Functional Safety 2016
November, 2016 - London
Page 7 of 17
Competency in relation to C
PT
The competency of the persons involved in all lifecycle aspects can have significant impact on
the SIFs ability to provide the required risk reduction. As stated (Nunns, 2002), persons
participating in all aspects of proof testing process should have; clearly demonstrable
competency to carry out their alloted task, clearly identified and communicated responsibilities
and documented verification that the proof test is suitable and sufficient in terms of content and
execution.
If the proof test is developed by a person who lacks the required knowledge and understanding
there is an increased probability elements essential to the safety path may be excluded from the
proof test therefore decrease the C
PT
. Equally if the person conducting the proof test does not
fully understand or appriciate why they are conducting the test or elements of the test there is
increase probability that these will inadequately completed and therefore decreasing the actual
risk reduction the SIF is providing.
What does the regulator expect
For the purposes of the UK HSE Enforcement Management Model the UK HSE rely on defined,
established and interpretative standards for which, based on the perceived risk gap, they may
issue verbal warnings, letters or improvement notices. With respect to proof testing the following
apply and the author has applied this approach to the review of current proof testing regimes
and the application of proof test coverage factors for a number of clients:
i)
BS EN 61508:2010 – Established Standard
ii) BS EN 61511:2004 – Established Standard
iii) UK HSE OG00054 - Interpretative Standard
iv) UK HSE CRR 428/2002 – Interpretative Standard
v) EEMUA Publication 222 - Established Standard
vi) ISA-TR84.00.03-2002 – Established Standard