Paragraph 4
That part of a system which is only a pressure system because it is–
(a)
subject to a leak test (except that this sub-paragraph shall not apply to a pipeline);
(b)
pressurised unintentionally, such pressurisation being not reasonably foreseeable; or
(c)
a pipeline pressurised by a relevant fluid solely as part of a test or line clearance operation, but this exception shall not apply if the pipeline–
(i)
is used for the conveyance of a relevant fluid, or
(ii)
is pressurised beyond its safe operating limits.