Page 394 - Offshore Electrical Engineering Manual

CHAPTER

Protection, Monitoring 6

and Control

PRECOMMISSIONING
Before commissioning, it is essential that the installation work has been properly
checked before any equipment or cables are energised. Cable connections are ‘rang
through’ and cable insulation is checked where possible. Hard-wired logic and con-
trol and monitoring software must be checked, although this may be limited to criti-
cal circuits if the factory acceptance tests are comprehensive and well documented.
The ‘sense’ of any current transformers must be checked to ensure terminals are not
reversed.
All such work is termed precommissioning.

PERMIT-TO-WORK SYSTEMS
Monitoring of all work being done (and being aware of all possible clashes) during
the major shutdown of an installation is vital to the safety of all personnel, and a
failure in the control of work was a major contributor to the Piper Alpha disaster. The
three-dimensional aspect of working offshore can make the control of work even
more difficult, and the permit controller is second only to the offshore installation
manager in having the most responsible job during a shutdown.
Let us consider two examples:

• Radiography with radioactive sources – what is the extent of the area that
must be barriered off, and how many platform decks are affected at any one
time?
• What isolations are required to replace a valve on a fuel-gas system – how many
other systems are affected? Will main generation be affected? How many disci-
plines are involved?

These are only a few of the questions which require consideration if such
tasks are to be completed safely. Even forgetting one could lead to injury or
death.
For more information refer to the Health and Safety Executive’s ‘The safe isola-
tion of plant and equipment’.

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