steel vessels require special design considerations subject to the limits imposed by the method
of construction which should have the agreement of the Inspecting Authority.1.1.4 This specification does not cover the following.
a) Storage tanks designed for the storage of liquids at near atmospheric pressures, i.e. where the
pressure additional to that due to the hydrostatic head does not exceed 140 mbar1 ) above or 6 mbar bel o w
atmospheric pressure.
b) Low pressure, above ground storage tanks which have a single vertical axis of revolution designed for
the storage of liquids at a pressure not exceeding 1.bar1)
c) Vessels in which the stresses calculated in accordance with the Equations given in Section 3 are less
than 10 % of the design stress permitted by Section 3.
d) Multilayered, autofrettaged, prestressed vessels or other special designs of vessels which may be
appropriate for very high pressures.
e) Transport vessels, i.e. vessels used for transport of contents under pressure.
f) Vessels for specific applications which are covered by standards listed in the BSI Cata.logue
BS PD 5500:2009+A1:2009 history
2021BS PD 5500:2021 Specification for unfired pressure vessels