Page 28 - Offshore Electrical Engineering Manual

Hydrocarbon Hazards 15

WATER HAZARDS

Hazards due to water coming into contact with electrical equipment are similar to
those experienced on ships but can be more catastrophic because on offshore installa-
tion, more power is often generated, at higher voltages, and with greater prospective
fault ratings.
Water may leak from large bore water-carrying pipes routed over switchboards or
generators. The following situations are two examples seen by the author where such
pipes were routed over switchboards.

Example 1 A fire–water main routed over a 4 MW gas turbine generator. The
fire main was flanged and valved directly over the alternator. When the valve was
serviced while the generator was running, the pipe fitter inadvertently drained an
isolated section of fire main over the alternator. The generator promptly shut down,
because of the operation of the differential protection, with a stator winding fault.
Example 2 In an accommodation module a sewage pipe from the floor above
was routed directly above a low-voltage switchboard and along almost its entire
length. Although some minor leaking had taken place, it was fortunate that the
only problem for the electrical maintenance staff was one of hygiene.

If routing of water-carrying pipes over switchgear is unavoidable, there should be
no flanges in the section of the pipe over the switchboard.

HYDROCARBON HAZARDS
In the planning of platform superstructures, designers try to arrange to segregate the
wellhead and process areas from the accommodation and other normally manned areas
to the greatest possible extent. This involves not only horizontal and vertical segrega-
tion but also segregation of all piped or ducted services such as ventilation ducting
and drains. Following the Piper Alpha disaster, the whole philosophy regarding the
segregation of accommodation areas on offshore platforms has been rethought, and
safety philosophies have become more ‘goal setting’ rather than prescriptive. As is
common knowledge, 165 people lost their lives either as a result of the initial explo-
sions, dense smoke and fire or following the ensuing riser fires which led to the loss
of structural integrity and the falling of the Piper Alpha accommodation module into
the sea. The Cullen Report gives over 100 recommendations, covering all aspects of
offshore installation design, construction, operation and safety. In one of, in my view,
the most important recommendations, Lord Cullen states that the operator should be
required by regulation to submit to the regulatory body a Safety Case in respect of each
of its installations. It is important that the safety aspects of each installation are consid-
ered uniquely so as to meet objectives, rather than impose fixed solutions which may
or may not work on a particular installation. Safety Case Regulations have now been
in force for almost as long as the first edition of this book has been published and these
statutory regulations are considered in PART 9 Chapter 1.